Nitrogen releasing dynamics of needle litter affected by thinning intensity and litter N content in a Larix principis-rupprechtii plantation

This experiment investigated the effects on nitrogen (N) releasing dynamics of needle litter from a Larix principis-rupprechtii plantation with different N content resulting from varied thinning intensities. The needle litter was divided into different types according to its N content. The litter with different N content was put back into the forest floor of 4 sites of varied thinning intensities to separately investigate the impact of micro-climatic conditions and litter properties on litter decomposition. The N content of L. principis-rupprechtii litter increased by thinning of the plantation, from(0.128 0.01)g with very light thinning, to(0.210 0.02)g with light thinning, (0.233 0.02)g with medium thinning, and(0.125 0.01)g with heavy thinning. Litter types with different N contents influenced N decomposition dynamics. Decomposition of litter with medium and high N content followed a pattern of release-accumulation- release of N, but litter with a low N content followed an accumulation-release-accumulation pattern. The different litter types influenced the N net release in litter during decomposition, with medium and high N litter releasing more N than that in low N litter. Thinning intensity had no significant effects on the N net release. The different litter types and thinning intensity had an effect on the accumulation of N in litter during decomposition, with low N litter accumulating more N than that in medium and high N litter. There was an interaction between thinning intensity and litter types affecting N net accumulation. Medium thinning decreased litter N accumulation and heavy thinning significantly increased the N net release from high N litter during decomposition. Our results suggest that moderate thinning could increase N content in the needles of L. principis-rupprechtii, thus increase the N net release and promote nutrient cycling.