The Effects of Nitrogen Fertilisation on Plant Species Richness in European Permanent Grasslands: A Systematic Review and Meta-Analysis

Nitrogen fertilisation is a common form of agricultural intensification, aimed at increasing biomass, which can affect plant species diversity and ecosystem functioning. Using systematic review meta-analysis nitrogen studies in European permanent grasslands, we asked: (i) what relationship exists between application rate change diversity, compared to zero controls; (ii) how grassland, management study characteristics this relationship. Meta-analysis 34 control-treatment effects from 14 conducted across nine countries revealed negative linear richness, equivalent approximately 1.5 species/m2 lost for every 100 Kg ha−1 yr−1 added. Fertilisation induced reductions richness were greater when defoliation rates lower. We found some evidence that grasslands with higher baseline more fertilised poor although uncertainty was high. Due the diverse grassland types included analysis, variability fertilisation-driven changes identified several remaining limitations our understanding, including about non-linear effects, could aid efforts optimise trade-off yields.