Multifaceted leaf litter traits shape soil fauna communities: Evidence from subtropical monocultural plantations

The important role of litter traits in shaping soil fauna communities has been increasingly acknowledged. It remains uncertain how fauna community features are associated with multiple litter traits, especially over the long term. With equal-aged monocultural plantations of 20 species in a subtropical climate in Hunan, China, we tested whether fauna communities were different after 40 years due to the landuse and choice of tree species, and the extent to which such disparity can be explained by litter traits. For each plantation plus a natural forest plot, we inventoried fauna in three layers (fresh litter, fragmentation and humus), measured fresh litter traits (leaf economics, size and shape and defenses), litter quantity and soil characteristics (soil properties, root and microbial biomass). Compared with natural forests, most plantations had similar fauna diversity indexes, but markedly lower density (-53.84%). Both density and diversity indexes generally increased from litter layers to humus: 0.89–1.71 for density, 32.45–38.03 for richness, 2.46–3.01 for Shannon-Wiener index, 0.82–0.92 for Gini-Simpson index and 0.74–0.84 for Pielou's evenness, respectively. Significant correlations between soil fauna indicators and litter traits were almost absent for litter layers, but were frequently observed in the humus layer. In the humus layer, soil fauna density was associated with traits related to economics (e.g., specific leaf area and dry matter content), defenses (e.g., phenol concentration) and metal element concentrations, but not with any size and shape traits, whereas soil fauna diversity could be associated with all the above trait categories. Both the leaf economics spectrum and size and shape spectrum could be significantly associated with the fauna indicators of the humus layer. Soil fauna indicators were more closely associated with litter traits than litter quantity and soil characteristics. This study reveals a link between soil fauna communities and litter traits at both individual traits and overall spectrum levels. The results emphasize the significance of segregating litter and soil layers in soil fauna studies, and the essential role of natural forests in preserving soil biodiversity.