Nitrogen addition is known to significantly affect litter decomposition of terrestrial ecosystem. However, the theories for the explanations: Stoichiometry and N Excavation by Microbes are contradictory. The effect of litter quality on litter decomposition and N availability is also poorly understood. 

Dr. ZHANG Weidong at the research group of Plantation Ecology Institute of Applied Ecology (IAE) of Chinese Academy of Sciences and co-workers investigated the effect of N addition (0, 0.4, 1.6, and 4.0 mol·N·m⁻²·yr⁻¹) on decomposition rate of 18 types of litter with various quality with/without soil fauna exclusion in subtropical forest. The results were published in Ecology.

In the experiment without soil fauna exclusion, the results show that after one year, N addition significantly reduced the litter decomposition rate and the effect is closely related to the N addition levels. The higher the litter quality, the more the decomposition rate was reduced. The decomposition rate of high-and middle quality litter was reduced 26% ± 5% and 29% ± 4%, respectively, that effect was significantly higher than the litters with low quality.

In the experiment with soil fauna exclusion, the N addition showed effect similar to that without soil fauna exclusion. Fauna exclusion reduced rate of litter decomposition 17% ± 1.5%. However, the fauna effect showed no significant correlation with N addition and litter quality. The results implicated that the variations in litter quality, N addition and Soil fauna all have significant controlling effect on litter decomposition and nutrient cycling in subtropical forest ecosystems. 

The work was supported by National Key R&D Project.