喀斯特土层厚度异质性对草地群落结构和优势种生长的影响

喀斯特地区破碎陡峭的地形地貌和严重缺乏的土壤资源,使得该地区的土壤分布在空间上具有强烈的异质性。土壤是植物获取水分和养分的主要途径,土壤分布的不均匀会直接影响到植被的生长和分布。因此,选择重庆典型喀斯特山地草地植物群落为研究对象,采用样地调查法,对不同土层厚度生境中(0~15cm、15~25cm和25cm)草地的群落结构、物种分布和优势种生长状况等展开研究。结果表明,1)研究区域内草地群落的优势种主要是一年生、二年生或多年的草本植物,随生境土层厚度增加,群落的优势植物中逐渐有木本植物的出现,群落优势种的优势地位也随土层厚度的增加越来越稳定;2)群落的物种丰富度指数、物种多样性指数和均匀度指数随生境土层厚度改变均未发生显著变化(P0.05);3)非禾本科植物,主要是菊科和豆科的物种数目和重要值随土层厚度的增加而增加,禾本科物种数目随土层厚度增加而减少,重要值无明显变化;4)优势种荩草(Arthraxon hispidus)的株高、叶面积和地上部生物量均随土层厚度增加而表现出显著上升的趋势(P0.05)。可见,随生境土层厚度增加,喀斯特草地的群落结构表现出越来越成熟和稳定的趋势,优势种的生长受到显著促进,但各科的优势度和群落的物种多样性未发生显著变化。

The effects of soil thickness heterogeneity on grassland plant community structure and growth of dominant species in karst area

The karst ecosystem is a special and fragile ecosystem type.In karst areas,crushed and steep terrain and a serious lack of soil resources result in strong spatial heterogeneity in soil distribution.Soil is the main me dium for plants to acquire water and nutrients,and uneven soil distribution will directly affect the growth and distribution of vegetation.Therefore,a typical karst grassland community in Chongqing was selected as the research model to study community structure,species distribution,and dominant species growth status of grassland communities in different soil thickness habitats (0～15 cm,15～25 cm,and ＞ 25 cm).The following results were obtained:1) The predominant species of grassland communities in the study area were mainly annu al,biennial,or herbs and,with an increase in soil thickness,woody plants gradually appeared as the dominant species of the community.The position of the dominant species in the community was more stable with an in crease in soil thickness;2) The species richness index (D1 and D2),species diversity index (SW and SN),and evenness index (R) of the plant community in the karst mountain grassland did not change significantly with soil thickness changes (P＞0.05);3) The species and importance of non-gramineous plants,mainly Compositae and legumes,increased with increasing soil thickness.The number of gramineous species decreased with an increase in soil thickness and the significance value did not change significantly;4) Plant height,leaf area,and aboveground biomass of dominant species (Arthraxon hispidus) showed a significant upward trend with an increase in soil thickness (P＜0.05).Therefore,with an increase in soil thickness,the community structure of karst grassland showed greater maturity and stability,and the growth of dominant species was significantly promoted;however,the dominance of each family and the species diversity of the community did not change significantly.