@article {6298, title = {Accounting for herbaceous communities in process-based models will advance our understanding of {\textquotedblleft}grassy{\textquotedblright} ecosystems}, journal = {Global Change Biology}, volume = {29}, year = {2023}, pages = {6453 - 6477}, keywords = {LTER-KNZ}, issn = {1354-1013}, doi = {10.1111/gcb.v29.2310.1111/gcb.16950}, url = {https://onlinelibrary.wiley.com/doi/10.1111/gcb.16950}, author = {K.R. Wilcox and Chen, Anping and M.L. Avolio and Butler, Ethan E. and S.L Collins and Fisher, Rosie and Keenan, Trevor and Kiang, Nancy Y. and Alan K. Knapp and Koerner, S.E. and Kueppers, Lara and Liang, Guopeng and Lieungh, Eva and Loik, Michael and Luo, Yiqi and Poulter, Ben and Reich, Peter and Renwick, Katherine and M. D. Smith and Walker, Anthony and Weng, Ensheng and Komatsu, K.J.} } @article {6167, title = {Effect of genotypic richness, drought and mycorrhizal associations on productivity and functional traits of a dominant C4 grass}, journal = {Journal of Plant Ecology}, volume = {16}, year = {2023}, pages = {rtac045}, keywords = {LTER-KNZ}, doi = {10.1093/jpe/rtac045}, url = {https://academic.oup.com/jpe/article/doi/10.1093/jpe/rtac045/6545842}, author = {Pehim Limbu, Smriti and M.L. Avolio} } @article {6164, title = {Multiple global change drivers show independent, not interactive effects: a long-term case study in tallgrass prairie}, journal = {Oecologia}, volume = {201}, year = {2023}, pages = {143{\textendash}154}, abstract = {

Ecosystems are faced with an onslaught of co-occurring global change drivers. While frequently studied independently, the effects of multiple global change drivers have the potential to be additive, antagonistic, or synergistic. Global warming, for example, may intensify the effects of more variable precipitation regimes with warmer temperatures increasing evapotranspiration and thereby amplifying the effect of already dry soils. Here, we present the long-term effects (11 years) of altered precipitation patterns (increased intra-annual variability in the growing season) and warming (1 \°C year-round) on plant community composition and aboveground net primary productivity (ANPP), a key measure of ecosystem functioning in mesic tallgrass prairie. Based on past results, we expected that increased precipitation variability and warming would have additive effects on both community composition and ANPP. Increased precipitation variability altered plant community composition and increased richness, with no effect on ANPP. In contrast, warming decreased ANPP via reduction in grass stems and biomass but had no effect on the plant community. Contrary to expectations, across all measured variables, precipitation and warming treatments had no interactive effects. While treatment interactions did not occur, each treatment did individually impact a different component of the ecosystem (i.e., community vs. function). Thus, different aspects of the ecosystem may be sensitive to different global change drivers in mesic grassland ecosystems.

}, keywords = {LTER-KNZ}, doi = {10.1007/s00442-022-05295-5}, url = {https://link.springer.com/10.1007/s00442-022-05295-5}, author = {Koerner, S.E. and M.L. Avolio and J. M. Blair and Alan K. Knapp and M. D. Smith} } @article {6163, title = {Do trade-offs govern plant species{\textquoteright} responses to different global change treatments?}, journal = {Ecology}, volume = {103}, year = {2022}, pages = {e3626}, keywords = {LTER-KNZ}, issn = {0012-9658}, doi = {10.1002/ecy.3626}, url = {https://esajournals.onlinelibrary.wiley.com/doi/10.1002/ecy.3626}, author = {Langley, J. Adam and Grman, Emily and K.R. Wilcox and M.L. Avolio and Kimberly J. Komatsu and Collins, Scott L. and Koerner, S.E. and M. D. Smith and Baldwin, Andrew H. and Bowman, William and Chiariello, Nona and Eskelinen, Anu and Harmens, Harry and Hovenden, Mark and Klanderud, Kari and McCulley, Rebecca L. and Onipchenko, Vladimir G. and Robinson, Clare H. and K.N. Suding} } @article {6125, title = {Making sense of multivariate community responses in global change experiments}, journal = {Ecosphere}, volume = {13}, year = {2022}, pages = {e4249}, keywords = {LTER-KNZ}, doi = {10.1002/ecs2.4249}, url = {https://esajournals.onlinelibrary.wiley.com/doi/10.1002/ecs2.4249}, author = {M.L. Avolio and Kimberly J. Komatsu and Koerner, S.E. and Grman, Emily and Isbell, Forest and Johnson, David S. and K.R. Wilcox and Alatalo, Juha M. and Baldwin, Andrew H. and Beierkuhnlein, Carl and Britton, Andrea J. and Foster, Bryan L. and Harmens, Harry and Kern, Christel C. and Li, Wei and McLaren, Jennie R. and Reich, Peter B. and Souza, Lara and Yu, Qiang and Zhang, Yunhai} } @article {5968, title = {Determinants of community compositional change are equally affected by global change}, journal = {Ecology Letters}, volume = {24}, year = {2021}, pages = {1892-1904}, abstract = {

Global change is impacting plant community composition, but the mechanisms underlying these changes are unclear. Using a dataset of 58 global change experiments, we tested the five fundamental mechanisms of community change: changes in evenness and richness, reordering, species gains and losses. We found 71\% of communities were impacted by global change treatments, and 88\% of communities that were exposed to two or more global change drivers were impacted. Further, all mechanisms of change were equally likely to be affected by global change treatments\—species losses and changes in richness were just as common as species gains and reordering. We also found no evidence of a progression of community changes, for example, reordering and changes in evenness did not precede species gains and losses. We demonstrate that all processes underlying plant community composition changes are equally affected by treatments and often occur simultaneously, necessitating a wholistic approach to quantifying community changes.

}, keywords = {LTER-KNZ}, doi = {10.1111/ele.13824}, url = {https://onlinelibrary.wiley.com/doi/10.1111/ele.13824}, author = {M.L. Avolio and Kimberly J. Komatsu and S.L Collins and Grman, Emily and Koerner, S.E. and Tredennick, A.T. and Wilcox, K.R. and Baer, S.G. and E.H. Boughton and Britton, Andrea J. and Foster, Bryan and Gough, Laura and Hovenden, Mark and Isbell, Forest and Jentsch, Anke and Johnson, David S. and Knapp, Alan K. and Kreyling, Juergen and Langley, J. Adam and Lortie, Christopher and McCulley, Rebecca L. and McLaren, Jennie R. and Reich, Peter B. and Seabloom, Eric W. and Smith, Melinda D. and Suding, Katharine N. and Suttle, K. Blake and Tognetti, Pedro M.}, editor = {Anderson, Marti} } @article {KNZ002001, title = {Mass ratio effects underlie ecosystem responses to environmental change}, journal = {Journal of Ecology}, volume = {108}, year = {2020}, pages = {855-864}, abstract = {

1. Random species loss has been shown experimentally to reduce ecosystem function, sometimes more than other anthropogenic environmental changes. Yet, controversy surrounds the importance of this finding for natural systems where species loss is non-random.
2. We compiled data from 16 multi-year experiments located at a single native tallgrass prairie site. These experiments included responses to 11 anthropogenic environmental changes, as well as non-random biodiversity loss either the removal of uncommon/rare plant species or the most common (dominant) species.
3. As predicted by the mass ratio hypothesis, loss of a dominant species had large impacts on productivity that were comparable to other anthropogenic drivers. In contrast, the loss of uncommon/rare species had small effects on productivity despite having the largest effects on species richness.
4. The anthropogenic drivers that had the largest effects on productivity nitrogen, irrigation, and fire experienced not only loss of species but also significant changes in the abundance and identity of dominant species.
5. Synthesis. These results suggest that mass ratio effects, rather than species loss per se, are an important determinant of ecosystem function with environmental change.

}, keywords = {LTER-KNZ}, doi = {10.1111/1365-2745.13330}, url = {https://besjournals.onlinelibrary.wiley.com/doi/abs/10.1111/1365-2745.13330}, author = {M.D. Smith and Koerner, S.E. and Alan K. Knapp and M.L. Avolio and Chaves, F.A. and Denton, E.M. and Dietrich, J. and Gibson, D.J. and Gray, J. and Hoffman, A.M. and Hoover, D.L. and Kimberly J. Komatsu and Silletti, A. and K.R. Wilcox and Yu, Q. and John M. Blair} } @article {KNZ001953, title = {A comprehensive approach to analyzing community dynamics using rank abundance curves}, journal = {Ecosphere}, volume = {10}, year = {2019}, pages = {e02881}, abstract = {

Univariate and multivariate methods are commonly used to explore the spatial and temporaldynamics of ecological communities, but each has limitations, including oversimplification or abstractionof communities. Rank abundance curves (RACs) potentially integrate these existing methodologies bydetailing species-level community changes. Here, we had three goals:first, to simplify analysis of commu-nity dynamics by developing a coordinated set of R functions, and second, to demystify the relationshipsamong univariate, multivariate, and RACs measures, and examine how each is influenced by the commu-nity parameters as well as data collection methods. We developed new functions for studying temporalchanges and spatial differences in RACs in an update to the R package library(\“codyn\”), alongside othernew functions to calculate univariate and multivariate measures of community dynamics. We also devel-oped a new approach to studying changes in the shape of RAC curves. The R package update presentedhere increases the accessibility of univariate and multivariate measures of community change over timeand difference over space. Next, we use simulated and real data to assess the RAC and multivariate mea-sures that are output from our new functions, studying (1) if they are influenced by species richness andevenness, temporal turnover, and spatial variability and (2) how the measures are related to each other.Lastly, we explore the use of the measures with an example from a long-term nutrient addition experiment.Wefind that the RAC and multivariate measures are not sensitive to species richness and evenness andthat all the measures detail unique aspects of temporal change or spatial differences. We alsofind that spe-cies reordering is the strongest correlate of a multivariate measure of compositional change and explainsmost community change observed in long-term nutrient addition experiment. Overall, we show that spe-cies reordering is potentially an understudied determinant of community changes over time or differencesbetween treatments. The functions developed here should enhance the use of RACs to further explore thedynamics of ecological communities.

}, keywords = {LTER-KNZ}, doi = {10.1002/ecs2.2881}, url = {https://esajournals.onlinelibrary.wiley.com/doi/epdf/10.1002/ecs2.2881}, author = {M.L. Avolio and Carroll, I. and Scott. L. Collins and Houseman, Gregory R. and Hallett, L.M. and Isbell, F.L. and Koerner, S.E. and Kimberly J. Komatsu and M.D. Smith and K.R. Wilcox} } @article {KNZ001938, title = {Demystifying dominant species}, journal = {New Phytologist}, volume = {223}, year = {2019}, pages = {1106 - 1126}, abstract = {

The pattern of a few abundant species and many rarer species is a defining characteristic of communities worldwide. These abundant species are often referred to as dominant species. Yet, despite their importance, the term dominant species is poorly defined and often used to convey different information by different authors. Based on a review of historical and contemporary definitions we develop a synthetic definition of dominant species. This definition incorporates the relative local abundance of a species, its ubiquity across the landscape, and its impact on community and ecosystem properties. A meta-analysis of removal studies shows that the loss of species identified as dominant by authors can significantly impact ecosystem functioning and community structure. We recommend two metrics that can be used jointly to identify dominant species in a given community and provide a roadmap for future avenues of research on dominant species. In our review, we make the case that the identity and effects of dominant species on their environments are key to linking patterns of diversity to ecosystem function, including predicting impacts of species loss and other aspects of global change on ecosystems.

}, keywords = {LTER-KNZ}, doi = {10.1111/nph.15789}, url = {https://onlinelibrary.wiley.com/doi/abs/10.1111/nph.15789}, author = {M.L. Avolio and Forrestel, Elisabeth J. and Chang, Cynthia C. and Kimberly J. La Pierre and Burghardt, Karin T. and M.D. Smith} } @article {KNZ001965, title = {Global change effects on plant communities are magnified by time and the number of global change factors imposed}, journal = {Proceedings of the National Academy of Sciences}, volume = {116}, year = {2019}, pages = {17867-17873}, abstract = {

Global change drivers (GCDs) are expected to alter community structure and consequently, the services that ecosystems provide. Yet, few experimental investigations have examined effects of GCDs on plant community structure across multiple ecosystem types, and those that do exist present conflicting patterns. In an unprecedented global synthesis of over 100 experiments that manipulated factors linked to GCDs, we show that herbaceous plant community responses depend on experimental manipulation length and number of factors manipulated. We found that plant communities are fairly resistant to experimentally manipulated GCDs in the short term (\<10 y). In contrast, long-term (\≥10 y) experiments show increasing community divergence of treatments from control conditions. Surprisingly, these community responses occurred with similar frequency across the GCD types manipulated in our database. However, community responses were more common when 3 or more GCDs were simultaneously manipulated, suggesting the emergence of additive or synergistic effects of multiple drivers, particularly over long time periods. In half of the cases, GCD manipulations caused a difference in community composition without a corresponding species richness difference, indicating that species reordering or replacement is an important mechanism of community responses to GCDs and should be given greater consideration when examining consequences of GCDs for the biodiversity\–ecosystem function relationship. Human activities are currently driving unparalleled global changes worldwide. Our analyses provide the most comprehensive evidence to date that these human activities may have widespread impacts on plant community composition globally, which will increase in frequency over time and be greater in areas where communities face multiple GCDs simultaneously.

}, keywords = {LTER-KNZ}, doi = {10.1073/pnas.1819027116}, url = {https://www.pnas.org/content/early/2019/08/14/1819027116}, author = {Kimberly J. Komatsu and M.L. Avolio and Lemoine, Nathan P. and Isbell, Forest and Grman, Emily and Houseman, Gregory R. and Koerner, Sally E. and Johnson, D.S. and K.R. Wilcox and Juha M. Alatalo and Anderson, J.P. and Aerts, R. and S.G. Baer and Baldwin, Andrew H. and Bates, J. and Beierkuhnlein, C. and Belote, R.T. and John M. Blair and Bloor, J.M.G. and Bohlen, P.J. and Edward W. Bork and Elizabeth H. Boughton and W.D. Bowman and Britton, Andrea J. and Cahill, James F. and Chaneton, Enrique J. and Chiariello, N.R. and Cheng, Jimin. and Scott. L. Collins and Cornelissen, J.H.C. and G. Du and Eskelinen, Anu and Firn, Jennifer and Foster, B. and Gough, L. and Gross, K. and Hallett, L.M. and Han, X. and Harmens, H. and Hovenden, M.J. and Jagerbrand, A. and Jentsch, A. and Kern, Christel and Klanderud, Kari and Alan K. Knapp and Kreyling, Juergen and Li, W. and Luo, Yiqi and McCulley, R.L. and McLaren, Jennie R. and Megonigal, Patrick and J.W. Morgan and Onipchenko, Vladimir and Pennings, S.C. and Prev{\'e}y, J.S. and Price, Jodi N. and P.B. Reich and Robinson, Clare H. and Russell, L.F. and Sala, O.E. and Seabloom, E.W. and M.D. Smith and Soudzilovskaia, Nadejda A. and Souza, Lara and K.N. Suding and Suttle, B.K. and Svejcar, T. and Tilman, David and Tognetti, P. and Turkington, R. and White, S. and Xu, Zhuwen and Yahdjian, L. and Yu, Q. and Zhang, Pengfei and Zhang, Yunhai} } @article {KNZ001898, title = {Ambient changes exceed treatment effects on plant species abundance in long-term global change experiments}, journal = {Glob Chang Biol}, volume = {24}, year = {2018}, pages = {5668 - 5679}, abstract = {

The responses of species to environmental changes will determine future community composition and ecosystem function. Many syntheses of global change experiments examine the magnitude of treatment effect sizes, but we lack an understanding of how plant responses to treatments compare to ongoing changes in the unmanipulated (ambient or background) system. We used a database of long-term global change studies manipulating CO2 , nutrients, water, and temperature to answer three questions: (a) How do changes in plant species abundance in ambient plots relate to those in treated plots? (b) How does the magnitude of ambient change in species-level abundance over time relate to responsiveness to global change treatments? (c) Does the direction of species-level responses to global change treatments differ from the direction of ambient change? We estimated temporal trends in plant abundance for 791 plant species in ambient and treated plots across 16 long-term global change experiments yielding 2,116 experiment-species-treatment combinations. Surprisingly, for most species (57\%) the magnitude of ambient change was greater than the magnitude of treatment effects. However, the direction of ambient change, whether a species was increasing or decreasing in abundance under ambient conditions, had no bearing on the direction of treatment effects. Although ambient communities are inherently dynamic, there is now widespread evidence that anthropogenic drivers are directionally altering plant communities in many ecosystems. Thus, global change treatment effects must be interpreted in the context of plant species trajectories that are likely driven by ongoing environmental changes.

}, keywords = {LTER-KNZ, elevated CO2, nitrogen, Phosphorus, plant community, Warming, water}, doi = {10.1111/gcb.14442}, url = {https://onlinelibrary.wiley.com/doi/abs/10.1111/gcb.14442}, author = {Langley, A. and Chapman, S.K. and Kimberly J. La Pierre and M.L. Avolio and W.D. Bowman and Johnson, D. and Isbell, F. and K.R. Wilcox and Foster, B. and Hovenden, M. and Alan K. Knapp and Koerner, S.E. and Lortie, C. and Megonigal, J. and Newton, P. and Reich, B. and M.D. Smith and Suttle, B.K. and Tilman, D.} } @article {KNZ001888, title = {Change in dominance determines herbivore effects on plant biodiversity}, journal = {Nature Ecology and Evolution}, volume = {2}, year = {2018}, pages = {1925-1932}, abstract = {

Herbivores alter plant biodiversity (species richness) in many of the world\’s ecosystems, but the magnitude and the direction of herbivore effects on biodiversity vary widely within and among ecosystems. One current theory predicts that herbivores enhance plant biodiversity at high productivity but have the opposite effect at low productivity. Yet, empirical support for the importance of site productivity as a mediator of these herbivore impacts is equivocal. Here, we synthesize data from 252 large-herbivore exclusion studies, spanning a 20-fold range in site productivity, to test an alternative hypothesis\—that herbivore-induced changes in the competitive environment determine the response of plant biodiversity to herbivory irrespective of productivity. Under this hypothesis, when herbivores reduce the abundance (biomass, cover) of dominant species (for example, because the dominant plant is palatable), additional resources become available to support new species, thereby increasing biodiversity. By contrast, if herbivores promote high dominance by increasing the abundance of herbivory-resistant, unpalatable species, then resource availability for other species decreases reducing biodiversity. We show that herbivore-induced change in dominance, independent of site productivity or precipitation (a proxy for productivity), is the best predictor of herbivore effects on biodiversity in grassland and savannah sites. Given that most herbaceous ecosystems are dominated by one or a few species, altering the competitive environment via herbivores or by other means may be an effective strategy for conserving biodiversity in grasslands and savannahs globally.

}, keywords = {LTER-KNZ}, doi = {https://doi.org/10.1038/s41559-018-0696-y}, url = {https://www.nature.com/articles/s41559-018-0696-y$\#$article-info}, author = {Koerner, S.E. and M.D. Smith and Burkepile, D.E. and N.P. Hanan and M.L. Avolio and Scott. L. Collins and Alan K. Knapp and N.P. Lemoine and E.J. Forrestel and S. Eby and D.I. Thompson and G. Aguado-Santacruz and J.P. Anderson and Anderson, M. and A. Angassa and S. Bagchi and E.S. Bakker and Bastin, Gary and L.E. Baur and K.H. Beard and E.A. Beever and P.J. Bohlen and Elizabeth H. Boughton and Canestro, Don and Cesa, Ariela and Chaneton, Enrique and Cheng, Jimin and C.M. D{\textquoteright}Antonio and C. Deleglise and Fadiala. Demb{\'e}l{\'e} and Josh. Dorrough and David. J. Eldridge and Barbara. Fernandez-Going and Silvia. Fern{\'a}ndez-Lugo and Lauchlan. H. Fraser and Bill. Freedman and Gonzalo. Garc{\'\i}a-Salgado and Jacob. R. Goheen and Liang. Guo and Sean. Husheer and Moussa. Karemb{\'e} and Johannes. M. H. Knops and Tineke. Kraaij and Andrew. Kulmatiski and Minna-Maarit. Kyt{\"o}viita and Felipe. Lezama and Gregory. Loucougaray and Alejandro. Loydi, Dan G. Milchunas, and Dan.G. Milchunas, and Suzanne. J. Milton and J.W. Morgan and Claire. Moxham and Kyle. C. Nehring and Han. Olff and Todd. M. Palmer and Salvador. Rebollo and Corinna. Riginos and Anita. C. Risch and Marta Rueda and Mahesh. Sankaran and Takehiro. Sasaki and Kathryn. A. Schoenecker and Nick. L. Schultz and Martin. Sch{\"u}tz and Angelika. Schwabe and Frances. Siebert and Christian. Smit and Karen. A. Stahlheber and Christian. Storm and Dustin. J. Strong and Jishuai. Su and Yadugiri. V. Tiruvaimozhi and Claudia. Tyler and James. Val and Martijn. L. Vandegehuchte and Kari. E. Veblen and Lance. T. Vermeire and David. Ward and Jianshuang. Wu and Truman. P. Young and Qiang. Yu and Tamara. Jane. Zelikova} } @article {KNZ001865, title = {Codominant grasses differ in gene expression under experimental climate extremes in native tallgrass prairie}, journal = {PeerJ}, year = {2018}, pages = {e4394}, abstract = {

Extremes in climate, such as heat waves and drought, are expected to become more frequent and intense with forecasted climate change. Plant species will almost certainly differ in their responses to these stressors. We experimentally imposed a heat wave and drought in the tallgrass prairie ecosystem near Manhattan, Kansas, USA to assess transcriptional responses of two ecologically important C4 grass species, Andropogon gerardii and Sorghastrum nutans. Based on previous research, we expected that S. nutans would regulate more genes, particularly those related to stress response, under high heat and drought. Across all treatments, S. nutans showed greater expression of negative regulatory and catabolism genes while A. gerardii upregulated cellular and protein metabolism. As predicted, S. nutans showed greater sensitivity to water stress, particularly with downregulation of non-coding RNAs and upregulation of water stress and catabolism genes. A. gerardii was less sensitive to drought, although A. gerardii tended to respond with upregulation in response to drought versus S. nutans which downregulated more genes under drier conditions. Surprisingly, A. gerardii only showed minimal gene expression response to increased temperature, while S. nutans showed no response. Gene functional annotation suggested that these two species may respond to stress via different mechanisms. Specifically, A. gerardii tends to maintain molecular function while S. nutans prioritizes avoidance. Sorghastrum nutans may strategize abscisic acid response and catabolism to respond rapidly to stress. These results have important implications for success of these two important grass species under a more variable and extreme climate forecast for the future.

}, keywords = {LTER-KNZ}, doi = {https://doi.org/10.7717/peerj.4394}, url = {https://peerj.com/articles/4394/}, author = {Hoffman, Ava M. and M.L. Avolio and Alan K. Knapp and M.D. Smith} } @article {KNZ001899, title = {Linking gene regulation, physiology, and plant biomass allocation in Andropogon gerardii in response to drought}, journal = {Plant Ecology}, volume = {219}, year = {2018}, pages = {1 - 15}, abstract = {

Plant responses to drought are often initiated at the molecular level and cascade upwards to affect physiology and growth. How plants respond to and recover from drought have consequences for their growth and survival in drier climates predicted with climate change. We studied four ecologically relevant genotypes of a common C4 grass, Andropogon gerardii. These genotypes had differential responses to a decade of more variable precipitation patterns in a field experiment in native tallgrass prairie. Here, we conducted a greenhouse experiment examining how these genotypes responded to repeated 10-day drought-recovery cycles when experiencing either a severe or moderate drought. We did this twice over the course of the experiment, early, after 5\ weeks, and late, after 9\ weeks of drought. We studied nine genes involved in water stress signaling and drought response in leaf tissue using real-time reverse-transcriptase polymerase chain reaction (qRT-PCR). We also measured photosynthesis, stomatal conductance, and biomass accumulation and allocation. In early drought, we found consistent differences among genotypes in gene expression, leaf-level physiology, and biomass accumulation and allocation. We found genes involved in ABA, proline synthesis, and mitigating oxidative stress were differentially expressed between genotypes, while genes that coded for aquaporins and chaperones were not. In late drought, we found fewer overall differences, and little regulation of drought responsive genes. Ultimately, we found genotypes either had greater phenotypic plasticity, suggesting an ability to avoid drought and maximize water resources when they were present, or genotypes were better at tolerating drought.

}, keywords = {LTER-KNZ}, doi = {10.1007/s11258-017-0773-3}, url = {http://link.springer.com/10.1007/s11258-017-0773-3}, author = {M.L. Avolio and Hoffman, Ava M. and M.D. Smith} } @article {KNZ001842, title = {Asynchrony among local communities stabilises ecosystem function of metacommunities}, journal = {Ecology Letters}, year = {2017}, abstract = {

Temporal stability of ecosystem functioning increases the predictability and reliability of ecosystem services, and understanding the drivers of stability across spatial scales is important for land management and policy decisions. We used species-level abundance data from 62 plant communities across five continents to assess mechanisms of temporal stability across spatial scales. We assessed how asynchrony (i.e. different units responding dissimilarly through time) of species and local communities stabilised metacommunity ecosystem function. Asynchrony of species increased stability of local communities, and asynchrony among local communities enhanced metacommunity stability by a wide range of magnitudes (1\–315\%); this range was positively correlated with the size of the metacommunity. Additionally, asynchronous responses among local communities were linked with species\’ populations fluctuating asynchronously across space, perhaps stemming from physical and/or competitive differences among local communities. Accordingly, we suggest spatial heterogeneity should be a major focus for maintaining the stability of ecosystem services at larger spatial scales.

}, keywords = {LTER-KNZ, Alpha diversity, alpha variability, beta diversity, Biodiversity, CoRRE data base, patchiness, Plant communities, Primary productivity, species synchrony}, doi = {10.1111/ele.12861}, url = {http://onlinelibrary.wiley.com/doi/10.1111/ele.12861/epdf}, author = {K.R. Wilcox and Tredennick, Andrew T. and Koerner, Sally E. and Grman, Emily and Hallett, Lauren M. and M.L. Avolio and Kimberly J. La Pierre and Houseman, Gregory R. and Isbell, Forest and Johnson, David Samuel and Juha M. Alatalo and Baldwin, Andrew H. and Edward W. Bork and Elizabeth H. Boughton and W.D. Bowman and Britton, Andrea J. and Cahill, James F. and Scott. L. Collins and G. Du and Eskelinen, Anu and Gough, Laura and Jentsch, Anke and Kern, Christel and Klanderud, Kari and Alan K. Knapp and Kreyling, Juergen and Luo, Yiqi and McLaren, Jennie R. and Megonigal, Patrick and Onipchenko, Vladimir and Prev{\'e}y, Janet and Price, Jodi N. and Robinson, Clare H. and Sala, Osvaldo E. and M.D. Smith and Soudzilovskaia, Nadejda A. and Souza, Lara and Tilman, David and White, Shannon R. and Xu, Zhuwen and Yahdjian, Laura and Yu, Qiang and Zhang, Pengfei and Zhang, Yunhai}, editor = {Gurevitch, Jessica} } @article {KNZ001783, title = {Pushing precipitation to the extremes in distributed experiments: recommendations for simulating wet and dry years}, journal = {Global Change Biology}, volume = {23}, year = {2017}, pages = {1774-1782}, abstract = {

Intensification of the global hydrological cycle, ranging from larger individual precipitation events to more extreme multiyear droughts, has the potential to cause widespread alterations in ecosystem structure and function. With evidence that the incidence of extreme precipitation years (defined statistically from historical precipitation records) is increasing, there is a clear need to identify ecosystems that are most vulnerable to these changes and understand why some ecosystems are more sensitive to extremes than others. To date, opportunistic studies of naturally occurring extreme precipitation years, combined with results from a relatively small number of experiments, have provided limited mechanistic understanding of differences in ecosystem sensitivity, suggesting that new approaches are needed. Coordinated distributed experiments (CDEs) arrayed across multiple ecosystem types and focused on water can enhance our understanding of differential ecosystem sensitivity to precipitation extremes, but there are many design challenges to overcome (e.g., cost, comparability, standardization). Here, we evaluate contemporary experimental approaches for manipulating precipitation under field conditions to inform the design of \‘Drought-Net\’, a relatively low-cost CDE that simulates extreme precipitation years. A common method for imposing both dry and wet years is to alter each ambient precipitation event. We endorse this approach for imposing extreme precipitation years because it simultaneously alters other precipitation characteristics (i.e., event size) consistent with natural precipitation patterns. However, we do not advocate applying identical treatment levels at all sites \– a common approach to standardization in CDEs. This is because precipitation variability varies \>fivefold globally resulting in a wide range of ecosystem-specific thresholds for defining extreme precipitation years. For CDEs focused on precipitation extremes, treatments should be based on each site\&$\#$39;s past climatic characteristics. This approach, though not often used by ecologists, allows ecological responses to be directly compared across disparate ecosystems and climates, facilitating process-level understanding of ecosystem sensitivity to precipitation extremes.

}, keywords = {LTER-KNZ}, doi = {10.1111/gcb.13504}, url = {https://onlinelibrary.wiley.com/doi/abs/10.1111/gcb.13504}, author = {Alan K. Knapp and M.L. Avolio and Beier, C. and Carroll, C.J.W. and Scott. L. Collins and Dukes, J.S. and Fraser, L.H. and Griffin-Nolan, R.J. and Hoover, D.L. and Jentsch, A. and Loik, M.E. and Phillips, R.P. and Post, A.K. and Sala, O.E. and Slette, I.J. and Yahdjian, L. and M.D. Smith} } @article {KNZ001869, title = {Gene expression patterns of two dominant tallgrass prairie species differ in response to warming and altered precipitation}, journal = {Scientific Reports}, volume = {6}, year = {2016}, pages = {25522}, abstract = {

To better understand the mechanisms underlying plant species responses to climate change, we compared transcriptional profiles of the co-dominant C4 grasses, Andropogon gerardii Vitman and Sorghastrum nutans (L.) Nash, in response to increased temperatures and more variable precipitation regimes in a long-term field experiment in native tallgrass prairie. We used microarray probing of a closely related model species (Zea mays) to assess correlations in leaf temperature (Tleaf) and leaf water potential (LWP) and abundance changes of ~10,000 transcripts in leaf tissue collected from individuals of both species. A greater number of transcripts were found to significantly change in abundance levels with Tleaf and LWP in S. nutans than in A. gerardii. S. nutans also was more responsive to short-term drought recovery than A. gerardii. Water flow regulating transcripts associated with stress avoidance (e.g., aquaporins), as well as those involved in the prevention and repair of damage (e.g., antioxidant enzymes, HSPs), were uniquely more abundant in response to increasing Tleaf in S. nutans. The differential transcriptomic responses of the co-dominant C4 grasses suggest that these species may cope with and respond to temperature and water stress at the molecular level in distinct ways, with implications for tallgrass prairie ecosystem function.

}, keywords = {LTER-KNZ}, doi = {10.1038/srep25522}, url = {https://www.nature.com/articles/srep25522}, author = {M.D. Smith and Hoffman, A.M. and M.L. Avolio} } @article {KNZ001733, title = {Nutrient additions cause divergence of tallgrass prairie plant communities resulting in loss of ecosystem stability}, journal = {Journal of Ecology}, volume = {104}, year = {2016}, pages = {1478-1487}, abstract = {

1.Nitrogen (N) and phosphorus (P) deposition due to pollution and land-use change are dramatically altering biogeochemical cycles. These altered nutrient inputs affect plant communities by generally increasing dominance and reducing diversity, as well as altering community variability (heterogeneity). Less well studied are effects of changes in community variability on ecosystem functions, such as productivity, or the stability of those functions. 2.Here we use a twelve-year nutrient addition experiment in tallgrass prairie to determine variability in community responses to N and P additions and link these responses to ecosystem productivity and stability. We added two levels of N and four levels of P in a fully factorial design to 25-m2 plots in native tallgrass prairie in northeastern Kansas, USA. Each year percent cover of each species was measured in June and August in a 1-m2 subplot of each plot, and annual net primary productivity was measured in two 0.1-m2 subplots in each plot at the end of each growing season. 3.The addition of N and P together increased plant community variability across space (i.e., the replicates were significantly more different from each other in the N + P treatments than they were in the control treatment). We also found that variability of the plant community within a single plot through time increased with the addition of N alone and N and P together. The highest level of both spatial and temporal variability occurred in plots with the highest level of nutrient addition (10 g m\−2 of both N and P). 4.While we found no linkage between spatial variability of community composition and the spatial stability of productivity, the temporal stability of productivity decreased with increasing temporal plant community variability. Additionally, the ability to predict the productivity response to growing season precipitation, a key environmental variable, also decreased under higher temporal community variability. 5.Synthesis. Using a 12-yr nutrient addition experiment, we found that nutrient addition leads to both spatial and temporal community variability in mesic tallgrass prairie. The changes in community variability through time were directly related to ecosystem stability. While overall shifts in community structure in response to nutrient additions are important, the change in variability of local communities has significant implications for our ability to predict how patterns of biodiversity and ecosystem function will respond to a rapidly changing world.

}, keywords = {LTER-KNZ}, doi = {10.1111/1365-2745.12610}, url = {https://besjournals.onlinelibrary.wiley.com/doi/full/10.1111/1365-2745.12610}, author = {Koerner, S.E. and M.L. Avolio and Kimberly J. La Pierre and K.R. Wilcox and M.D. Smith and Scott. L. Collins} } @article {KNZ001684, title = {Characterizing differences in precipitation regimes of extreme wet and dry years: Implications for climate change experiments}, journal = {Global Change Biology}, volume = {21}, year = {2015}, pages = {2624 -2633}, abstract = {

Climate change is intensifying the hydrologic cycle and is expected to increase the frequency of extreme wet and dry years. Beyond precipitation amount, extreme wet and dry years may differ in other ways, such as the number of precipitation events, event size, and the time between events. We assessed 1614 long-term (100 year) precipitation records from around the world to identify key attributes of precipitation regimes, besides amount, that distinguish statistically extreme wet from extreme dry years. In general, in regions where mean annual precipitation (MAP) exceeded 1000 mm, precipitation amounts in extreme wet and dry years differed from average years by ~40\% and 30\%, respectively. The magnitude of these deviations increased to \>60\% for dry years and to \>150\% for wet years in arid regions (MAP\<500 mm). Extreme wet years were primarily distinguished from average and extreme dry years by the presence of multiple extreme (large) daily precipitation events (events \>99th percentile of all events); these occurred twice as often in extreme wet years compared to average years. In contrast, these large precipitation events were rare in extreme dry years. Less important for distinguishing extreme wet from dry years were mean event size and frequency, or the number of dry days between events. However, extreme dry years were distinguished from average years by an increase in the number of dry days between events. These precipitation regime attributes consistently differed between extreme wet and dry years across 12 major terrestrial ecoregions from around the world, from deserts to the tropics. Thus, we recommend that climate change experiments and model simulations incorporate these differences in key precipitation regime attributes, as well as amount into treatments. This will allow experiments to more realistically simulate extreme precipitation years and more accurately assess the ecological consequences.

}, keywords = {LTER-KNZ, rainfall patterns}, doi = {10.1111/gcb.12888}, url = {https://onlinelibrary.wiley.com/doi/abs/10.1111/gcb.12888}, author = {Alan K. Knapp and D.L. Hoover and K.R. Wilcox and M.L. Avolio and Koerner, S.E. and Kimberly J. La Pierre and Loik, M.E. and Luo, Y. and Sala, O.E. and M.D. Smith} } @article {KNZ001657, title = {The effects of genotype richness and genomic dissimilarity of Andropogon gerardii on invasion resistance and productivity}, journal = {Plant Ecology and Diversity}, volume = {8}, year = {2015}, pages = {61 -71}, abstract = {

Background: The genetic diversity within populations has been shown to affect ecosystem functions, including productivity and invasion resistance. To date most experiments have focused on manipulation of genotypic richness and have ignored other measures of genetic diversity. Aims: In the present study we aimed to establish whether manipulated genotypic richness and genomic dissimilarity of Andropogon gerardii affect productivity and invasion resistance. Methods: We created experimental mesocosms with three levels of genotypic richness: one-, three-, and nine-genotypes. In the three-genotype treatment, we manipulated a range of genomic dissimilarity values (genetic relatedness among individuals). At the end of one growing season we measured above-ground, below-ground and total biomass of the mesocosms, and invasion resistance to Andropogon bladhii. Results: Overall, we found no significant effect of genotypic richness on any measure of ecosystem function, although there tended to be more root biomass (due to complementarity) and invasive seedling biomass with higher levels of genotypic richness. Within the three-genotype treatment we found a significant positive relationship between genomic dissimilarity and above-ground biomass, which was caused by a selection effect. We also found a positive relationship between genomic dissimilarity and biomass of A. bladhii. Conclusions: Using these two measures of genetic diversity we detected differences in the strength and mechanism of positive diversity effects within the same experiment, demonstrating the value of manipulating multiple measures of diversity when performing biodiversity\–ecosystem function experiments.

}, keywords = {LTER-KNZ, Andropogon bladhii, biodiversity ecosystem function, complementarity, dominant species, genomic dissimilarity, genotypic richness, invasion resistance, productivity, tallgrass prairie}, doi = {10.1080/17550874.2013.866990}, url = {https://www.tandfonline.com/doi/abs/10.1080/17550874.2013.866990}, author = {M.L. Avolio and Chang, C.C. and Weis, J.J. and M.D. Smith} } @article {KNZ001701, title = {Invasibility of a mesic grassland depends on the time-scale of fluctuating resources}, journal = {Journal of Ecology}, volume = {103}, year = {2015}, pages = {1538 - 1546}, abstract = {

1. Global change is increasing the frequency and magnitude of resource fluctuations (pulses) at multiple time-scales. According to the fluctuating resource availability hypothesis (FRAH), susceptibility of an ecosystem to invasion (i.e. invasibility) is expected to increase whenever resource supply exceeds that which is utilized by native communities. Thus, global change has the potential to increase invasibility around the world. 2. Here, we test the FRAH by adding seeds of a target invader grass species to a long-term climate change experiment manipulating precipitation pulse size in tallgrass prairie in Kansas, USA. 3. Our experimental work yielded three important findings. First, contrary to predictions of the FRAH, invasibility was reduced with short time-scale resource pulses (intra-annual time-scale). Secondly, we found evidence to suggest that at inter-annual time-scales, the FRAH is supported. Wet years resulted in an increase in the number of established seedlings as well as the number of seedlings that persisted to the end of the season. Finally, we found that invasibility was positively related to native community richness and the density of individuals in the community suggesting that native communities facilitate establishment of invader species. Perhaps more importantly, results from this 10-year invasion study also show that resource availability drives invasion and that the biotic filters of plant community structure and diversity are secondary. 4. Synthesis. Our findings suggest that intensification of precipitation regimes may enhance resistance to invasion at intra-annual time-scales, but will have opposing effects if precipitation regimes include more wet years.

}, keywords = {LTER-KNZ}, doi = {10.1111/1365-2745.12479}, url = {https://besjournals.onlinelibrary.wiley.com/doi/full/10.1111/1365-2745.12479}, author = {Koerner, S.E. and M.L. Avolio and Chang, C.C. and Grey, J. and D.L. Hoover and M.D. Smith} } @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} } @article {KNZ001546, title = {Correlations between genetic and species diversity: effects of resource quantity and heterogeneity}, journal = {Journal of Vegetation Science}, volume = {24}, year = {2013}, pages = {1185 -1194}, abstract = {

Questions It is hypothesized that species and genetic diversity are correlated because niche differentiation among species and genotypes is either affected by the same processes (positive) or each level restricts the amount of diversity in the other (negative). Although many studies have observed both positive and negative relationships, others have found no correlation between the two diversity measures. Are measures of species (richness, diversity and evenness) and genetic diversity correlated, and how does resource (soil moisture, light, nitrogen and phosphorus) quantities and heterogeneity affect both levels of diversity? Location Intact tallgrass prairie at Konza Prairie Biological Station, northeast Kansas, US. Methods We investigate the correlation between plant species and genetic diversity in a long-term precipitation manipulation experiment \– the Rainfall Manipulation Plots (RaMPs) \– located in intact tallgrass prairie as well as adjacent non-manipulated prairie. The RaMPs experiment has been imposing ambient and more variable precipitation regimes (a 50\% increase in timing between rainfall events without changing total rainfall amount) during the growing season since 1998, resulting in reduced mean soil moisture and increased soil moisture variability. Thus, the RaMPs and non-manipulated prairie plots capture a range of soil moisture amounts and variability. Genetic diversity (measured as genotype richness and genomic dissimilarity among individuals) was quantified for the dominant grass species, Andropogon gerardii, which has large impacts on plant community structure and ecosystem function. Results We found species and genetic diversity were not significantly correlated. Genotypic richness was negatively related to soil moisture variability, but measures of species diversity were not. In the non-manipulated plots only, we found generally negative relationships between resource quantity (light and nitrogen) and community diversity, and positive relationships between resource heterogeneity (CV of light) and community diversity. Conclusions Our results suggest that a lack of a positive or negative relationship between species and genetic diversity could be due to these two levels of diversity responding differently to the identity, quantity and heterogeneity of resources.

}, keywords = {LTER-KNZ, Andropogon gerardii, C4 grass, dominant species, grassland, Resource heterogeneity, Resource quantity, Species genetic diversity correlation}, doi = {10.1111/jvs.12042}, url = {https://onlinelibrary.wiley.com/doi/abs/10.1111/jvs.12042}, author = {M.L. Avolio and M.D. Smith} } @article {KNZ001505, title = {Genetic diversity of a dominant C4 grass is altered with increased precipitation variability}, journal = {Oecologia}, volume = {171}, year = {2013}, pages = {571 -581}, abstract = {

Climate change has the potential to alter the genetic diversity of plant populations with consequences for community dynamics and ecosystem processes. Recent research focused on changes in climatic means has found evidence of decreased precipitation amounts reducing genetic diversity. However, increased variability in climatic regimes is also predicted with climate change, but the effects of this aspect of climate change on genetic diversity have yet to be investigated. After 10 years of experimentally increased intra-annual variability in growing season precipitation regimes, we report that the number of genotypes of the dominant C4 grass, Andropogon gerardii Vitman, has been significantly reduced in native tallgrass prairie compared with unmanipulated prairie. However, individuals showed a different pattern of genomic similarity with increased precipitation variability resulting in greater genome dissimilarity among individuals when compared to unmanipulated prairie. Further, we found that genomic dissimilarity was positively correlated with aboveground productivity in this system. The increased genomic dissimilarity among individuals in the altered treatment alongside evidence for a positive correlation of genomic dissimilarity with phenotypic variation suggests ecological sorting of genotypes may be occurring via niche differentiation. Overall, we found effects of more variable precipitation regimes on population-level genetic diversity were complex, emphasizing the need to look beyond genotype numbers for understanding the impacts of climate change on genetic diversity. Recognition that future climate change may alter aspects of genetic diversity in different ways suggests possible mechanisms by which plant populations may be able to retain a diversity of traits in the face of declining biodiversity.

}, keywords = {LTER-KNZ, AFLP, Andropogon gerardii, Dice dissimilarity, dominant species, Genotypic structure}, doi = {10.1007/s00442-012-2427-4}, url = {https://link.springer.com/article/10.1007\%2Fs00442-012-2427-4}, author = {M.L. Avolio and Beaulieu, J. and M.D. Smith} } @article {KNZ002018, title = {Intra-specific responses of a dominant C4 grass to altered precipitation patterns}, journal = {Plant Ecology}, volume = {214}, year = {2013}, pages = {1377 - 1389}, abstract = {

The mechanisms by which global change alters the genotypic structure of populations by selection remain unclear. Key to this understanding is elucidating genotype\–phenotype relationships under different environmental conditions as genotypes could differ in their plasticity or in their tolerance to changing environmental conditions. We have previously observed selection of certain genotypes of the dominant C4 grass Andropogon gerardii L. within the on-going Rainfall Manipulation Plots (RaMPs) experiment at Konza Prairie Biological Station in Kansas. The RaMPs experiment has been experimentally imposing ambient and more variable (altered) precipitation patterns since 1998. Here, we studied phenotypic differences among six genotypes to gain insight into what drove the pattern of selection previously observed and assess potential genotype \× environmental interactions. In 2008 and 2009 we sampled individuals of genotypes in the RaMPs and within unmanipulated reference plots located adjacent to the RaMPs experiment. For each individual, we measured both leaf-level (specific leaf area, stomatal conductance) and whole-plant growth (height, biomass) traits. We consistently detected differences among genotypes in the reference plots. Additionally, when focusing on two genotypes found in the altered and ambient RaMPs we observed no genotype \× environment interactions. Overall, we found in an intact population of A. gerardii there exists phenotypic variability among genotypes, but no genotype \× environment interactions. Thus our results demonstrate that differences in plasticity of genotypes do no explain the pattern of selection we observed.

}, keywords = {LTER-KNZ}, doi = {10.1007/s11258-013-0258-y}, url = {http://link.springer.com/10.1007/s11258-013-0258-y}, author = {M.L. Avolio and M.D. Smith} } @article {KNZ001543, title = {Mechanisms of selection: Phenotypic differences among genotypes explain patterns of selection in a dominant species}, journal = {Ecology}, volume = {94}, year = {2013}, pages = {953 -965}, abstract = {

Predicted changes in precipitation means and variability are expected to alter genotype composition of plant populations; however, it remains unclear whether selection will be for trait differences among genotypes or phenotypic plasticity. This is especially true for more variable precipitation patterns that simultaneously alter soil moisture means and variability. In a previous study we found that a decade of more variable growing-season precipitation patterns changed the genotypic composition of a dominant C4 grass population (Andropogon gerardii) in native tallgrass prairie located in northeastern Kansas. Here, we assessed potential mechanisms underlying the changes observed in population structure of this species by studying how changes in both the size and variability of watering events affected ecophysiological, growth, biomass-allocation, and fitness traits of five common genotypes of A. gerardii in a greenhouse experiment. Three of these genotypes had greater abundances or were only present in field plots receiving 10 years of greater intra-annual variability in growing-season precipitation patterns. In a fully factorial experiment, we subjected the five genotypes to three water amounts (average for Kansan study site, a 40\% decrease, and a 60\% increase) and two watering frequency treatments (every 5 or 10 days) to produce differences in soil moisture amount and variability, respectively. We found genotype \× water amount interactions for traits related to leaf-level physiology and biomass allocation; in many cases genotypes that performed better under low soil moisture conditions were outperformed by other genotypes under high soil moisture conditions. For the three genotypes that had greater abundance in field plots that received more variable precipitation patterns, we found evidence that genotypes differed in their allocation to above- vs. belowground biomass, demonstrating phenotypic trait divergence. Our results suggest that a genetically diverse population can have enough trait variation among genotypes for adaptation to occur, and thus, for dominant species, microevolution may be an important aspect of adaptation to changing environmental conditions.

}, keywords = {LTER-KNZ}, doi = {10.1890/12-1119.1}, url = {https://esajournals.onlinelibrary.wiley.com/doi/abs/10.1890/12-1119.1}, author = {M.L. Avolio and M.D. Smith} } @phdthesis {KNZ001480, title = {Genetic diversity of Andropogon gerardii: Impacts of altered precipitation patterns on a dominant species}, volume = {PhD Dissertation}, year = {2012}, pages = {1 -258}, school = {Yale University}, type = {Ph.D. Thesis}, address = {New Haven, CT}, abstract = {

Global change is expected to shift climatic regimes and cause whole communities of organisms to experience novel environments. Key aspects of forecast climate change are alterations in both the amount of precipitation and the variability of precipitation regimes. The ability of a population to adapt will depend on the genetic diversity of the population, and the traits of the genotypes present in the population. Here, I assess the response a dominant C4 tallgrass population to novel environmental conditions resulting from forecast climate change by studying whether more variable precipitation patterns affect the genetic diversity of Andropogon gerardii. I then investigate the potential mechanisms driving the observed response. Ultimately, the way in which population genetic diversity is affected by more variable precipitation patterns will shed insight into how this important species will adapt to future climate change. First, I developed the tools to study the genetic diversity of A. gerardii at the plant neighborhood scale, the scale at which individuals compete for resources. I designed amplified fragment length polymorphism primers for A. gerardii and determined the appropriate scale at which to sample individuals to accurately capture genetic diversity. I also examined how genetic diversity is measured in ecological studies by comparing genotype-based measures and genome-based measures of diversity. Ultimately, I argue that genome-based measures should be included in future studies alongside genotypic-based measures because they capture a greater spectrum of genetic differences among individuals. Next, using what I established for studying genetic diversity, I examined how a decade of altered precipitation patterns affected the genetic diversity of A. gerardii. To do this I worked within the Rainfall Manipulation Plots (RaMPs) experiment at Konza Prairie Biological Station in Kansas, which experimentally imposes ambient and more variable precipitation patterns. After ten years of experimentally increased intra-annual variability in growing season precipitation regimes, I report that the number of genotypes of the dominant C4 grass, Andropogon gerardii Vitman, has been significantly reduced in native tallgrass prairie compared with unmanipulated prairie. However, individuals showed a different pattern of genomic similarity with increased precipitation variability \– there was greater genome dissimilarity among individuals when compared to unmanipulated prairie. In my next two chapters, I aim to understand the mechanism that drove the observed shift in genetic diversity. First, I studied phenotypic differences among six common genotypes of Andropogon gerardii across three different environmental conditions to study genotype \× environmental interactions. I consistently detected differences among the focal genotypes for all traits measured across environmental treatments, however, I observed no genotype \× year interactions, and phenotypic differences among genotypes were diminished within environmental conditions. To assess potential mechanisms underlying the changes observed in population structure of this species, I continued to study five of the same genotypes, three of which had greater abundances or were only present in plots receiving more variable rainfall patterns. In a greenhouse study, I investigated how both changes in the size and variability of watering events affected ecophysiological, growth, biomass allocation and fitness traits. I found genotype \× water amount interactions for traits related to leaf level physiology and biomass allocation; genotypes that performed better under low soil moisture conditions were outperformed by other genotypes under high soil moisture conditions. For the three genotypes that had greater abundance in plots that received a decade of altered rainfall regimes, I found evidence of phenotypic trait divergence as well as greater plasticity for ecophysiological traits. Lastly, I investigated correlations between species and genetic diversity in tallgrass prairie across an experimental manipulation of soil moisture. I found species and genetic diversity were not correlated, and that genotypic richness was negatively related to soil moisture variability, but measures of species diversity were not related to soil moisture. My results suggest that a lack relationship between species and genetic diversity at the populations scale could be because species and genetic diversity are responding differently to environmental resources. Ultimately, my dissertation is an in-depth examination of how environmental conditions affect the genetic diversity of a dominant species. I found that for genetically diverse species, such as dominant species, microevolution might be an important aspect of adaptation to novel environmental conditions experienced with climate change.

}, keywords = {LTER-KNZ}, url = {http://search.proquest.com/docview/1272028956}, author = {M.L. Avolio} } @article {KNZ001481, title = {Measuring genetic diversity in ecological studies}, journal = {Plant Ecology}, volume = {213}, year = {2012}, pages = {1105 -1115}, abstract = {

There is an increasing interest in how genetic diversity may correlate with and influence community and ecosystem properties. Genetic diversity can be defined in multiple ways, and currently lacking in ecology is a consensus on how to measure genetic diversity. Here, we examine two broad classes of genetic diversity: genotype-based and genome-based measures. Genotype-based measures, such as genotypic richness, are more commonly used in ecological studies, and often it is assumed that as genotypic diversity increases, genomic diversity (the number of genetic polymorphisms and/or genomic dissimilarity among individuals) also increases. However, this assumption is rarely assessed. We tested this assumption by investigating correlations between genotype- and genome-based measures of diversity using two plant population genetic datasets: one observational with data collected at Konza Prairie, KS, and the other based on simulated populations with five levels of genotypic richness, a typical design of genetic diversity experiments. We found conflicting results for both datasets; we found a mismatch between genotypic and genomic diversity measures for the field data, but not the simulated data. Last, we tested the consequences of this mismatch and found that correlations between genetic diversity and community/ecosystem properties depended on metric used. Ultimately, we argue that genome-based measures should be included in future studies alongside genotypic-based measures because they capture a greater spectrum of genetic differences among individuals.

}, keywords = {LTER-KNZ, Community diversity, Ecosystem function, Genome diversity, Phenotype, SGDC}, doi = {10.1007/s11258-012-0069-6}, url = {https://link.springer.com/article/10.1007\%2Fs11258-012-0069-6}, author = {M.L. Avolio and Beaulieu, J. and Lo, E. and M.D. Smith} } @article {KNZ001420, title = {Assessing fine-scale genotypic structure of a dominant species in native grasslands}, journal = {The American Midland Naturalist}, volume = {165}, year = {2011}, pages = {211 -224}, abstract = {

Genotypic diversity of dominant species has been shown to have important consequences for community and ecosystem processes at a fine spatial scale. We examined the fine-scale (i.e., plant neighborhood scale, \<1 m2) genotypic structure of Andropogon gerardii, a dominant species in the tallgrass prairie, which is a productive and endangered grassland ecosystem, employing the commonly used amplified fragment length polymorphism (AFLP) technique. In this paper we used two methods to assess the fine-scale genetic spatial structure of a dominant perennial grass, (1) we determined how many tillers to sample in a 1 m2 area and (2) we developed AFLP markers that would differentiate between genotypes. By determining appropriate sampling and molecular techniques, our findings can be applied to questions addressing how genetic diversity of dominant species affect ecosystem processes in the tallgrass prairie.

}, keywords = {LTER-KNZ}, doi = {10.1674/0003-0031-165.2.211}, url = {https://doi.org/10.1674/0003-0031-165.2.211}, author = {M.L. Avolio and Chang, C.C. and M.D. Smith} } @article {KNZ001411, title = {Explaining temporal variation in above-ground productivity in a mesic grassland: the role of climate and flowering}, journal = {Journal of Ecology}, volume = {99}, year = {2011}, pages = {1250 -1262}, abstract = {

1. Annual above-ground net primary productivity (ANPP) in mesic grasslands is known to be highly temporally variable. While yearly precipitation or average yearly temperature can explain some of this temporal variability, much of the variation in ANPP remains unexplained. 2. Here we address the heretofore unexplained variation in 25 years of productivity data from a mesic grassland at Konza Prairie (north-eastern Kansas) by examining the effects of precipitation and temperature during periods relevant to the phenology and growth cycle of the dominant C4 grasses and the flowering stalk production of these species. We assessed both the direct effects and indirect effects via flowering of phenologically relevant climate periods on ANPP using structural equation modelling (SEM). 3. We found ANPP to be strongly positively influenced by flowering stalk production of the dominant C4 grasses, precipitation during periods relevant to vegetative growth (15 April\–14 July) and flowering stalk elongation (15 July\–14 August) of the dominant grasses, and fire. In addition, flowering stalk production was negatively influenced by high temperatures during the flowering stalk elongation period, which therefore resulted in a negative indirect effect on ANPP. We found little evidence for the effects of the previous year\’s total annual precipitation or mean annual temperature on ANPP. 4. By including flowering stalk production and separating climate variables into phenologically relevant periods we were able to increase the percentage of observed variance in ANPP explained by six models, relating to different topographic positions and burn regimes, from an average of 22\% to 48\%, with the best model explaining 61\% of variation in ANPP. 5.Synthesis. The link between climatic periods relevant to the phenology and growth of dominant C4 grasses, flowering stalk production of these grasses and ANPP shown here improves our ability to predict productivity in mesic grasslands, an ecologically and economically important ecosystem.

}, keywords = {LTER-KNZ}, doi = {10.1111/j.1365-2745.2011.01844.x}, url = {https://besjournals.onlinelibrary.wiley.com/doi/full/10.1111/j.1365-2745.2011.01844.x}, author = {Kimberly J. La Pierre and Yuan, S.H. and Chang, C.C. and M.L. Avolio and Hallett, L.M. and Schreck, T. and M.D. Smith} }