砒砂岩区不同立地类型人工油松林下草本种群生态位特征及其环境解释

黄土高原砒砂岩区是我国水土流失最为严重的地区之一,油松(Pinus tabuliformis)是该区水土保持与水源涵养的优势乔木。以几种不同立地类型人工油松林为对象,应用Levins生态位宽度指数、Pianka生态位重叠指数和冗余度分析(RDA),研究林下草本群落生态位特征及其与环境的相互响应。结果表明:所调查的150个油松林下草本样方中,共发现31种草本植物,隶属于11科24属,阳性旱生植物居多。不同立地类型人工油松林下草本群落生态位特征不同,生态位宽度指数及生态位重叠指数均表现阳坡大于阴坡,平坡好于斜缓坡,但整体指数均较小,表明物种对环境资源利用程度较低,种间竞争度不大,群落处于相对稳定状态。通过对比典范对应分析(CCA)及冗余度分析(RDA),RDA排序更能较好揭示生态位特征与环境因素的关系,得出乔灌层郁闭度、土壤有机质、土壤含水率和坡度是林下草本群落生态位特征各异的主导环境因子。

Environmental interpretation of ecological niche characteristics of herbaceous populations under different site types of Pinus tabuliformis forest in feldspathic sandstone region

Pinus tabuliformis is a dominant tree for soil conservation and water conservation in the arsenic sandstone region of the Loess Plateau, one of the most serious areas of soil erosion in China. The Levins ecotone width index, Pianka ecotone overlap index, and redundancy analysis (RDA) were applied to study the ecotone characteristics of understorey herbaceous communities and their interactions with the environment in several different stand types of planted P. tabuliformis forests.On the basis of the variation among sites,the planted forests of P. tabuliformis were classified into six types.At each site,topography ( slope,aspect,and slope position) and forest stand characteristics(canopy density,stand density) of P. tabuliformis was recorded,herb species were measured in 1×1m² quadrats,and soil samples were collected adjacent to each quadrat.In this study,we used the niche breadth and Niche overlap indices for analysis of herb species ecological niche characteristics under different site types of P. tabuliformis forests in a feldspathic sandstone region,and studied the relationship between ecological niche characteristics and the environment through CCA and RDA.The results showed that 31 species of herbaceous plants belonging to 11 families and 24 genera were found in the 150 herbaceous samples of P. tabuliformis sylvestris understorey surveyed, with a predominance of positive dry plants. The ecological niche characteristics of the herbaceous communities in different types of P. tabuliformis forests were different. The ecological niche width index and the ecological niche overlap index both showed that the sunny slopes were larger than the shady slopes, and the flat slopes were better than the gentle slopes, but the overall indices were smaller, indicating that the species used the environmental resources to a less extent, the interspecific competition was not too great, and the communities were in a relatively stable state. By comparing canonical correspondence analysis (CCA) and redundancy analysis (RDA), the RDA ranking better reveals the relationship between ecological niche characteristics and environmental factors. It concludes that tree and shrub layer depression, soil organic matter, soil water content and slope were the dominant environmental factors for the different ecological niche characteristics of understorey herbaceous communities.