金沙江干热河谷人工赤桉林群落结构

 为干热河谷地区的生态林建设提供理论依据,从反映群落稳定性的群落结构、物种多样性以及生长量和生物量等常用指标分析,金沙江干热河谷地区人工赤桉(Eucalyptuscamaldulensis)林密度普遍偏高,结构比较简单,群落稳定性较差。3种密度的赤桉林群落,随着林分密度的增大,林下植被层的群落分异性越大,林分中主要分布优势种(乔木为赤桉,林下植物为扭黄茅),其他种群的数量极少,林下植被层的结构比较简单,随着林分密度的增大,物种的丰富度、ShannonWiener指数、物种均匀度和生态优势度等4个指标不断减小,群落物种多样性在不断降低,结构合理性越差;群落生长量和生物量的变化,基本随赤桉林的密度增加而减小,密度最小的林分F1的生物量是其他2种高密度林分生物量的2倍以上。各林分林木生长缓慢,即使密度最小的林分F1的年平均胸径和树高生长量,分别只有0.72cm和0.78m。为了增加干热河谷地区人工乔木林群落的稳定性,使其逐步实现正向演替,发挥其应有的生态防护功能,应该考虑降低乔木层群落密度。

The Community Structure of Artificial Eucalyptus Camaldulensis Stands in the Dry-Hot Valley of Jinsha River

Through analyse on indexes in common use of community stability describing such as community structure, plant species diversity, growth yield and biomass yield, the density of artificial Eucalyptus camaldulensis forests are high widely, the structure is simple and the community stability is lower in dry-hot valley of Jinsha River. With increasing of stands density of three Eucalyptus camaldulensis form,the vegetation communities difference under forest canopy increased, there was mainly dominant species in forest (arbor species is Eucalyptus camaldulensis, the species under forest canopy is Cheteropogon contortus), the few other species was exist in forest, the vegetation layer structure under forest canopy was simple. With increasing of stands density, the species enrichment (S), Shannon-Wiener index (SW), species equality (E) and ecological dominance (ED) minished, the species diversity of community decreased, the community structure changed to badness. The growth yield and biomass yield of community reduced with increasing of stands density also. The biomass yield of the lowest density forest (F₁) was more than the double of that one of the other higher density forest. The tree growth of all forests was slowness. The average annual growth quantity of diameter and height was 0.72cm and 0.78m respectively even in the lowest density forest (F₁). To improve the stability of artificial arbor community and advance their positive succession in Jinsha River dry-hot valley, bring into play their ecological function, it is should be considered to reduce the arbor layer community density of artificial forest.