Objective:
The Nutrient Network (NutNet) is a globally distributed, bottom-up network of research sites and scientists interested in the impacts of nutrient enrichment on grassland ecosystems. Sites represent the regional flora (e.g. tallgrass prairie, desert grassland, alpine meadow, agronomic pasture, etc.) and are situated in a relatively homogeneous ~1000-m2 vegetation. By using a standardized experimental setup that is consistent across all study sites, NutNet addresses questions of whether plant diversity and productivity are co-limited by multiple nutrients and if so, whether these trends are predictable on a global scale. The NutNet site at SEV was started by the LTER in 2007.
Novelty:
Two of the most pervasive human impacts on ecosystems are the alteration of global nutrient budgets and changes in the abundance and identity of consumers. Fossil fuel combustion and agricultural fertilization have doubled and quintupled, respectively, global pools of nitrogen and phosphorus relative to pre-industrial levels. In spite of the global impacts of these human activities, there have been no globally coordinated experiments to quantify the general impacts on ecological systems. This has important implications for understanding how future atmospheric deposition of nutrients (N, S, Ca, K) might affect community and ecosystem-level responses.
Design:
At SEV, and globally, the fertilization treatments are applied at the scale of 5 m x 5 m plots (n=5 replicates) with 1m of buffer separation between every plot in a completely randomized design as follows: Three nutrient treatments (N, P and K plus micronutrients), each with two levels (control, added), are crossed in a factorial design, for a total of eight treatment combinations, to test multiple nutrient limitation on plant composition and ecosystem function. Nutrient addition rates and sources are: 10 gNm-2 year-1 as NH4NO3, 10 g P m-2 year-1 as triple-super phosphate [Ca(H2PO4)2], 10 g K m-2 year-1 as potassium sulphate [K2SO4] and 100 g m-2 micronutrient mix of Fe (15%), S (14%), Mg (15%), Mn (25%), Cu (1%), Zn (1%), B (02%) and Mo (005%). N, P and K are applied annually (prior to the monsoon season at SEV); micronutrients were applied once at the start of the experiment to avoid toxicity. Each plot contains one permanently located 1 m2 quadrat, marked at the corners with fiberglass stakes for measuring species composition and net primary production. The NutNet site was burned in the 2009 wildfire.
Responses:
Response variables include plant species composition; percentage ground cover of live perennial grasses, herbaceous dicots, shrubs, cactus, litter, and bare ground and aboveground net primary production. Soil parameters (organic matter content, pH, P, field available nitrogen (NO3-N and NH4-N), potentially mineralizable N) are measured occasionally. This experiment was initiated in May 2007 with one year of pre-treatment data. Nutrients are applied annually at the beginning of the monsoon season starting in 2008.
Supporting Documents:
Effects of Multiple Resource Additions on Community and Ecosystem Processes: NutNet NPP Quadrat Sampling at the Sevilleta National Wildlife Refuge, New Mexico. https://portal.edirepository.org/nis/mapbrowse?scope=knb-lter-sev&identifier=231
Data from SEV NutNet have been included in a large number of multi-site publications.
Risch, A.C., S. Zimmerman, R. Ochoa-Hueso, M. Schütz, B. Frey, J.L. Firn, P.A. Fay, F. Hagedorn, E.T. Borer, E.W. Seabloom, W.S. Harpole, J.M.H. Knops, R.L. McCulley, A.D.D. Broadbent, C.J. Stevens, P.B. Adler, J.V.S. Báez, L.A. Biederman, J.M. Blair, C.S. Brown, M.C. Caldeira, S.L. Collins, P. Daleo, A. di Virgilio, A. Ebling, E. Esch, A. Eskelinen, S. Guesewell, N. Hagenah, Y. Hautier, K.P. Kirkman, A.S. MacDougall, J.L. Moore, S.A. Power, S.M. Prober, C. Roscher, M. Sankaran, M.L. Speziale, P.M. Tognetti, R. Virtanen, L. Yahdjian and B. Moser. 2019. Soil net nitrogen mineralization across global grasslands. Nature Communications. https://doi.org/10.1038/s41467-019-12948-2.
Ochoa-Hueso, R., E.T. Borer, E.W. Seabloom, S.E. Hobbie, A.C. Risch, S.L. Collins, C.S. Brown, J. Alberti, H.A. Bahamonde, M.C. Caldeira, P. Daleo, C.R. Dickman, A. Ebeling, N. Eisenhauer, E. Esch, A. Eskelinen, S. Güsewell, B. Gutierrez-Larruga, K. Hofmockel, R. Laungani, E. Lind, A. López, R.L. McCulley, J. Moore, P. Peri, S.A. Power, J.N. Price, S.M. Prober, C. Roscher, J.M. Sarneel, M. Schütz, J. Siebert, R.J. Standish, S. Velasco Ayuso, R. Virtanen, G.M. Wardle, G. Wiehl, L. Yahdjian, T. Zamin. 2020. Microbial processing of plant remains is co-limited by multiple nutrients in global grasslands. Global Change Biology 26: 4572–4582. https://doi.org/10.1111/gcb.15146.
Hautier, Y., P. Zhang, M. Loreau, K.R. Wilcox, E.W. Seabloom, E.T. Borer, J.E.K. Byrnes, S.E. Koerner, K.J. Komatsu, J.S. Lefcheck, A. Hector, P.B. Adler, J. Alberti, C.A. Arnillas, J.D. Bakker, L.A. Brudvig, M.N. Bugalho, M. Cadotte, M.C. Caldeira, O. Carroll, M.J. Crawley, S.L. Collins, P. Daleo, L.E. Dee, N. Eisenhauer, A. Eskelinen, P.A. Fay, B. Gilbert, A. Hansar, F. Isbell, J.M.H. Knops, A.S. MacDougall, R.L. McCulley, J.L. Moore, J.W. Morgan, A.S. Mori, P.L. Peri, E.T. Pos, S.A. Power, J. Price, P.B. Reich, A.C. Risch, C. Roscher, M. Sankaran, M. Schütz, M.D. Smith, C. Stevens, P.M. Tognetti, R. Virtanen, G. Wardle, P.A. Wilfahrt and S. Wang. 2020. General destabilizing effects of eutrophication on grassland productivity at multiple spatial scales. Nature Communications 11. https://doi.org/10.1038/s41467-020-19252-4.
Baldarelli, L.M., H.L. Throop, S.L. Collins and D. Ward. 2021. Nutrient additions have direct and indirect effects on biocrust biomass in a long-term Chihuahuan Desert grassland experiment. Journal of Arid Environments. https://doi.org/10.1016/j.jaridenv.2020.104317
Seabloom, E.W., P.B. Adler, J. Alberti, L. Biederman, Y.M. Buckley, M.W. Cadotte, S.L. Collins, L. Dee, F.A. Fay, J. Firn, N. Hagenah, W.S. Harpole, Y. Hautier, A. Hector, S.E. Hobbie, F. Isbell, J.M.H. Knops, K.J. Komatsu, R. Laungani, A. MacDougall, R.L. McCulley, J.L. Moore, J.W. Morgan, T. Ohlert, S.M. Prober, A.C. Risch, M. Schuetz, C.J. Stevens and E.T. Borer. 2021. Increasing effects of chronic nutrient enrichment on plant diversity loss and ecosystem productivity over time. Ecology 102: e03218. https://doi.org/10.1002/ecy.3218