黄土丘陵区沙棘人工林发育过程中物种多样性及种间关联变化

根据野外调查资料,分析了不同发育阶段沙棘人工群落物种多样性及种间关联的变化特征.结果表明,群落各层及总体物种多样性基本呈“S”形波动变化.在不同发育阶段的沙棘群落中,物种丰富度和多样性指数均呈现草本层＞灌木层的趋势.灌木层物种多样性指数在撂荒地中较低,随群落发育逐渐增加,灌木层物种均匀度指数在13年生的沙棘林中较高;草本层多样性指数在3年生的人工林中较高,在8年生的人工林中较低,在25年生的人工林中较高.人工沙棘林中种间关联正负绝对值基本呈抛物线形变化,13年生左右显著程度和联结强度较弱,群落内物种间物种替代速度缓慢,竞争较少,群落组成和结构相对稳定.在沙棘人工林的经营和管理上,应是13年生以前以保护为主,到25年生时进行适度择伐,抚育萌生幼苗,促进种群更新发育.

Species diversity and interspecific association in development sequence of Hippophae rhamnoides plantations in loess hilly region

Based on field investigation, this paper analyzed the characteristics of species diversity and interspecific association at different development stages of Hippophcze rhamnoides plantations. The results showed that the species diversities of shrub layer, grass layer, and whole community of H. rharnnoides plantations were all fluctuated in "S" shape. At different development stages, the species richness and diversity were higher in grass layer than in shruh layer. The shrub species diversity was lower on hare land, but increased gradually with development stage. Shrub evenness index was higher in 13-year forest stand, while grass diversity index was higher in 3-year plantation, lower in 8-year plantation, and higher in 25-year plantation. The positive and negative absolute values of interspecific association between H. rharnnoides and other principal species changed in parabola shape, and the notable degree and the interspecific association intensity were weaker in 13-year plantation, showing that the species substitution rate was slower, competition was less, and community composition and its structure were relatively stable. To improve ecological environment, the H. rhamnoides plantations younger than 13 years old should he given priority to protection, while for those of 25 years old, moderate thinning should be made to promote the regeneration.