Soil invertebrates are the key drivers of litter decomposition in tropical forests

Forest litter decomposition is an essential component of global carbon and nutrient turnover. Soil invertebrates play important roles in litter decomposition, but the regional pattern of their effects is poorly understood. We examined 476 case studies across 93 sites and performed a meta-analysis to estimate regional effects of invertebrates on forest litter decomposition. We then assessed how invertebrate diversity, climate and soil pH drive regional variations in invertebrate-mediated decomposition. We found that (1) invertebrate contributions to litter decomposition are 1.5 times higher in tropical forests than forests outside the tropics, with an overall contribution of 31% to global forest litter decomposition; and (2) invertebrate diversity, particularly of termites, together with warm, humid and acidic environments in the tropics are positively associated with forest litter decomposition by soil invertebrates. Our results demonstrate the significant difference in invertebrate effects on mediating forest litter decomposition between the tropics and elsewhere. We demonstrate, also, the significance of termites in driving litter mass loss in the tropics. These results are particularly pertinent in the tropics where climate change and human disturbance threaten soil invertebrate biodiversity and the ecosystem services it provides.