鼎湖山黄果厚壳桂群落的凋落物及其氮素动态

 对鼎湖山季风常绿阔叶林的黄果厚壳桂、鼎湖钓樟群落的凋落物量进行了两周年的观测，结果分别是12.16和6.58t·ha-1·yr-1。不仅年间凋落物量有差别，各月凋落物量也不尽相同。气候的变化对凋落物影响较大。用自然分解法Ⅰ和Ⅱ测得凋落物年分解失重率分别为72.4%和70.2%，t-检验结果表明两种方法无明显差别。用网袋法测得凋落物的年分解失重率为64.9%，稍低于自然分解法，与尼龙袋阻隔了某些分解凋落物的生物进入袋内有关。试验开始时测得地被物层重2.87t·ha-1，含氮量36.63kg·ha-1，一年试验期间通过凋落物进入地被物层的氮量为172.19kg·ha-1，合计地被物层应有208.82kg·ha-1的氮。但经一年分解后，在试验结束时再次测定地被物的重量和含氮量，则分别为4.32t·ha-1和55.25kg·ha-1。经计算(208.82—55.25)，已有153.57kg·ha-1·yr-1的氮从地被物层流人土壤。这部分氮相当于该群落年生长需氮量的71%，营养循环相当旺盛，反映了群落处于生长发展盛期。

LITTER MASS AND ITS NITROGEN DYNAMICS OF CRYPTOC-ARYA CONCINNA COMMUNITY IN THE DINGHUSHAN BOOSPHERE RESERVE

The litter mass in Cryptocarya concinna, Lindera chunii community belonging to monsoon evergreen broad-leaf forest in the Dinghushan Biosphere Reserve was 12.16 and 6.58t·ha-1 yr-1, investigated from February 1989 to January 1990 and from June 1990 to May 1991. The litter mass not only varied in different months and years, but also varied in the same month of different years due to the influence of climatic fluctuations.The rate of litter decomposition was determined by natural decomposition method Ⅰ and Ⅱ. The results were 72.4 and 70.2%, respectively. There was no significant difference by t-test. The rate of litter decomposition determined by using the nylon bag method was 64.9%, which was lower than that by natural decomposition methods because nylon networks prevented some animals from entering the nylon bags. The mass and nitrogen content in the litter layer at the beginning of our experiment were 2.87t·ha-1 and 36.63kg·ha-1, respectively. On the other hand, the amount of yearly nitrogen input to the litter layer by litterfall during the experimental period was 172.19kg·ha-1. However, there were only 4.3t·ha-1 of litter mass and 55.2kg of nitrogen in litter layer at the end of the experiment. Therefore, 153.57kgN·ha-1·yr-1 was released from litter layer to the soil. The amount of nitrogen released from litter decomposition is 71% of the nitrogen requirement for vegetation growth