Effects of soil fauna on N and P dynamics at different stages during the first year of litter decomposition in subalpine and alpine forests of western Sichuan

Aims Soil fauna has an important effect on litter nutrient release in cold regions, and the effect could vary with litter types and be controlled by environmental factors such as temperature and precipitation. Our objective was to characterize the effect of soil fauna on N and P dynamics during litter decomposition in subalpine and alpine forests.
Methods A field litterbag experiment was conducted in subalpine and alpine forests of western Sichuan, China, from November 2011 through October 2012. Samples of air-dried leaf litter for Salix paraplesia, Sabina saltuaria, Betula albosinensis, and Abies fargesii var. faxoniana were placed in nylon litterbags (20 cm × 20 cm, 10 g per bag) of two different mesh sizes (i.e. 3.00 mm and 0.04 mm). The amount of N and P released were investigated at different stages during the first year of decomposition, i.e., onset of freezing period, deep freezing period, thawing stage, early growing season, mid-growing season, and late growing season.
Important findings The N dynamics during decomposition differed between the leaf litter of broadleaf trees and that of coniferous trees: they were of a release–enrichment–release pattern in Salix paraplesia and B. albosinensis, and of a release–enrichment pattern in Sabina saltuaria and A. fargesii var. faxoniana. The P generally displayed a declining trend, but with an obvious enrichment process in the mid-growing season. During the first year of litter decomposition, soil fauna imposed a positive effect on N release, and a negative effect on P release. There was a significant difference in the amount of litter N and P released through soil fauna among different stages during the first year of decomposition. The amount of N released through soil fauna was positively related to the positive accumulated temperature; whereas the amount of P released through soil fauna was highly negatively related to the positive accumulated temperature. Soil fauna affected more on the litter of broadleaf trees than on the litter ofconiferous trees in N and P dynamics during decomposition.