The effects of litter quantity and quality on soil nutrients and litter invertebrates in the understory of two forests in southern China

We designed and carried out a short-term litter decomposition experiment to test the direct effects of litter manipulations on soil nutrients and litter invertebrates in a tropical lowland forest and a diverse subtropical montane evergreen broad-leaved forest in southern China. Our experimental design involved testing both litter quantity and litter quality. To test for the effects of litter quantity, we manipulated different depths of mixed litter, with and without periodic topping-up. To test for the effects of litter quality, we compared four different species of litter individually with mixed, natural, litter control plots. The response by soil nutrients to these manipulations was monitored using ion-exchange membranes and the response by litter invertebrates was estimated using pitfall traps. We show a clear difference in the available soil nutrients and litter invertebrate composition between the two sites. The only response detected in the more diverse montane forests was an invertebrate response to litter quantity. In contrast, we detected both nutrient and invertebrate responses to litter quantity and an invertebrate response to litter species (quality) in the lower diversity forests. We conclude that many of the differences may be attributed to the general temperature and rainfall conditions at the two sites. At the local scale, differences in soil nutrients and invertebrate abundance may partially be explained by litter quantity and the diversity of the forests, and litter abundance has a more significant impact on soil nutrients and litter invertebrates than litter species composition.