杉木人工林凋落物量对氮沉降增加的初期响应

Responses of litterfall production in Chinese fir plantation to increased nitrogen deposition

通过野外模拟试验,研究了杉木人工林凋落物对氮沉降增加的初期响应。试验设计为4种处理,分别为N0(0kgN.hm-2.a-1,对照)、N1(60kgN.hm-2.a-1)、N2(120kgN.hm-2.a-1)、N3(240kgN.hm-2.a-1),3次重复。通过2年监测发现,对照样地的年凋落量为2427.51kg.hm-2,而经N1、N2、N3处理后,其年凋落物量分别为2238.10、2286.66和2599.50kg.hm-2。表明高氮(N3)处理显著增加了杉木林凋落物量(P<0.05),而中低氮处理(N1、N2)没有显著影响。各处理的总凋落物量表现出明显的季节动态,在2、5和7月出现3个比较明显的峰值。在凋落物的组成中,落叶占总凋落量的70.49%～73.67%,其次分别为落枝(19.38%～20.39%)、碎屑物(4.98%～7.70%)、落果(1.11%～2.16%)和树皮(0.29%～0.33%)。LSD多重比较显示,N3处理对落叶和落果产生显著影响,对其它组分的影响不明显。

A field simulated test was conducted to study the effects of nitrogen deposition on the litterfall production of Chinese fir plantation. Treatments were designed as N0（0 kg N · hm^-2 · a^-1）, Nl（60 kgN· hm^-2 · a^-1）, N2（120 kg N· hm^-2 · a^-1） and N3（240 kg N· hm^-2 · a^-1）, with three replicates in each treatment. Two years observation showed in treatments N1, N2 and N3, the annual litterfall production was 2 238.10, 2 286.66 and 2 599.50 kg · hm^-2, respectively, in contrast to 2 427.51 kg· hm^-2 in the control （ N0）. High N deposition （ N3 ） increased the litterfall production significantly, while low-to-medium N loads （N1 and N2 ） had no obvious effects on it. The monthly litterfall production in all treatments showed similar seasonal dynamics, with three peaks occurring in February, May and July, respectively. In the litterfalls, fallen leaf accounted for 70.49%-73.67% of the total, followed by bra.nch （19.38%- 20. 39% ） , debris （4.98%-7.70%） , fruit （ 1.11%-2. 16% ） , and bark （0. 29%-0.33% ）. Treatment N3 had significant effects on the amount of fallen leaves and fruits, but less effects on other litterfall components.