Effects of soil mesofauna and microclimate on nitrogen dynamics in leaf litter decomposition along an elevation gradient

The nutrient dynamics in decomposing litter has proved to play a crucial role in regulating the nutrient status of ecosystems and vegetation productivity. Little is known, however, about the effect mechanism of decomposer and its environment on the nitrogen (N) mineralisation of litter along an elevation gradient in such sites. We investigated the effects of soil mesofauna using litter bags on N dynamics in decomposing Castanopsis carlesii litter along an elevation gradient across four types of ecosystems in southeastern China: evergreen broadleaf forest (EVB), coniferous forest (COF), dwarf forest (DWF) and alpine meadow (ALM). The mean contribution of soil mesofauna to N concentration was 12.6% at EVB, 10.6% at COF, 5.4% at DWF, and 3.1% at ALM. The N concentration of litter with mesofauna was significantly related to H′ (Shannon-Wiener) and GN (group number) across the four sites. The effects of soil mesofauna on N concentration of litter were significantly linked to some special faunal groups, including Oribatida, Mesostigmata and Collembola. The N concentration in litter bags were positively related with mean annual air temperature, soil temperature and litter moisture along the elevation gradient. We concluded that the rapid accumulation of N in lower elevation sites during the first few months can result in the retention of mobile N in soils and the effects of soil mesofauna on N dynamics may be intimately associated with microclimate (warm and humid) and faunal diversity along the elevation gradient. Key words : Nitrogen concentration, mesofauna, faunal diversity, elevation gradient, Wuyi National Nature Reserve, China.