Authors: Gallego-Zamorano, Juan; de Jonge, Melinda M.J.;Runge, Katharina;Hulls, Steven;Wang, Jiaqi;Huijbregts, Mark A.J.;Schipper, Aafke;

Anthropogenic nitrogen (N) inputs not only alter soil and vegetation characteristics, but may also affect terrestrial invertebrate communities. Local studies are, however, typically insufficient to uncover general response patterns. Here we performed a meta-analysis of 3,871 observations from 124 papers reporting the effect of N addition on the abundance or richness of terrestrial arthropods or nematodes worldwide. We explored how different N addition levels together with environmental and trait moderators shape the response of invertebrates while controlling for the heterogeneity between studies and phylogenetic relationships between invertebrate groups. We found that arthropods performing a full metamorphosis decreased in abundance with increasing N, while those with incomplete metamorphosis may increase in response to N addition. Moreover, arthropods without metamorphosis presented an optimum of N after which they may decrease in abundance. Nematodes abundance increased with N in wet areas (high precipitation) but decreased otherwise. Arthropod richness was not affected by N, while nematodes richness showed an optimum but negative response. These changes in invertebrate’s communities due to anthropogenic N can ultimately affect their ecosystem services such as decreased pollination or increased pests.