红壤侵蚀区微地形上芒萁分布与地形湿度指数特征

Spatial Distribution Pattern of Topographic Wetness Index and Dicranopteris dichotoma on Micro-Landform in Eroded Red Soil Region of South China

南方红壤侵蚀退化区由于土壤侵蚀在均匀坡面上形成细沟、浅沟、切沟等不同规模的侵蚀沟,以及大小不等、形状各异的微地形。为研究芒萁分布与地形湿度和地表起伏的关系,本研究在实测微地形生成高精度DEM的基础上,进行地形湿度指数的计算;在以地形位置指数和坡度为主要判定依据划分坡位的基础上,采用随机采样的方法,调查实验样区芒萁生长特征。结果表明,在地表起伏的微地形上,芒萁趋向于分布在0~15°坡度的沟谷和缓坡范围内;沟底芒萁生物量、生长密度、高度分别为沟坡的2.25倍、1.57倍和1.68倍。模拟结果显示,地形湿度指数：沟谷〉缓坡〉陡坡〉脊部;有芒萁覆盖区与无芒萁覆盖区的地形湿度指数平均值分别为2.13和1.15,前者明显大于后者。基于上述结果,为研究南方红壤严重侵蚀退化区芒萁的生长蔓延提供理论基础和实践指导。

Eroded Red Soil Region of South China is the second largest eroded area after Loess Plateau.The gully erosion of different scale,such as rill and shallow ridges,appeared in a homogeneous slope for soil erosion in Eroded Red Soil Region of South China.Dicranopteris dichotomais much more tolerant of poor and acid soils,and is widely distributed in South China.It plays an important role in controlling soil and water loss and therefore,it can be used as pioneer vegetation in soil and water conservation and ecological restoration of the study area.The growth characteristics of Dicranopteris dichotoma,such as biomass,plant height and density,were surveyed to study the relationship between vegetation distribution and surface fluctuations,by using sampling surveys and random sampling.And soil temperature and humidity of 5cm below the surface was measured by the automatic temperature-humidity observation instrument.On the basis of Dicranopteris dichotomainvestigation and automatic temperature-humidity observation data at micro-landform,the vegetation characteristics of Dicranopteris dichotoma and the relationship of them was analyzed.Results showed that,Dicranopteris dichotomais distributed mostly at slope gully of 0-15°and slope range;the biomass of Dicranopteris dichotomain the bottom of ditch is about 2times as much as side slope,and the Dicranopteris dichotoma density and height is far greater than gully slope.The topographic wetness index（TWI）is strongly correlated to soil temperature and humidity of 5cm below the surface（R2=0.6）.The average value of the TWI on Dicranopteris dichotoma coverage area is 2.13,while the same index on the region with no vegetation is only 1.15.The former was obviously higher than the later（P〈0.01）.