关键词: 氮沉降, 杉木人工林, 凋落叶, 碳氮磷归还

Abstract: Aims The objective of this study was to explore the initial response of leaf litter production and its carbon, nitrogen, and phosphorus restitution of Cunninghamia lanceolata plantation forests in the rain area of Western China to multiple levels of nitrogen addition. Methods A short-term N addition manipulation experiment with seven levels (0 kg·hm-2·a-1; 10 kg·hm-2·a-1; 20 kg·hm-2·a-1; 40 kg·hm-2·a-1; 80 kg·hm-2·a-1; 120 kg·hm-2·a-1; and 160 kg·hm-2·a-1) was conducted to examine the effects of N addition on leaf litter production, concentrations of leaf litter carbon (C), N, and phosphorus (P), as well as their return within C. lanceolata plantation forests located on the rain area of Western China. Important findings (1) The annual litterfall production of C. lanceolata ranged from 2595.88 to 3043.98 kg·hm-2·a-1, with a bimodal monthly dynamic pattern peaking in May and August. Low nitrogen additions (N10, N40) significantly promoted the withered leaf yield, but from N80 onwards, its promotion was significantly weakened until it turned to inhibition (N120, N160). (2) The mean annual C, N, and P contents of C. lanceolata litterfall were 313.89-498.12, 10.17-22.03, and 0.13-0.30 g·kg⁻¹, respectively. the carbon content of C. lanceolata withered leaves declined with the increase of the leaves of nitrogen addition, and the nitrogen and phosphorus contents showed the opposite trend. (3) The mean annual C, N, and P return of C. lanceolata litterfall ranged from 1032.91–1205.09, 43.61–36.85, and 0.50–0.61 kg·hm-2, respectively, and the carbon, nitrogen and phosphorus return was mainly regulated by yield. The short-term study showed that low N additions significantly increased the yield and carbon, nitrogen and phosphorus restitution of cedar plantation forests, while high N additions showed some negative effects, and 80 kg-N-hm-2-a-1 was the response threshold of N additions in C. lanceolata plantation forests in the West China rainforest area.

Key words: Nitrogen deposition, Cunninghamia lanceolata, Leaf litter, Carbon、 Nitrogen and Phosphorus return flux