香溪河流域一条一级支流河岸林凋落物季节动态

对神农架南坡的一条一级支流河岸林的凋落物进行了一年的连续收集研究。结果表明：凋落物干重年输入量为438．72g／m^2，其中树叶凋落物是凋落物的主要成分，占整个凋落物年产量的84％。凋落物的输入明显存在季节性的时间格局。凋落物在秋季的产量占全年产量的75％，春季占6．2％，夏季占13．6％，冬季为5．5％。凋落物组成中，树叶和花果的产量显示出季节变化的趋势；枝条的产量并未显示出明显的季节趋势。在秋季，树叶的产量占全年树叶总量的83％；枝条最高值出现于秋季，产量占全年总员的29％；花果在整个凋落物中所占比重分小，最高值出现在夏季，占年产量的63％。着生藻类的密度月际间的变化较大，存在着显著的差异。最大值与最小值的出现月份与凋落物最大、最低值的出现月份相同。通过统计分析表明，着生藻类的密度变化与凋落物和树叶凋落物的动态具有明显的相关性。

Seasonal Dynamics of Litter in a Headwater Stream of Riparian Forest in Xiangxi River Catchment

Based on the litter collection of riparian forest in a headwater stream during one year,annual litterfall at the site was 438 72 g/m 2.Leaves are chief component,and it accounted for 84% of annual litterfall.Temporal pattern of litter inputs are clearly seasonal:75% of the annual litterfall occurred in autumn (September to November),6 2% in spring(March to May),13 6% in summer (June to August),and 5 5% in winter (December to February) .The production of leaves,flowers and fruits litter also show a seasonal trend in litter composition.There was no seasonal trend in that of branches.The high peak period of leaves litter in autumn accounting for 83% of the annual amount of leaves,and 29% of the annual amount of branches.And that of flowers and fruits in summer accounting for 63% of the annual amount of flowers and fruits.The density of epilithic algae showed a significant difference during one year.The highest peak appeared in November,and was 72 individuals cm -2 .The lowest peak in January was 7 individuals cm -2 .The changes of epilithic algae had a significant relationship with the dynamic of litter and leaf litter (r= 0 57,P<0 05).