@article {KNZ001901, title = {What drives grassland ecosystem multifunctionality: Grazing pressure or plant community parameters?}, journal = {Functional Ecology}, year = {In Press}, keywords = {LTER-KNZ}, author = {Ren, H. and Zhang, Y. and Gui, W. and Yang, G. and G.T. Wilson and Cobb, A.B. and Eviner, V.T. and Hu, S. and Yongfei Bai} } @article {KNZ002007, title = {Plant{\textendash}microbial interactions facilitate grassland species coexistence at the community level}, journal = {Oikos}, volume = {129}, year = {2020}, pages = {533-543}, abstract = {

Interspecific competition and plant\–soil feedbacks are powerful drivers of plant community structure. However, across a range of edaphic conditions the interactive effects of these drivers on complex plant communities remain unclear. For example, plant\–soil feedback studies focus on soil trained by a single plant species. We developed a method to assess effects of plant\–microbial interactions (PMI) on a complex plant community. We established mesocosms with 13 grassland species, grown individually or together, in overgrazed or restored soil, with or without soil microbial inoculum collected from a productive and diverse native grassland. We assessed biomass production as influenced by edaphic conditions, interspecific competition and PMI. Furthermore, we assessed potential influences of interspecific competition and edaphic conditions on strength and direction of PMI. Our results indicate PMI drives negative growth responses for graminoids while forbs experience positive growth responses. Generally, interspecific competition did not alter the magnitude or direction of PMI-mediated growth responses. Edaphic conditions altered the influence of soil microbial communities on individual plant growth while PMI facilitated plant evenness. In plant community mesocosms, PMI-associated benefits were observed in overgrazed soil. However, interspecific competition overwhelmed plant growth benefits associated with soil microbial communities when plant communities were grown in restored soil. In mesocosms containing dominant grass species, interspecific competition had negative effects on species coexistence, but both positive and negative PMI partially counterbalanced this influence on plant species evenness. Understanding these mechanisms may improve our capacity to manage diverse and productive grasslands by enabling prediction of plant community composition following disturbance and subsequent restoration.

}, keywords = {LTER-KNZ}, issn = {0030-1299}, doi = {10.1111/oik.06609}, url = {https://onlinelibrary.wiley.com/doi/abs/10.1111/oik.06609}, author = {Li, Jiahuan and Xie, Shu and G.T. Wilson and Cobb, Adam B. and Tang, Shiming and Guo, Lizhu and Wang, Kun and Deng, Bo} } @article {KNZ001951, title = {Climate affects plant-soil feedback of native and invasive grasses: negative feedbacks in stable but not in variable environments}, journal = {Frontiers in Ecology and Evolution}, volume = {7}, year = {2019}, abstract = {

The plant-soil feedback framework allows researchers to target the interaction of plants and root-associated microbes and to determine its interplay on plant-plant interactions. Plant-soil feedbacks in terrestrial ecology are well-documented, but the strength and direction of feedbacks as influenced by abiotic environmental factors, such as temperature and soil moisture, has not been fully explored. In our study, we examined plant-soil feedback responses of both cool- and warm-season native and non-native grasses to elevated temperatures (ambient and +5\°C) and soil moisture (100 and 75\% field capacity). In a previous experiment, grasses were grown under temperature and soil moisture conditions similar to our current study. The resultant trained soil communities served as the inoculum sources for our current experiment. We found that consistent training and experimental temperatures resulted in negative PSF, where plants produced greater biomass in soils conditioned by heterospecifics. However, the direction of PSF was reversed when training and experimental conditions were mismatched. That is, when training and experimental temperatures mirrored one another, negative PSF occurred, suggesting coexistence between the two species is likely under these conditions. However, when only training or testing temperatures were elevated, positive PSF were detected, favoring the non-native species. These alterations in plant-soil feedbacks were relatively consistent across pairings of warm- and cool-season grasses. Overall, our results indicate inconsistent year-to-year environmental conditions, such as extreme temperatures, may undermine the stabilizing forces of negative PSF and favor of non-native grasses.

}, keywords = {LTER-KNZ}, doi = {10.3389/fevo.2019.00419}, url = {https://www.frontiersin.org/articles/10.3389/fevo.2019.00419/full$\#$h6}, author = {E.B. Duell and Zaiger, Katherine and Bever, James D. and G.T. Wilson} } @article {KNZ001963, title = {Following legume establishment, microbial and chemical associations facilitate improved productivity in degraded grasslands}, journal = {Plant and Soil}, volume = {443}, year = {2019}, pages = {273 - 292}, keywords = {LTER-KNZ}, doi = {10.1007/s11104-019-04169-9}, url = {http://link.springer.com/10.1007/s11104-019-04169-9}, author = {Zhou, Jiqiong and Zhang, Fengge and Huo, Yunqian and G.T. Wilson and Cobb, Adam B. and Xu, Xixi and Xiong, Xue and Liu, Lin and Zhang, Yingjun} } @article {KNZ001981, title = {Phosphorus and mowing improve native alfalfa establishment, facilitating restoration of grassland productivity and diversity}, journal = {Land Degradation \& Development}, volume = {30}, year = {2019}, pages = {647 - 657}, keywords = {LTER-KNZ}, doi = {10.1002/ldr.v30.610.1002/ldr.3251}, url = {https://onlinelibrary.wiley.com/doi/abs/10.1002/ldr.3251}, author = {Zhou, Jiqiong and G.T. Wilson and Cobb, Adam B. and Yang, Gaowen and Zhang, Yingjun} } @article {KNZ001905, title = {Defoliation and arbuscular mycorrhizal fungi shape plant communities in overgrazed semiarid grasslands}, journal = {Ecology}, volume = {99}, year = {2018}, pages = {1847 - 1856}, abstract = {

Overgrazing substantially contributes to global grassland degradation by decreasing plant community productivity and diversity through trampling, defoliation, and removal of nutrients. Arbuscular mycorrhizal (AM) fungi also play a critical role in plant community diversity, composition, and primary productivity, maintaining ecosystem functions. However, interactions between grazing disturbances, such as trampling and defoliation, and AM fungi in grassland communities are not well known. We examined influences of trampling, defoliation, and AM fungi on semiarid grassland plant community composition for 3\ yr, by comparing all combinations of these factors. Benomyl fungicide was applied to reduce AM fungal abundance. Overgrazing typically resulted in reduced dominance of Stipa Krylovii, contributing to degradation of typical steppe grasslands. Our results indicated trampling generally had little effect on plant community composition, unless combined with defoliation or AM fungal suppression. Defoliation was the main component of grazing that promoted dominance of Potentilla acaulis over Stipa krylovii and Artemisia frigida, presumably by alleviating light limitation. In non-defoliated plots, AM fungi promoted A.\ frigida, with a concomitant reduction in S.\ krylovii growth compared to corresponding AM suppressed plots. Our results indicate AM fungi and defoliation jointly suppress S.\ krylovii biomass; however, prolonged defoliation weakens mycorrhizal influence on plant community composition. These findings give new insight into dominant plant species shifts in degraded semiarid grasslands.

}, keywords = {LTER-KNZ}, doi = {10.1002/ecy.2401}, url = {https://doi.org/10.1002/ecy.2401}, author = {Yang, Xin and Shen, Yue and Liu, Nan and G.T. Wilson and Cobb, Adam B. and Zhang, Yingjun} } @article {KNZ001906, title = {Evolutionary history of plant hosts and fungal symbionts predicts the strength of mycorrhizal mutualism}, journal = {Communications Biology}, volume = {116}, year = {2018}, abstract = {

Most plants engage in symbioses with mycorrhizal fungi in soils and net consequences for plants vary widely from mutualism to parasitism. However, we lack a synthetic understanding of the evolutionary and ecological forces driving such variation for this or any other nutritional symbiosis. We used meta-analysis across 646 combinations of plants and fungi to show that evolutionary history explains substantially more variation in plant responses to mycorrhizal fungi than the ecological factors included in this study, such as nutrient fertilization and additional microbes. Evolutionary history also has a different influence on outcomes of ectomycorrhizal versus arbuscular mycorrhizal symbioses; the former are best explained by the multiple evolutionary origins of ectomycorrhizal lifestyle in plants, while the latter are best explained by recent diversification in plants; both are also explained by evolution of specificity between plants and fungi. These results provide the foundation for a synthetic framework to predict the outcomes of nutritional mutualisms.

}, keywords = {LTER-KNZ}, doi = {10.1038/s42003-018-0120-9}, url = {http://www.nature.com/articles/s42003-018-0120-9}, author = {Hoeksema, Jason D. and Bever, James D. and Chakraborty, Sounak and Chaudhary, V. Bala and Gardes, Monique and Gehring, Catherine A. and Hart, Miranda M. and Housworth, Elizabeth Ann and Kaonongbua, Wittaya and Klironomos, John N. and Lajeunesse, Marc J. and Meadow, James and Milligan, Brook G. and Piculell, Bridget J. and Pringle, Anne and R{\'u}a, Megan A. and Umbanhowar, James and Viechtbauer, Wolfgang and Wang, Yen-Wen and G.T. Wilson and Zee, Peter C.} } @article {KNZ001903, title = {Long-term effects of grazing and topography on extra-radical hyphae of arbuscular mycorrhizal fungi in semi-arid grasslands}, journal = {Mycorrhiza}, volume = {28}, year = {2018}, pages = {117 - 127}, abstract = {

Grazing and topography have drastic effects on plant communities and soil properties. These effects are thought to influence arbuscular mycorrhizal (AM) fungi. However, the simultaneous impacts of grazing pressure (sheep\ ha-1) and topography on plant and soil factors and their relationship to the production of extra-radical AM hyphae are not well understood. Our 10-year study assessed relationships between grazing, plant species richness, aboveground plant productivity, soil nutrients, edaphic properties, and AM hyphal length density (HLD) in different topographic areas (flat or sloped). We found HLD linearly declined with increasing grazing pressure (1.5-9.0 sheep\ ha-1) in sloped areas, but HLD was greatest at moderate grazing pressure (4.5 sheep\ ha-1) in flat areas. Structural equation modeling indicates grazing reduces HLD by altering soil nutrient dynamics in sloped areas, but non-linearly influences HLD through plant community and edaphic changes in flat areas. Our findings highlight how topography influences key plant and soil factors, thus regulating the effects of grazing pressure on extra-radical hyphal production of AM fungi in grasslands. Understanding how grazing and topography influence AM fungi in semi-arid grasslands is vital, as globally, severe human population pressure and increasing demand for food aggravate the grazing intensity in grasslands.

}, keywords = {LTER-KNZ}, doi = {10.1007/s00572-017-0812-x}, url = {http://link.springer.com/10.1007/s00572-017-0812-x}, author = {Ren, Haiyan and Gui, Weiyang and Yongfei Bai and Stein, Claudia and Rodrigues, Jorge L. M. and G.T. Wilson and Cobb, Adam B. and Zhang, Yingjun and Yang, Gaowen} } @article {KNZ001902, title = {Mycorrhizal symbioses influence the trophic structure of the Serengeti}, journal = {Journal of Ecology}, volume = {106}, year = {2018}, pages = {536 - 546}, abstract = {
  1. It is known that tropical grasslands such as Serengeti host large populations of arbuscular mycorrhizal (AM) fungi and that they respond to abiotic and biotic factors. It is also known that AM symbioses are important for the uptake of essential plant nutrients, which, in turn, influences the biomass and nutritional quality of herbivores and their predators. The purpose of this study was to investigate the influence of AM symbioses on the biomass of different trophic levels of an ecosystem.
  2. To do this, we first measured the neutral lipid fatty acid biomarker 16:1ω5 to estimate the biomass of AM fungi in a long-term grazing exclusion experiment. Then, we used model selection of Bayesian linear regressions to infer the primary factors that influence AM fungal biomass. Using model selection of different combinations of soil characteristics, we selected the best model using the leave-one-out cross-validation information criterion. Finally, we used the Madingley model to simulate the influence of AM fungi on higher trophic levels. We combined spatially explicit information about soil phosphorus and AM fungal biomass to explore the emergent patterns of the Serengeti resulting from AM symbioses.
  3. Our Bayesian analysis indicated that total soil phosphorus was the strongest predictor of AM fungal biomass, and there were significant interactions with grazing. Arbuscular mycorrhizal fungal biomass is lowest in soil where phosphorus is limited and increases with increasing phosphorus concentration. Biomass was also significantly higher in plots that were not grazed. The Madingley model indicated that nutritional benefits of AM symbioses maintain a substantial proportion of the biomass across all trophic levels.
  4. Synthesis. Our analysis shows that inputs of phosphorus through arbuscular mycorrhizal symbioses substantially increase the ability of plants to grow and maintain nutritional quality, cascading through the biomass of consumers and predators in the ecosystem. Although they account for less than 1\% of the total modelled biomass, the predicted nutritional benefit provided by arbuscular mycorrhizal fungi increased the biomass of macro-organisms in the Serengeti by 48\%. When considering the management of biodiversity, future ecosystem models should account for the influence of arbuscular mycorrhizal fungi on all trophic levels.

}, keywords = {LTER-KNZ}, doi = {10.1111/1365-2745.12916}, url = {http://doi.wiley.com/10.1111/1365-2745.12916}, author = {Stevens, Bo Maxwell and Propster, Jeffrey and G.T. Wilson and Abraham, Andrew and Ridenour, Chase and Doughty, Christopher and Johnson, Nancy Collins}, editor = {Wurzburger, Nina} } @article {KNZ001900, title = {Plant functional group influences arbuscular mycorrhizal fungal abundance and hyphal contribution to soil CO2 efflux in temperate grasslands}, journal = {Plant and Soil}, volume = {432}, year = {2018}, pages = {157-170}, abstract = {

Background and aims: Arbuscular mycorrhizal (AM) fungi are abundant in grassland ecosystem. We assessed AM hyphal contributions to soil CO2 efflux across plant functional groups to better quantify AM fungal influences on soil carbon dynamics.


Methods: We conducted a field experiment using in-growth mesocosms to partition soil CO2 efflux from roots, AM hyphae, and free-living soil microbes associated with C3 grasses, C4 grasses, forbs, and diverse plant communities from May to August in 2017.


Results: AM hyphae contributed \<10\% to total soil respiration in forb communities and diverse plant communities but accounted for as much as 32\% in C3 grasses. Plant functional groups differed in hyphal production efficiencies (the ratio of AM hyphal length to aboveground biomass), with the lowest in C3 grasses (0.47?\±?0.15 m g-1) and the greatest in forbs (3.27?\±?0.55 m g-1). Mowing reduced hyphal production efficiency of C4 grasses and forbs but did not affect total soil respiration. AM hyphal and microbial respiration peaked at the middle of the growing season, however there was no significant seasonal variation in root respiration.


Conclusion: AM hyphal respiration is an important pathway of carbon flux from plants to atmosphere. Shifts in plant community composition can influence soil carbon processes by regulating hyphal production and respiration.

}, keywords = {LTER-KNZ}, doi = {10.1007/s11104-018-3789-0}, url = {http://link.springer.com/10.1007/s11104-018-3789-0}, author = {Gui, Weiyang and Ren, Haiyan and Liu, Nan and Zhang, Yingjun and Cobb, Adam B. and G.T. Wilson and Sun, Xiao and Hu, Jian and Xiao, Yan and Zhang, Fengge and Yang, Gaowen} } @article {KNZ001904, title = {Trichoderma biofertilizer links to altered soil chemistry, altered microbial communities, and improved grassland biomass}, journal = {Frontiers in Microbiology}, volume = {9}, year = {2018}, pages = {848}, abstract = {

In grasslands, forage and livestock production results in soil nutrient deficits as grasslands typically receive no nutrient inputs, leading to a loss of grassland biomass. The application of mature compost has been shown to effectively increase grassland nutrient availability. However, research on fertilization regime influence and potential microbial ecological regulation mechanisms are rarely conducted in grassland soil. We conducted a two-year experiment in meadow steppe grasslands, focusing on above- and belowground consequences of organic or Trichoderma biofertilizer applications and potential soil microbial ecological mechanisms underlying soil chemistry and microbial community responses. Grassland biomass significantly (p = 0.019) increased following amendment with 9,000 kg ha\−1 of Trichoderma biofertilizer (composted cattle manure + inoculum) compared with other assessed organic or biofertilizer rates, except for BOF3000 (fertilized with 3,000 kg ha\−1 biofertilizer). This rate of Trichoderma biofertilizer treatment increased soil antifungal compounds that may suppress pathogenic fungi, potentially partially responsible for improved grassland biomass. Nonmetric multidimensional scaling (NMDS) revealed soil chemistry and fungal communities were all separated by different fertilization regime. Trichoderma biofertilizer (9,000 kg ha\−1) increased relative abundances of Archaeorhizomyces and Trichoderma while decreasing Ophiosphaerella. Trichoderma can improve grassland biomass, while Ophiosphaerella has the opposite effect as it may secrete metabolites causing grass necrosis. Correlations between soil properties and microbial genera showed plant-available phosphorus may influence grassland biomass by increasing Archaeorhizomyces and Trichoderma while reducing Ophiosphaerella. According to our structural equation modeling (SEM), Trichoderma abundance was the primary contributor to aboveground grassland biomass. Our results suggest Trichoderma biofertilizer could be an important tool for management of soils and ultimately grassland plant biomass.

}, keywords = {LTER-KNZ}, doi = {10.3389/fmicb.2018.00848}, url = {http://journal.frontiersin.org/article/10.3389/fmicb.2018.00848/full}, author = {Zhang, Fengge and Huo, Yunqian and Cobb, Adam B. and Luo, Gongwen and Zhou, Jiqiong and Yang, Gaowen and G.T. Wilson and Zhang, Yingjun} } @article {KNZ001907, title = {Small vegetation gaps increase reseeded yellow-flowered alfalfa performance and production in native grasslands}, journal = {Basic and Applied Ecology}, volume = {24}, year = {2017}, pages = {41 - 52}, abstract = {

Reseeding yellow-flowered alfalfa (YFA) in degraded grasslands may require a vegetation-free microsite for germination and subsequent establishment. This study aimed to examine the role of microclimates of different-sized vegetation gaps on seedling performance and adult plant production of YFA. Field microsites were established in the meadow steppe of Hulunber, Inner Mongolia, China. Seedling performance, plant production, the microclimate within vegetation gaps, and soil nutrients (plant-available N, P, and K, total N concentration) were assessed at the end of each growing season from 2013 to 2015. Our results indicate light availability, and topsoil temperature of each gap were significantly increased as gap size increased, while topsoil moisture and air relative moisture were decreased in larger gaps. Small gaps (diameter \≤10cm) improved seedling emergence, survival, biomass, and root nodulation, as compared with seedling performance associated with the larger gaps, presumably in response to increased shade and moisture. Additionally, large gaps (\>20 or \>40\ cm) were characterized by significantly lower plant-available P, total N concentrations, plant-available K, and soil pH. However, root exclusion treatments did not improve overall seedling performance, plant production, or soil properties, as compared to corresponding microsites with root presence, regardless of gap size. Our results suggest that reseeding YFA into grasslands where disturbance, such as light grazing, has resulted in small gaps will be more effective than in highly degraded grasslands.

}, keywords = {LTER-KNZ}, doi = {10.1016/j.baae.2017.08.002}, url = {https://linkinghub.elsevier.com/retrieve/pii/S1439179117300464}, author = {Zhou, Jiqiong and Zhang, Yingjun and G.T. Wilson and Cobb, Adam B. and Lu, Wenjie and Guo, Yanping} } @article {KNZ001771, title = {Above- and below-ground responses of native and invasive prairie grasses to future climate scenarios}, journal = {Botany}, volume = {94}, year = {2016}, pages = {471 - 479}, abstract = {

More intense and frequent droughts, coupled with elevated temperatures, are projected for grasslands worldwide. Although it has been suggested that alterations in temperature and precipitation will increase the success of biological invasions, studies that combine these climate change scenarios are limited. These changes in climate may increase the success of non-native, invasive plant species directly, as these species often possess traits that are favored by variable climates, or indirectly through negative impacts on native vegetation or alterations in soil microbial communities, such as arbuscular mycorrhizal (AM) fungi. The goal of our research was to assess above- and below-ground production and mycorrhizal fungal abundance of functionally similar native and invasive non-native grass species under projected climate-change scenarios. We assessed plant biomass, intra-radical AM root colonization, and relative abundance of extra-radical fungal biomass of two native (Schizachyrium scoparium (Michx.) Nash, Pascopyrum smithii (Rydb.) {\'A}.L{\"o}ve) and two invasive (Bothriochloa ischaemum (L.) Keng, Bromus inermis Leyss.) grass species subjected to increased temperature and decreased soil water availability. Regardless of temperature or soil moisture, the invasive grasses in our study displayed greater seedling growth as compared with paired native species. Invasive grasses were also generally characterized by greater intra-radical colonization by AM fungi, compared with native species. Our data suggest that invasive grasses will continue to be problematic and successfully out-compete native grasses following increased temperatures and reduced water availability, as projected by climate-change models.

}, keywords = {LTER-KNZ, Bothriochloa ischaemum, Bromus imermis, Climate change, Invasive species, Pascopyrum smithii, Schizachyrium scoparium}, doi = {10.1139/cjb-2015-0238}, url = {http://www.nrcresearchpress.com/doi/10.1139/cjb-2015-0238}, author = {E.B. Duell and G.T. Wilson and Hickman, K.R.} } @article {KNZ001770, title = {Belowground interactions with aboveground consequences: Invasive earthworms and arbuscular mycorrhizal fungi}, journal = {Ecology}, volume = {97}, year = {2016}, pages = {605 - 614}, abstract = {

A mounting body of research suggests that invasive nonnative earthworms substantially alter microbial communities, including arbuscular mycorrhizal fungi (AMF). These changes to AMF can cascade to affect plant communities and vertebrate populations. Despite these research advances, relatively little is known about (1) the mechanisms behind earthworms\’ effects on AMF and (2) the factors that determine the outcomes of earthworm\–AMF interactions (i.e., whether AMF abundance is increased or decreased and subsequent effects on plants). We predict that AMF-mediated effects of nonnative earthworms on ecosystems are nearly universal because (1) AMF are important components of most terrestrial ecosystems, (2) nonnative earthworms have become established in nearly every type of terrestrial ecosystem, and (3) nonnative earthworms, due to their burrowing and feeding behavior, greatly affect AMF with potentially profound concomitant effects on plant communities. We highlight the multiple direct and indirect effects of nonnative earthworms on plants and review what is currently known about the interaction between earthworms and AMF. We also illustrate how the effects of nonnative earthworms on plant\–AMF mutualisms can alter the structure and stability of aboveground plant communities, as well as the vertebrate communities relying on these habitats. Integrative studies that assess the interactive effects of earthworms and AMF can provide new insights into the role that belowground ecosystem engineers play in altering aboveground ecological processes. Understanding these processes may improve our ability to predict the structure of plant and animal communities in earthworm-invaded regions and to develop management strategies that limit the numerous undesired impacts of earthworms.

}, keywords = {LTER-KNZ}, doi = {10.1890/15-1085}, url = {https://esajournals.onlinelibrary.wiley.com/doi/abs/10.1890/15-1085}, author = {Paudel, S. and Longcore, T. and MacDonald, B. and McCormick, M.K. and Szlavecz, K. and G.T. Wilson and Loss, S.R.} } @mastersthesis {KNZ001813, title = {Environmental extremes drive plant and soil community dynamics of native and disturbed grasslands}, volume = {MS Thesis}, year = {2016}, school = {Oklahoma State University}, type = {M.S. Thesis}, address = {Stillwater, OK}, keywords = {LTER-KNZ}, url = {https://shareok.org/handle/11244/49188}, author = {Zaiger, K.} } @article {KNZ001668, title = {Mycorrhizal phenotypes and the law of the minimum}, journal = {New Phytologist}, volume = {205}, year = {2015}, pages = {1473 -1484}, abstract = {

Mycorrhizal phenotypes arise from interactions among plant and fungal genotypes and the environment. Differences in the stoichiometry and uptake capacity of fungi and plants make arbuscular mycorrhizal (AM) fungi inherently more nitrogen (N) limited and less phosphorus (P) limited than their host plants. Mutualistic phenotypes are most likely in P-limited systems and commensal or parasitic phenotypes in N-limited systems. Carbon (C) limitation is expected to cause phenotypes to shift from mutualism to commensalism and even parasitism. Two experiments compared the influence of fertilizer and shade on mycorrhizas in Andropogon gerardii across three naturally N-limited or P-limited grasslands. A third experiment examined the interactive effects of N and P enrichment and shade on A. gerardii mycorrhizas. Our experiments generated the full spectrum of mycorrhizal phenotypes. These findings support the hypothesis that mutualism is likely in P-limited systems and commensalism or parasitism is likely in N-limited systems. Furthermore, shade decreased C-assimilation and generated less mutualistic mycorrhizal phenotypes with reduced plant and fungal biomass. Soil fertility is a key controller of mycorrhizal costs and benefits and the Law of the Minimum is a useful predictor of mycorrhizal phenotype. In our experimental grasslands arbuscular mycorrhizas can ameliorate P-limitation but not N-limitation.

}, keywords = {LTER-KNZ, stoichiometry}, doi = {10.1111/nph.13172}, url = {https://nph.onlinelibrary.wiley.com/doi/full/10.1111/nph.13172}, author = {Johnson, N.C. and G.T. Wilson and Wilson, J.A. and Miller, R.M. and M. Bowker} } @article {KNZ001667, title = {Changes in plant community composition, not diversity, during a decade of nitrogen and phosphorus additions drive above-ground productivity in a tallgrass prairie}, journal = {Journal of Ecology}, volume = {102}, year = {2014}, pages = {1649 -1660}, abstract = {

Nutrient additions typically increase terrestrial ecosystem productivity, reduce plant diversity and alter plant community composition; however, the effects of P additions and interactions between N and P are understudied. We added both N (10 g m\−2) and three levels of P (2.5, 5 and 10 g m\−2) to a native, ungrazed tallgrass prairie burned biennially in northeastern Kansas, USA, to determine the independent and interactive effects of N and P on plant community composition and above-ground net primary productivity (ANPP). After a decade of nutrient additions, we found few effects of P alone on plant community composition, N alone had stronger effects, and N and P additions combined resulted in much larger effects than either alone. The changes in the plant community were driven by decreased abundance of C4 grasses, perhaps in response to altered interactions with mycorrhizal fungi, concurrent with increased abundance of non-N-fixing perennial and annual forbs. Surprisingly, this large shift in plant community composition had little effect on plant community richness, evenness and diversity. The shift in plant composition with N and P combined had large but variable effects on ANPP over time. Initially, N and N and P combined increased above-ground productivity of C4 grasses, but after 4 years, productivity returned to ambient levels as grasses declined in abundance and the community shifted to dominance by non-N-fixing and annual forbs. Once these forbs increased in abundance and became dominant, ANPP was more variable, with pulses in forb production only in years when the site was burned. Synthesis. We found that a decade of N and P additions interacted to drive changes in plant community composition, which had large effects on ecosystem productivity but minimal effects on plant community diversity. The large shift in species composition increased variability in ANPP over time as a consequence of the effects of burning. Thus, increased inputs of N and P to terrestrial ecosystems have the potential to alter stability of ecosystem function over time, particularly within the context of natural disturbance regimes.

}, keywords = {LTER-KNZ}, doi = {10.1111/1365-2745.12312}, url = {https://besjournals.onlinelibrary.wiley.com/doi/full/10.1111/1365-2745.12312}, author = {M.L. Avolio and Koerner, S.E. and Kimberly J. La Pierre and K.R. Wilcox and G.T. Wilson and M.D. Smith and Scott. L. Collins} } @mastersthesis {KNZ001670, title = {Did selective breeding of a non-native grass promote invasiveness?}, volume = {MS Thesis}, year = {2014}, school = {Oklahoma State University}, type = {M.S. Thesis}, address = {Stillwater, OK}, abstract = {

Concerns with invasive species have included exotic forage grasses that have undergone extensive breeding through development programs for greater success of establishment. These grasses have been widely distributed for soil erosion control and livestock forage production throughout the United States and many of these species have become invasive in native habitats. To determine whether plant breeding procedures increased the invasiveness of these exotic grasses relative to their native counterparts, we assessed the competitiveness of an old world bluestem (Bothriochloa ischaemum ; OWB) a known invader of the Great Plains in the United States, relative to its \"wildtype\" from the Czech Republic, and two native tallgrass prairie grasses (big bluestem [Andropogon gerardii] and little bluestem [Schizachyrium scoparium]). To assess inter-and intraspecific competition a substitutive design greenhouse competition experiment was conducted in Stillwater, Oklahoma with partners from the Czech University of Life Sciences. Growth of the invasive B. ischaemum was enhanced when grown with the native S. scoparium. However, the Czech Republic wildtype did not exhibit increased production when grown in competition with natives compared to conspecifics, suggesting the extensive breeding of B. ischaemum may have enhanced its competitive abilities. To further assess plant-soil feedbacks we conducted a second greenhouse study which examined soil biotic communities using soil inoculums associated with either wildtype or invasive B. ischaemum cultivars. Growth and reproduction of native grass species, the wildtype, and invasive B. ischaemum were assessed 16 weeks following inoculation with soil microbial communities. Phospholipid and neutral lipid fatty acids were quantified at the end of the study to determine microbial biomass associated with each soil inoculum and species or cultivar combination. Total biomass production and abundance of AMF was enhanced when the wildtype was grown with inoculum associated with the invasive cultivar compared to wildtype inoculum, indicating the wildtype favors soil biotic communities associated with the invasive cultivar. When assessing responses of native grasses, A. gerardii illustrated greater production and abundance of AMF compared to S. scoparium suggesting seeding to A. gerardii may lead to greater success in grassland restorations following eradication of B. ischaemum, compared to restorations seeded to S. scoparium.

}, keywords = {LTER-KNZ, ecology, natural resource management, range management}, url = {https://shareok.org/handle/11244/25654}, author = {Grischkowsky, S.A.} } @article {KNZ001663, title = {Experimental evidence that invasive grasses use allelopathic biochemicals as a potential mechanism for invasion: Chemical warfare in nature}, journal = {Plant and Soil}, volume = {385}, year = {2014}, pages = {165 -179}, abstract = {

Background and aims Bothriochloa spp. are non-native warm-season grasses invading native grasslands of the southern and central Great Plains, altering ecological services these grasslands supply. Our study investigated potential allelopathic effects of the invasive grass species B. ischaemum on native grass germination, growth, and survival. Methods Leachate or litter from Andropogon gerardii (native) or B. ischaemum were applied to two native grass species (A. gerardii; Schizachyrium scoparium). Leachate and litter were also added to B. ischaemum and a water control was included. Germination, above- and belowground biomass, and survival were determined. Results Application of B. ischaemum leachate or litter significantly reduced the germination, growth, and survival of both A. gerardii and S. scoparium but had no conspecific effects, while A. gerardii treatments had no effect on any species. Conclusions Bothriochloa spp. may gain a competitive advantage through allelopathic biochemicals. It is unclear if these allelopathic effects directly hinder competitors or indirectly hinder them through alterations in soil microbial communities, however, reductions in germination of native seeds strongly support direct allelopathic effects. Greater phenolic content in native grass leachates suggest allelopathic biochemical production may not be unique to non-native species and may be a mechanism for maintenance of plant species biodiversity in native systems.

}, keywords = {LTER-KNZ, Allelopathy, Bothriochloa spp, Invasive species, Leachate, Leaf litter, Yellow bluestem}, doi = {10.1007/s11104-014-2209-3}, url = {https://link.springer.com/article/10.1007\%2Fs11104-014-2209-3}, author = {Greer, M.J. and G.T. Wilson and Hickman, K.R. and Wilson, S.} } @article {KNZ001662, title = {Restoration ecology: introduction in a {\textquotedblleft}timely{\textquotedblright} manner}, journal = {Bulletin of the Ecological Society of America}, volume = {95}, year = {2014}, pages = {274 -280}, keywords = {LTER-KNZ}, doi = {10.1890/0012-9623-95.3.274}, url = {https://esajournals.onlinelibrary.wiley.com/doi/full/10.1890/0012-9623-95.3.274}, author = {Greer, M.J. and G.T. Wilson} } @article {KNZ001566, title = {Patterns of diversity and adaptation in Glomeromycota from three prairie grasslands}, journal = {Molecular Ecology}, volume = {22}, year = {2013}, pages = {2573 -2587}, abstract = {

Arbuscular mycorrhizal (AM) fungi are widespread root symbionts that often improve the fitness of their plant hosts. We tested whether local adaptation in mycorrhizal symbioses would shape the community structure of these root symbionts in a way that maximizes their symbiotic functioning. We grew a native prairie grass (Andropogon gerardii) with all possible combinations of soils and AM fungal inocula from three different prairies that varied in soil characteristics and disturbance history (two native prairie remnants and one recently restored). We identified the AM fungi colonizing A. gerardii roots using PCR amplification and cloning of the small subunit rRNA gene. We observed 13 operational taxonomic units (OTUs) belonging to six genera in three families. Taxonomic richness was higher in the restored than the native prairies with one member of the Gigaspora dominating the roots of plants grown with inocula from native prairies. Inoculum source and the soil environment influenced the composition of AM fungi that colonized plant roots. Correspondingly, host plants and AM fungi responded significantly to the soil\–inoculum combinations such that home fungi often had the highest fitness and provided the greatest benefit to A. gerardii. Similar patterns were observed within the soil\–inoculum combinations originating from two native prairies, where five sequence types of a single Gigaspora OTU were virtually the only root colonizers. Our results indicate that indigenous assemblages of AM fungi were adapted to the local soil environment and that this process occurred both at a community scale and at the scale of fungal sequence types within a dominant OTU.

}, keywords = {LTER-KNZ}, doi = {10.1111/mec.12268}, url = {https://onlinelibrary.wiley.com/doi/abs/10.1111/mec.12268}, author = {Ji, B. and Gehring, C.A. and G.T. Wilson and Miller, R.M. and Flores-Renteria, L. and Johnson, N.C.} } @article {KNZ001548, title = {Variation in root system traits among African semi-arid savanna grasses: implications for drought tolerance}, journal = {Austral Ecology}, volume = {38}, year = {2013}, pages = {383 -392}, abstract = {

In arid to semi-arid grasslands and savannas, plant growth, population dynamics, and productivity are consistently and strongly limited by soil water and nutrient availability. Adaptive traits of the root systems of grasses in these ecosystems are crucial to their ability to cope with strong water and/or nutrient limitation and the increasing drought stress associated with ecosystem degradation or projected climate change. We studied 18 grass species in semi-arid savanna of the Kalahari region of Botswana to quantify interspecific variation in three important root system traits including root system architecture, rhizosheath thickness and mycorrhizal colonization. Drought-tolerant species and shorter-lived species showed greater rhizosheath thickness and fine root development but lower mycorrhizal colonization compared to later successional climax grasses and those characteristic of wetter sites. In addition, there was a significant positive correlation between root fibrousness index and rhizosheath thickness among species and a weak negative correlation between root fibrousness index and mycorrhizal colonization. These patterns suggest that an extensive fine root system and rhizosheath development may be important complementary traits of grasses coping with drought conditions, the former aiding in the acquisition of water by the grass plant and the latter aiding in water uptake and retention, and reducing water loss in the rhizosphere. Within species, both rhizosheath development and mycorrhizal colonization were significantly greater in a wet year than in a year with below-average precipitation. The observed patterns suggest that the primary benefit of rhizosheath development in African savanna grasses is improved drought tolerance and that it is a plastic trait that can be adjusted annually to changing environmental conditions. The functioning of mycorrhizal symbiosis is likely to be relatively more important in infertile savannas where nutrient limitation is higher relative to water limitation.

}, keywords = {LTER-KNZ, grass, mycorrhiza, rhizosheath, root architecture, savanna}, doi = {10.1111/j.1442-9993.2012.02422.x}, url = {https://onlinelibrary.wiley.com/doi/abs/10.1111/j.1442-9993.2012.02422.x}, author = {D.C. Hartnett and Ott, J.P. and G.T. Wilson and Setshogo, M.} } @inbook {KNZ001507, title = {Arbuscular Mycorrhizae and Grassland Ecosystems}, booktitle = {Biocomplexity of Plant-Fungal Interactions}, year = {2012}, pages = {59 -85}, publisher = {Wiley-Blackwell}, organization = {Wiley-Blackwell}, address = {Oxford, UK}, keywords = {LTER-KNZ}, doi = {10.1002/9781118314364.ch3}, url = {https://onlinelibrary.wiley.com/doi/abs/10.1002/9781118314364.ch3}, author = {Miller, R.M. and G.T. Wilson and Johnson, N.C.}, editor = {Southwood, D.} } @article {KNZ001551, title = {Controls on bud activation and tiller initiation in C3 and C4 tallgrass prairie grasses: the role of light and nitrogen}, journal = {Botany}, volume = {90}, year = {2012}, pages = {1221 -1228}, abstract = {

Population dynamics of perennial grasses in tallgrass prairie ecosystems are strongly influenced by vegetative outgrowth from their belowground bud banks. We examined the role of light and nitrogen in regulating tiller initiation and tested an integrated model of controls on bud dormancy and activation in several C3 and C4 grasses. In addition, we assessed the interaction of nitrogen and light quantity and red \– far red spectral composition on tiller initiation. Belowground perennating organs of three C3 and three C4 species were grown under full light or dark conditions, amended with one of four nitrogen concentrations (0 to 350 ppm N). Dormant buds were also subjected to full light under different spectral compositions or to continuous darkness. Our results among C3 grasses support the integrated model as light and nitrogen played important and interacting roles in the regulation of bud banks. However, differences in responses among C4 grasses and a lack of light \× nitrogen interactions suggest that an alternative model may be necessary for this functional group. Our results provide predictions of responses to nitrogen enrichment or light imitations in prairie ecosystems due to interacting disturbances such as reduction in fire frequencies, alterations in grazing intensities, or climate change.

}, keywords = {LTER-KNZ, bud banks, C3 grasses, C4 grasses, perennial grasses, Tiller recruitment, Vegetative reproduction}, doi = {10.1139/b2012-091}, url = {http://www.nrcresearchpress.com/doi/10.1139/b2012-091}, author = {Williamson, M. and G.T. Wilson and D.C. Hartnett} } @article {KNZ001490, title = {Invasive warm-season grasses reduce mycorrhizal root colonization and biomass production of native prairie grasses}, journal = {Mycorrhiza}, volume = {22}, year = {2012}, pages = {327 -336}, abstract = {

Soil organisms play important roles in regulating ecosystem-level processes and the association of arbuscular mycorrhizal (AM) fungi with a plant species can be a central force shaping plant species\’ ecology. Understanding how mycorrhizal associations are affected by plant invasions may be a critical aspect of the conservation and restoration of native ecosystems. We examined the competitive ability of old world bluestem, a non-native grass (Caucasian bluestem [Bothriochloa bladhii]), and the influence of B. bladhii competition on AM root colonization of native warm-season prairie grasses (Andropogon gerardii or Schizachyrium scoparium), using a substitutive design greenhouse competition experiment. Competition by the non-native resulted in significantly reduced biomass production and AM colonization of the native grasses. To assess plant\–soil feedbacks of B. bladhii and Bothriochloa ischaemum, we conducted a second greenhouse study which examined soil alterations indirectly by assessing biomass production and AM colonization of native warm-season grasses planted into soil collected beneath Bothriochloa spp. This study was conducted using soil from four replicate prairie sites throughout Kansas and Oklahoma, USA. Our results indicate that a major mechanism in plant growth suppression following invasion by Bothriochloa spp. is the alteration in soil microbial communities. Plant growth was tightly correlated with AM root colonization demonstrating that mycorrhizae play an important role in the invasion of these systems by Bothriochloa spp. and indicating that the restoration of native AM fungal communities may be a fundamental consideration for the successful establishment of native grasses into invaded sites.

}, keywords = {LTER-KNZ, Arbuscular mycorrhizas, Big bluestemm, Bothriochloa bladhii, Bothriochloa ischaemum, Little bluestem, Old world bluestems, plant{\textendash}soil feedback, tallgrass prairie, Warm-season grasses}, doi = {10.1007/s00572-011-0407-x}, url = {https://link.springer.com/article/10.1007\%2Fs00572-011-0407-x}, author = {G.T. Wilson and Hickman, K.R. and Williamson, M.M.} } @article {KNZ001491, title = {Predicting plant responses to mycorrhizae: integrating evolutionary history and plant traits}, journal = {Ecology Letters}, volume = {15}, year = {2012}, pages = {689 -695}, abstract = {

We assessed whether (1) arbuscular mycorrhizal colonization of roots (RC) and/or plant responses to arbuscular mycorrhizae (MR) vary with plant phylogeny and (2) MR and RC can be more accurately predicted with a phylogenetic predictor relative to a null model and models with plant trait and taxonomic predictors. In a previous study, MR and RC of 95 grassland species were measured. We constructed a phylogeny for these species and found it explained variation in MR and RC. Next, we used multiple regressions to identify the models that most accurately predicted plant MR. Models including either phylogenetic or phenotypic and taxonomic information similarly improved our ability to predict MR relative to a null model. Our study illustrates the complex evolutionary associations among species and constraints of using phylogenetic information, relative to plant traits, to predict how a plant species will interact with AMF.

}, keywords = {LTER-KNZ}, doi = {10.1111/j.1461-0248.2012.01786.x}, url = {https://onlinelibrary.wiley.com/doi/abs/10.1111/j.1461-0248.2012.01786.x}, author = {Reinhart, K.O. and G.T. Wilson and Rinella, M.J.} } @article {KNZ001425, title = {Mycorrhizal suppression alters plant productivity and forb establishment in a grass-dominated prairie restoration}, journal = {Plant Ecology}, volume = {212}, year = {2011}, pages = {1675 -1685}, abstract = {

A fundamental goal of restoration is the re-establishment of plant diversity representative of native vegetation. However, many prairie restorations or Conservation Reserve Program sites have been seeded with warm-season grasses, leading to grass-dominated, low-diversity restorations not representative of native grasslands. These dominant grasses are strongly mycotrophic, while many subordinate forb species appear to be less dependent on mycorrhizal symbiosis. Therefore, manipulating arbuscular mycorrhizal fungi (AMF) may be useful in promoting establishment and growth of forb species in grass-dominated prairie restorations. To assess the potential role of mycorrhizae in affecting the productivity and community composition of restored tallgrass prairie, we conducted a 4-year field experiment on an 8-year-old grassland restoration at the Konza Prairie in northeastern Kansas, USA. At the initiation of our study, seeds of 12 forb species varying in degree of mycorrhizal dependence were added to established grass-dominated plots. Replicate plots were treated bi-weekly with a soil drench of fungicide (Topsin-M\®) over four growing seasons and compared to non-treated control plots to assess the role of AMF in affecting plant species composition, productivity, leaf tissue quality, and diversity in restored tallgrass prairie. Topsin applications successfully reduced mycorrhizal colonization of grass roots to approximately 60\–80\% relative to roots in control plots. Four years of mycorrhizal suppression reduced productivity of the dominant grasses and increased plant species richness and diversity. These results highlight the importance of mycorrhizae as mediators of plant productivity and community dynamics in restored tallgrass prairie and indicate that temporarily suppressing AMF decreases productivity of the dominant C4 grasses and allows for establishment of seeded forb species

}, keywords = {LTER-KNZ, Arbuscular mycorrhizal fungi, forbs, Fungicide, Grassland restoration, Warm-season grass}, doi = {10.1007/s11258-011-9940-0}, url = {https://link.springer.com/article/10.1007\%2Fs11258-011-9940-0}, author = {McCain, K.N.S. and G.T. Wilson and John M. Blair} } @article {KNZ001362, title = {Rhus glabra response to season and intensity of fire in tallgrass prairie}, journal = {International Journal of Wildland Fire}, volume = {20}, year = {2011}, pages = {709 -720}, abstract = {

Altered fire regimes play a key role in shrub expansion in grasslands worldwide. We assessed how season and type or intensity of fire affected the growth and demography of Rhus glabra, a common woody invader in North American mesic grasslands. Fire during any season killed 99\% of ramets but stimulated new ramet recruitment from belowground buds, resulting in a near-complete turnover of ramet populations. During the first 2 years following fire, populations on spring-burned sites had the greatest post-fire ramet densities and population growth rates, and winter- and spring-burned populations showed the highest resprouting rates. However, after 10 years, R. glabra cover on summer-burned sites was 3.5 times greater than on autumn- or winter-burned treatments. Thus, short-term post-fire responses may not be good predictors of long-term changes in abundance. Low-intensity spring backfires resulted in the highest ramet population growth rates, whereas high-intensity headfires in any season resulted in slower growth, and populations burned with low-intensity winter fires declined. In addition, season of fire influenced browsing pressure, suggesting that plant responses may be partially a result of indirect effects of fire on rates of herbivory. Overall, our results demonstrate that the application of frequent autumn or winter backfires is an effective management tool for limiting R. glabra expansion in grasslands, and that long-term data are critical for management decision-making, particularly in systems characterised by high interannual climate variability.

}, keywords = {LTER-KNZ, shrub demography, shrub encroachment, smooth sumac}, doi = {10.1071/WF09127}, url = {http://www.publish.csiro.au/wf/WF09127}, author = {K.M. Hajny and D.C. Hartnett and G.T. Wilson} } @article {KNZ001285, title = {Dominant grasses suppress local diversity in restored tallgrass prairie}, journal = {Restoration Ecology}, volume = {18}, year = {2010}, pages = {40 -49}, abstract = {

Warm-season (C4) grasses commonly dominate tallgrass prairie restorations, often at the expense of subordinate grasses and forbs that contribute most to diversity in this ecosystem. To assess whether the cover and abundance of dominant grass species constrain plant diversity, we removed 0, 50, or 100\% of tillers of two dominant species (Andropogon gerardii or Panicum virgatum) in a 7-year-old prairie restoration. Removing 100\% of the most abundant species, A. gerardii, significantly increased light availability, forb productivity, forb cover, species richness, species evenness, and species diversity. Removal of a less abundant but very common species, P. virgatum, did not significantly affect resource availability or the local plant community. We observed no effect of removal treatments on critical belowground resources, including inorganic soil N or soil moisture. Species richness was inversely correlated with total grass productivity and percent grass cover and positively correlated with light availability at the soil surface. These relationships suggest that differential species richness among removal treatments resulted from treatment induced differences in aboveground resources rather than the belowground resources. Selective removal of the dominant species A. gerardii provided an opportunity for seeded forb species to become established leading to an increase in species richness and diversity. Therefore, management practices that target reductions in cover or biomass of the dominant species may enhance diversity in established and grass-dominated mesic grassland restorations.

}, keywords = {LTER-KNZ, Andropogon gerardii, Competition, diversity, mesic grassland restoration, Panicum virgatum, species removal}, doi = {10.1111/j.1526-100X.2010.00669.x}, url = {https://onlinelibrary.wiley.com/doi/abs/10.1111/j.1526-100X.2010.00669.x}, author = {McCain, K.N.S. and S.G. Baer and John M. Blair and G.T. Wilson} } @article {KNZ001314, title = {Resource limitation is a driver of local adaptation in mycorrhizal symbioses}, journal = {Proceedings of the National Academy of Sciences of the United States of America}, volume = {107}, year = {2010}, pages = {2093 -2098}, abstract = {

Symbioses may be important mechanisms of plant adaptation to their environment. We conducted a reciprocal inoculation experiment to test the hypothesis that soil fertility is a key driver of local adaptation in arbuscular mycorrhizal (AM) symbioses. Ecotypes of Andropogon gerardii from phosphorus-limited and nitrogen-limited grasslands were grown with all possible \“home and away\” combinations of soils and AM fungal communities. Our results indicate that Andropogon ecotypes adapt to their local soil and indigenous AM fungal communities such that mycorrhizal exchange of the most limiting resource is maximized. Grasses grown in home soil and inoculated with home AM fungi produced more arbuscules (symbiotic exchange structures) in their roots than those grown in away combinations. Also, regardless of the host ecotype, AM fungi produced more extraradical hyphae in their home soil, and locally adapted AM fungi were, therefore, able to sequester more carbon compared with nonlocal fungi. Locally adapted mycorrhizal associations were more mutualistic in the two phosphorus-limited sites and less parasitic at the nitrogen-limited site compared with novel combinations of plants, fungi, and soils. To our knowledge, these findings provide the strongest evidence to date that resource availability generates evolved geographic structure in symbioses among plants and soil organisms. Thus, edaphic origin of AM fungi should be considered when managing for their benefits in agriculture, ecosystem restoration, and soil-carbon sequestration.

}, keywords = {LTER-KNZ, coevolution, geographic mosaics, mutualism, parasitism}, doi = {10.1073/pnas.0906710107}, url = {https://www.pnas.org/content/107/5/2093}, author = {Johnson, N.C. and G.T. Wilson and M. Bowker and Wilson, J.A. and Miller, R.M.} } @article {KNZ001290, title = {Mysterious mycorrhizae? A field trip and classroom experiment to demystify the symbioses formed between plants and fungi}, journal = {American Biology Teacher}, volume = {71}, year = {2009}, pages = {424 -429}, keywords = {LTER-KNZ}, url = {https://ecommons.luc.edu/cgi/viewcontent.cgi?article=1002\&context=ies_facpubs}, author = {Johnson, N.C. and Chaudhary, V.B. and Hoeksema, J.D. and Moore, J.M. and Pringle, A. and Umbanhowar, J.A. and G.T. Wilson} } @article {KNZ001248, title = {Soil aggregation and carbon sequestration are tightly correlated with the abundance of arbuscular mycorrhizal fungi: results from long-term field experiments}, journal = {Ecology Letters}, volume = {12}, year = {2009}, pages = {452 -461}, abstract = {

We examined the role of arbuscular mycorrhizal fungi (AMF) in ecosystems using soil aggregate stability and C and N storage as representative ecosystem processes. We utilized a wide gradient in AMF abundance, obtained through long-term (17 and 6 years) large-scale field manipulations. Burning and N-fertilization increased soil AMF hyphae, glomalin-related soil protein (GRSP) pools and water-stable macroaggregates while fungicide applications reduced AMF hyphae, GRSP and water-stable macroaggregates. We found that AMF abundance was a surprisingly dominant factor explaining the vast majority of variability in soil aggregation. This experimental field study, involving long-term diverse management practices of native multispecies prairie communities, invariably showed a close positive correlation between AMF hyphal abundance and soil aggregation, and C and N sequestration. This highly significant linear correlation suggests there are serious consequences to the loss of AMF from ecosystems.

}, keywords = {LTER-KNZ}, doi = {10.1111/j.1461-0248.2009.01303.x}, url = {https://onlinelibrary.wiley.com/doi/abs/10.1111/j.1461-0248.2009.01303.x}, author = {G.T. Wilson and C. W. Rice and Rillig, M.C. and Springer, A. and D.C. Hartnett} } @article {KNZ001223, title = {Topsin-M: the new benomyl for mycorrhizal-suppression experiments}, journal = {Mycologia}, volume = {100}, year = {2008}, pages = {548 -554}, abstract = {

The fungicide benomyl was the most commonly used biocide for both field and greenhouse experiments in which arbuscular mycorrhizal fungal (AMF) suppression is desired. Unfortunately benomyl is no longer manufactured and therefore is not available for experimental use and no fungicide has been proposed as a successful alternative for experimentally suppressing mycorrhizal fungi. In this study we examined the potential for the fungicide Topsin M\® (topsin) to suppress mycorrhizal symbiosis in both field and greenhouse experiments. Topsin reduced AMF colonization of the obligately mycotrophic, warm-season grass Andropogon gerardii with a large and significant reduction in plant biomass production. Topsin reduced AMF colonization of the facultatively mycotrophic, cool-season grass Pascopyron smithii but did not significantly reduce biomass production. Fertilization with nitrogen and phosphorus was able to compensate for reductions in biomass due to the application of fungicide because biomass production of plants that received topsin fungicide was not significantly different from fertilized controls not receiving topsin. While we are not advocating that topsin fungicide is a universal mechanism for mycorrhizal-suppressed controls, in systems where benomyl was found to be successful topsin appears to be a useful, available and successful alternative.

}, keywords = {LTER-KNZ}, doi = {10.3852/08-024R}, url = {https://www.tandfonline.com/doi/abs/10.3852/08-024R?journalCode=umyc20}, author = {G.T. Wilson and Williamson, M.M.} } @article {KNZ001097, title = {Consumptionof mycorrhizal and saprophytic fungi by Collembola in grassland soils}, journal = {Soil Biology and Biochemistry}, volume = {39}, year = {2007}, pages = {2594 -2602}, abstract = {Although soil-dwelling Collembola can influence plant growth and nutrient cycling, their specific role in soil food webs is poorly understood. Soil-free microcosm studies suggest that Collembola are primarily fungivores where they feed preferentially on saprophytic fungi (SF) over other fungal types. We directly assessed collembolan consumption of arbuscular mycorrhizal fungi (AMF) and SF using plant{\textendash}soil mesocosms and natural abundance stable carbon isotope techniques. Mycorrhizal Andropogon gerardii (C4 grass) seedlings were placed in pots containing Collembola and soil from a C3 plant dominated site, while mycorrhizal Pascopyrum smithii (C3 grass) seedlings were placed in pots with Collembola and soil collected at a C4 plant dominated site. After 6 weeks, collembolans assimilated carbon derived from C3 and C4 sources in both A. gerardii and P. smithii treatments. Comparing Collembola isotope values in AMF vs. AMF-suppressed treatments, our data show that both AMF and SF were consumed in these experimental soil environments.}, keywords = {LTER-KNZ, Andropogon gerardii, Arbuscular mycorrhizal fungi, Collembola, grassland, Natural abundance stable isotopes, Pascopyrum smithii, Saprophytic fungi, δ13C}, doi = {10.1016/j.soilbio.2007.05.004}, author = {Jonas, J.L. and G.T. Wilson and White, P.M. and Anthony Joern} } @article {KNZ001046, title = {Mycorrhizal-mediated phosphorus transfer between tallgrass prairie plants Sorghastrum nutans and Artemisia ludoviciana}, journal = {Functional Ecology}, volume = {20}, year = {2006}, pages = {427 -435}, abstract = {1A glasshouse 32P-labelling study examined arbuscular mycorrhizal (AM)-mediated transfer of phosphorus between individuals of two tallgrass prairie species, an obligately mycotrophic grass (Sorghastrum nutans Vitm.) and a facultatively mycotrophic forb (Artemisia ludoviciana Nutt.). 2Regardless of which species served as donor, 32P was transferred between both intra- and interspecific neighbours via AM mycelia. However, nutrient transfer via AM fungi was not uniform between neighbouring species. 3Conservative estimates indicate that interplant transfer via AM fungi accounted for >50\% of the total 32P acquisition by S. nutans, but accounted for only 20\% of 32P uptake into A. ludoviciana. 4While this study did not show conclusively that a common mycelial network acted as a conduit for nutrient transfer, it clearly demonstrated that mycorrhizae facilitated transfer. 5The results indicate that differential movement of plant resources via AM mycelium may be a mechanism whereby a dominant, highly mycotrophic grass extends competitive advantage over a less mycotrophic, subdominant forb species in grasslands.}, keywords = {LTER-KNZ}, doi = {10.1111/j.1365-2435.2006.01134.x}, author = {G.T. Wilson and D.C. Hartnett and C. W. Rice} } @article {KNZ001042, title = {The use of pasture reflectance characteristics and arbuscular mycorrhizal root colonization to predict pasture characteristics of tallgrass prairie grazed by cattle and bison}, journal = {Grass and Forage Science}, volume = {61}, year = {2006}, pages = {32 -41}, abstract = {An experiment was conducted to evaluate the potential for using arbuscular mycorrhizal fungal (AMF) root colonization and pasture reflectance characteristics as indicators of changes in tallgrass prairie vegetation resulting from differences in grazing history. The experiment was conducted within the context of a separate long-term experiment in which eight 4{\textperiodcentered}9-ha pastures were grazed by either bison or cattle for nine consecutive years. Two separate ungrazed pastures were selected for comparison with grazed areas on the basis of similarity in burning regime, vegetation, soil and topographic characteristics. Four 45 m-long transects were located in the upland sites within each pasture, and four plots were clipped to ground level along each transect. Reflectance readings were taken with a hand-held radiometer at each sampling location and a soil core was collected within each plot for analysis of AMF root colonization. Reflectance readings at sixteen different wavelengths were used directly as inputs during multiple regression development or were transformed into each of three vegetation indices (normalized difference vegetation index, soil-adjusted vegetation index and wide-dynamic-range vegetation index) and used in simple linear regressions. Ungrazed pastures were characterized by higher (P < 0{\textperiodcentered}01) grass biomass, total biomass and canopy height than grazed pastures, but had a lower proportional abundance of forbs (P < 0{\textperiodcentered}01) and amounts of forb biomass (P = 0{\textperiodcentered}04). Species of herbivore did not significantly influence above-ground characteristics that were measured. In general, AMF root colonization was relatively small and was not significantly affected by treatment and, accordingly, the variation was insufficient to test its potential as an indicator of grazing effects on vegetation or its potential relationship with pasture reflectance. Multiple regression equations based on individual wavelength reflectance values explained significantly more of the variation in above-ground vegetation characteristics than did simple regressions using vegetation indices as predictor variables (r2 values from 0{\textperiodcentered}36 to 0{\textperiodcentered}46 vs. 0{\textperiodcentered}11 to 0{\textperiodcentered}27) and have the potential to predict above-ground vegetation characteristics in heterogeneous rangelands.}, keywords = {LTER-KNZ, Arbuscular mycorrhizal fungi, bison, Cattle, pasture characteristics, reflectance methods, tallgrass prairie}, doi = {10.1111/j.1365-2494.2006.00505.x}, author = {Villarreal, M. and Cochran, R.C. and Johnson, D.E. and Towne, E.G. and G.T. Wilson and D.C. Hartnett and Goodin, D.G.} } @article {KNZ00976, title = {Mycorrhizal symbiosis and insect herbivory in tallgrass prairie microcosms}, journal = {Ecology Letters}, volume = {81}, year = {2005}, pages = {61 -69}, keywords = {LTER-KNZ}, author = {Kula, A.R. and D.C. Hartnett and G.T. Wilson} } @article {KNZ00900, title = {Fire effects on mycorrhizal symbiosis and root system architecture in southern African savanna grasses}, journal = {African Journal of Ecology}, volume = {42}, year = {2004}, pages = {1 -10}, abstract = {Mycorrhizal symbiosis is a key factor influencing aspects of grassland and savanna structure and functioning including plant growth, competition, population and community dynamics, and responses to fire and herbivory. This study assessed the effects of fire on mycorrhizal symbiosis and root system architecture (RSA) in South African savanna grasses. Eighteen grass species were sampled across contrasting fire frequency treatments in the Kruger National Park experimental burn plots. All eighteen species studied were highly colonized by arbuscular mycorrhizal fungi (AMF). Both mycorrhizal symbiosis and RSA were strongly affected by fire, with an increase in AMF colonization and a decrease in root branching and fine root development with decreasing fire frequency. Greater water limitation in frequently burned savanna may result in greater fine root development, thus reducing plant dependency on AMF for acquisition of soil resources. Reduced mycorrhizal colonization in frequently burned savanna may also be driven by higher phosphorus : nitrogen ratios, or indirect effects related to higher grazing intensities in frequently burned sites.}, keywords = {LTER-KNZ, fire, Grasses, mycorrhizas, root architecture, Savannas}, doi = {10.1111/j.1365-2028.2004.00533.x}, author = {D.C. Hartnett and Potgieter, A.L.F. and G.T. Wilson} } @article {KNZ00937, title = {Interactive effects of burn regime and bison activity on tallgrass prairie vegetation}, journal = {American Midland Naturalist}, volume = {152}, year = {2004}, pages = {237 -247}, keywords = {LTER-KNZ}, author = {Trager, M. and G.T. Wilson and D.C. Hartnett} } @phdthesis {KNZ00912, title = {Mycorrhizal symbiosis in the tallgrass prairie: above- and belowground linkages}, volume = {PhD Dissertation}, year = {2003}, pages = {1 -211}, school = {Kansas State University}, type = {Ph.D. Thesis}, address = {Manhattan, KS}, keywords = {LTER-KNZ}, author = {G.T. Wilson} } @article {KNZ00829, title = {The role of mycorrhizas in plant community structure and dynamics: lessons from grasslands}, journal = {Plant and Soil}, volume = {244}, year = {2002}, pages = {319 -331}, abstract = {Research on the mycorrhizal associations over the past several decades has yielded increased understanding and appreciation of the important role of this symbiosis in the functioning and performance of plants in a wide array of terrestrial ecosystems. We now understand that the role of mycorrhizal fungi extends beyond the symbiotic acquisition of phosphorus for the host plant and reciprocal carbon provision from the host to fungus. Additional effects of mycorrhizal fungi on the functioning of their host plants including increased disease resistance, improved water relations, acquisition of other soil nutrients, and alterations in other soil physico-chemical properties have been documented. Other aspects of the ecology of mycorrhizas, including variation in the costs and benefits of carbon and nutrient exchange, the ecological significance of mycelial networks, the role of mycorrhizal symbiosis in multi-species interactions, and the extent and consequences of host-specificity in these associations have also recently been explored.}, keywords = {LTER-KNZ}, doi = {10.1007/978-94-017-1284-2_31}, author = {D.C. Hartnett and G.T. Wilson} } @article {KNZ0017, title = {Effects of mycorrhizas on growth and demography of tallgrass prairie forbs}, journal = {American Journal of Botany}, volume = {88}, year = {2001}, pages = {1452 -1457}, abstract = {The effects of arbuscular mycorrhizal (AM) symbiosis on ramet and genet densities, vegetative growth rates, and flowering of three forb species were studied in native tallgrass prairie in northeastern Kansas. Mycorrhizal activity was experimentally suppressed for six growing seasons on replicate plots in an annually burned and an infrequently burned watershed with the fungicide benomyl. Benomyl reduced mycorrhizal root colonization to an average of 4.2\%, approximately a two-thirds reduction relative to controls (13.7\% colonization). Mycorrhizae influenced the population structure of these forbs. Although mycorrhizal suppression had no long-term effect on genet densities and no effect on ramet survivorship throughout the growing season, the number of ramets per individual was significantly increased such that ramet densities of all three species were approximately doubled in response to long-term mycorrhizal suppression. Effects of mycorrhizae on ramet growth and reproduction varied among species. Ramet growth rates, biomass, and flowering of Salvia azurea were greater in plots with active mycorrhizal symbiosis, whereas mycorrhizae reduced ramet growth rates and biomass of Artemesia ludoviciana. Aster sericeus ramet growth rates and biomass were unaffected by the fungicide applications, but its flowering was reduced.The pattern of responses of these three species to mycorrhizae differed considerably between the two sites of contrasting fire regime, indicating that the interaction of fire-induced shifts in resource availability and mycorrhizal symbiosis together modulates plant responses and the intensity and patterns of interspecific competition between and among tallgrass prairie grass and forb species. Further, the results indicate that effects of mycorrhizae on community structure are a result of interspecific differences in the balance between direct positive effects of the symbiosis on host plant performance and indirect negative effects mediated through altered competitive interactions.}, keywords = {LTER-KNZ, demography, forb, tallgrass prairie}, url = {http://www.ncbi.nlm.nih.gov/pubmed/21669678}, author = {G.T. Wilson and D.C. Hartnett and M.D. Smith and Kobbeman, K.} } @article {KNZ00768, title = {Effects of ungulate grazers on arbuscular mycorrhizal symbiosis and fungal community structure in tallgrass prairie}, journal = {Mycology}, volume = {93}, year = {2001}, pages = {233 -242}, abstract = {Complex interactions among mycorrhizal fungi, plants, and herbivores occur in grasslands. Grazing of aboveground vegetation may influence plants directly and indirectly through the alteration of mycorrhizal symbiosis and other below-ground processes, and mycorrhizae in turn can influence plant responses to defoliation. An understanding of these interactions is important to our understanding of the dynamics of plant and fungal communities and to the sound management and conservation of grass- land ecosystems. In this study, the effects of grazing in tallgrass prairie on mycorrhizal colonization of plant roots, fungal community composition, and ex- traradical mycorrhizal hyphal (EMH) development were examined. In October 1994 and 1995 rhizo- sphere samples were taken at different topographical positions in tallgrass prairie sites grazed for several years by cattle at varying intensities, in ungrazed sites, and inside and outside permanent 25-m2 exclosures at each site. Spores of 19 species of AM fungi were encountered in these sites, and Glomus heterosporum was the most abundant species present. Moderate and intense grazing increased root colonization by mycorrhizal fungi in both years of this study. Similar root colonization levels inside and outside permanent exclosures in the ungrazed sites indicated no confounding effects of the exclosure structure itself. In 1995, EMH development was also increased under intense grazing. AM fungal species diversity (based on AM fungal spores present) decreased with grazing under both moderate and high grazer densities in both years. Different fungal species varied in abun- dance with topographical position, however topography did not significantly affect AM fungal spore species diversity, mycorrhizal root colonization or EMH development in either year. Although overall total spore density was unaffected by grazing intensity or soil type, several individual species increased or decreased in response to these factors. These results suggest that defoliation alters plant resources which stimulates greater development of mycorrhizal symbiosis. The shifts in fungal species composition and decrease in diversity with grazing also indicates that defoliation, or alteration of the soil microenviron- ment by grazers, favors certain species of grazing- adapted AM fungi that increase under grazed conditions. The high mycorrhizal dependency of many tallgrass prairie grasses and these results together suggest significant interactions between plant-grazer and plant-fungal relationships in tallgrass prairie. In addition to direct effects of herbivory, our results indicate that grazers may influence grassland plants in- directly through alterations in soil communities and in mycorrhizal symbiosis. }, keywords = {LTER-KNZ, fungal communities, fungal diversity, Glomus, hyphal development, mycorrhizae}, url = {http://www.jstor.org/stable/3761643?seq=1$\#$page_scan_tab_contents}, author = {Eom, A.H. and G.T. Wilson and D.C. Hartnett} } @article {KNZ00732, title = {Host plant species effects on arbuscular mycorrhizal fungal communities in tallgrass prairie}, journal = {Oecologia}, volume = {122}, year = {2000}, pages = {435 -444}, abstract = {Symbiotic associations between plants and arbuscular mycorrhizal (AM) fungi are ubiquitous in many herbaceous plant communities and can have large effects on these communities and ecosystem processes. The extent of species-specificity between these plant and fungal symbionts in nature is poorly known, yet reciprocal effects of the composition of plant and soil microbe communities is an important assumption of recent theoretical models of plant community structure. In grassland ecosystems, host plant species may have an important role in determining development and sporulation of AM fungi and patterns of fungal species composition and diversity. In this study, the effects of five different host plant species [Poa pratensis L., Sporobolus heterolepis (A. Gray) A. Gray, Panicum virgatum L., Baptisia bracteata Muhl. ex Ell., Solidago missouriensis Nutt.] on spore communities of AM fungi in tallgrass prairie were examined. Spore abundances and species composition of fungal communities of soil samples collected from patches within tallgrass prairie were significantly influenced by the host plant species that dominated the patch. The AM fungal spore community associated with B. bracteata showed the highest species diversity and the fungi associated with Pa. virgatum showed the lowest diversity. Results from sorghum trap cultures using soil collected from under different host plant species showed differential sporulations of AM fungal species. In addition, a greenhouse study was conducted in which different host plant species were grown in similar tallgrass prairie soil. After 4 months of growth, AM fungal species composition was significantly different beneath each host species. These results strongly suggest that AM fungi show some degree of host-specificity and are not randomly distributed in tallgrass prairie. The demonstration that host plant species composition influences AM fungal species composition provides support for current feedback models predicting strong regulatory effects of soil communities on plant community structure. Differential responses of AM fungi to host plant species may also play an important role in the regulation of species composition and diversity in AM fungal communities.}, keywords = {LTER-KNZ, Arbuscular mycorrhizal fungi, fungal diversity, Grasslands, Host specificity, Soil communities}, doi = {10.1007/s004420050050}, author = {Eom, A.H. and D.C. Hartnett and G.T. Wilson} } @article {KNZ00685, title = {The Effects of fire, mowing, and fertilizer amendments on arbuscular mycorrhizas in tallgrass prairie}, journal = {American Midland Naturalist}, volume = {142}, year = {1999}, pages = {55 -69}, abstract = {Tallgrass prairie sites subjected to 10 y of annual burning, mowing, nitrogen (N) fertilization or phosphorus (P) fertilization and untreated reference sites were studied to examine effects of these management practices on arbuscular mycorrhizal (AM) symbiosis. Spring burning of native prairie field plots significantly reduced AM fungal species diversity, while increasing spore abundance. This increase in total spore number was due to a general increase in most of the 17 fungal species present. In general, the management treatments had larger effects on the richness component of diversity than on the evenness of AM species abundances. Burning and mowing had no significant effects on AM fungal colonization of roots or extraradical mycorrhizal hyphae (EMH) development. However, nitrogen fertilization significantly increased root colonization and EMH development, and P amendment decreased EMH development. There was no significant effect of fertilizer amendment on AM spore abundance, fungal species diversity or richness, but N and P fertilization decreased fungal species evenness. Effects of management practices on AM fungi may be mediated through changes in soil resources or microclimate or through changes in their host plants. These effects on AM symbiosis and community structure are important because AM fungi strongly influence the growth, demography, competitive relationships, relative abundances and diversity of plants in grassland communities.}, keywords = {LTER-KNZ, tallgrass prairie}, doi = {10.1674/0003-0031(1999)142[0055:TEOFMA]2.0.CO;2}, author = {Eom, A.H. and D.C. Hartnett and G.T. Wilson and Figge, D.A.} } @article {KNZ00709, title = {Interacting influence of mycorrhizal symbiosis and competition on plant diversity in tallgrass prairie}, journal = {Oecologia}, volume = {121}, year = {1999}, pages = {574 -582}, abstract = {In tallgrass prairie, plant species interactions regulated by their associated mycorrhizal fungi may be important forces that influence species coexistence and community structure; however, the mechanisms and magnitude of these interactions remain unknown. The objective of this study was to determine how interspecific competition, mycorrhizal symbiosis, and their interactions influence plant community structure. We conducted a factorial experiment, which incorporated manipulations of abundance of dominant competitors, Andropogon gerardii and Sorghastrum nutans, and suppression of mycorrhizal symbiosis using the fungicide benomyl under two fire regimes (annual and 4-year burn intervals). Removal of the two dominant C4 grass species altered the community structure, increased plant species richness, diversity, and evenness, and increased abundance of subdominant graminoid and forb species. Suppression of mycorrhizal fungi resulted in smaller shifts in community structure, although plant species richness and diversity increased. Responses of individual plant species were associated with their degree of mycorrhizal responsiveness: highly mycorrhizal responsive species decreased in abundance and less mycorrhizal responsive species increased in abundance. The combination of dominant-grass removal and mycorrhizal suppression treatments interacted to increase synergistically the abundance of several species, indicating that both processes influence species interactions and community organization in tallgrass prairie. These results provide evidence that mycorrhizal fungi affect plant communities indirectly by influencing the pattern and strength of plant competitive interactions. Burning strongly influenced the outcome of these interactions, which suggests that plant species diversity in tallgrass prairie is influenced by a complex array of interacting processes, including both competition and mycorrhizal symbiosis.}, keywords = {LTER-KNZ, Arbuscular mycorrhizal fungi, Competition, diversity, Species coexistence, tallgrass prairie}, doi = {10.1007/s004420050964}, author = {M.D. Smith and D.C. Hartnett and G.T. Wilson} } @article {KNZ00692, title = {Mycorrhizae influence plant community structure and diversity in tallgrass prairie}, journal = {Ecology}, volume = {80}, year = {1999}, pages = {1187 -1195}, abstract = {In grassland ecosystems, symbiotic associations between plants and mycorrhizal fungi are widespread and have important influences on the life histories, demography, and species interactions of plants, and on belowground ecosystem processes. To assess the consequences of the symbiosis at the plant community level, we conducted a 5-yr field experiment in tallgrass prairie to investigate the influence of arbuscular mycorrhizal fungi on plant species composition, relative abundances, and diversity. Replicate plots in which mycorrhizal fungi were suppressed with benomyl application every two weeks during each growing season, were compared to nontreated mycorrhizal control plots on six watershed units at the Konza Prairie in northeastern Kansas. Benomyl successfully reduced mycorrhizal colonization to <25\% of mycorrhizal control plots. Mycorrhizal colonization of roots in control plots was inversely related to annual precipitation. Suppression of mycorrhizae resulted in decreases in abundances of the dominant, obligately mycotrophic C4 tall grasses, compensatory increases in abundances of many subordinate facultatively mycotrophic C3 grasses and forbs, but no change in total aboveground biomass, as estimated from canopy density. Suppression of mycorrhizal symbiosis resulted in a large increase in plant species diversity. Two possible mechanisms for mycorrhizal mediation of plant species composition and diversity are: (1) alterations in resource distribution among neighbors via hyphal connections, and (2) differential host species responses to mycorrhizal fungal colonization in communities in which the competitive dominants are more strongly or more weakly mycotrophic than their neighbors. The results of this study demonstrate that mycorrhizal symbiosis can have large effects on plant community structure, and that differential host species response to fungal colonization is a key factor explaining the dominance of warm-season C4 grasses in tallgrass prairie and limiting plant species evenness and diversity. The results also underscore the importance of above- and belowground linkages in tallgrass prairie and indicate that alterations in belowground fungi and rhizosphere processes can have large effects on aboveground floristic composition and diversity in grasslands.}, keywords = {LTER-KNZ, tallgrass prairie}, doi = {10.1890/0012-9658(1999)080[1187:MIPCSA]2.0.CO;2}, author = {D.C. Hartnett and G.T. Wilson} } @inbook {KNZ00661, title = {Belowground biology and processes}, booktitle = {Grassland Dynamics: Long-Term Ecological Research in Tallgrass Prairie}, year = {1998}, pages = {244 -264}, publisher = {Oxford University Press}, organization = {Oxford University Press}, address = {New York}, keywords = {LTER-KNZ, tallgrass prairie}, author = {C. W. Rice and Todd, T.C. and John M. Blair and Seastedt, T.R. and Ramundo, R.A. and G.T. Wilson}, editor = {Alan K. Knapp and J. M. Briggs and D.C. Hartnett and Scott. L. Collins} } @article {KNZ00669, title = {Interspecific variation in plant responses to mycorrhizal colonization in prairie grasses and forbs}, journal = {American Journal of Botany}, volume = {85}, year = {1998}, pages = {1732 -1738}, keywords = {LTER-KNZ}, author = {G.T. Wilson and D.C. Hartnett} } @article {KNZ00616, title = {Effects of mycorrhizae on plant productivity and species abundances in tallgrass prairie microcosms}, journal = {American Journal of Botany}, volume = {84}, year = {1997}, pages = {478 -482}, abstract = {Experimental microcosms (40 X 52 X 32 cm) containing an assemblage of eight tallgrass prairie grass and forb species in native prairie soil were maintained under mycorrhizal (untreated control) or mycorrhizal-suppressed (fungicide-treated) conditions to examine plant growth, demographic, and community responses to mycorrhizal symbiosis. The fungicide benomyl successfully reduced mycorrhizal root colonization in the fungicide-treated microcosms to only 6.4\% (an 83\% reduction relative to mycorrhizal controls). Suppression of mycorrhizas resulted in a 31\% reduction in total net aboveground plant production and changes in the relative production of C4 and C3 plants. The C4 tallgrasses Andropogon gerardi and Sorghastrum nutans produced less plant biomass in the fungicide-treated microcosms, and had a greater ratio of reproductive to vegetative biomass. Cool-season C3 grasses, Koeleria pyramidata and Poa pratensis accumulated more biomass and were a significantly greater proportion of total community biomass in mycorrhizal-suppressed microcosms. Forbs showed variable responses to mycorrhizal suppression. The two legumes Amorpha canescens and Dalea purpurea had significantly lower survivorship in the fungicide-treated microcosms, relative to the controls. The results confirm the high mycorrhizal dependency and growth responsiveness of dominant prairie grasses, and indicate that differential growth and demographic responses to mycorrhizal colonization among species may significantly affect plant productivity and species relative abundances in tallgrass prairie}, keywords = {LTER-KNZ, tallgrass prairie}, url = {http://www.ncbi.nlm.nih.gov/pubmed/21708601}, author = {G.T. Wilson and D.C. Hartnett} } @article {KNZ00604, title = {Mycorrhizal fungi affect root stele tissue in grasses}, journal = {Canadian Journal of Botany}, volume = {75}, year = {1997}, pages = {1778 -1784}, abstract = {Although arbuscular mycorrhizal symbiosis was initially believed to have little or no impact on root morphology, we now recognize that subtle changes do occur and that these changes may be of considerable consequence to host growth and nutrition, as well as functional growth strategy. In examining the stele and root diameters of C3 and C4 grasses, C4 grasses were demonstrated to have a significantly larger proportion of their fibrous roots occupied by stele tissue than do C3 grasses. In fact, functional growth strategy (C3 versus C4) was observed to be a relatively good predictor of stele area. Mycorrhizal fungi also influenced the amount of stele tissue, but the effect was not the same for both C3 and C4 grasses. The stele area of all C4 grasses except for Sorghastrum nutans was greater in the presence of mycorrhizal colonization. Among the C3 grasses, only Bromus inermis showed a significant increase, although Elymus cinereus and Lolium perenne displayed significant decreases in response to arbuscular mycorrhizal colonization. Changes in the stele area of the plant species were closely related to their responsiveness to mycorrhizal symbiosis and might in part explain both beneficial and detrimental responses of plants to mycorrhizae. An increase in stele circumference induced by mycorrhizae would allow for greater uptake and passage of water and nutrients to the vascular cylinder, and growth depressions could be a direct outcome of reduced stele circumference. Thus, differences in stele circumference represent a possible mechanism for mycorrhizal impacts on host plants. These findings indicate that structural differences among grasses are related to different functional capabilities and further emphasize the need for better integration of comparative anatomy and morphology procedures in the study of mycorrhizal symbiosis. Key words: stele, root anatomy, mycorrhizal dependency, functional growth strategy, mycorrhiza, C3 and C4 grasses.}, keywords = {LTER-KNZ}, doi = {10.1139/b97-892}, author = {Miller, R.M. and Hetrick, B.A.D. and G.T. Wilson} } @article {KNZ00447, title = {Effects of mycorrhizal and plant density on yield relationships among competing tallgrass prairie grasses}, journal = {Canadian Journal of Botany}, volume = {72}, year = {1994}, pages = {168 -176}, abstract = {A replacement series experiment was used to investigate the effects of mycorrhizae, phosphorus availability, and plant density on competitive relationships between three tallgrass prairie species of varying mycorrhizal dependencies. Under mycorrhizal conditions, the obligately mycorrhizal dependent warm-season grass Andropogon gerardii (big bluestem) was a better competitor in mixture with the nonmycorrhiza-dependent cool-season grass Koeleria pyramidata (Junegrass). In the absence of mycorrhizae, however, competitive effects of big bluestem were greatly reduced and Junegrass experienced competitive release. Relative yield totals increased when mycorrhizae were suppressed, suggesting greater intensity of interspecific competition in the presence of mycorrhizae. Thus, the competitive dominance of big bluestem in tallgrass prairie is strongly related to its mycorrhizal status. Elymus canadensis (Canada wild rye) outcompeted big bluestem both with and without mycorrhizae. Relative yield totals of this species mixture were also lower under mycorrhizal conditions, indicating that mycorrhizae increase the intensity of interspecific competition between them. Relative yields of wild rye competing with big bluestem increased in the absence of mycorrhizae, suggesting that it also experiences competitive release when big blue-stem are not mycorrhizal. The outcomes of competition were generally similar among the three total plant density treatments and between P-fertilized and nonfertilized treatments. However, interactions between mycorrhizal effects and plant density confirm that outcomes of interspecific competitive interactions may be density dependent in some cases.}, keywords = {LTER-KNZ, Andropogon gerardii, arbuscular mycorrhizae, de Wit replacement series, Elymus canadensis, Koeleria pyramidata}, doi = {10.1139/b94-023}, author = {Hetrick, B.A.D. and D.C. Hartnett and G.T. Wilson and D.J. Gibson} } @article {KNZ00448, title = {Mycorrhizal activity in warm-and cool-season grasses: variation in nutrient uptake strategies}, journal = {Canadian Journal of Botany}, volume = {72}, year = {1994}, pages = {1002 -1008}, abstract = {Because cool-season grasses display little or no mycorrhizal responsiveness in prairie soil, it is unclear whether the high levels of mycorrhizal activity observed previously in these grasses represent nutrient uptake by external hyphae or simply metabolism of stored fungal reserves in roots. To distinguish between these hypotheses, a warm-season grass, Andropogon gerardii, or a cool-season grass, Bromus inermis, were grown at two temperatures on one side of a pot divided by a 43-μm nylon root barrier. Mycorrhizal function was assessed by measuring the amount of 32P translocated from one side of the pot to plants on the other side. As a control, mycorrhizal hyphae crossing the barrier were severed manually. Approximately 100 times more 32P was observed in mycorrhizal B. inermis grown at 18 {\textdegree}C versus 29 {\textdegree}C, and in B. inermis with intact versus severed hyphae at the cooler temperature. In contrast, A. gerardii accumulated approximately 4 times more 32P at 29 {\textdegree}C than at 18 {\textdegree}C, and approximately 100 times more with intact versus severed hyphae at the warmer temperature. Thus, it appears that mycorrhizal hyphae are highly active in both plant species regardless of the host{\textquoteright}s mycorrhizal responsiveness. Furthermore, mycorrhizal activity is highest at the temperature that favors growth of each species. The considerable activity of mycorrhizae in B. inermis is enigmatic since it usually has no biomass response. To further clarify the relationship between nutrient uptake and biomass response, both plant species were fertilized with a range of P levels and grown at a neutral temperature that supported the growth of both species. Although the concentration of P in B. inermis plant tissue increased in response to fertilization, there was no corresponding increase in biomass. In contrast, for A. gerardii, there was a direct and positive relationship between P fertilization and biomass produced, but tissue P concentrations remained relatively stable. Mycorrhizal symbiosis had no overall effect on biomass of B. inermis but significantly improved the growth of A. gerardii. These experiments showed clear differences in the growth strategies used by these two plant species. It is unclear whether these are differences that can be attributed to warm- and cool-season grasses in general. Short-term biomass responses as a measure of a plant{\textquoteright}s reliance on the symbiosis may not entirely reflect the contribution of the symbiosis if plants store nutrients with subsequent and perhaps delayed effects on fecundity, offspring performance, or even biomass. However, if the stored nutrient merely represents luxury consumption, this could still affect competitive ability because luxury consumption preempts the availability of nutrients for competitors. }, keywords = {LTER-KNZ, big bluestem, mycorrhizal dependence, mycorrhizal responsiveness, smooth bromegrass}, doi = {10.1139/b94-126}, author = {Hetrick, B.A.D. and G.T. Wilson and Schwab, A.P.} } @article {KNZ00432, title = {Mycorrhizal dependence of Andropogon gerardii and Schizachyrium scoparium in two prairie soils}, journal = {American Midland Naturalist}, volume = {132}, year = {1994}, pages = {366 -376}, abstract = {Previous research in tallgrass prairie in Kansas indicated that warm-season, C4, grasses are obligate mycotrophs and do not grow normally in the absence of mycorrhizal symbiosis. However, the degree to which such grasses depend on mycorrhizae in other prairie soils has not been examined. Growth and mycorrhizal colonization of roots of Andropogon gerardii and Schizachyrium scoparium were compared in soil collected from Konza Prairie Research Natural Area (KPRNA), Riley County, Kansas and from Sand Ridge State Forest (SRSF), Mason County, Illinois. Plants of both species were grown in the two soils and were inoculated with Glomus etunicatum spores originally collected from KPRNA or colonized root pieces from S. scoparium plants collected from SRSF. Glomus etunicatum inoculum resulted in significantly greater root colonization and biomass of both plant species in steamed KPRNA soil than did root piece inoculum. There was no benefit from inoculation in non-sterile soil which contained indigenous mycorrhizal fungi. In SRSF soil, there was no response to inoculation with mycorrhizal fungi from either source. The lack of mycorrhizal response in SRSF soil is attributed to the greater plant-available P level of this soil. For S. scoparium grown in SRSF soil, plants grown in steamed soil produced more biomass than plants grown in steamed soil amended with nonsterile soil sievings (containing soil organisms other than mycorrhizal fungi), or in nonsterile soil. These differences could be due to competition for inorganic nutrients between soil microbes and the plant or antagonistic relationships between the plant or the mycorrhizal association and the soil microbes. Thus, the mycorrhizal dependence of these plant species is related to both soil and inoculum type or species.}, keywords = {LTER-KNZ}, doi = {10.2307/2426592}, author = {Anderson, R.C. and Hetrick, B.A.D. and G.T. Wilson} } @article {KNZ00405, title = {VA-Mycorrhizal influence on intra- and interspecific neighbor interactions among co-occurring prairie grasses}, journal = {Journal of Ecology}, volume = {81}, year = {1993}, pages = {787 -795}, abstract = {1 A strongly obligately mycorrhiza-dependent grass, Andropogon gerardii, and a less dependent species, Elymus canadensis, were grown in intra- and interspecific combination in a target-neighbour experiment with and without mycorrhizal fungi to examine their influence on competition. 2 Mycorrhizal fungi significantly influenced the competitive effects and responses of both plant species. Strong competitive effects of Andropogon disappeared in the absence of mycorrhizas indicating that its competitive dominance in tallgrass prairie is highly dependent upon its mycorrhizal associations. The influence of mycorrhizal fungi on Andropogon responses to neighbours decreased with increasing neighbour density indicating reduced host plant benefit from mycorrhizas under crowded conditions. 3 Effects of mycorrhizas on competition were generally smaller for the less mycorrhiza-dependent Elymus. Elymus effects on target plants were not strongly affected by mycorrhizas. Elymus target plants in competition with Andropogon neighbours performed better when nonmycorrhizal, due to the lack of significant competitive suppression by Andropogon in the absence of mycorrhizas. The influence of mycorrhizal fungi on Elymus responses to Andropogon neighbours increased with increasing neighbour density. Neither mycorrhizas nor phosphorus fertilization had a significant effect on intraspecific competition among Elymus. 4 Patterns of tiller production by target plants were similar to patterns in their total dry weight, indicating that competitive and mycorrhizal effects on target plant size were primarily a result of effects on tiller numbers rather than individual tiller size. 5 The results show that mycorrhizal symbiosis can strongly influence the patterns and intensity of both intraspecific density effects and interspecific competition between co-occurring prairie grasses and that the degree of host-plant benefit derived from mycorrhizas is density dependent.}, keywords = {LTER-KNZ}, doi = {10.2307/2261676}, author = {D.C. Hartnett and Hetrick, B.A.D. and G.T. Wilson and D.J. Gibson} } @article {KNZ00360, title = {Relationships of mycorrhizal symbiosis, rooting strategy and phenology among tallgrass prairie forbs}, journal = {Canadian Journal of Botany}, volume = {70}, year = {1992}, pages = {1521 -1528}, keywords = {LTER-KNZ, tallgrass prairie}, doi = {10.1139/b92-191}, author = {Hetrick, B.A.D. and G.T. Wilson and Todd, T.C.} } @article {KNZ00321, title = {Effects of mycorrhizal fungus species and metalaxyl application on microbial suppression of mycorrhizal symbiosis}, journal = {Mycologia}, volume = {83}, year = {1991}, pages = {97 -102}, keywords = {LTER-KNZ}, doi = {10.2307/3759836}, author = {Hetrick, B.A.D. and G.T. Wilson} } @article {KNZ00322, title = {Root architecture of warm and cool-season grasses: relationship to mycorrhizal dependence}, journal = {Canadian Journal of Botany}, volume = {69}, year = {1991}, pages = {112 -118}, keywords = {LTER-KNZ}, doi = {10.1139/b91-016}, author = {Hetrick, B.A.D. and G.T. Wilson and Leslie, J.F.} } @article {KNZ00283, title = {Differential responses of C3 and C4 grasses to mycorrhizal symbiosis, phosphorus fertilization, and soil microorganisms}, journal = {Canadian Journal of Botany}, volume = {68}, year = {1990}, pages = {461 -467}, abstract = {

The responses of five C4, warm-season and five C3, cool-season tallgrass prairie grasses to phosphorus (P) fertilization, mycorrhizae, and soil microorganisms were compared in greenhouse studies. The warm-season grasses responded positively to mycorrhizae and to P fertilization, but mycorrhizal plants did not respond to P. The soil microflora reduced mycorrhizal plant dry weight and root colonization. In contrast, cool-season grasses did not respond to mycorrhizae or P fertilization. Soil microorganisms did not suppress cool-season plant growth, but root colonization was reduced in nonsterile soil. For the warm-season grasses there was an inverse relationship between mycorrhizal root colonization and P fertilization and a positive relationship between root colonization and plant dry weight. For the cool-season grasses there was also an inverse relationship between root colonization and P fertilization, but the relationship between root colonization and plant dry weight was negative. In both the warm-season and cool-season grasses, low levels of mycorrhizal root colonization persisted even when P fertilization was sufficient to eliminate mycorrhizal effects on plant growth. Thus, warm-and cool-season grasses display profoundly different strategies for nutrient acquisition. Key words: cool-season grasses, warm-season grasses, vesicular-arbuscular mycorrhizae

}, keywords = {LTER-KNZ, tallgrass prairie}, doi = {10.1139/b90-061}, author = {Hetrick, B.A.D. and G.T. Wilson and Todd, T.C.} } @article {KNZ00282, title = {The influence of mycorrhizae on big bluestem rhizome regrowth and clipping tolerance}, journal = {Journal of Range Management}, volume = {43}, year = {1990}, pages = {286 -290}, abstract = {

Mycorrhizal symbiosis is critical to growth of many warm-season prairie grass seedlings, but its effect on regrowth of rhizomes has not been determined. As forage species, the effect of grazing on the symbiosis is also important. When the impact of mycorrhizae on regrowth of Andropogon gerardii Vit. rhizomes was assessed, A. gerardii rhizomes collected from the field and grown with mycorrhizal inoculum produced larger plants than rhizomes grown in the absence of the symbiont. The effect of the symbiosis on clipping (simulated grazing) tolerance was quantified by growing A. gerardii in steamed or nonsterile prairie soil, with or without mycorrhizal fungus inoculation. Plants were cliped and a portion of the plants harvested at 6, 12, 18, 24, and 30 weeks after planting. As an additional control, Benomyl fungicide was applied to plants to inhibit the symbiosis. Mycorrhizal clipped plants were larger than nonmycorrhizal clipped plants, but the difference diminished with successive clippings. Mycorrhizal root colonization also decreased in response to repeated clipping. Maximum shoot and root biomass of mycorrhizal plants was produced at 12 and 18 weeks, respectively. Fungicide-treated plants did not grow appreciably after the first clipping. Thus, mycorrhizae improved clipping tolerance, but with repeated intensive clipping, significant changes in root/shoot ratio occurred and eventually mycorrhizal root colonization and growth benefit were lost. Key words: grazing, vesicular-arbuscular mycorrhizae, big bluestem, herbage yield

}, keywords = {LTER-KNZ}, doi = {10.2307/3898918}, author = {Hetrick, B.A.D. and G.T. Wilson and Owensby, C.E.} } @article {KNZ00281, title = {Relationship of native and introduced mycorrhizal fungi to mycorrhizal dependence of Andropogon gerardii and Koeleria pyranidata}, journal = {Mycologia}, volume = {82}, year = {1990}, pages = {779 -782}, abstract = {

To determine whether VAM (vesicular-arbuscular mycorrhizal) fungi from prairie soil would alter the mycorrhizal dependence of warm- and cool-season grasses or the response of these hosts to the soil microbiota, 2-wk old seedlings of A. gerardii or K. pyranidata were planted in 6x25 cm pots containing 525 g (dry weight) steam-pasteurized soil (2 h at 80 C and allowed to cool and equilibrate for 72 h thereafter), pasteurized soil amended with 100 ml/pot non-sterile soil sievings, or non-sterile prairie soil

}, keywords = {LTER-KNZ}, doi = {10.2307/3760166}, author = {Hetrick, B.A.D. and G.T. Wilson} } @article {KNZ00234, title = {Influence of mycorrhizal fungi and fertilization on big bluestem seedling biomass}, journal = {Journal of Range Management}, volume = {42}, year = {1989}, pages = {213 -216}, abstract = {

The relationship between fertilization of prairie soils and mycorrhizal symbiosis in big bluestem (Andropogon gerardii Vit.) was explored. In 10 steamed prairie soils of varied P level, inoculation with a mycorrhizal fungus resulted in a 7- to 70-fold increase in big bluestem seedling biomass, compared to noninoculated controls. Fertilization with N and K (25-0-25) significantly increased biomass of mycorrhizal seedlings but did not alter growth of nonmycorrhizal seedlings. In a second experiment which assessed the impact of N and P on seedling growth, in both steamed and nonsterile soil, P fertilization did not significantly increase plant biomass, while N fertilization did substantially increase biomass of mycorrhizal, but not nonmycorrhizal plants. Fertilization with N and P together produced the greatest biomass in both mycorrhizal and nonmycorrhizal plants. Apparently, in the range soils tested N is the most limiting nutrient, despite the low P availability exhibited by these soils. In the absence of mycorrhizae, however, P is most limiting and no response to N is observed unless sufficient P is also applied. These studies confirm an extremely important role for mycorrhizal fungi on big bluestem seedling growth. Key words: phosphorous, nitrogen, Glomus etunicatum, mycorrhizae, Andropogon gerardii

}, keywords = {LTER-KNZ}, doi = {10.2307/3899475}, author = {Hetrick, B.A.D. and G.T. Wilson and Owensby, C.E.} } @article {KNZ00232, title = {Relationship between mycorrhizal dependence and competitive ability of two tallgrass prairie grasses}, journal = {Canadian Journal of Botany}, volume = {67}, year = {1989}, pages = {2608 -2615}, abstract = {

The impact of mycorrhizal symbiosis on growth of Andropogon gerardii (big bluestem) and Koeleria pyranidata (junegrass) was compared. Andropogon gerardii was 98\% dependent on the symbiosis, whereas K. pyranidata displayed less than 0.02\% dependence. Mycorrhizal fungus inoculation resulted in 50 times larger A. gerardii plants but did not alter growth of K. pyradidata. When competing in pairs, A. gerardii dominated when the mycorrhizal symbiosis was present and K. pyradidata dominated when it was not present. Dry weight of mycorrhizal A. perardii was altered, whether grown alone or with K. pyranidata, but mycorrhizal K. pyranidata grew well only in the absence of competition and failed to grow appreciably if A. gerardii was present. Without mycorrhizal fungus inoculation, A. gerardii did not grow and had no deleterious effects on K. pyranidata. When P. fertilization was substituted for mycorrhizal fungus inoculation, A. gerardii grew better alone than in competition with K. pyranidata at low P levels but was not affected by competition at high P levels. Koeleria pyranidata was not affected by competition at low P levels, but high P fertilization resulted in reduced dry weight of K. pyranidata plants when in competition with A. gerardii. Phenologic separation of growing seasons avoids interspecific competition between these two grasses and may be one mechanism contributing toward their coexistence. Since low temperatures limit mycorrhizal nutrient uptake, phenologic separation of growing seasons could also avoid the competitive advantage of warm-season grasses conferred by their mycorrhizal dependence

}, keywords = {LTER-KNZ, tallgrass prairie}, doi = {10.1139/b89-337}, author = {Hetrick, B.A.D. and G.T. Wilson and Harnett, D.C.} } @article {KNZ00233, title = {Suppression of mycorrhizal fungus spore germination in nonsterile soil: relationship to mycorrhizal growth response in big bluestem}, journal = {Mycologia}, volume = {81}, year = {1989}, pages = {382 -390}, keywords = {LTER-KNZ}, doi = {10.2307/3760076}, author = {Hetrick, B.A.D. and G.T. Wilson} } @article {KNZ00259, title = {Suppression of vesicular-arbuscular mycorrhizal fungus spore germination by nonsterile soil}, journal = {Canadian Journal of Botany}, volume = {67}, year = {1989}, pages = {18 -23}, keywords = {LTER-KNZ}, doi = {10.1139/b89-003}, author = {G.T. Wilson and Hetrick, B.A.D. and Kitt, D.G.} } @article {KNZ00184, title = {Effects of soil microorganisms on mycorrhizal contribution to growth of big bluestem grass in nonsterile soil}, journal = {Soil Biology \& Biochemistry}, volume = {20}, year = {1988}, pages = {501 -507}, abstract = {

Plant dry weight and mycorrhizal root colonization of big bluestem (Andropogon gerardii Vitman) inoculated with Glomus etunicatum Becker and Gerd. were suppressed if non-sterile prairie soil sievings were added to pasteurized soil. Addition of prairie soil microorganisms, isolated onto peptone yeast extract, King\&$\#$39;s B, or starch casein agar media, to pasteurized soil also reduced dry weight and mycorrhizal root colonization of big bluesteam inoculated with G. etunicatum. In contrast, addition of non- sterile soil sievings or filtrate or organisms isolated onto potato dextrose or pseudomonas isolation agar to pasteurized soil improved growth of non-mycorrhizal big bluestem. These effects of soil microorganisms on plant growth were further quantified by comparing 32P uptake by fungicide treated and untreated mycorrhizal plants and by non-mycorrhizal plants in pasteurized and non-sterile soil. Mycorrhizal plants grown in pasteurized soil absorbed approximately 10 times more 32P than mycorrhizal plants grown in non-sterile soil. Application of propiconazole (Tilt) or fenarimol (Rubigan), fungicides which inhibit non-sterile soil, respectively. Thus, more 32P is absorbed in pasteurized than in non-sterile soil, probably because soil microorganisms limit mycorrhizal activity in non-sterile soil. Assessments of mycorrhizal contribution to plant growth conducted in sterilized soil may significantly overestimate the effects of VAM fungi because other soil microorganisms are not considered

}, keywords = {LTER-KNZ}, doi = {10.1016/0038-0717(88)90065-X}, author = {Hetrick, B.A.D. and G.T. Wilson and Kitt, D.G. and Schwab, A.P.} } @article {KNZ00183, title = {Mycorrhizal dependence and growth habit of warm-season and cool-season tallgrass prairie plants}, journal = {Canadian Journal of Botany}, volume = {66}, year = {1988}, pages = {1376 -1380}, abstract = {

Warm-season (C4) and cool-season (C3) mycorrhizal grasses were 63-215 and 0.12-4.1 times larger in dry weight than non-inoculated controls, respectively. Nonmycorrhizal warm-season plants did not grow and frequently died, while cool-season plants grew moderately well in the absense of mycorrhizal symbiosis. Like warm-season grasses, tallgrass prairie forbs were highly dependent on mycorrhizal symbiosis, even though they are not known to employ the C4 photosynthetic pathway. Thus, phenology may be more critical than photosynthetic pathway in determining mycorrhizal dependence. Warm-season grasses and forbs had coarser, less frequently branched root systems than cool-season grasses, supporting the hypothesis that mycorrhizal dependence is related to root morphology. Cool-season grasses may have developed more fibrous root systems because mycorrhizal nutrient uptake was not effective in the colder temperature environment in which they evolved. In contrast, warm-season plants and dependence on mycorrhizal fungi may have coevolved, because both symbionts are of tropical origin

}, keywords = {LTER-KNZ, tallgrass prairie}, doi = {10.1139/b88-193}, author = {Hetrick, B.A.D. and Kitt, D.G. and G.T. Wilson} } @article {KNZ00181, title = {Physical and topological assessment of vesicular-arbuscular mycorrhizal fungus on root architecture of big bluestem}, journal = {New Phytologist}, volume = {110}, year = {1988}, pages = {85 -96}, abstract = {

The influence of vesicular-arbuscular (VA) mycorrhizal fungus, phosphorus (P) fertilization, and soil microorganisms on growth and root architecture of big bluestem (Andropogon gerardii Vitman) was investigated. In pasteurized soil, mycorrhizal inoculation significantly improved plant growth and increased root length and the number and the diameter of the primary, secondary and tertiary roots. These differences between mycorrhizal and non-mycorrhizal plants diminished with added P. In pasteurized soil amended with non-sterile soil sievate, differences between mycorrhizal and non-mycorrhizal plants were still obvious, but in may treatments these plants grew more poorly (had less dry weight, root length, number or diameter) than their counterparts in unamended pasteurized soil. Growth in non-sterile soil was also suppressed, and mycorrhizal responses were not detected since all of the plants in non-sterile soil became mycorrhizal whether or not they were inoculated. Two analyses of calculated parameters which describe root- system architecture were conducted. The first, specific root length (SRL), revealed that mycorrhizal symbiosis dramatically alters root morphology in soils of low fertility. These changes were similar to the changes evoked by added P. The second, path length (Pe) revealed that mycorrhizal fungi (and to some degree other soil microbes) significantly alter root architecture by reducing the relative amount of root branching. Apparently, mycorrhizal plants develop a more elongate, exploratory growth pattern which permits the fungal hyphae to extract nutrients from a larger volume of soil. In contract roots of non-mycorrhizal plants maintain a more highly branched pattern of root growth, and the roots themselves play a more critical role in the direct extraction of nutrients from the soil. These differences in root topology were not directly associated with the concentration of exogenous P, but instead appeared to be controlled by the mycorrhizal fungi themselves. Thus, while internal P content of plants mediates the establishment of the mycorrhizal symbiosis, the fungi can alter the root architecture of the plant to a form which best accommodates the symbiosis under the prevailing fertility and rhizosphere conditions in the soil. By altering root-system architecture in this manner, the mycorrhizal fungi can control, at least to some degree, the dependence of the host on the symbiosis. Thus, the topology of the root system is contingent upon the microflora in the rhizosphere. The topological analysis revealed differences in root architecture not detected by any of the other measures of root morphology. These differences suggest that mycorrhizal fungi affect root architecture and plant growth in ways not directly associated with phosphorus uptake. Key words: path length, phosphorus, root morphology, specific root length

}, keywords = {LTER-KNZ}, doi = {10.1111/j.1469-8137.1988.tb00240.x}, author = {Hetrick, B.A.D. and Leslie, J.F. and G.T. Wilson and Kitt, D.G.} } @article {KNZ00194, title = {Relationships of soil fertility to suppression of the growth response of mycorrhizal big bluestem in nonsterile soil}, journal = {New Phytologist}, volume = {109}, year = {1988}, pages = {473 -482}, abstract = {

When growth of vesicular-arbuscular (VA) mycorrhizal and non-mycorrhizal big bluestem was evaluated in 15 soils, three different growth response groups were evident. Group one, which included the prairie soils, displayed high mycorrhizal dependency as well as significant suppression of plant growth in non- sterile soil. Group two showed no mycorrhizal dependency; however, plant growth was suppressed in non- sterile soil. The last group exhibited no mycorrhizal dependency or suppression in non-sterile soil. Mycorrhizal dependency of big bluestem was not highly correlated with any individual soil parameter; however, concentrations of soil K, Ca, Cu, and Fe were used to successfully classify \"high\" and \"low\" mycorrhizal dependency. Suppression of plant growth in non-sterile soil was also related to soil fertility. The magnitude of non-sterile suppression was described by equations using soil Na, Zn, Mn, organic matter, Mg, and NH4. The mechanism of this suppression is still unclear; however, the nutrients which predict suppression may be related to the development of mycorrhizal symbiosis or in demand by plants and other microbes, while those nutrients which predict mycorrhizal dependency may be related to those supplied to the plant by the symbiosis. Key words: Glomus etunicatum, mycorrhial ependency, vesicular-arbuscular mycorrhizas

}, keywords = {LTER-KNZ}, doi = {10.1111/j.1469-8137.1988.tb03723.x}, author = {Kitt, D.G. and Hetrick, B.A.D. and G.T. Wilson} } @article {KNZ00212, title = {Suppression of mycorrhizal growth response of big bluestem by nonsterile soil}, journal = {Mycologia}, volume = {80}, year = {1988}, pages = {338 -343}, abstract = {

Inoculum potential of Glomus mosseae and Glomus etunicatum was reduced significantly in pasteurized soil amended with a sieved suspension from non-sterile soil. Regardless of mycorrhizal fungus inoculum dosage, dry weight and root colonization of plants grown in pasteurized soil with non-sterile soil seievings never equalled those of plants grown in pasteurized alone. However, plants exposed to non-sterile soil were more colonized and grew faster than plants in pasteurized soil alone. Only after 13 wk were plants in pasteurized soil significantly more colonized, and after 16 wk larger in dry weight than their counterparts in non-sterile soil or pasteurized soil with sievings. Apparently, loss of inoculum potential alone cannot fully explain the suppression of plant growth observed in non-sterile soil. The suppressive effects of non-sterile soil may be best related to microbial mediation of nutrient availability in soil. Key words: inoculum potential, Glomus etunicatum, Glomus mosseae, inoculum dosage

}, keywords = {LTER-KNZ}, doi = {10.2307/3807630}, author = {G.T. Wilson and Daniels, B.A.H. and Kitt, D.G.} } @article {KNZ00147, title = {Sporulation of two vesicular-abuscular mycorrhizal fungi in nonsterile soil}, journal = {Mycologia}, volume = {79}, year = {1987}, pages = {896 -899}, abstract = {

Spore numbers and species diversity of vesicular-arbuscular mycorrhizal (VAM) fungi from agricultural soils may be significantly lower than those observed in native soils (Hetrick and Bloom, 1983). In a survey of corn fields from four locations throughout a growing season, one soil (Scandia, Kansas) contained primarily Gigaspora spp. at all sample dates (G. rosea was present on two of the sample dates) while the others contained primarily or exclusively Glomus spp., including G. etunicatum (Hetrick et al., 1984). The present study was initiated to determine whether the Scandia soil favored sporulation of Gifasopra spp. and conversely whether a soil containing predominantly Glomus spp. would preferentially stimulate Glomus spp. sporulation. Because nonsterile soil has been shown to suppress mycorrhizal growth response and root colonization (Hetrick et al., 1986), the effect of nonsterile versus sterilized soil and interspecific competition on sporulation was also studied to determine whether these factors influenced species dominance and might also explain the low spore numbers observed in agricultural soils

}, keywords = {LTER-KNZ}, doi = {10.2307/3807692}, author = {Kitt, D.G. and Heterick, B.A.D. and G.T. Wilson} }