天山云杉林冠层结构对草本物种多样性的影响

Effects of Canopy Structure on Herbaceous Species Diversity in Picea schrenkiana var.tianschanica Forest

为研究天山云杉林冠层特征与林下草本物种多样性的相互关系,以新疆天格尔森林公园天山云杉林的4个龄级的林分(幼林龄、中林龄、近熟林、成熟林)为研究对象,以冠层分析仪获得的冠层结构特征和林下光环境指数等野外实际调查数据为依据,通过计算α多样性指数分析4个龄级的草本物种多样性,利用多元统计方法研究冠层结构对草本多样性的影响。结果表明,各个指标在不同龄级间均有一定的差异,且随着林分的生长和更新,天山云杉林呈现林冠开度逐渐减小、叶面积指数增大、林下光辐射均减弱、物种多样性指数均减小的趋势;典型模型表明林冠开度对冠层结构起到主要作用(呈极显著正相关P<0.01),叶面积指数次之(呈极显著负相关P<0.01);在林下辐射中,林下总辐射对林内光环境起主要作用;相比冠层结构,林下光照对草本层物种多样性的作用更大,其中林冠开度和丰富度指数之间呈显著正相关,林下总辐射、林下直射辐射和多样性指数、均匀度指数之间均呈显著正相关。

In order to understand the relationship between the characteristics of canopy structure of Picea schrenkiana var.tianschanica and species diversity of understory herbs,stands of P.schrenkiana var.tianschanica with four age levels(young growth,mid-mature,nearly mature,and mature)occurring in the Xinjiang Tiangeer Forest Park were taken as the research objects.Based on the data collected from field investigation,such as canopy structure characteristics(obtained from canopy analyzer)and understory light environment index,the diversities of the understory herbs in four-age-level stands were analyzed byα-diversity index.Multivariate statistical method was adopted to examine the influence of canopy structure on herb diversity.The results showed that 1)all the indicators had certain differences among different age levels,and with the growth and renewal of stands,canopy opening decreased,leaf area index increased,understory light radiation decreased,and species diversity index decreased.2)According to the current typical model,canopy openness played a major role in canopy structure(highly significant positive correlation,P<0.01),and leaf area index ranked the second(highly significant negative correlation,P<0.01).The total understory radiation played a major role in the light environment of the forest.3)Compared with canopy structure,understory light had greater impact on species diversity in the herb layer,in which canopy openness was significantly and positively correlated with richness index,and total understory radiation,direct understory were significantly and positively correlated with diversity index and evenness index.