Conventional experiments simulating nitrogen (N)-deposition have been conducted by applying N solutions directly onto forest floors. However, in reality, atmospheric N passes through the canopy layer before it reaches the forest floor. Understanding how N-deposition impacts soil biodiversity and soil ecosystem functions is necessary to improve our knowledge of soil ecosystem responses to global change. 

In a study published in Geoderma, researchers from the Xishuangbanna Tropical Botanical Garden (XTBG) tried to investigate the impact of N-deposition approaches and N-concentrations on soil fauna and leaf litter decomposition rate. They used a novel experiment to contrast canopy addition of N (CAN) to understory addition of N (UAN) in a subtropical forest and a temperate forest. 

They first determined how the density, Shannon-Wiener index of diversity (H′), taxonomic richness and different taxonomic groups of soil fauna responded to N-deposition approaches and concentrations.  

They then assessed soil fauna community composition across the different N treatments using non-metric multidimensional scaling. 

They found that CAN accelerated the litter decomposition rate and increased diversity of soil fauna. In contrast, UAN had no significant impact on soil fauna index and litter decomposition compared with control. 

In addition, N-deposition concentration significantly influenced soil fauna density, H′ diversity, and species richness at the subtropical forest, but only affected H′ diversity of soil fauna at the temperate forest. 

"Our data suggest that increasing in the diversity of soil fauna under CAN deposition would consequently accelerate the rate of litter decomposition," said Dr. LIU Shengjie, first author of the study.