Dominant Species Drive Biomass and Diversity Responses to Nutrient Inputs

Authors: Fay, Philip; RISCH, ANITA - Swiss Federal Research Institute Wsl; ASPINWALL, MICHAEL - University Of Texas At Austin; HECKMAN, ROBERT - University Of Texas At Austin; KHASANOVA, ALBINA - University Of Texas At Austin; REICHMANN, LARA - University Of California

Submitted to: Ecology and Evolution
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/12/2026
Publication Date: 2/17/2026
Citation: Fay, P.A., Risch, A.C., Aspinwall, M.J., Heckman, R.W., Khasanova, A.R., Reichmann, L.G. 2026. Dominant Species Drive Biomass and Diversity Responses to Nutrient Inputs. Ecology and Evolution. https://doi.org/10.1002/ece3.73022.
DOI: https://doi.org/10.1002/ece3.73022

Interpretive Summary: Grasslands worldwide are being increasingly impacted by fertilizers lost from agricultural production systems or from atmospheric nutrient deposition. While fertilization with limiting plant nutrients may increase grassland productivity, they also often reduce plant species diversity and alter the composition of plant communities, with negative effects on the stability of impacted grasslands. Management practices such as haying may alter the magnitude or detectability of these effects. Results from a nine-year study testing for the presence of limitation by nitrogen, phosphorus, or potassium found strong evidence for multiple nutrient co-limitation of ANPP by nitrogen (N) and Phosphorus (P) when litter and aboveground standing dead was removed as part of haying operations. The productivity of aboveground plant biomass increased by up to 58% when fertilized with N paired with P, grassland plant communities switched from dominance by grasses to dominance by forbs, and productivity, and the number and diversity of plant species fluctuated more with varying precipitation inputs compared to unfertilized grassland. These findings indicate that multiple nutrient limitation, which is widespread and common in grasslsands, stabilizes them against climate variability. These findings suggest that land managers and policy makers should consider ways to mitigate unintended nutrient inputs into grasslands in order to increase long-term stability of these ecosystems and the goods and services they provide.

Technical Abstract: Grassland net primary productivity is commonly limited by water and by one or more nutrients. Chronic inputs of limiting nutrients often reduce plant species diversity and alter community dominance, and increased precipitation variability may amplify the impacts of limiting nutrient inputs on productivity or biodiversity. However, anthropogenic drivers, particularly management practices, may alter the magnitude or detectability of nutrient limitation. The combined effects of limiting nutrients, precipitation, and grassland management have not been explored. We conducted a nine-year study testing for the presence of single and multiple nutrient limitation of grassland aboveground net primary productivity (ANPP) and biodiversity in a mesic grassland in the southern extent of the North American tallgrass prairie. Yearly pre-growing season litter removal began in year five. In years with litter removal, we found strong evidence for multiple nutrient co-limitation of ANPP by nitrogen (N) and Phosphorus (P). ANPP increased by up to 58% when fertilized with N paired with P. Co-limitation of ANPP by N and P was superadditive, because the response to N paired with P was greater than the sum of the response to N (28%) or P alone (no increase). Forb biomass increases with nutrient enrichment were associated with decreased grass biomass, species richness, and community similarity (R2 = 0.56 to 0.82), indicating that release from multiple nutrient co-limitation shifted communities from grass to forb dominance, reduced biodiversity, and increased the divergence of plant communities from their pre-treatment composition. Enrichment with N caused greater variation in ANPP, species richness, and community similarity in response to interannual and intra-annual precipitation variability, indicating that enrichment with limiting nutrients increased community and ecosystem responses to climatic variability. None of these responses were present in years when litter was not removed. These findings indicate that multiple nutrient limitation stabilizes grassland net primary productivity and community composition and buffers the effects of precipitation variability, and that site management may obscure the presence of nutrient limitation of primary productivity or its interactions with climate drivers.