@article {5993, title = {Effects of compounded precipitation pattern intensification and drought occur belowground in a mesic grassland}, journal = {Ecosystems}, year = {2021}, abstract = {

Climate change is altering precipitation regimes globally, with expectations of intensified precipitation patterns (for example, larger but fewer rainfall events) and more frequent and extreme drought. Both aspects of precipitation change can impact ecosystem function individually, but it is more likely that they will occur in combination. In a central US mesic grassland, we imposed an extreme 2-year drought (growing season precipitation reduced by 66\%) on plots with a long-term (16-year) history of exposure to either ambient or intensified precipitation patterns (average threefold increase in event size and threefold decrease in event number during the growing season). While this intensified pattern did not alter total precipitation amount, it generally led to ecosystem responses consistent with a drier environment (for example, reduced soil moisture, aboveground net primary production (ANPP), and soil CO2 flux, but little evidence for altered root biomass). Surprisingly, this history of intensified precipitation patterns did not affect the response of ANPP to the subsequent extreme drought. In contrast, previous exposure to intensified precipitation patterns reduced root production and muted soil CO2 flux responses to rainfall events during drought. Reduced root production in plots experiencing compounded precipitation extremes was driven not by the dominant C4 grass species, Andropogon gerardii, but collectively by the subdominant species in the plant community. Overall, our results reveal that compound changes in precipitation patterns and amount affected this grassland in ways that were less apparent (that is, belowground) than responses to either change individually and significantly reduced ecosystem carbon uptake.

}, keywords = {LTER-KNZ}, doi = {10.1007/s10021-021-00714-9}, url = {https://doi.org/10.1007/s10021-021-00714-9}, author = {Slette, I.J. and J. M. Blair and Fay, P.A. and M. D. Smith and Alan K. Knapp} } @article {KNZ002041, title = {Increasing effects of chronic nutrient enrichment on plant diversity loss and ecosystem productivity over time}, journal = {Ecology}, volume = {102}, year = {2021}, pages = {e03218}, abstract = {

Human activities are enriching many of Earth\’s ecosystems with biologically limiting mineral nutrients such as nitrogen (N) and phosphorus (P). In grasslands, this enrichment generally reduces plant diversity and increases productivity. The widely demonstrated positive effect of diversity on productivity suggests a potential negative feedback, whereby nutrient-induced declines in diversity reduce the initial gains in productivity arising from nutrient enrichment. In addition, plant productivity and diversity can be inhibited by accumulations of dead biomass, which may be altered by nutrient enrichment. Over longer timeframes, nutrient addition may increase soil fertility by increasing soil organic matter and nutrient pools. We examined the effects of 5-11 years of nutrient addition at 47 grasslands in twelve countries. Nutrient enrichment increased aboveground live biomass and reduced plant diversity at nearly all sites, and these effects became stronger over time. We did not find evidence that nutrient-induced losses of diversity reduced the positive effects of nutrients on biomass, however nutrient effects on live biomass increased more slowly at sites where litter was also increasing, regardless of plant diversity. This work suggests that short-term experiments may underestimate the long-term nutrient enrichment effects on global, grassland ecosystems.

}, keywords = {LTER-KNZ}, doi = {10.1002/ecy.3218}, url = {https://onlinelibrary.wiley.com/doi/10.1002/ecy.3218}, author = {Seabloom, E.W. and Adler, P.B. and Alberti, J. and Biederman, L. and Buckley, Y.M. and Cadotte, M.W. and S.L Collins and Dee, L. and Fay, P.A. and Firn, J. and Hagenah, N. and Harpole, W. S. and Hautier, Y. and Hector, A. and Hobbie, S.E. and Isbell, F. and Knops, J.M.H. and Kimberly J. Komatsu and Laungani, R. and MacDougall, A. and McCulley, R.L. and Moore, J.L. and Morgan, J.W. and Ohlert, T. and Prober, S.M. and Risch, A.C. and Schuetz, M. and Stevens, C.J. and Borer, E.T.} } @article {KNZ001814, title = {How do extra nutrients affect the timing of flowering in prairies}, journal = {Environmental Science Journal for Teens}, year = {2017}, keywords = {LTER-KNZ}, url = {http://www.sciencejournalforkids.org/uploads/5/4/2/8/54289603/flowers_article.pdf}, author = {L.A. Biederman and Mortensen, Brent and Fay, P.A. and Hagenah, Nicole and Knops, Johannes and Kimberly J. La Pierre and Laungani, Ramesh and Lind, Eric and McCulley, Rebecca and Power, Sally and Seabloom, Eric and Tognetti, Pedro} } @article {KNZ001868, title = {Nutrient addition shifts plant community composition towards earlier flowering species in some prairie ecoregions in the U.S. Central Plains}, journal = {PLOS ONE}, year = {2017}, pages = {e0178440}, abstract = {

The distribution of flowering across the growing season is governed by each species\’ evolutionary history and climatic variability. However, global change factors, such as eutrophication and invasion, can alter plant community composition and thus change the distribution of flowering across the growing season. We examined three ecoregions (tall-, mixed, and short-grass prairie) across the U.S. Central Plains to determine how nutrient (nitrogen (N), phosphorus, and potassium (+micronutrient)) addition alters the temporal patterns of plant flowering traits. We calculated total community flowering potential (FP) by distributing peak-season plant cover values across the growing season, allocating each species\’ cover to only those months in which it typically flowers. We also generated separate FP profiles for exotic and native species and functional group. We compared the ability of the added nutrients to shift the distribution of these FP profiles (total and sub-groups) across the growing season. In all ecoregions, N increased the relative cover of both exotic species and C3 graminoids that flower in May through August. The cover of C4 graminoids decreased with added N, but the response varied by ecoregion and month. However, these functional changes only aggregated to shift the entire community\’s FP profile in the tall-grass prairie, where the relative cover of plants expected to flower in May and June increased and those that flower in September and October decreased with added N. The relatively low native cover in May and June may leave this ecoregion vulnerable to disturbance-induced invasion by exotic species that occupy this temporal niche. There was no change in the FP profile of the mixed and short-grass prairies with N addition as increased abundance of exotic species and C3 graminoids replaced other species that flower at the same time. In these communities a disturbance other than nutrient addition may be required to disrupt phenological patterns.

}, keywords = {LTER-KNZ}, doi = {10.1371/journal.pone.0178440}, url = {http://dx.plos.org/10.1371/journal.pone.0178440ttp}, author = {L.A. Biederman and Mortensen, B. and Fay, P.A. and Hagenah, N. and Knops, J. and Kimberly J. La Pierre and Laungani, R. and Lind, E. and McCulley, R. and Power, S. and Seabloom, E. and Tognetti, P.} } @article {KNZ001755, title = {Addition of multiple limiting resources reduces grassland diversity}, journal = {Nature}, volume = {537}, year = {2016}, pages = {93-96}, abstract = {

Niche dimensionality provides a general theoretical explanation for biodiversity\—more niches, defined by more limiting factors, allow for more ways that species can coexist1. Because plant species compete for the same set of limiting resources, theory predicts that addition of a limiting resource eliminates potential trade-offs, reducing the number of species that can coexist2. Multiple nutrient limitation of plant production is common and therefore fertilization may reduce diversity by reducing the number or dimensionality of belowground limiting factors. At the same time, nutrient addition, by increasing biomass, should ultimately shift competition from belowground nutrients towards a one-dimensional competitive trade-off for light3. Here we show that plant species diversity decreased when a greater number of limiting nutrients were added across 45 grassland sites from a multi-continent experimental network4. The number of added nutrients predicted diversity loss, even after controlling for effects of plant biomass, and even where biomass production was not nutrient-limited. We found that elevated resource supply reduced niche dimensionality and diversity and increased both productivity5 and compositional turnover. Our results point to the importance of understanding dimensionality in ecological systems that are undergoing diversity loss in response to multiple global change factors.

}, keywords = {LTER-KNZ}, doi = {10.1038/nature19324}, url = {https://www.nature.com/articles/nature19324}, author = {Harpole, W. S. and L.L. Sullivan and Lind, E.M. and Firn, J. and P. Adler and E.T. Borer and Chase, J. and Fay, P.A. and Hautier, Y. and Hillebrand, H. and MacDougall, A.S. and Seabloom, E.W. and Williams, R. and J.D. Bakker and Cadotte, M.W. and Chaneton, E.J. and Chu, C. and Cleland, E.E. and Antonio, C. and Davies, K.F. and Gruner, D.S. and Hagenah, N. and Kirkman, K. and Knops, J.M.H. and Kimberly J. La Pierre and McCulley, R.L. and Joslin L. Moore and J.W. Morgan and Prober, S.M. and A. Risch and Schuetz, M. and Stevens, C.J. and Wragg, P.D.} } @article {KNZ001747, title = {Climate modifies response of non-native and native species richness to nutrient enrichment}, journal = {Philosophical Transactions of the Royal Society B: Biological Sciences}, volume = {3719371}, year = {2016}, pages = {20150273}, abstract = {

Ecosystem eutrophication often increases domination by non-natives and causes displacement of native taxa. However, variation in environmental conditions may affect the outcome of interactions between native and non-native taxa in environments where nutrient supply is elevated. We examined the interactive effects of eutrophication, climate variability and climate average conditions on the success of native and non-native plant species using experimental nutrient manipulations replicated at 32 grassland sites on four continents. We hypothesized that effects of nutrient addition would be greatest where climate was stable and benign, owing to reduced niche partitioning. We found that the abundance of non-native species increased with nutrient addition independent of climate; however, nutrient addition increased non-native species richness and decreased native species richness, with these effects dampened in warmer or wetter sites. Eutrophication also altered the time scale in which grassland invasion responded to climate, decreasing the importance of long-term climate and increasing that of annual climate. Thus, climatic conditions mediate the responses of native and non-native flora to nutrient enrichment. Our results suggest that the negative effect of nutrient addition on native abundance is decoupled from its effect on richness, and reduces the time scale of the links between climate and compositional change.

}, keywords = {LTER-KNZ}, issn = {0962-8436}, doi = {10.1098/rstb.2015.0273}, url = {https://royalsocietypublishing.org/doi/10.1098/rstb.2015.0273}, author = {Flores-Moreno, H. and P.B. Reich and Lind, E.M. and L.L. Sullivan and Seabloom, E.W. and Yahdjian, L. and MacDougall, A.S. and Reichmann, L.G. and J. Alberti and B{\'a}ez, S. and J.D. Bakker and Cadotte, M.W. and Caldeira, M.C. and Chaneton, E.J. and D{\textquoteright}Antonio, C.M. and Fay, P.A. and Firn, J. and Hagenah, N. and Harpole, W. S. and Iribarne, O. and Kirkman, K.P. and Knops, J.M. H. and Kimberly J. La Pierre and Laungani, R. and Leakey, A.D. B. and McCulley, R.L. and Joslin L. Moore and Pascual, J. and E.T. Borer} } @article {KNZ001730, title = {Few multiyear precipitation{\textendash}reduction experiments find a shift in the productivity{\textendash}precipitation relationship}, journal = {Global Change Biology}, volume = {22}, year = {2016}, pages = {2570-2581}, abstract = {

Well-defined productivity\–precipitation relationships of ecosystems are needed as benchmarks for the validation of land models used for future projections. The productivity\–precipitation relationship may be studied in two ways: the spatial approach relates differences in productivity to those in precipitation among sites along a precipitation gradient (the spatial fit, with a steeper slope); the temporal approach relates interannual productivity changes to variation in precipitation within sites (the temporal fits, with flatter slopes). Precipitation\–reduction experiments in natural ecosystems represent a complement to the fits, because they can reduce precipitation below the natural range and are thus well suited to study potential effects of climate drying. Here, we analyse the effects of dry treatments in eleven multiyear precipitation\–manipulation experiments, focusing on changes in the temporal fit. We expected that structural changes in the dry treatments would occur in some experiments, thereby reducing the intercept of the temporal fit and displacing the productivity\–precipitation relationship downward the spatial fit. The majority of experiments (72\%) showed that dry treatments did not alter the temporal fit. This implies that current temporal fits are to be preferred over the spatial fit to benchmark land-model projections of productivity under future climate within the precipitation ranges covered by the experiments. Moreover, in two experiments, the intercept of the temporal fit unexpectedly increased due to mechanisms that reduced either water loss or nutrient loss. The expected decrease of the intercept was observed in only one experiment, and only when distinguishing between the late and the early phases of the experiment. This implies that we currently do not know at which precipitation\–reduction level or at which experimental duration structural changes will start to alter ecosystem productivity. Our study highlights the need for experiments with multiple, including more extreme, dry treatments, to identify the precipitation boundaries within which the current temporal fits remain valid.

}, keywords = {LTER-KNZ}, doi = {10.1111/gcb.13269}, url = {https://onlinelibrary.wiley.com/doi/abs/10.1111/gcb.13269}, author = {Estiarte, M. and Vicca, S. and Pe{\~n}uelas, J. and Michael Bahn and Beier, C. and Emmett, B.A. and Fay, P.A. and Hanson, P.J. and R. Hasibeder and Kigel, J. and Kr{\"o}el-Dulay, G. and Larsen, K.S. and Lellei-Kov{\'a}cs, E. and Limousin, J-M. and Ogaya, R. and Ourcival, J-M. and Reinsch, S. and Sala, O.E. and Schmidt, I.K. and Sternberg, M. and Tielb{\"o}rger, K. and Tietema, A. and Janssens, I.A.} } @article {KNZ001787, title = {Integrative modelling reveals mechanisms linking productivity and plant species richness}, journal = {Nature}, volume = {529}, year = {2016}, pages = {390 - 393}, abstract = {

How ecosystem productivity and species richness are interrelated is one of the most debated subjects in the history of ecology1. Decades of intensive study have yet to discern the actual mechanisms behind observed global patterns2, 3. Here, by integrating the predictions from multiple theories into a single model and using data from 1,126 grassland plots spanning five continents, we detect the clear signals of numerous underlying mechanisms linking productivity and richness. We find that an integrative model has substantially higher explanatory power than traditional bivariate analyses. In addition, the specific results unveil several surprising findings that conflict with classical models4, 5, 6, 7. These include the isolation of a strong and consistent enhancement of productivity by richness, an effect in striking contrast with superficial data patterns. Also revealed is a consistent importance of competition across the full range of productivity values, in direct conflict with some (but not all) proposed models. The promotion of local richness by macroecological gradients in climatic favourability, generally seen as a competing hypothesis8, is also found to be important in our analysis. The results demonstrate that an integrative modelling approach leads to a major advance in our ability to discern the underlying processes operating in ecological systems.

}, keywords = {LTER-KNZ}, doi = {10.1038/nature16524}, url = {https://www.nature.com/articles/nature16524}, author = {Grace, J.B. and Anderson, T.M. and Seabloom, E.W. and E.T. Borer and P. Adler and Harpole, W.S. and Hautier, Y. and Hillebrand, H. and Lind, E.M. and P{\"a}rtel, M. and J.D. Bakker and Buckley, Y.M. and Crawley, M.J. and Damschen, E.I. and Davies, K.F. and Fay, P.A. and Firn, J. and Gruner, D.S. and Hector, A. and Knops, J.M.H. and MacDougall, A.S. and Melbourne, B.A. and J.W. Morgan and Orrock, J.L. and Prober, S.M. and M.D. Smith} } @article {KNZ001788, title = {Grassland productivity limited by multiple nutrients}, journal = {Nature Plants}, volume = {1}, year = {2015}, pages = {15080}, abstract = {

Terrestrial ecosystem productivity is widely accepted to be nutrient limited1. Although nitrogen (N) is deemed a key determinant of aboveground net primary production (ANPP)2,3, the prevalence of co-limitation by N and phosphorus (P) is increasingly recognized4,​5,​6,​7,​8. However, the extent to which terrestrial productivity is co-limited by nutrients other than N and P has remained unclear. Here, we report results from a standardized factorial nutrient addition experiment, in which we added N, P and potassium (K) combined with a selection of micronutrients (K+μ), alone or in concert, to 42 grassland sites spanning five continents, and monitored ANPP. Nutrient availability limited productivity at 31 of the 42 grassland sites. And pairwise combinations of N, P, and K+μ co-limited ANPP at 29 of the sites. Nitrogen limitation peaked in cool, high latitude sites. Our findings highlight the importance of less studied nutrients, such as K and micronutrients, for grassland productivity, and point to significant variations in the type and degree of nutrient limitation. We suggest that multiple-nutrient constraints must be considered when assessing the ecosystem-scale consequences of nutrient enrichment.

}, keywords = {LTER-KNZ}, doi = {10.1038/nplants.2015.80}, url = {https://www.nature.com/articles/nplants201580}, author = {Fay, P.A. and Prober, S.M. and Harpole, W.S. and Knops, J.M.H. and J.D. Bakker and E.T. Borer and Lind, E.M. and MacDougall, A.S. and Seabloom, E.W. and Wragg, P.D. and P. Adler and D.M. Blumenthal and Buckley, Y.M. and Chu, C. and Cleland, E.E. and Scott. L. Collins and Davies, K.F. and G. Du and Feng, X. and Firn, J. and Gruner, D.S. and Hagenah, N. and Hautier, Y. and Heckman, R.W. and Jin, V.L. and Kirkman, K.P. and Klein, J. and L. Ladwig and Li, Q. and McCulley, R.L. and Melbourne, B.A. and Mitchell, C.E. and Joslin L. Moore and J.W. Morgan and A. Risch and sch{\"u}tz, M. and Stevens, C.J. and Wedin, D.A. and Yang, L.H.} } @article {KNZ001697, title = {Plant species{\textquoteright} origin predicts dominance and response to nutrient enrichment and herbivores in global grasslands}, journal = {Nature Communications}, volume = {6}, year = {2015}, pages = {7710 -}, abstract = {

Exotic species dominate many communities; however the functional significance of species\’ biogeographic origin remains highly contentious. This debate is fuelled in part by the lack of globally replicated, systematic data assessing the relationship between species provenance, function and response to perturbations. We examined the abundance of native and exotic plant species at 64 grasslands in 13 countries, and at a subset of the sites we experimentally tested native and exotic species responses to two fundamental drivers of invasion, mineral nutrient supplies and vertebrate herbivory. Exotic species are six times more likely to dominate communities than native species. Furthermore, while experimental nutrient addition increases the cover and richness of exotic species, nutrients decrease native diversity and cover. Native and exotic species also differ in their response to vertebrate consumer exclusion. These results suggest that species origin has functional significance, and that eutrophication will lead to increased exotic dominance in grasslands.

}, keywords = {LTER-KNZ, Biological sciences, ecology, Plant sciences}, doi = {10.1038/ncomms8710}, url = {https://www.nature.com/articles/ncomms8710}, author = {Seabloom, E.W. and E.T. Borer and Buckley, Y. and Cleland, E.E. and Davies, K.F. and Firn, J. and Harpole, W.S. and Hautier, Y. and Lind, E. and MacDougall, A.S. and Orrock, J.L. and Prober, S.M. and P. Adler and Anderson, T.M. and J.D. Bakker and L.A. Biederman and D.M. Blumenthal and C.S. Brown and Brudvig, L.A. and Cadotte, M. and Chu, C. and Cottingham, K.L. and Crawley, M.J. and Damschen, E.I. and D{\textquoteright}Antonio, C.M. and CeCrappeo, N.M. and G. Du and Fay, P.A. and Frater, P. and Gruner, D.S. and Hagenah, N. and Hector, A. and Hillebrand, H. and Hofmockel, K.S. and Humphries, H.C. and Jin, V.L. and Kay, A.D. and Kirkman, K.P. and Klein, J.A. and Knops, J.M.H. and Kimberly J. La Pierre and L. Ladwig and Lambrinos, J.G. and Li, Q. and Li, W. and Marushia, R.} } @article {KNZ001792, title = {Anthropogenic-based regional-scale factors most consistently explain plot-level exotic diversity in grasslands}, journal = {Global Ecology and Biogeography}, volume = {23}, year = {2014}, pages = {802 - 810}, abstract = {

Aim Evidence linking the accumulation of exotic species to the suppression of native diversity is equivocal, often relying on data from studies that have used different methods. Plot-level studies often attribute inverse relationships between native and exotic diversity to competition, but regional abiotic filters, including anthropogenic influences, can produce similar patterns. We seek to test these alternatives using identical scale-dependent sampling protocols in multiple grasslands on two continents. Location Thirty-two grassland sites in North America and Australia. Methods We use multiscale observational data, collected identically in grain and extent at each site, to test the association of local and regional factors with the plot-level richness and abundance of native and exotic plants. Sites captured environmental and anthropogenic gradients including land-use intensity, human population density, light and soil resources, climate and elevation. Site selection occurred independently of exotic diversity, meaning that the numbers of exotic species varied randomly thereby reducing potential biases if only highly invaded sites were chosen. Results Regional factors associated directly or indirectly with human activity had the strongest associations with plot-level diversity. These regional drivers had divergent effects: urban-based economic activity was associated with high exotic\ :\ native diversity ratios; climate- and landscape-based indicators of lower human population density were associated with low exotic\ :\ native ratios. Negative correlations between plot-level native and exotic diversity, a potential signature of competitive interactions, were not prevalent; this result did not change along gradients of productivity or heterogeneity. Main conclusion We show that plot-level diversity of native and exotic plants are more consistently associated with regional-scale factors relating to urbanization and climate suitability than measures indicative of competition. These findings clarify the long-standing difficulty in resolving drivers of exotic diversity using single-factor mechanisms, suggesting that multiple interacting anthropogenic-based processes best explain the accumulation of exotic diversity in modern landscapes.

}, keywords = {LTER-KNZ}, doi = {10.1111/geb.12157}, url = {https://onlinelibrary.wiley.com/doi/abs/10.1111/geb.12157}, author = {MacDougall, A.S. and Bennett, J.R. and Firn, J. and Seabloom, E.W. and E.T. Borer and Lind, E.M. and Orrock, J.L. and Harpole, W.S. and Hautier, Y. and P. Adler and Cleland, E. and Davies, K. and Melbourne, B. and Prober, S.M. and J.D. Bakker and Fay, P.A. and Jin, V.L. and Kendig, A. and Kimberly J. La Pierre and Joslin L. Moore and J.W. Morgan and Stevens, C.J.} } @article {KNZ001632, title = {Eutrophication weakens stabilizing effects of diversity in natural grasslands}, journal = {Nature}, volume = {508}, year = {2014}, pages = {521 -525}, abstract = {

Studies of experimental grassland communities1, 2, 3, 4, 5, 6, 7 have demonstrated that plant diversity can stabilize productivity through species asynchrony, in which decreases in the biomass of some species are compensated for by increases in others1, 2. However, it remains unknown whether these findings are relevant to natural ecosystems, especially those for which species diversity is threatened by anthropogenic global change8, 9, 10, 11. Here we analyse diversity\–stability relationships from 41 grasslands on five continents and examine how these relationships are affected by chronic fertilization, one of the strongest drivers of species loss globally8. Unmanipulated communities with more species had greater species asynchrony, resulting in more stable biomass production, generalizing a result from biodiversity experiments to real-world grasslands. However, fertilization weakened the positive effect of diversity on stability. Contrary to expectations, this was not due to species loss after eutrophication but rather to an increase in the temporal variation of productivity in combination with a decrease in species asynchrony in diverse communities. Our results demonstrate separate and synergistic effects of diversity and eutrophication on stability, emphasizing the need to understand how drivers of global change interactively affect the reliable provisioning of ecosystem services in real-world systems.

}, keywords = {LTER-KNZ, Biodiversity, Community ecology, Grassland ecology}, doi = {10.1038/nature13014}, url = {https://www.nature.com/articles/nature13014}, author = {Hautier, Y. and Seabloom, E.W. and E.T. Borer and P. Adler and Harpole, W.S. and Hillebrand, H. and Lind, E.M. and MacDougall, A.S. and Stevens, C.J. and J.D. Bakker and Buckley, Y.M. and Chu, C. and Scott. L. Collins and Daleo, P. and Damschen, E.I. and Davies, K.F. and Fay, P.A. and Firn, J. and Gruner, D.S. and Jin, V.L. and Klein, J.A. and Knops, J.M.H. and Kimberly J. La Pierre and Li, W. and McCulley, R.L. and Melbourne, B.A. and Joslin L. Moore and O{\textquoteright}Halloran, L.R. and Prober, S.M. and A. Risch and Sankaran, M. and Schuetz, M. and Hector, A.} } @article {KNZ001790, title = {Predicting invasion in grassland ecosystems: is exotic dominance the real embarrassment of richness?}, journal = {Global Change Biology}, volume = {19}, year = {2013}, pages = {3677 - 3687}, abstract = {

Invasions have increased the size of regional species pools, but are typically assumed to reduce native diversity. However, global-scale tests of this assumption have been elusive because of the focus on exotic species richness, rather than relative abundance. This is problematic because low invader richness can indicate invasion resistance by the native community or, alternatively, dominance by a single exotic species. Here, we used a globally replicated study to quantify relationships between exotic richness and abundance in grass-dominated ecosystems in 13 countries on six continents, ranging from salt marshes to alpine tundra. We tested effects of human land use, native community diversity, herbivore pressure, and nutrient limitation on exotic plant dominance. Despite its widespread use, exotic richness was a poor proxy for exotic dominance at low exotic richness, because sites that contained few exotic species ranged from relatively pristine (low exotic richness and cover) to almost completely exotic-dominated ones (low exotic richness but high exotic cover). Both exotic cover and richness were predicted by native plant diversity (native grass richness) and land use (distance to cultivation). Although climate was important for predicting both exotic cover and richness, climatic factors predicting cover (precipitation variability) differed from those predicting richness (maximum temperature and mean temperature in the wettest quarter). Herbivory and nutrient limitation did not predict exotic richness or cover. Exotic dominance was greatest in areas with low native grass richness at the site- or regional-scale. Although this could reflect native grass displacement, a lack of biotic resistance is a more likely explanation, given that grasses comprise the most aggressive invaders. These findings underscore the need to move beyond richness as a surrogate for the extent of invasion, because this metric confounds monodominance with invasion resistance. Monitoring species\&$\#$39; relative abundance will more rapidly advance our understanding of invasions.

}, keywords = {LTER-KNZ}, doi = {10.1111/gcb.12370}, url = {https://onlinelibrary.wiley.com/doi/abs/10.1111/gcb.12370}, author = {Seabloom, E.W. and E.T. Borer and Buckley, Y. and Cleland, E.E. and Davies, K. and Firn, J. and Harpole, W.S. and Hautier, Y. and Lind, E. and MacDougall, A. and Orrock, J.L. and Prober, S.M. and P. Adler and J. Alberti and Anderson, M.T. and J.D. Bakker and L.A. Biederman and D.M. Blumenthal and C.S. Brown and Brudvig, L.A. and Caldeira, M. and Chu, C. and Crawley, M.J. and Daleo, P. and Damschen, E.I. and D{\textquoteright}Antonio, C.M. and DeCrappeo, N.M. and Dickman, C.R. and G. Du and Fay, P.A. and Frater, P. and Gruner, D.S. and Hagenah, N. and Hector, A. and Helm, A. and Hillebrand, H. and Hofmockel, K.S. and Humphries, H.C. and Iribarne, O. and Jin, V.L. and Kay, A. and Kirkman, K.P. and Klein, J.A. and Knops, J.M.H. and Kimberly J. La Pierre and L. Ladwig and Lambrinos, J.G. and Leakey, A.D.B. and Li, Q. and Li, W. and McCulley, R. and Melbourne, B. and Mitchell, C.E. and Joslin L. Moore and J.W. Morgan and Mortensen, B. and O{\textquoteright}Halloran, L.R. and P{\"a}rtel, M. and Pascual, J and Pyke, D.A. and A. Risch and Salguero-Gomez, R. and Sankaran, M. and Schuetz, M. and Simonsen, A. and M.D. Smith and Stevens, C. and Sullivan, L. and Wardle, G.M. and Wolkovich, E.M. and Wragg, P.D. and Wright, J. and Yang, L.} } @article {KNZ001455, title = {Abundance of introduced species at home predicts abundance away in herbaceous communities}, journal = {Ecology Letters}, volume = {14}, year = {2011}, pages = {274 -281}, keywords = {LTER-KNZ}, doi = {10.1111/j.1461-0248.2010.01584.x}, url = {https://onlinelibrary.wiley.com/doi/abs/10.1111/j.1461-0248.2010.01584.x}, author = {Firn, J. and Joslin L. Moore and MacDougall, A.S. and E.T. Borer and Seabloom, E.W. and HilleRisLambers, J. and Harpole, W.S. and Cleland, E.E. and C.S. Brown and Knops, J.M.H. and Prober, S.M. and Pyke, D.A. and Farrell, K.A. and J.D. Bakker and O{\textquoteright}Halloran, L.R. and P. Adler and Scott. L. Collins and D{\textquoteright}Antonio, C.M. and Crawley, M.J. and Wolkovich, E.M. and Kimberly J. La Pierre and Melbourne, B.A. and Hautier, Y. and J.W. Morgan and Leakey, A.D.B. and Kay, A.D. and McCulley, R. and Davies, K.F. and Stevens, C.J. and Chu, C. and Holl, K.D. and Klein, J.A. and Fay, P.A. and Hagenah, N. and Kirkman, K.P. and Buckley, Y.M.} } @article {KNZ001448, title = {Productivity is a poor predictor of plant species richness}, journal = {Science}, volume = {333}, year = {2011}, pages = {1750 -1753}, abstract = {

For more than 30 years, the relationship between net primary productivity and species richness has generated intense debate in ecology about the processes regulating local diversity. The original view, which is still widely accepted, holds that the relationship is hump-shaped, with richness first rising and then declining with increasing productivity. Although recent meta-analyses questioned the generality of hump-shaped patterns, these syntheses have been criticized for failing to account for methodological differences among studies. We addressed such concerns by conducting standardized sampling in 48 herbaceous-dominated plant communities on five continents. We found no clear relationship between productivity and fine-scale (meters\−2) richness within sites, within regions, or across the globe. Ecologists should focus on fresh, mechanistic approaches to understanding the multivariate links between productivity and richness.

}, keywords = {LTER-KNZ}, doi = {10.1126/science.1204498}, url = {http://science.sciencemag.org/content/333/6050/1750}, author = {P. Adler and Seabloom, E.W. and E.T. Borer and Hillebrand, H. and Hautier, Y. and Hector, A. and Harpole, W.S. and O{\textquoteright}Halloran, L.R. and Grace, J.B. and Anderson, T.M. and J.D. Bakker and L.A. Biederman and C.S. Brown and Buckley, Y.M. and Calabrese, L.B. and Chu, C.J. and Cleland, E.E. and Scott. L. Collins and Cottingham, K.L. and Crawley, M.J. and Damschen, E.I. and Davies, K.F. and DeCrappeo, N.M. and Fay, P.A. and Firn, J. and Frater, P. and Gasarch, E.I. and Gruner, D.S. and Hagenah, N. and HilleRisLambers, J. and Humphries, H.C. and Jin, V.L. and Kay, A. and Kirkman, K.P. and Klein, J.A. and Knops, J.M.H. and Kimberly J. La Pierre and Lambrinos, J.G. and Li, W. and MacDougall, A.S. and McCulley, R.L. and Melbourne, B.A. and Mitchell, C.E. and Joslin L. Moore} } @article {KNZ001449, title = {Relative effects of precipitation variability and warming on tallgrass prairie ecosystem function}, journal = {Biogeosciences}, volume = {8}, year = {2011}, pages = {3053 -3068}, abstract = {

Precipitation and temperature drive many aspects of terrestrial ecosystem function. Climate change scenarios predict increasing precipitation variability and temperature, and long term experiments are required to evaluate the ecosystem consequences of interannual climate variation, increased growing season (intra-annual) rainfall variability, and warming. We present results from an experiment applying increased growing season rainfall variability and year round warming in native tallgrass prairie. During ten years of study, total growing season rainfall varied 2-fold, and we found ~50\–200\% interannual variability in plant growth and aboveground net primary productivity (ANPP), leaf carbon assimilation (ACO2), and soil CO2 efflux (JCO2) despite only ~40\% variation in mean volumetric soil water content (0\–15 cm, Θ15). Interannual variation in soil moisture was thus amplified in most measures of ecosystem response. Differences between years in Θ15 explained the greatest portion (14\–52\%) of the variation in these processes. Experimentally increased intra-annual season rainfall variability doubled the amplitude of intra-annual soil moisture variation and reduced Θ15 by 15\%, causing most ecosystem processes to decrease 8\–40\% in some or all years with increased rainfall variability compared to ambient rainfall timing, suggesting reduced ecosystem rainfall use efficiency. Warming treatments increased soil temperature at 5 cm depth, particularly during spring, fall, and winter. Warming advanced canopy green up in spring, increased winter JCO2, and reduced summer JCO2 and forb ANPP, suggesting that the effects of warming differed in cooler versus warmer parts of the year. We conclude that (1) major ecosystem processes in this grassland may be substantially altered by predicted changes in interannual climate variability, intra-annual rainfall variability, and temperature, (2) interannual climate variation was a larger source of variation in ecosystem function than intra-annual rainfall variability and warming, and (3) effects of increased growing season rainfall variability and warming were small, but ecologically important. The relative effects of these climate drivers are likely to vary for different ecosystem processes and in wetter or drier ecosystems.

}, keywords = {LTER-KNZ}, doi = {10.5194/bg-8-3053-2011}, url = {https://www.biogeosciences.net/8/3053/2011/}, author = {Fay, P.A. and John M. Blair and M.D. Smith and Jesse B. Nippert and Carlisle, J.D. and Alan K. Knapp} } @article {KNZ001293, title = {Variation in gene expression of Andropogon gerardii in response to altered environmental conditions associated with climate change}, journal = {Journal of Ecology}, volume = {98}, year = {2010}, pages = {374 -383}, abstract = {

1.\ If we are to understand the mechanisms underlying species responses to climate change in natural systems, studies are needed that focus on responses of non-model species under field conditions. We measured transcriptional profiles of individuals of Andropogon gerardii, a C4 grass native to North American grasslands, in a field experiment in which both temperature and precipitation were manipulated to simulate key aspects of forecasted climate change. 2.\ By using microarrays developed for a closely related model species, Zea mays, we were able to compare the relative influence of warming versus altered soil moisture availability on expression levels of over 7000 genes, identify responsive functional groups of genes and correlate changes in gene transcription with physiological responses. 3.\ We observed more statistically significant shifts in transcription levels of genes in response to thermal stress than in response to water stress. We also identified candidate genes that demonstrated transcription levels closely associated with physiological variables, in particular chlorophyll fluorescence. 4.Synthesis. These results suggest that an ecologically important species responds differently to different environmental aspects of forecast climate change. These translational changes have the potential to influence phenotypic characters and ultimately adaptive responses.

}, keywords = {LTER-KNZ}, doi = {10.1111/j.1365-2745.2009.01618.x}, url = {https://besjournals.onlinelibrary.wiley.com/doi/full/10.1111/j.1365-2745.2009.01618.x}, author = {Travers, S.E. and Tang, Z. and Caragea, D. and Garrett, K.A. and Hulbert, S.H. and Leach, J.E. and Bai, J. and Saleh, A. and Alan K. Knapp and Fay, P.A. and Jesse B. Nippert and Schnable, P.S. and M.D. Smith} } @article {KNZ001238, title = {Ecophysiological responses of two dominant grasses to altered temperature and precipitation regimes}, journal = {Acta Oecologia}, volume = {35}, year = {2009}, pages = {400 -408}, abstract = {

Ecosystem responses to climate change will largely be driven by responses of the dominant species. However, if co-dominant species have traits that lead them to differential responses, then predicting how ecosystem structure and function will be altered is more challenging. We assessed differences in response to climate change factors for the two dominant C4 grass species in tallgrass prairie, Andropogon gerardii and Sorghastrum nutans, by measuring changes in a suite of plant ecophysiological traits in response to experimentally elevated air temperatures and increased precipitation variability over two growing seasons. Maximum photosynthetic rates, stomatal conductance, water-use efficiency, chlorophyll fluorescence, and leaf water potential varied with leaf and canopy temperature as well as with volumetric soil water content (0\–15 cm). Both species had similar responses to imposed changes in temperature and water availability, but when differences occurred, responses by A. gerardii were more closely linked with changes in air temperature whereas S. nutans was more sensitive to changes in water availability. Moreover, S. nutans was more responsive overall than A. gerardii to climate alterations. These results indicate both grass species are responsive to forecast changes in temperature and precipitation, but their differential sensitivity to temperature and water availability suggest that future population and community structure may vary based on the magnitude and scope of an altered climate.

}, keywords = {LTER-KNZ, Andropogon gerardii, Climate variability, Leaf gas exchange, RaMPs, Sensitivity, Sorghastrum nutans}, doi = {10.1016/j.actao.2009.01.010}, url = {https://www.sciencedirect.com/science/article/pii/S1146609X09000204?via\%3Dihub}, author = {Jesse B. Nippert and Fay, P.A. and Carlisle, J.D. and Alan K. Knapp and M.D. Smith} } @article {KNZ001174, title = {Changes in grassland ecosystem function due to extreme rainfall events: implications for responses to climate change}, journal = {Global Change Biology}, volume = {14}, year = {2008}, pages = {1600 -1608}, abstract = {

Climate change is causing measurable changes in rainfall patterns, and will likely cause increases in extreme rainfall events, with uncertain implications for key processes in ecosystem function and carbon cycling. We examined how variation in rainfall total quantity (Q), the interval between rainfall events (I), and individual event size (SE) affected soil water content (SWC) and three aspects of ecosystem function: leaf photosynthetic carbon gain (inline image), aboveground net primary productivity (ANPP), and soil respiration (inline image). We utilized rainout shelter-covered mesocosms (2.6 m3) containing assemblages of tallgrass prairie grasses and forbs. These were hand watered with 16 I\×Q treatment combinations, using event sizes from 4 to 53 mm. Increasing Q by 250\% (400\–1000 mm yr\−1) increased mean soil moisture and all three processes as expected, but only by 20\–55\% (P\≤0.004), suggesting diminishing returns in ecosystem function as Q increased. Increasing I (from 3 to 15 days between rainfall inputs) caused both positive (inline image) and negative (inline image) changes in ecosystem processes (20\–70\%, P\≤0.01), within and across levels of Q, indicating that I strongly influenced the effects of Q, and shifted the system towards increased net carbon uptake. Variation in SE at shorter I produced greater response in soil moisture and ecosystem processes than did variation in SE at longer I, suggesting greater stability in ecosystem function at longer I and a priming effect at shorter I. Significant differences in ANPP and inline image between treatments differing in I and Q but sharing the same SE showed that the prevailing pattern of rainfall influenced the responses to a given event size. Grassland ecosystem responses to extreme rainfall patterns expected with climate change are, therefore, likely to be variable, depending on how I, Q, and SE combine, but will likely result in changes in ecosystem carbon cycling.

}, keywords = {LTER-KNZ}, doi = {10.1111/j.1365-2486.2008.01605.x}, url = {https://onlinelibrary.wiley.com/doi/abs/10.1111/j.1365-2486.2008.01605.x}, author = {Fay, P.A. and Kaufman, D.M. and Jesse B. Nippert and Carlisle, J.D. and Harper, C.W.} } @article {KNZ001187, title = {Consequences of more extreme precipitation regimes for terrestrial ecosystems}, journal = {BioScience}, volume = {58}, year = {2008}, pages = {811 -821}, abstract = {

mplification of the hydrological cycle as a consequence of global warming is forecast to lead to more extreme intra-annual precipitation regimes characterized by larger rainfall events and longer intervals between events. We present a conceptual framework, based on past investigations and ecological theory, for predicting the consequences of this underappreciated aspect of climate change. We consider a broad range of terrestrial ecosystems that vary in their overall water balance. More extreme rainfall regimes are expected to increase the duration and severity of soil water stress in mesic ecosystems as intervals between rainfall events increase. In contrast, xeric ecosystems may exhibit the opposite response to extreme events. Larger but less frequent rainfall events may result in proportional reductions in evaporative losses in xeric systems, and thus may lead to greater soil water availability. Hydric (wetland) ecosystems are predicted to experience reduced periods of anoxia in response to prolonged intervals between rainfall events. Understanding these contingent effects of ecosystem water balance is necessary for predicting how more extreme precipitation regimes will modify ecosystem processes and alter interactions with related global change drivers.

}, keywords = {LTER-KNZ, Climate change, Drought, Ecosystems, Precipitation, soil water}, doi = {10.1641/B580908}, url = {https://academic.oup.com/bioscience/article/58/9/811/250853}, author = {Alan K. Knapp and Beier, C. and Briske, D.D. and Classen, A.T. and Luo, Y. and Reichstein, M. and M.D. Smith and Smith, S.D. and Bell, J.E. and Fay, P.A. and Heisler, J.L. and Leavitt, S.W and Sherry, R. and Smith, B. and Weng, E.} } @article {KNZ001083, title = {Ecological genomics: making the leap from model systems in the lab to native populations in the field. Frontiers in Ecology and the Environment}, journal = {Frontiers in Ecology and the Environment}, volume = {5}, year = {2007}, pages = {19 -24}, abstract = {Recent reviews have emphasized the need to incorporate genomics into ecological field studies to further understand how species respond to changing environmental conditions. Genomic tools, such as cDNA (complementary DNA) microarrays, allow for the simultaneous analysis of gene expression of thousands of genes from all or part of an organism{\textquoteright}s genome (the transcription profile), thereby revealing the genetic mechanisms that underlie species{\textquoteright} responses to environmental change. However, despite their potential, two major limitations have hindered the incorporation of microarrays and other genomic tools into field studies: (1) the limited availability of microarrays for ecologically relevant, non-model species and limited financial resources for developing new microarrays; and (2) concern that high sensitivity of gene expression to even subtle alterations in environmental conditions will hinder detection of relevant changes in field measures of transcription profiles. Here, we show that with cross-species hybridizations of microarrays developed for a closely related model organism, an appropriate experimental design, and sufficient replication, transcriptional profiling can successfully be incorporated into field studies. In this way, relevant changes in gene expression with changing environmental conditions can be detected.}, keywords = {LTER-KNZ}, doi = {10.1890/1540-9295(2007)5[19:EGMTLF]2.0.CO;2}, author = {Travers, S.E. and M.D. Smith and Bai, J. and Hulbert, S.H. and Leach, J.E. and Schnable, P.S. and Alan K. Knapp and Milliken, G.A. and Fay, P.A. and Saleh, A. and Garrett, K.A.} } @article {KNZ001119, title = {Photosynthetic traits in C3 and C4 grassland species in mesocosm and field environments}, journal = {Environmental and Experimental Botany}, volume = {60}, year = {2007}, pages = {412 -420}, abstract = {The North American tallgrass prairie is composed of a diverse mix of C3 and C4 plant species that are subject to multiple resource limitations. C4 grasses dominate this ecosystem, purportedly due to greater photosynthetic capacity and resource-use efficiency associated with C4 photosynthesis. We tested the hypothesis that intrinsic physiological differences between C3 and C4 species are consistent with C4 grass dominance by comparing leaf gas exchange and chlorophyll fluorescence variables for seven C4 and C3 herbaceous species (legumes and non-legumes) in two different settings: experimental mesocosms and natural grassland sites. In the mesocosms, C4 grasses had higher photosynthetic rates, water potentials and water-use efficiency than the C3 species. These differences were absent in the field, where photosynthetic rates declined similarly among non-leguminous species. Thus, intrinsic photosynthetic advantages for C4 species measured in resource-rich mesocosms could not explain the dominance of C4 species in the field. Instead, C4 dominance in this ecosystem may depend more on the ability of the grasses to grow rapidly when resources are plentiful and to tolerate multiple limitations when resources are scarce.}, keywords = {LTER-KNZ, A:Ci curves, C3, C4, Chlorophyll fluorescence, gas exchange, Konza, tallgrass prairie}, doi = {10.1016/j.envexpbot.2006.12.012}, author = {Jesse B. Nippert and Fay, P.A. and Alan K. Knapp} } @article {KNZ001061, title = {Superstatistics of hydro-climatic fluctuations and interannual ecosystem productivity}, journal = {Geophysical Research Letters}, volume = {33}, year = {2006}, pages = {15402 -}, abstract = {[1] Ecosystems driven by hydro-climatic fluctuations at different time scales can be interpreted as non-equilibrium dynamical systems. Here we explore the propagation of daily and interannual rainfall fluctuations through the soil-plant system using the theory of superstatistics. With the help of simplified stochastic models of rainfall, we show how interactions of daily and interannual rainfall fluctuations may qualitatively change the probability distributions of rainfall toward higher frequencies of extreme droughts and intense storms. This in turn is likely to induce marked changes in productivity of mesic ecosystems, while more xeric ecosystems might be insensitive or even benefit from them. This study provides a theoretical basis for predictions of ecosystem responses to the increased precipitation variability expected in future North American climate regimes.}, keywords = {LTER-KNZ}, doi = {10.1029/2006GL026412}, author = {Porporato, A. and Vico, G. and Fay, P.A.} } @article {KNZ001002, title = {Branching responses in Silphium integrifolium (Asteraceae) following mechanical or gall damage to apical meristems and neighbor removal}, journal = {American Journal of Botany}, volume = {92}, year = {2005}, pages = {954 -959}, abstract = {Branching in plants increases plant access to light and provides pathways for regrowth following damage or loss of the apical meristem. We conducted two experiments in an eastern Kansas tallgrass prairie to determine how apical meristem loss (by clipping), apical meristem damage (by insect galling), and increased light availability affected growth, reproduction, and branching in Silphium integrifolium (Asteraceae). The first experiment compared clipping with galling. Clipping increased axillary shoot numbers, while galling increased axillary shoot lengths, reflecting different allocation responses among damage types and inhibition of branching by galls. However, total capitulum production was less in all gall/clip treatments than in intact shoots. The second experiment compared clipping with mowing the surrounding vegetation to increase light availability. Mowing increased total leaf, total capitulum, and axillary shoot length and axillary capitulum production in clipped and unclipped plants and in large vs. small shoots. The presence of the neighboring canopy, not of an intact apical meristem, was therefore the stronger limitation on leaf and capitulum production. These experiments suggest that damage and light competition affected both branching frequency and the partitioning of resources among shoots, branches, and leaves. Because Silphium{\textquoteright}s growth form is widespread, similar responses may occur in other grassland forbs.}, keywords = {LTER-KNZ, Antistrophus silphii, apical dominance, Asteraceae, branching competition, galls, Herbivory, Konza Prairie}, doi = {10.3732/ajb.92.6.954}, author = {Fay, P.A. and Throop, H.L.} } @article {KNZ00939, title = {Increased rainfall variability and reduced rainfall amount decreases soil CO2 flux in a grassland ecosystem}, journal = {Global Change Biology}, volume = {11}, year = {2005}, pages = {322 -344}, abstract = {Predicted climate changes in the US Central Plains include altered precipitation regimes with increased occurrence of growing season droughts and higher frequencies of extreme rainfall events. Changes in the amounts and timing of rainfall events will likely affect ecosystem processes, including those that control C cycling and storage. Soil carbon dioxide (CO2) flux is an important component of C cycling in terrestrial ecosystems, and is strongly influenced by climate. While many studies have assessed the influence of soil water content on soil CO2 flux, few have included experimental manipulation of rainfall amounts in intact ecosystems, and we know of no studies that have explicitly addressed the influence of the timing of rainfall events. In order to determine the responses of soil CO2 flux to altered rainfall timing and amounts, we manipulated rainfall inputs to plots of native tallgrass prairie (Konza Prairie, Kansas, USA) over four growing seasons (1998{\textendash}2001). Specifically, we altered the amounts and/or timing of growing season rainfall in a factorial combination that included two levels of rainfall amount (100\% or 70\% of naturally occurring rainfall quantity) and two temporal patterns of rain events (ambient timing or a 50\% increase in length of dry intervals between events). The size of individual rain events in the altered timing treatment was adjusted so that the quantity of total growing season rainfall in the ambient and altered timing treatments was the same (i.e. fewer, but larger rainfall events characterized the altered timing treatment). Seasonal mean soil CO2 flux decreased by 8\% under reduced rainfall amounts, by 13\% under altered rainfall timing, and by 20\% when both were combined (P<0.01). These changes in soil CO2 flux were consistent with observed changes in plant productivity, which was also reduced by both reduced rainfall quantity and altered rainfall timing. Soil CO2 flux was related to both soil temperature and soil water content in regression analyses; together they explained as much as 64\% of the variability in CO2 flux across dates under ambient rainfall timing, but only 38{\textendash}48\% of the variability under altered rainfall timing, suggesting that other factors (e.g. substrate availability, plant or microbial stress) may limit CO2 flux under a climate regime that includes fewer, larger rainfall events. An analysis of the temperature sensitivity of soil CO2 flux indicated that temperature had a reduced effect (lower correlation and lower Q10 values) under the reduced quantity and altered timing treatments. Recognition that changes in the timing of rainfall events may be as, or more, important than changes in rainfall amount in affecting soil CO2 flux and other components of the carbon cycle highlights the complex nature of ecosystem responses to climate change in North American grasslands.}, keywords = {LTER-KNZ}, doi = {10.1111/j.1365-2486.2005.00899.x}, author = {Harper, C.W. and John M. Blair and Fay, P.A. and Alan K. Knapp and Carlisle, J.D.} } @article {KNZ00917, title = {Convergence across biomes to a common rain-use efficiency}, journal = {Nature}, volume = {429}, year = {2004}, pages = {651 -654}, keywords = {LTER-KNZ}, doi = {10.1038/nature02561}, author = {Huxman, T.E. and M.D. Smith and Fay, P.A. and Alan K. Knapp and Shaw, M.R. and Loik, M.E. and Smith, S.D. and Tissue, D.T. and Zak, J.C. and Weltzin, J.F. and Pockman, W.T. and Sala, O.E. and Haddad, B.M. and Harte, J. and Koch, G.W. and Schwinning, S. and Small, E.E. and Williams, D.G.} } @article {KNZ00881, title = {Assessing the response of terrestrial ecosystems to potential changes in precipitation}, journal = {BioScience}, volume = {53}, year = {2003}, pages = {941 -952}, abstract = {Changes in Earth{\textquoteright}s surface temperatures caused by anthropogenic emissions of greenhouse gases are expected to affect global and regional precipitation regimes. Interactions between changing precipitation regimes and other aspects of global change are likely to affect natural and managed terrestrial ecosystems as well as human society. Although much recent research has focused on assessing the responses of terrestrial ecosystems to rising carbon dioxide or temperature, relatively little research has focused on understanding how ecosystems respond to changes in precipitation regimes. Here we review predicted changes in global and regional precipitation regimes, outline the consequences of precipitation change for natural ecosystems and human activities, and discuss approaches to improving understanding of ecosystem responses to changing precipitation. Further, we introduce the Precipitation and Ecosystem Change Research Network (PrecipNet), a new interdisciplinary research network assembled to encourage and foster communication and collaboration across research groups with common interests in the impacts of global change on precipitation regimes, ecosystem structure and function, and the human enterprise.}, keywords = {LTER-KNZ, Community, ecosystem, global change, Precipitation, soil moisture}, doi = {doi: 10.1641/0006-3568(2003)053[0941:ATROTE]2.0.CO;2}, author = {Weltzin, J.F. and Loik, M.E. and Schwinning, S. and Williams, D.G. and Fay, P.A. and Haddad, B. and Harte, J. and Huxman, T.E. and Alan K. Knapp and Lin, G. and Pockman, W.T. and Shaw, M.R. and Small, E. and M.D. Smith and Tissue, D.T. and Zak, J.C.} } @inbook {KNZ00907, title = {Climate variability in tallgrass prairie at multiple timescales: Konza Prairie Biological Station}, booktitle = {Climate Variability and Ecosystem Response at Long-Term Ecological Research Sites}, year = {2003}, pages = {411 -424}, publisher = {Oxford University Press}, organization = {Oxford University Press}, address = {New York}, keywords = {LTER-KNZ}, author = {Goodin, D.G. and P. Fay and McHugh, M.J.}, editor = {Greenland, D. and Goodin, D.G. and Smith, R.C.} } @article {KNZ00820, title = {The influence of disturbance from military training activities on terrestrial-aquatic linkages in a tallgrass prairie ecosystem}, journal = {Ecological Applications}, volume = {13}, year = {2003}, pages = {432 -442}, abstract = {The role of allochthonous organic matter in lotic ecosystems has been an important research topic among aquatic ecologists since the seminal work by Lindeman was published in 1942. Since 1986, studies on organic matter budgets, ecosystem metabolism, and decomposition published in J-NABS have made significant contributions to the overall understanding of organic matter dynamics in streams. In this review, we summarize the utility of organic matter budgets, cover the major advances in research on ecosystem metabolism, and describe the intrinsic and extrinsic factors influencing organic matter decomposition. We also discuss future directions and current applications of research and highlight the need for additional studies on the role of land use and climate change, as well as continued use of organic matter processing as a functional metric in biomonitoring studies. We emphasize the need for continued data synthesis into comprehensive organic matter budgets. Such comparative studies can elucidate important drivers of organic matter dynamics and can assist in the understanding of large continental/global changes that might be occurring now and in the near future. In general, continued emphasis on synthesizing information into a larger framework for streams and rivers will improve our overall understanding of the importance of organic matter in lotic ecosystems.}, keywords = {LTER-KNZ, carbon cycling, decomposition, litter breakdown, metabolism, organic matter budgets, organic matter dynamics, streams}, doi = {10.1899/08-170.1}, author = {Quist, M.C. and P. Fay and Guy, C.S. and Alan K. Knapp and Rubenstein, B.N.} } @article {KNZ00877, title = {Insect diversity in two burned and grazed grasslands}, journal = {Environmental Entomology}, volume = {32}, year = {2003}, pages = {1099 -1104}, abstract = {This study examined insect diversity in two native grassland ecosystems undergoing burning and grazing by bison and cattle, the Niobrara Valley Preserve (Nebraska) and the Tallgrass Prairie Preserve (Oklahoma). Sweep-sampling for insects was conducted during July 1994 and 1995 along transects in management units that were grazed by bison and partially burned, grazed by cattle and either burned (Tallgrass) or unburned (Niobrara), or ungrazed and unburned. At both sites, species richness (S) and diversity (log series ) were higher and similarity (Sorensen{\textquoteright}s index) lower for bison than for cattle or ungrazed management units. High bison management unit diversity was associated with significantly higher S and  in burned (Tallgrass) and unburned (Niobrara) portions of bison units compared with their respective cattle units, suggesting that habitat heterogeneity in terms of plant productivity, composition, and structure were higher in bison versus cattle and ungrazed management units. Replicated factorial experiments and sampling of additional taxa and time points are needed to verify how fire and grazing management impacts insect diversity in these grasslands.}, keywords = {LTER-KNZ, fire, Grazing, insects, sandhills prairie, tallgrass prairie}, doi = {10.1603/0046-225X-32.5.1099}, author = {P. Fay} } @article {KNZ00863, title = {Productivity responses to altered rainfall patterns in a C4-dominated grassland}, journal = {Oecologia}, volume = {137}, year = {2003}, pages = {245 -251}, abstract = {Rainfall variability is a key driver of ecosystem structure and function in grasslands worldwide. Changes in rainfall patterns predicted by global climate models for the central United States are expected to cause lower and increasingly variable soil water availability, which may impact net primary production and plant species composition in native Great Plains grasslands. We experimentally altered the timing and quantity of growing season rainfall inputs by lengthening inter-rainfall dry intervals by 50\%, reducing rainfall quantities by 30\%, or both, compared to the ambient rainfall regime in a native tallgrass prairie ecosystem in northeastern Kansas. Over three growing seasons, increased rainfall variability caused by altered rainfall timing with no change in total rainfall quantity led to lower and more variable soil water content (0{\textendash}30 cm depth), a ~10\% reduction in aboveground net primary productivity (ANPP), increased root to shoot ratios, and greater canopy photon flux density at 30 cm above the soil surface. Lower total ANPP primarily resulted from reduced growth, biomass and flowering of subdominant warm-season C4 grasses while productivity of the dominant C4 grass Andropogon gerardii was relatively unresponsive. In general, vegetation responses to increased soil water content variability were at least equal to those caused by imposing a 30\% reduction in rainfall quantity without altering the timing of rainfall inputs. Reduced ANPP most likely resulted from direct effects of soil moisture deficits on root activity, plant water status, and photosynthesis. Altered rainfall regimes are likely to be an important element of climate change scenarios in this grassland, and the nature of interactions with other climate change elements remains a significant challenge for predicting ecosystem responses to climate change.}, keywords = {LTER-KNZ, Climate change, Konza Prairie, Net primary productivity, Precipitation, soil moisture}, doi = {10.1007/s00442-003-1331-3}, author = {P. Fay and Carlisle, J.D. and Alan K. Knapp and John M. Blair and Scott. L. Collins} } @inbook {KNZ00847, title = {Rainfall timing, soil moisture dynamics, and plant responses in a mesic tallgrass prairie ecosystem}, booktitle = {Precipitation Regimes and Terrestrial Ecosystems. A North American Perspective}, year = {2003}, pages = {147 -163}, publisher = {University of Arizona Press}, organization = {University of Arizona Press}, address = {Tucson, AZ}, keywords = {LTER-KNZ, tallgrass prairie}, author = {P. Fay and Alan K. Knapp and John M. Blair and Carlisle, J.D. and Danner, B.T. and McCarron, J.K.}, editor = {Weltzin, J.F. and McPherson, G.R.} } @article {KNZ005, title = {Altered rainfall patterns, gas exchange and growth in C3 and C4 grassland species}, journal = {International Journal of Plant Sciences}, volume = {163}, year = {2002}, pages = {549 -557}, keywords = {LTER-KNZ}, author = {Fay, P.A. and Carlisle, J.D. and Danner, B.T. and Lett, M.S. and McCarron, J.K. and Stewart, C. and Alan K. Knapp and John M. Blair and Scott. L. Collins} } @proceedings {KNZ00934, title = {Climate variability at multiple time scales: implications for productivity in tallgrass prairie}, year = {2002}, pages = {312 -316}, publisher = {American Meteorological Society}, abstract = {Climate is a fundamental driver of biomass productivity in ecosystems. This is especially true for grassland systems, which display greater variability in net primary productivity in response to climate fluctuation than forest, desert, or arctic/alpine systems. Although basic climate/productivity relationships have been studied over shorter time scales, the effect of longer-term climate processes such as El Ni{\~n}o/Southern Oscillation (ENSO), North Atlantic Oscillation (NAO), solar activity cycles, and other quasiperiodic climatic patterns on grassland systems is largely unknown, due to the lack of long term productivity data sets to evaluate against climate data. Here, we examine how variability in temperature and rainfall at a tallgrass prairie site (Konza Prairie Biological Station, KPBS) is related to various teleconnection indices and how these indices may relate to patterns of above ground net primary productivity (ANPP). We use two data sets, a 20 year ANPP data set collected at KPBS and a 108 year precipitation and temperature record (1891-1999) from nearby Manhattan, KS. Patterns of variation are analyzed using period-spectrum analysis and correlation of climate variables to ANPP. Results show that at shorter time scales (one year or less), productivity is influenced by magnitude of precipitation and temperature, but also by the seasonal timing of precipitation events and heat accumulation. Long-term precipitation was influenced on the decadal time scale by the NAO and North Pacific (NP) circulation patterns. Long-term temperature patterns showed strongest periodicities at intradecadal time scales (" 5- 8 years), and correlated most strongly with ENSO indices. Although speculative, our results suggest that the influence of atmospheric teleconnection patterns (and their resulting weather patterns) on tallgrass productivity is indirect. Teleconnection patterns interact to influence both the magnitude and seasonal distribution of temperature and precipitation. The interplay of these variations in weather appears to exert significant control over tallgrass ANPP.}, keywords = {LTER-KNZ}, url = {https://ams.confex.com/ams/15BioAero/techprogram/paper_48840.htm}, author = {Goodin, D.G. and Fay, P.A. and McHugh, M.J.} } @article {KNZ00827, title = {Rainfall variability, carbon cycling and plant species diversity in a mesic grassland}, journal = {Science}, volume = {298}, year = {2002}, pages = {2202 -2205}, abstract = {

Ecosystem responses to increased variability in rainfall, a prediction of general circulation models, were assessed in native grassland by reducing storm frequency and increasing rainfall quantity per storm during a 4-year experiment. More extreme rainfall patterns, without concurrent changes in total rainfall quantity, increased temporal variability in soil moisture and plant species diversity. However, carbon cycling processes such as soil CO2 flux, CO2 uptake by the dominant grasses, and aboveground net primary productivity (ANPP) were reduced, and ANPP was more responsive to soil moisture variability than to mean soil water content. Our results show that projected increases in rainfall variability can rapidly alter key carbon cycling processes and plant community composition, independent of changes in total precipitation.

}, keywords = {LTER-KNZ}, doi = {10.1126/science.1076347}, url = {https://science.sciencemag.org/content/298/5601/2202}, author = {Alan K. Knapp and Fay, P.A. and John M. Blair and Scott. L. Collins and M.D. Smith and Carlisle, J.D. and Harper, C.W. and Danner, B.T. and Lett, M.S. and McCarron, J.K.} } @article {KNZ00864, title = {Carbon and water relations of juvenile Quercus species in tallgrass prairie}, journal = {Journal of Vegetation Science}, volume = {12}, year = {2001}, pages = {807 -816}, abstract = {In ecosystems where environments are extreme, such as deserts, adult plant species may facilitate the establishment and growth of seedlings and juveniles. Because high temperatures and evaporative demand characterize tall-grass prairies of the central United States (relative to forests), we predicted that the grassland-forest ecotone, by minimizing temperature extremes and moderating water stress, may function to facilitate the expansion of Quercus species into undisturbed tall-grass prairie. We assessed the carbon and water relations of juvenile Quercus macrocarpa and Q. muhlenbergii, the dominant tree species in gallery forests of northeast Kansas, in ecotone and prairie sites. To evaluate the potentially competitive effects of neighboring herbaceous biomass on these oaks, juveniles (< 0.5 m tall) of both species also were subjected to either: (1) removal of surrounding above-ground herbaceous biomass, or (2) control (prairie community intact) treatments. Herbaceous biomass removal had no significant effect on gas exchange or water relations in these oak species in either the prairie or the ecotone environment. Although the ecotone did alleviate some environmental extremes, photosynthetic rates and stomatal conductance were ca. 20 \% higher (p < 0.05) in both oaks in prairie sites vs. the ecotone. Moreover, although leaf temperatures on average were higher in oaks in the prairie, high leaf temperatures in the ecotone had a greater negative effect on photosynthesis. These data suggest that the grassland-forest ecotone did not facilitate the growth of Quercus juveniles expanding into this grassland. Moreover, the carbon and water relations of juvenile oaks in the prairie appeared to be unaffected by the presence of the dominant C4 grasses.}, keywords = {LTER-KNZ, Ecotone, Facilitation, forest expansion, Quercus, tallgrass prairie}, doi = {10.2307/3236868}, author = {Fay, P.A. and Carlisle, J.D. and Danner, B.T. and Lett, M.S. and McCarron, J.K. and Stewart, C. and Alan K. Knapp and John M. Blair and Scott. L. Collins} } @article {KNZ00858, title = {Altering rainfall timing and quantity in a mesic grassland ecosystem: Design and performance of rainfall manipulation shelters}, journal = {Ecosystems}, volume = {3}, year = {2000}, pages = {308 -319}, abstract = {Global climate change is predicted to alter growing season rainfall patterns, potentially reducing total amounts of growing season precipitation and redistributing rainfall into fewer but larger individual events. Such changes may affect numerous soil, plant, and ecosystem properties in grasslands and ultimately impact their productivity and biological diversity. Rainout shelters are useful tools for experimental manipulations of rainfall patterns, and permanent fixed-location shelters were established in 1997 to conduct the Rainfall Manipulation Plot study in a mesic tallgrass prairie ecosystem in northeastern Kansas. Twelve 9 x 14{\textendash}m fixed-location rainfall manipulation shelters were constructed to impose factorial combinations of 30\% reduced rainfall quantity and 50\% greater interrainfall dry periods on 6 x 6{\textendash}m plots, to examine how altered rainfall regimes may affect plant species composition, nutrient cycling, and above- and belowground plant growth dynamics. The shelters provided complete control of growing season rainfall patterns, whereas effects on photosynthetic photon flux density, nighttime net radiation, and soil temperature generally were comparable to other similar shelter designs. Soil and plant responses to the first growing season of rainfall manipulations (1998) suggested that the interval between rainfall events may be a primary driver in grassland ecosystem responses to altered rainfall patterns. Aboveground net primary productivity, soil CO2 flux, and flowering duration were reduced by the increased interrainfall intervals and were mostly unaffected by reduced rainfall quantity. The timing of rainfall events and resulting temporal patterns of soil moisture relative to critical times for microbial activity, biomass accumulation, plant life histories, and other ecological properties may regulate longer-term responses to altered rainfall patterns.}, keywords = {LTER-KNZ, Climate change, floristic diversity, Grasslands, Konza Prairie, life histories, long-term research, Net primary production, precipitation patterns, rainout shelters, soil moisture}, doi = {10.1007/s100210000028}, author = {Fay, P.A. and Carlisle, J.D. and Alan K. Knapp and John M. Blair and Scott. L. Collins} } @article {KNZ00714, title = {Effects of fire, browsers, and gallers on New Jersey Tea (Ceanothus herbaceous) growth and reproduction}, journal = {American Midland Naturalist}, volume = {141}, year = {1999}, pages = {51 -58}, abstract = {Woody plant species in grassland ecosystems can be subjected to damage from fire and multiple herbivore species, but interactions between fire and herbivory can modify their separate impacts on woody plant life histories. We studied how galling (by Periploca ceanothiella, Lepidoptera: Cosmopterigidae), deer browsing (Odocoilius virginianus) and fire affected the growth and reproduction of the woody shrub Ceanothus herbaceous (Rhamnaceae) on a burned and an unburned site at Konza Prairie Research Natural Area in eastern Kansas. Fire was the major influence on C. herbaceous growth, causing plants to produce long unbranched vegetative ramets from protected belowground meristems, while unburned plants were heavily branched and bore shorter shoots and numerous inflorescences. Unburned plants experienced higher gall frequencies, more galls on their longest shoots, but similar deer browsing compared to burned plants. Ramets with herbivore damage had more branches and inflorescences than undamaged ramets, especially where both herbivores were present. Ceanothus herbaceous{\textquoteright} flexible life history responses suggest tolerance of multiple forms of damage.}, keywords = {LTER-KNZ, fire}, doi = {10.1674/0003-0031(1999)141[0051:EOFBAG]2.0.CO;2}, author = {Throop, H.L. and Fay, P.A.} } @inbook {KNZ00649, title = {Animal populations and communities}, booktitle = {Grassland Dynamics: Long-Term Ecological Research in Tallgrass Prairie}, year = {1998}, pages = {113 -139}, publisher = {Oxford University Press}, organization = {Oxford University Press}, address = {New York}, keywords = {LTER-KNZ, tallgrass prairie}, author = {D.W. Kaufman and Kaufman, G.A. and Fay, P.A. and Zimmerman, J.L. and Evans, E.W.}, editor = {Alan K. Knapp and J. M. Briggs and D.C. Hartnett and Scott. L. Collins} } @inbook {KNZ00648, title = {Diversity of terrestrial macrofauna}, booktitle = {Grassland Dynamics: Long-Term Ecological Research in Tallgrass Prairie}, year = {1998}, pages = {101 -112}, publisher = {Oxford University Press}, organization = {Oxford University Press}, address = {New York}, keywords = {LTER-KNZ, tallgrass prairie}, author = {D.W. Kaufman and Fay, P.A. and Kaufman, G.A. and Zimmerman, J.L.}, editor = {Alan K. Knapp and J. M. Briggs and D.C. Hartnett and Scott. L. Collins} } @inbook {KNZ00645, title = {Plant populations: Patterns and processes}, booktitle = {Grassland Dynamics: Long-Term Ecological Research in Tallgrass Prairie}, year = {1998}, pages = {81 -100}, publisher = {Oxford University Press}, organization = {Oxford University Press}, address = {New York}, keywords = {LTER-KNZ, tallgrass prairie}, author = {D.C. Hartnett and Fay, P.A.}, editor = {Alan K. Knapp and J. M. Briggs and D.C. Hartnett and Scott. L. Collins} } @article {KNZ00638, title = {Responses to short-term shade in soybean leaves: Effects of leaf position and drought stress}, journal = {International Journal of Plant Science}, volume = {159}, year = {1998}, pages = {805 -811}, abstract = {This study examined how leaf position in the canopy affected photosynthetic and stomatal responses to short-term, minutes-long shade periods during a drought cycle in soybean (Glycine max [L.] Merr.). All soybean leaves had similar basic responses to short-term shade, including rapidly decreased photosynthetic rates (Aco2 ), slower decreases in stomatal conductance (g,), and delayed stomatal reopening and photosynthetic recovery after leaves were reilluminated. Drought stress lowered overall Aco2 and restricted photosynthetic and stomatal responses to short-term shade with the negative effects of drought being stronger in lower than in upper leaves. Some of the negative effects of drought persisted after drought was relieved, causing reduced overall water use efficiency, especially in lower leaves. These results indicate that leaf position effects on stomatal responses to short-term shade events become important during and after stress.}, keywords = {LTER-KNZ}, url = {http://www.jstor.org/stable/2475151}, author = {Fay, P.A. and Alan K. Knapp} } @inbook {KNZ00597, title = {Plant strategies for coping with variable light regimes}, booktitle = {Mechanisms of Environmental Stress Resistance in Plants}, year = {1997}, pages = {191 -212}, publisher = {Harwood Academic Press}, organization = {Harwood Academic Press}, address = {UK}, keywords = {LTER-KNZ}, url = {https://books.google.com/books?hl=en\&lr=\&id=cVUvZePMNfMC\&oi=fnd\&pg=PA191\&dq=\%22Plant\%2Bstrategies\%2Bfor\%2Bcoping\%2Bwith\%2Bvariable\%2Blight\%2Bregimes\%22+Knapp\&ots=4FA7O50id2\&sig=Iyq7j1EZaVkuv5Vkhqg25qu6b5c$\#$v=onepage\&q=\%22Plant\%2Bstrategies\%2Bfor\%2Bcoping\%2}, author = {Alan K. Knapp and Fay, P.A.}, editor = {Basra, A.S. and Basra, R.K.} } @article {KNZ00539, title = {Photosynthetic and stomatal responses to variable light in a cool-season and warm-season prairie forb}, journal = {International Journal of Plant Science}, volume = {157}, year = {1996}, pages = {303 -308}, abstract = {Species differences in photosynthetic and stomatal responses to steady-state and variable light were examined in two co-occurring tallgrass prairie forbs, the cool-season legume Baptisia bracteata var. glabrescens and the warm-season composite Helianthus annuus. Previous studies indicated that these species might have similar responses to short-term, minutes-long shade because of their similar growth forms. However, photosynthetic carbon gain, oxygen evolution, transpiration, and leaf xylem pressure potential measurements showed that Helianthus was far more responsive than Baptisia to changes in light availability. Helianthus had higher photosynthetic capacity, photosynthetic temperature optimum, stomatal conductance, and transpiration rates, rapid stomatal closure during shade, and delayed photosynthetic recovery when light levels increased, traits common to species exposed to high temperatures or periodic drought stress. Baptisia, active under cooler, wetter conditions than Helianthus, had lower photosynthetic capacity, photosynthetic temperature optimum, stomatal conductance, and transpiration, and no stomatal response to shade, responses typifying species that experience little water stress. We suggest that environmental and physiological factors may combine to reinforce greatly different photosynthetic and stomatal responses to short-term shade in species with similar growth form, especially in habitats with long, seasonally varying growing conditions.}, keywords = {LTER-KNZ}, url = {http://www.jstor.org/stable/2475266}, author = {Fay, P.A. and Alan K. Knapp} } @article {KNZ00540, title = {Plant tolerance of gall-insect attack and gall-insect performance}, journal = {Ecology}, volume = {77}, year = {1996}, pages = {521 -534}, abstract = {We examined plant tolerance of gall{\textemdash}insect attack and gall{\textemdash}insect performance in rosinweed (Silphium integrifolium, Asteraceae) and its apical meristem galler Antistrophus silphii (Hymenoptera: Cynipidae). Gall densities were varied in field rosinweed populations, while gall densities, water, and nutrients were varied for rosinweed in an experimental garden. Field plants grew under prevailing resource and competitive conditions, but garden plants grew free from competition, so gall{\textemdash}insect impacts, rosinweed regrowth, and gall{\textemdash}insect performance were observed under widely different growing conditions. Seasonal measures of rosinweed growth and leaf physiology, and end{\textemdash}of{\textemdash}season measures of biomass, reproduction, gall{\textemdash}wasp emergence, growth, sex ratios, and parasitism were made for both experiments. Rosinweed poorly tolerated Antistrophus gall damage in the field. Galls reduced plant height, leaf area, and inflorescence production. Rosinweed diverted biomass to stems, but produced no regrowth from axillary meristems. In the garden, rosinweed was much more tolerant of Antistrophus gall damage. Galls initially reduced plant height and leaf area, but axillary meristems grew profusely after gall formation, producing nearly all galled plant inflorescences and more than replacing leaf area initially lost to gall formation. Water{\textemdash} and nutrient{\textemdash}supplemented rosinweed were most tolerant of gall damage, experiencing little loss of total biomass or reproductive output. Field rosinweed failed to mount a tolerance{\textemdash}enhancing regrowth response because galls, resource availability, and competition combined to constrain axillary meristem growth. Gall{\textemdash}wasp performance was largely independent of rosinweed tolerance. Emergence, growth, sex ratios, and parasitism were comparable in field and garden, and only slightly affected by resource availability. Gall{\textemdash}insect performance may be buffered from environmental variation, disconnecting plant and herbivore population dynamics. Rosinweed{\textquoteright}s poor tolerance of gall damage may typify forb responses to herbivory in highly competitive grassland plant communities.}, keywords = {LTER-KNZ}, doi = {10.2307/2265627}, author = {Fay, P.A. and D.C. Hartnett and Alan K. Knapp} } @article {KNZ00486, title = {Stomatal and photosynthetic responses to variable light in sorghum, soybeans and eastern gammagrass}, journal = {Physiologia Plantarum}, volume = {94}, year = {1995}, pages = {613 -620}, abstract = {We studied photosynthetic and stomatal responses of grain sorghum (Sorghum bicolor [L.] Moench cv. Pioneer 8500), soybean (Glycine max L. cv. Flyer) and eastern gamagrass (Tripsacum dactyloides L.) during experimental sun and shade periods simulating summer cloud cover. Leaf gas exchange measurements of field plants showed that short-term (5 min) shading of leaves to 300{\textendash}400 μmol m-2 s-1 photosynthetic photon flux density reduced photosynthesis, leaf temperature, stomatal conductance, transpiration and water use efficiency and increased intercellular CO2 partial pressure. In all species, photosynthetic recovery was delayed when leaves were reilluminated, apparently by stomatal closure. The strongest stomatal response was in soybean. Photosynthetic recovery was studied further with soybeans grown indoors (maximum photosynthetic photon flux density 1 200 μmol m-2 s-1). Plants grown indoors had responses to shade similar to those of field plants, except for brief nonstomatal limitation immediately after reillumination. These responses indicated the importance of the light environment during leaf development on assimilation responses to variable light, and suggested different limitations on carbon assimilation in different parts of the soybean canopy. Photosynthetic oxygen evolution recovered immediately upon reillumination, indicating that the light reactions did not limit soybean photosynthetic recovery. While shade periods caused stomatal closure and reduced carbon gain and water loss in all species, the consequences for carbon gain/water loss were greatest in soybean. The occurrence of stomatal closure in all three species may arise from their shared phenologies and herbaceous growth forms.}, keywords = {LTER-KNZ, A:Ci curves, eastern gamagrass, Glycine max, induction, light, oxygen evolution, photosynthesis, sorghum, Sorghum bicolor, soybean, Stomatal Conductance, Tripsacum dactyloides, Water use efficiency}, doi = {10.1111/j.1399-3054.1995.tb00975.x}, author = {Fay, P.A. and Alan K. Knapp} } @article {KNZ00398, title = {Gallwasp (Hymenoptera: Cynipidae) mortality in a spring tallgrass prairie fire}, journal = {Environmental Entomology}, volume = {22}, year = {1993}, pages = {1333 -1337}, abstract = {The life history of the cynipid gall wasp, Antistrophus silphii Gillette, leaves it vulnerable to mortality in spring fires in the habitat of its host plant, Silphium integrifolium var. laeve Torrey and Gray. This article examines the mortality of gall wasp larvae during a prescribed bum at the Konza Prairie Research Natural Area in the tallgrass prairie of northeast Kansas. The three goals of the study were to determine (1) if A: silphii galls are most frequently found on the tallest S. integrifolium shoots, (2) if there is a relationship between growing season gall height and overwinter lodging, and (3) if gall wasps can survive fire at the heights at which they are found after overwinter lodging. A 1988 survey found that galls were relatively rare on short shoots (<100 cm), were most abundant on middle-length shoots (100{\textendash}140 cm), and occurred at random on long shoots (>140 cm), suggesting that gall wasps avoided short shoots but that gall placement did not maximize gall height. A 1992 survey found that growing season gall height was not related to overwinter lodging of galled shoots, indicating that any gall wasp shoot selection patterns affecting later gall height were disrupted by winter lodging. Gall wasps placed at post-overwinter lodging heights were unable to survive an experimental fire, but a few gall wasps survived when placed above the range of naturally-occurring gall heights. A. silphii and other species with similar life histories must re-establish after fire by immigration, with subsequent population levels affected by indirect effects of fire on host-plant quality.}, keywords = {LTER-KNZ, Antistrophus silphii, fire, mortality}, doi = {http://dx.doi.org/10.1093/ee/22.6.1333 }, author = {Fay, P.A. and Samenus, R.J.J.} } @article {KNZ00399, title = {Increased photosynthesis and water potentials in Silphium integrifolium galled by cynipid wasps}, journal = {Oecologia}, volume = {93}, year = {1993}, pages = {114 -120}, abstract = {Interactions between drought, insect herbivory, photosynthesis, and water potential play a key role in determining how plants tolerate and defend against herbivory, yet the effects of insect herbivores on photosynthesis and water potential are seldom assessed. We present evidence that cynipid wasp galls formed by Antistrophus silphii on Silphium integrifolium increase photosynthesis (A), stomatal conductance (g), and xylem water potential (Ψ). Preliminary data showed that in drought-stressed plants galled shoots had 36\% greater A, and 10\% greater stem Ψ than ungalled shoots, while in well-watered plants leaf gas exchange was not affected by galls. We hypothesized that 1) galled shoots have higher Ψ, g, and A than ungalled shoots, but this differences diminishes if plant drought stress is reduced, and 2) galls can reduce decreases in A and g if water availability decreases. A field experiment testing the first hypothesis found that galls increased g and Ψ, but that differences between galled and ungalled shoots did not diminish after plants were heavily watered. A laboratory test of the second hypothesis using potted Silphium found that galled plants had smaller drops in A and g over a 4-day dry-down period. A vs g and A vs intercellular CO2 concentration relationships were consistent with the explanation that increased Ψ allows galls to increase A by reducing stomatal limitation of A, rather than by altering sink-source relationships or by removing low-Ψ limitations on non-stomatal components of A. Our working hypothesis is that galls increase Ψ and A by reducing the shoot: root ratio so that the plant is exploiting a greater soil volume per unit leaf area. We argue that increased A is an ineffective way for Silphium to compensate for negative effects of gall insect attack. Instead, increased Ψ and A may protect gall insects from variation in resource availability caused by periodic drought stress, potentially reducing negative effects of drought on plant quality and on gall insect populations.}, keywords = {LTER-KNZ, Gall insect, photosynthesis, Plant-insect interactions, Silphium integrifolium, Water potential}, doi = {10.1007/BF00321200}, author = {Fay, P.A. and D.C. Hartnett and Alan K. Knapp} } @article {KNZ00397, title = {Photosynthetic and stomatal responses of Avena sativa (Poaceae) to a variable light environment}, journal = {American Journal of Botany}, volume = {80}, year = {1993}, pages = {1369 -1373}, abstract = {The net photosynthetic (A), stomatal conductance to water vapor (g), water use efficiency (WUE = A/transpiration), and leaf water potential (Ψ) responses of cultivated oats (Avena sativa) were determined under an experimental regime of alternating full sun (photosynthetic photon flux density, PPFD > 1,700 μmol{\textperiodcentered}m-2{\textperiodcentered}sec-1) and shade (300-400 μmol{\textperiodcentered}m-2 sec-1 PPFD). Less extensive measurements were made on winter wheat (Triticum aestivum) to test the generality of crop species{\textquoteright} responses. The rates of stomatal opening/closing after changes in PPFD in Avena and Triticum were compared with previously determined rates for native grasses and forbs to assess how domestication might have altered stomatal dynamics. Characteristics of Avena under alternating sun and shade were 1) rapid fluctuations in A between full sun (\~{}27 μmol{\textperiodcentered}m-2 sec-1) and shade rates (\~{}12-13 μmol m-2{\textperiodcentered}sec-1); 2) slower changes in g, causing progressive stomatal closure during the measurement sequence and possible stomatal limitation of A; 3) no change in leaf Ψ; and 4) a net reduction in WUE. Triticum had similar sun/shade A, g, and WUE dynamics, except that Triticum stomata returned to full-sun g between shade periods. The rates of change of g in Avena and Triticum were lower than for some desert and subalpine native species, but were similar to rates for species in adjoining native habitat. The basic stomatal dynamics of Avena and Triticum may typify many cultivated C3 species, and these data indicate that crop stomatal behavior has not diverged significantly from that of native species.}, keywords = {LTER-KNZ}, url = {http://www.jstor.org/stable/2445664}, author = {Fay, P.A. and Alan K. Knapp} } @phdthesis {KNZ00356, title = {The growth and physiological responses of Silphium integrifolium to gall insect attack}, volume = {PhD Dissertation}, year = {1992}, pages = {1 -102}, school = {Kansas State University}, type = {Ph.D. Thesis}, address = {Manhattan, KS}, keywords = {LTER-KNZ, insect}, author = {Fay, P.A.} } @article {KNZ00316, title = {Constraints on the growth and allocation patterns of Silphium integrifolium (Asteraceae ) caused by cynipid gall wasps}, journal = {Oecologia}, volume = {88}, year = {1991}, pages = {243 -250}, keywords = {LTER-KNZ}, doi = {10.1007/BF00320818}, author = {Fay, P.A. and D.C. Hartnett} } @article {KNZ0049, title = {Comparison of the diets of a caching and a noncaching rodent}, journal = {The American Naturalist}, volume = {122}, year = {1983}, pages = {576 -581}, abstract = {

We hypothesized that species which regularly cache food should have more diverse diets while feeding on their stores than species which have not evolved general caching behaviors. Such a diet by caching species would tend to reduce the probability of being left with only poor dietary items late in the period of cache use. To test this hypothesis, we designed an experiment to compare the diets of caching and noncaching species following a period of experimental feeding trials which simulated a caching situation

}, keywords = {LTER-KNZ, diet, rodent}, url = {https://www.jstor.org/stable/2461210}, author = {Reichman, O.J. and Fay, P.A.} }