Initial litter quality modulates the positive effects of soil fauna on litter mass and component loss: a global synthesis

Abstract

Soil fauna plays a crucial role in litter decomposition, but its contribution to the loss of mass and the associated litter components such as carbon (C), nitrogen (N), phosphorus (P), lignin, and cellulose, as well as litter stoichiometry (e.g., C:N, C:P, N:P, and lignin:N ratio) are not clear. Here, we performed a meta-analysis using 7973 paired observations from 198 peer-reviewed publications to fill this knowledge gap. These observations were from litterbags including and excluding soil fauna, using physical methods (mesh sizes ≤0.1 mm, from 0.1 up to 2 mm, and > 2 mm) or chemical techniques. We found that soil fauna showed an overall positive effect on litter decomposition, increasing the loss of litter mass, C, N, P, and lignin by 24.9, 15.3, 19.9, 19.2, and 20.9 % on average, respectively, but decreasing the C:P ratio by 12.3 %. Plant functional type and exclusion technique had significant impacts on C loss. Exclusion technique and leaf litter shape also significantly influenced the C:N ratio. The effect of soil fauna on the loss of litter mass and components increased along with the decomposing process. Initial litter quality, especially C concentration, C:N ratio, and lignin:N ratio, was the dominant factor controlling litter mass, N, and P loss. Our findings highlight the critical role of soil fauna in regulating litter decomposition and the associated C and nutrient loss processes.