松嫩平原碱化草地植物群落分布的空间和环境因素分析

Partitioning the Spatial and Environmental Variations of Plant Community Structure of Alkaline Grassland on Songnen Plain 

在１９９６年野外实地采样的基础上，运用ＤＣＡ消势对应分析（ｄｅｔｒｅｎｄｅｄｃｏｒｅｓｐｏｎｄｅｎｃｅａｎａｌｙｓｉｓ）对群落主要变化趋势及其与土壤环境因子之间的关系进行了分析。运用ＤＣＣＡ消势典范对应分析（ｄｅｔｒｅｎｄｅｄｃａｎｏｎｉｃａｌｃｏｒｅｓｐｏｎｄｅｎｃｅａｎａｌｙｓｉｓ）对影响松嫩平原碱化草地群落结构季节动态的空间和环境因素进行了定量的分解。结果表明：在影响群落分布的各因子中，环境因子独立约占４０％，而环境＿空间耦合因子占３５％，空间因子独立约占３％，其他因子约占２０％。在诸多因子中，土壤的盐渍化程度在整个生长季起着决定性作用，但土壤水分和氮素的作用因季节而变化。在干旱季节，植物生长的主要制约因子为土壤碱化度和土壤水分，而土壤氮素的作用处于次要地位。但在降雨较多、土壤湿润度较大的季节，土壤氮素的影响明显增强，成为仅次于土壤碱化度的决定性因素。

Changes of community structure of Songnen grassland and its relation to soil factors were analyzed based on field experiment in 1996. Variation of species abundance within an alkaline grassland in Northeast China plant community was partitioned into four portions: 40% of environmental variation, 3% of spatial variation, 35% environmental_cross_spatial variation, and 20% of undetermined variation due to biological factors and random factors. A canonical ordination analysis on the species abundance data constrained by environmental variables revealed that alkali and salinity are the determinant factors of ecological processes for the whole growth season. However, the relative importance of nitrogen and soil water varies with time, so that effect of nitrogen is less evident than soil water in dry seasons, but vice verse in wet seasons.