The global rise in anthropogenic reactive nitrogen and the negative impacts of N deposition on terrestrial plant diversity are well documented. The R* theory of resource competition predicts reversible decreases in plant diversity in response to N loading. However, empirical evidence for the reversibility of N-induced biodiversity loss is mixed. In a long-term N-enrichment experiment in Minnesota, a low-diversity state that emerged during N addition has persisted for decades after additions ceased. Hypothesized mechanisms preventing recovery of biodiversity include nutrient recycling, insufficient external seed supply, and litter inhibition of plant growth. Here, we present an ordinary differential equation model that unifies these mechanisms, produces bistability at intermediate N inputs, and qualitatively matches the observed hysteresis at Cedar Creek. Key features of the model, including native species’ growth advantage in low-N conditions and limitation by litter accumulation, generalize from Cedar Creek to North American grasslands. Our results suggest that effective biodiversity restoration in these systems may require management beyond reducing N inputs, such as burning, grazing, haying, and seed additions. By coupling resource competition with an additional interspecific inhibitory process, the model also illustrates a general mechanism for bistability and hysteresis that may occur in multiple ecosystem types.
Bibliographical noteFunding Information:
This project originated from a University of Minnesota Interdisciplinary Doctoral Fellowship at the Institute on the Environment granted to K.M., which supported collaboration among K.M., F.I., S.E.H., and R.M. Continued work by K.M., A.B., J.B., M.S.M., M.L.Z., R.M., R. Rossi-Goldthorpe, and N. Ding took place during the Math Climate Research Network’s 2018 Summer School at the American Institute of Mathematics, funded by National Science Foundation (NSF) grant DMS-1722578. Data used to parameterize the model were collected with support from the Cedar Creek Long Term Ecological Research Program (NSF grant DEB-1831944). NSF grant DMS-1645643 supported K.M. at Cornell University during 2019–2020. For constructive feedback during the modeling and writing process, we thank Cristina Portales-Reyes, the University of Minnesota EEB Theory Group, Stephen Ellner, and the Cornell University EcoTheory Group. K.M. thanks colleagues Laura Chihara and Claire Kelling at Carleton College for fielding coding questions while K.M. translated parameter estimation workflows into R.
© 2023 The University of Chicago. All rights reserved.
- alternative stable states
PubMed: MeSH publication types
- Journal Article
- Research Support, U.S. Gov't, Non-P.H.S.