Meta-analysis of nitrogen impacts on plant diversity.
Nitrogen enrichment is among the main drivers of the loss of plant diversity in terrestrial ecosystems. As part of the GLOBIO project, we have performed a systematic meta-analysis in which we synthesised the results of 115 experiments that assessed the effects of nitrogen addition on (semi-)natural terrestrial plant communities. The results of this analysis, which was led by Gabriele Midolo (Free University of Bozen-Bolzano), are now published in the journal Global Ecology and Biogeography
Effects of nitrogen addition on plant species richness and abundance
Nitrogen (N) enrichment is among the main drivers of the loss of plant biodiversity in terrestrial ecosystems. Yet, a meta-analysis covering multiple dimensions of biodiversity in multiple ecosystems across the globe was lacking. We performed a meta‐analysis of 115 experiments reported in 85 studies assessing the effects of N addition on terrestrial natural and semi‐natural plant communities. We quantified changes in local-scale plant biodiversity in relation to N addition using four complementary metrics: species richness, individual species abundance, mean species abundance and geometric mean abundance. For all the metrics, we found a negative relationship with N addition (so, greater amounts of annual N addition resulted in larger declines in plant diversity). However, the magnitude of the decline for a given amount of N addition differed among the metrics, with the smallest decline for species richness and the largest for individual species abundance. We further found that the relationships between the biodiversity metrics and N addition were modified by various experimental and environmental moderators (type of fertilizer, temperature, experimental duration, plot size and soil CEC). Finally, reductions in the abundance of individual species were larger for N‐sensitive plant life‐form types (legumes and non‐vascular plants).
This project was financed by PBL Netherlands Environmental Assessment Agency as part of the GLOBIO project. The results will be implemented in the next versions of GLOBIO, alongside response relationships for land‐use change, climate change and fragmentation. The study was led by Gabriele Midolo, who currently works as PhD student the department of Science and Technology at the Free University of Bozen-Bolzano (Italy). He cooperated with researchers from Wageningen University and Research (Wim de Vries), PBL (Aafke Schipper and Rob Alkemade), Radboud University (Ana Benítez-López) and Ghent University & the University of Western Australia (Mike Perring).