Nutrient supply and herbivores can regulate plant species composition, biodiversity and functioning of terrestrial ecosystems. Nutrient enrichment frequently increases plant productivity and decreases diversity while herbivores tend to maintain plant diversity in productive systems. However, the mechanisms by which nutrient enrichment and herbivores regulate plant diversity remain unclear. Abundance-based mechanisms propose that fertilization leads to the extinction of rare species due to random loss of individuals of all species. In contrast, functional-based mechanisms propose that species exclusion is based on functional traits which are disadvantageous under fertilized conditions. We tested mechanistic links between fertilization and diversity loss in the presence or absence of consumers using data from a 4-year fertilization and fencing experiment in an alpine meadow. We found that both abundance- and functional-based mechanisms simultaneously affected species loss in the absence of herbivores while only abundance-based mechanisms affected species loss in the presence of herbivores. Our results indicate that an abundance-based mechanism may consistently play a role in the loss of plant diversity with fertilization, and that diversity decline is driven primarily by the loss of rare species regardless of a plant’s functional traits and whether or not herbivores are present. Increasing efforts to conserve rare species in the context of ecosystem eutrophication is a central challenge for grazed grassland ecosystems.
Bibliographical noteFunding Information:
Special thanks to T. K. Rajaniemi for valuable discussion and comments. This project was supported by the Key Program of the National Natural Science Foundation of China (grant no. 41430749), the National Natural Science Foundation of China (grant no. 31300363), and the Postdoctoral Foundation of China (grant nos. 2013M541970, 2014T70675). The experiments comply with the current laws of China, where the experiments were performed.
© 2015, European Union.
- Alpine meadow
- Community composition
- Functional traits
- Rare species