Litter quality and climate regulate the effect of invertebrates on litter decomposition in terrestrial and aquatic ecosystems: A global meta-analysis

Although the exclusion effects of invertebrate decomposers on litter decomposition have been extensively studied in different experimental contexts, a thorough comparison of the exclusion effects of invertebrate decomposers with different body sizes on litter decomposition and its possible regulatory factors in terrestrial and aquatic ecosystems is still lacking. Here, through a meta-analysis of 1207 pairs of observations from 110 studies in terrestrial ecosystems and 473 pairs of observations from 60 studies in aquatic ecosystems, we found that invertebrate exclusion reduced litter decomposition rates by 36 % globally, 30 % in terrestrial ecosystems, and 44 % in aquatic ecosystems. At the global scale, the exclusion effects of macroinvertebrates and mesoinvertebrates on litter decomposition rates (reduced by 38 % and 36 %, respectively) were greater than those of the combination of macroinvertebrates and mesoinvertebrates (reduced by 30 %). In terrestrial and aquatic ecosystems, the effects of invertebrate exclusion on litter decomposition rates were mainly regulated by climate and initial litter quality, but the effects of invertebrate exclusion with different body sizes were regulated differently by climate, initial litter quality, and abiotic environmental variables. These findings will help us better understand the role of invertebrate decomposers in litter decomposition, especially for invertebrate decomposers with different body sizes, and underscore the need to incorporate invertebrate decomposers with different body sizes into dynamic models of litter decomposition to examine the potential effects and regulatory mechanisms of land-water-atmosphere carbon fluxes.