祁连山东部森林林分结构和环境因素对草本物种多样性的影响

Effects of stand structure and environmental factors on understory herbaceous plant diversity in eastern Qilian Mountains

林下草本物种多样性在维持西北干旱与半干旱地区的生态系统服务功能方面起着重要作用,探究其相关影响因素,可为祁连山东部地区的人工生态公益林的可持续经营提供理论基础。选取位于祁连山东部地区的针叶纯林、阔叶纯林、针叶混交林、针阔混交林(人工林)为研究对象,在相关性分析的基础上构建草本物种多样性的多因素参数预测模型和结构方程非参效应模型,探究多重因素(林分空间结构、林分非空间结构、环境因子)间的关系以及对林下草本物种多样性的影响程度。结果表明:(1)针阔混交林中林下草本的科、属、种数量最多。(2)平均胸径、平均树高、角尺度、混交度、大小比、坡度与草本物种多样性呈显著性相关(P<0.05)。(3)平均胸径是影响林下草本Simpson多样性指数的关键因子;坡度是影响林下草本Shannon-Wiener多样性指数的关键因子;角尺度、混交度是影响Pielou均匀性指数的关键因子;平均胸径、平均树高是影响物种丰富度的关键因子。(4)结构方程非参效应模型显示林分结构是影响草本物种多样性的关键因子(P<0.001),环境因子是影响草本物种多样性的重要因子(P<0.05)。因此,在后续森林植被恢复措施中,应当着重考虑林分的空间结构,形成随机分布的异龄复层混交林,以增加光合利用效率并遵循生态位互补理论,从而提高草本多样性。

Understory herbaceous species diversity plays an important role to maintain ecosystem services in arid and semiarid areas of northwest China.Exploring its related influencing factors can provide a theoretical basis for the sustainable management of artificial ecological public welfare forests in the eastern Qilian Mountains.In this study,coniferous pure forest,broadleaf pure forest,coniferous and broad mixed forest and mixed coniferous forest(planted forest)located in the eastern Qilian Mountains were selected as the research objects,and a multivariate parameter prediction model and structural equation non⁃parametric effect model of herbaceous species diversity were constructed on the basis of correlation analysis.The relationship between multiple factors(stand spatial structure,stand non⁃spatial structure,and environmental factors)and the degree of influence on the diversity of understory herbaceous species were explored.The results showed that:(1)among them,the number of Coniferous and broad⁃leaved mixed forest species was the largest,with a total of 132 species in 129 genera in 39 families.And in the coniferous and broad⁃wide mixed forest,Elymus dahuricus,Lolium perenne,Fragaria vesca,Carex spp.are the dominant species.(2)Pearson correlation analysis was indicating that mean diameter at breast height,mean tree height,angle index,mingling degree,neighborhood comparison,and slope were significantly correlated with herbaceous species diversity(P<0.05).(3)Multivariate parameter prediction model for herbaceous species diversity was indicating that the diameter at breast height was the key factor influencing the Simpson diversity index.Slope was a key factor influencing the Shannon⁃Wiener diversity index.Angle index and mingling degree were the key factors affecting Pielou′s diversity index.Mean diameter at breast height and mean tree height were the key factors affecting richness.(4)The structural equation of herbaceous species diversity was not effect⁃based model indicating that stand structure was the key factor influencing herbaceous species diversity(P<0.001),and environmental factors were important factors influencing herbaceous species diversity(P<0.05).Among them,angular scale and mingling degree were the main stand spatial structural factors affecting the diversity of herbaceous species,the mean tree height and mean breast diameter were the main stand non⁃spatial structural factors affecting the diversity of herbaceous species,and Slope was a major environmental factor affecting the diversity of herbaceous species.Moreover,slope not only had a direct effect on herbaceous species diversity,but also has an indirect effect by affecting stand structure.Therefore,in the subsequent forest vegetation restoration measures,the spatial structure of forest stands should be considered to form randomly distributed heterogeneous multi⁃layer mixed forests to increase photosynthetic use efficiency and follow the theory of niche complementarity,so as to improve herbaceous diversity.