杉木人工林凋落物分解对氮沉降增加的响应

Decomposition of leaf litter of Chinese fir in response to increased nitrogen deposition

通过野外模拟试验,研究了杉木人工林凋落叶分解对氮沉降增加的响应。试验设计为4种处理:N0(0 kg/(hm2.a),对照)、N1(60 kg/(hm2.a))、N2(120 kg/(hm2.a))、N3(240 kg/(hm2.a)),每种处理重复3次。经660 d分解后,N0、N1、N2、N3处理凋落物残留率分别为24.58%、21.99%、15.46%和25.17%,分解系数分别为0.776 4、0.807 6、1.018 8和0.760 8,95%的凋落物分解所需时间分别为3.99、3.95、3.06和4.11年,表明N1、N2促进了凋落物的分解,而N3则表现出一定的抑制作用。模拟氮沉降在一定程度增加了凋落叶中的氮含量,从而降低了碳氮比。除N3处理外,凋落物分解系数与凋落物中的氮含量呈显著的正线性关系,而与碳氮比呈负相关。

A field simulated experiment was conducted in a Chinese fir plantation in central western Fujian Province, to study the decomposition of leaf litter of Chinese fir in response to increased nitrogen deposition. Treatments were designed as NO （0 kg/（ hm^2· year ） ）, N 1 （60 kg/（ hm^2·year ） ）, N2 （ 120 kg/（ hm^2· year ） ） and N3 （240 kg/（hm^2·year） ）, with three replicates in each treatment. After 660 days of leaf litter decomposition, the litter remaining rate was estimated to be 24.58 %, 21.99 %, 15.46% and 25.17 % for N0, N1, N2, N3 treatments, respectively. Based on Olson equations, decomposition coefficient k for the above treatments was estimated to be 0.776 4,0.807 6,1.018 8 and 0.760 8,with 95% litter decomposition time of 3.99,3.95, 3.06,4.11 years, respectively, suggesting that the low-to-medium N loads （N1 and N2） increased the litter decomposition rate, but high levels of N deposition （N3） was found to inhibit the decomposition to some extent. The N concentrations of leaf litter increased with the increased nitrogen loads, leading to lower C/N ratios. Decomposition coefficient was observed to have positive linear relationship with N concentrations in leaf litter,but negative relationship with C/N ratios for the treatments except for N3.