@article {6110, title = {Nutrient identity modifies the destabilising effects of eutrophication in grasslands}, journal = {Ecology Letters}, volume = {259}, year = {2022}, pages = {754 - 765}, abstract = {

Nutrient enrichment can simultaneously increase and destabilise plant biomass production, with co-limitation by multiple nutrients potentially intensifying these effects. Here, we test how factorial additions of nitrogen (N), phosphorus (P) and potassium with essential nutrients (K+) affect the stability (mean/standard deviation) of aboveground biomass in 34 grasslands over 7 years. Destabilisation with fertilisation was prevalent but was driven by single nutrients, not synergistic nutrient interactions. On average, N-based treatments increased mean biomass production by 21\–51\% but increased its standard deviation by 40\–68\% and so consistently reduced stability. Adding P increased interannual variability and reduced stability without altering mean biomass, while K+ had no general effects. Declines in stability were largest in the most nutrient-limited grasslands, or where nutrients reduced species richness or intensified species synchrony. We show that nutrients can differentially impact the stability of biomass production, with N and P in particular disproportionately increasing its interannual variability.

}, keywords = {LTER-KNZ}, issn = {1461-023X}, doi = {10.1111/ele.v25.410.1111/ele.13946}, url = {https://onlinelibrary.wiley.com/doi/abs/10.1111/ele.13946}, author = {Carroll, Oliver and Batzer, Evan and Bharath, Siddharth and Borer, Elizabeth T. and Campana, {\'\i}a and Esch, Ellen and Hautier, Yann and Ohlert, Timothy and Seabloom, Eric W. and Adler, Peter B. and Bakker, Jonathan D. and Biederman, Lori and Bugalho, Miguel N. and Caldeira, Maria and Chen, Qingqing and Davies, Kendi F. and Fay, Philip A. and Knops, Johannes M. H. and Kimberly J. Komatsu and Martina, Jason P. and McCann, Kevin S. and Moore, Joslin L. and Morgan, John W. and Muraina, Taofeek O. and Osborne, Brooke and Risch, Anita C. and Stevens, Carly and Wilfahrt, Peter A. and Yahdjian, Laura and MacDougall, Andrew S.}, editor = {Pe{\~n}uelas, Josep} } @article {KNZ002029, title = {Global impacts of fertilization and herbivore removal on soil net nitrogen mineralization are modulated by local climate and soil properties}, journal = {Global Change Biology}, volume = {26}, year = {2020}, abstract = {

Soil nitrogen (N) availability is critical for grassland functioning. However, human activities have increased the supply of biologically limiting nutrients, and changed the density and identity of mammalian herbivores. These anthropogenic changes may alter net soil N mineralization (soil net Nmin), that is, the net balance between N mineralization and immobilization, which could severely impact grassland structure and functioning. Yet, to date, little is known about how fertilization and herbivore removal individually, or jointly, affect soil net Nmin across a wide range of grasslands that vary in soil and climatic properties. Here we collected data from 22 grasslands on five continents, all part of a globally replicated experiment, to assess how fertilization and herbivore removal affected potential (laboratory-based) and realized (field-based) soil net Nmin. Herbivore removal in the absence of fertilization did not alter potential and realized soil net Nmin. However, fertilization alone and in combination with herbivore removal consistently increased potential soil net Nmin. Realized soil net Nmin, in contrast, significantly decreased in fertilized plots where herbivores were removed. Treatment effects on potential and realized soil net Nmin were contingent on site-specific soil and climatic properties. Fertilization effects on potential soil net Nmin were larger at sites with higher mean annual precipitation (MAP) and temperature of the wettest quarter (T.q.wet). Reciprocally, realized soil net Nmin declined most strongly with fertilization and herbivore removal at sites with lower MAP and higher T.q.wet. In summary, our findings show that anthropogenic nutrient enrichment, herbivore exclusion and alterations in future climatic conditions can negatively impact soil net Nmin across global grasslands under realistic field conditions. This is an important context-dependent knowledge for grassland management worldwide.

}, keywords = {LTER-KNZ}, doi = {10.1111/gcb.15308}, url = {https://onlinelibrary.wiley.com/doi/full/10.1111/gcb.15308}, author = {Risch, Anita C. and Zimmermann, Stefan and Moser, Barbara and Sch{\"u}tz, Martin and Hagedorn, Frank and Firn, Jennifer and Fay, Philip A. and Adler, Peter B. and Biederman, Lori A. and J. M. Blair and Borer, Elizabeth T. and Broadbent, Arthur A. D. and Brown, Cynthia S. and Cadotte, Marc W. and Caldeira, Maria C. and Davies, Kendi F. and Virgilio, Augustina and Eisenhauer, Nico and Eskelinen, Anu and Knops, Johannes M. H. and MacDougall, Andrew S. and McCulley, Rebecca L. and Melbourne, Brett A. and Moore, Joslin L. and Power, Sally A. and Prober, Suzanne M. and Seabloom, Eric W. and Siebert, Julia and Silveira, Maria L. and Speziale, Karina L. and Stevens, Carly J. and Tognetti, Pedro M. and Virtanen, Risto and Yahdjian, Laura and Ochoa-Hueso, Raul} } @article {KNZ001945, title = {Belowground biomass response to nutrient enrichment depends on light limitation across globally distributed grasslands}, journal = {Ecosystems}, volume = {22}, year = {2019}, pages = {1466{\textendash}1477}, abstract = {

Anthropogenic activities are increasing nutrient inputs to ecosystems worldwide, with consequences for global carbon and nutrient cycles. Recent meta-analyses show that aboveground primary production is often co-limited by multiple nutrients; however, little is known about how root production responds to changes in nutrient availability. At twenty-nine grassland sites on four continents, we quantified shallow root biomass responses to nitrogen (N), phosphorus (P) and potassium plus micronutrient enrichment and compared below- and aboveground responses. We hypothesized that optimal allocation theory would predict context dependence in root biomass responses to nutrient enrichment, given variation among sites in the resources limiting to plant growth (specifically light versus nutrients). Consistent with the predictions of optimal allocation theory, the proportion of total biomass belowground declined with N or P addition, due to increased biomass aboveground (for N and P) and decreased biomass belowground (N, particularly in sites with low canopy light penetration). Absolute root biomass increased with N addition where light was abundant at the soil surface, but declined in sites where the grassland canopy intercepted a large proportion of incoming light. These results demonstrate that belowground responses to changes in resource supply can differ strongly from aboveground responses, which could significantly modify predictions of future rates of nutrient cycling and carbon sequestration. Our results also highlight how optimal allocation theory developed for individual plants may help predict belowground biomass responses to nutrient enrichment at the ecosystem scale across wide climatic and environmental gradients.

}, keywords = {LTER-KNZ, belowground biomass, Fertilization, nitrogen, Nutrient Network, optimal allocation, phosphorus roots}, doi = {10.1007/s10021-019-00350-4}, url = {https://link.springer.com/article/10.1007\%2Fs10021-019-00350-4}, author = {Cleland, Elsa E. and Lind, Eric M. and DeCrappeo, Nicole M. and DeLorenze, Elizabeth and Wilkins, Rachel Abbott and P. Adler and Bakker, Jonathan D. and Brown, Cynthia S. and Davies, Kendi F. and Esch, Ellen and Firn, Jennifer and Gressard, Scott and Gruner, Daniel S. and Hagenah, Nicole and Harpole, W. Stanley and Hautier, Yann and Hobbie, Sarah E. and Hofmockel, Kirsten S. and Kirkman, Kevin and Knops, Johannes and Kopp, Christopher W. and Kimberly J. La Pierre and MacDougall, Andrew and McCulley, Rebecca L. and Melbourne, Brett A. and Joslin L. Moore and Prober, Suzanne M. and Riggs, Charlotte and Risch, Anita C. and Schuetz, Martin and Stevens, Carly and Wragg, Peter D. and Wright, Justin and E.T. Borer and Seabloom, Eric W.} }