色季拉山急尖长苞冷杉林凋落物特征

Litter Characteristics of Abies georgei var.Smithii Forest in Sejila Mountain

通过西藏东南部色季拉(山)急尖长苞冷杉(Abies georgei var.smithii)原始林不同胸径级立木的凋落物调查,以树冠投影面积推算林地凋落物量,分别对凋落物组成、年输入量与月动态变化等特征进行分析。结果表明,色季拉山急尖长苞冷杉林年平均凋落量为3.42T hm^(-2) year^(-1)。凋落物主要由针叶、树枝、球果、树皮、花序和碎屑六种组分构成,其中,针叶凋落量最大2097.15 kg,针叶所占凋落量比率为61.5%,其次是枝682.87 kg占比为20.0%;球果436.48 kg和树皮103.62 kg分别所占比例为12.8%和3%,花序和碎屑68.2 kg的凋落量所占比率约为2%左右。针叶和枯枝是冷杉林凋落物最主要的组分,占凋落物总量81.5%。急尖长苞冷杉林的凋落物年动态总体呈双峰型曲线,10-11月是凋落的高峰期,该期凋落量占全年凋落总量的37%;4月会出现一个小峰期,凋落物量占15%;1-3月、8-9月是凋落的峰谷期,其中1月的凋落量仅占2.7%。不同径级立木的凋落量有显著性差异,凋落量排序依次为:径级Ⅰ>径级Ⅲ>径级Ⅱ>径级Ⅳ>径级Ⅴ;立木不同方位的凋落物量东侧>南侧>北侧>西侧,不同方位的凋落量有显著性差异。

This study investigates the litterfall characteristics in the original forest of Abies georgei var.smithii,located in the southeastern part of the Sajila Mountains in Tibet.The survey was conducted on litterfall from standing trees of different the diameter at breast height(DBH),and the litterfall quantity was estimated using the canopy projection area.The analysis focused on the composition of litterfall,annual input,and monthly dynamics.The findings indicated that the average annual litterfall in the A.georgei var.smithii forest was 3.42 tons per hectare per year.Litterfall was primarily composed of six components:needles,branches,cones,bark,inflorescences,and debris,and among these,needles accounted for the largest portion,with a litterfall mass of 2,097.15 kg and a contribution rate of 61.5%.Branches followed with 682.87 kg,accounting for 20.0% of the litterfall.Cones contributed 436.48 kg(12.8%),while bark and inflorescences accounted for 103.62 kg(3%)and 68.2 kg,respectively,making up approximately 2% of the litterfall.Needles and dead branches constituted the major components,representing 81.5% of the total litterfall.The annual dynamics of litterfall in the A.georgei var.smithii forest exhibited a bimodal pattern,and the peak litterfall period occurred from October to November,accounting for 37% of the total annual litterfall.A minor peak was observed in April,contributing 15% of the litterfall,and the months of January to March and August to September represented periods of lower litterfall,with January contributing only 2.7%.Significant differences in litterfall were observed among different diameter classes of standing trees,with the highest litterfall in Diameter Class Ⅰ,followed by Diameter Class Ⅲ,Diameter Class Ⅱ,Diameter Class Ⅳ,and Diameter Class Ⅴ.Furthermore,litterfall varied significantly among different compass directions,with the highest amount found on the east side,followed by the south,north,and west sides.