内蒙古典型草原区芨芨草群落适生生境

Suitable habitat for the Achnatherum splendens community in typical steppe region of Inner Mongolia

芨芨草群落是干旱与半干旱地区重要的植被资源,内蒙古典型草原区常在地形稍低的部位镶嵌有芨芨草群落,且芨芨草群落常与低洼湿草甸群落相连。为了探究芨芨草群落的适生生境,在锡林郭勒盟典型草原区选取了4个代表性调查区,从芨芨草群落及其相邻群落分布的地形特征、调查区的地下水埋深、1 m深土层的土壤电导率、土壤pH值和土壤质地等指标上对芨芨草适生生境进行探究,结果表明,芨芨草群落在内蒙古典型草原区常分布在河漫滩和丘间蝶形洼地地区,呈现出由高程梯度导致的与地带性针茅群落、湿草甸群落带状分布的特点,导致这种成带分布的原因与地下水埋深及地表径流有关,芨芨草群落生境的地下水埋深一般在1—3 m且有地表径流的补充;芨芨草群落耐盐碱性强,其生境也与反映土壤盐分含量的土壤电导率和土壤pH值有关;但芨芨草群落生境的形成不是由土壤机械组成所致。

The Achnatherum splendens community is an important vegetation resource in arid and semi-arid regions.A mosaic A.splendens community often exists in the slightly lower topographical parts of typical steppe regions in Inner Mongolia,and often adjoins the low-lying wetlands.At present,little research has been done on suitable habitat for the A.splendens community.Four representative study areas of typical steppe in the Xilinguole Grassland were selected to study the suitable habitat for this community in the steppe region of Inner Mongolia： 1 and 2） Huahushuo and Borenaobao of Baiyinxile Ranch,3） Laomaodeng hamlet of Maodeng Ranch,and 4） Xinlinhaote′s penal farm.We selected an area in each plot to measure the local topography by using an optical theodolite（TDJ6E）,including the length,width,and heigh of each plot.Also we surveyed the vegetation of the A.splendens community and its adjacent communities,which were zonal Stipa communities and wet meadow communities.When possible,we measured the underground water level in wells in the plots using the optical theodolite（TDJ6E） at the topographic control point;a soil sample 1 meter in depth was collected,and divided into 10 equal layers.Soil conductivity was tested using a Multi-340i multi-parameter measuring instrument.The soil pH value was tested with a DELTA320-type pH meter produced by the Mettler Toledo Company.Soil texture feature was assessed by testing soil grain size with a Microtrac S3500 Particle Size Analyzer.By comparing the above indices with the other adjacent communities,some conclusions can be made.The A.splendens community of typical steppe in Inner Mongolia is a result of an elevation gradient.It has a kind of zonal distribution among the communities of A.splendens,zonal Stipa communities,and wet meadow communities.First,it is clear the A.splendens community occurs in areas with groundwater at 1—3 m below the surface,in addition to surface runoff.The deep root system of A.splendens reaches the groundwater directly.Secondly,it is also relevant to the soil pH value and the soil conductivity tests reflect the soil salt content.The salt tolerance of A.splendens community is well known to be very high.Soil salinity,low at the soil surface,was relatively higher as depth increased.The soil pH is significantly higher in this community than in the adjacent wet meadow community and zonal Stipa community.However,it can be concluded that the formation of the A.splendens community suitable habitat is unrelated to soil texture.