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通过野外模拟试验,研究了亚热带常绿阔叶林凋落物量对氮沉降的初期响应。试验设计4种处理,分别为对照(CK)、低氮(LN,50 kg·hm-2·a-1)、高氮(HN,100kg·hm-2·a-1)和高氮加磷(HN+P,100 kg N·hm-2·a-1+50 kg P·hm-2·a-1),每个处理重复3次。通过2年的试验观测,甜槠林对照林分年总凋落物量为7.78 t·hm-2,经LN、HN、HN+P处理后,年总凋落物量分别为8.81、9.08、9.41 t·hm-2,不同处理间没有显著差异,表明氮沉降增加没有显著提高凋落物产量,但高氮处理林分,叶凋落物量表现出抑制效果,低于低氮处理;高氮+磷处理的林分凋落物总量及落叶、落枝量均明显高于高氮、低氮处理,磷添加呈现凋落物量增加的效应。甜槠林分总凋落物量表现出明显的季节动态,在春季4—5月以及秋季11月出现2个明显的峰值,不同处理趋势一致。凋落物组成中,落叶的比例占总凋落物量的53.78%~58.84%,花果杂物占28.29%~33.66%,落枝占10.79%~12.87%。研究表明,高氮处理可能引起了土壤氮素过剩,造成氮、磷失衡。
Field experiments were conducted to study the initial response of litterfall to nitrogen deposition in subtropical evergreen broad-leaved forests. The four treatments were as follows: CK, LN (50 kg · hm-2 · a-1), HN (100 kg · hm-2 · a-1) (HN + P, 100 kg N · hm-2 · a-1 + 50 kg P · hm-2 · a-1) were added and each treatment was repeated 3 times. Through two years of experimental observation, the total annual litterfall in the stands was 7.78 t · hm-2, and the total annual litterfall was 8.81, 9.08 and 9.41 t · hm after treatment with LN, HN and HN + P -2. There was no significant difference among the treatments, which indicated that the increase of nitrogen deposition did not significantly increase the litter yield, but the litterfall content of high-nitrogen stands and leaf litters showed a lower effect than low-nitrogen treatments; The total amount of litter, the number of fallen leaves and the number of fallen branches were significantly higher than those under high and low nitrogen treatments, and phosphorus addition showed the effect of increased litter amount. The total litter quantity of Castanopsis kawakamii showed obvious seasonal dynamics. There were two obvious peaks in April-May and November in the spring, and the trend of different treatments was the same. The litter composition accounted for 53.78% ~ 58.84% of the total litter, the flower and fruit debris accounted for 28.29% ~ 33.66%, and the branches and branches accounted for 10.79% ~ 12.87%. Studies have shown that high nitrogen treatment may cause soil nitrogen excess, resulting in nitrogen and phosphorus imbalance.