浑善达克沙地丘间低地植物群落的分类与排序

Classification and ordination analysis of plant communities in Inter-dune lowland in Hunshandak Sandy Land

对浑善达克沙地中部丘间低地的草本植物群落进行 TWINSPAN分类和 DCA排序的研究结果表明 ,这些植物群落可分为 4组 :第 1组为大针茅 (Stipa grandis) +糙隐子草 (Cleistogenessquarrosa)群落 ,固定时间长 ,比较稳定 ,土壤全氮和有机质含量在四组群落中最高 ;第 2组为冰草 (Agropyron cristatum)群落 ,主要物种有冰草、冷蒿 (Artemisia frigida)、苔草 (Carex sp.)和糙隐子草 ,土壤全氮和有机质含量比第一组的低 ;第 3组为羊草 (Leymus chinensis) +赖草 (Leymus secalinus)群落 ,群落物种少且主要为 1年生种 ,有过严重的干扰 ,土壤全氮和有机质含量在 4组群落中最低 ;第 4组为西伯利亚剪股颖 (Agrostissibiri-ca)群落 ,属于草甸性质的群落 ,土壤可溶性钠和可溶性钾含量高。群落 DCA排序及排序轴与土壤因素的相关分析表明 ,土壤可溶性钠和 p H值对群落的分布有显著影响 ,但群落在可溶性钠的梯度上分异更明显 ,说明盐分是影响浑善达克沙地中部丘间低地草本植物群落分布的主要因素。

Hunshandak Sandy Land is located in the south part of Xilingol League of Inner M ongolia (N 42°10′ ～43°50′,E 112°10′～116°30′). It is about 260 km lon g from east to west, 30 to 100 km in width with the altitude ranging from 1100 t o 1300 m. Sand dune and inter-dune lowland are the two main physiognomy types, which have a significant effect on the vegetation. The sharply heterogeneous env ironmental conditions result in the occurrence of diverse vegetation types inclu ding woodland, shrubs, steppes and meadows, although the typical zonal vegetatio n in this region is steppe. A site that occupied some 2700 hm 2 was established to study dynamics of sandy land ecosystem and the restoration of degraded vegetation in the middle of Hunsh andak Sandy Land in 2001. A vegetation survey was performed in the summer of 200 2. The result indicates that the herbaceous communities were abundant in inter-dune lowland of this site. Grassland is important for local stockbreeding deve lopment, as it is the main mowing or grazing field for the people in Hunshandak Sandy Land. To well understand the main factors determining the structure and di stribution pattern of herbaceous communities of this site, classification and or dination analysis were made by using the two-way indicator species analysis (T WINSPAN) and the detrended correspondence analysis (DCA). The result of classification indicates that all communities were classified into four groups. The first group was a type of relatively stable communities domina ted by Stipa grandis and Cleistogenes squarrosa. The contents of its tot al nitrogen and organic matter of the soil were the highest among the four group s. The second one was dominated by Agropyron cristatum, with Artemisia fri gida, Cleistogenes squarrosa and Carex sp. as common species. The contents of its total nitrogen and organic matter of the soil were relatively less than those of the first group. The third group was dominated by Leymus chinensis and Leymus secalinus, commonly with a few annual species, and had suffered h eavy disturbance. The contents of its total nitrogen and organic matter of the s oil were the lowest among the four groups. The fourth group was a type of meadow dominated by Agrostis sibirica and contents of its soluble sodium and potas sium of the soil were highest. DCA ordination of those communities and correlation a nalysis with soil factors shows that the soluble sodium content and pH values of the soil significantly affected the distribution pattern of those communities. The communities were more distinct from each other along the gradient of soluble sodium content than along that of pH values. It was suggested that salinity of the soil might be the main factor affecting the structure and distribution patte rn of those herbaceous communities in inter-dune lowland in the middle of Hunsh andak Sandy Land.