科尔沁沙质草地封育过程中的植被变化及其机制

对科尔沁沙地乌兰敖都地区的沙质草地封育后的植被变化及其机制进行分析研究。结果表明：① 围栏封育使植被物种丰富度、密度显著提高，群落的优势种发生明显变化；围封地的Simpson多样性指数和Shannon-Wiener多样性指数均表现为随封育时间增加而下降，而Pielou均匀度指数随围封时间增加表现出先增加后下降的趋势。② 围栏封育可以增加土壤表层（0~10 cm）的养分含量，但电导率随围封时间表现出先降低后增加的趋势，同时围栏封育使土壤水分含量下降。③ 土壤表层（0~10 cm）各因子对多样性的影响不同，全氮和pH与Pielou指数呈显著(P<0.05)负相关；全氮对于丰富度指数呈显著(P<0.05)正相关；其他土壤环境因子与多样性指数间关系均不显著，表明在沙质草地封育不利于植物多样性的维持，但有利于土壤养分的积累。

Change and Mechanism of Vegetation in the Fenced Sandy Grassland in Horqin Sandy Land

In this paper,the change and mechanism of vegetation in sandy grassland in Horqin Sandy Land during the natural regeneration process was studied.The study was carried out at Ulan'aodu in Horqin Sandy Land.The results are as follows:(1) Vegetation density and species richness in the fenced grassland were obviously improved,and the dominant species of plant community were changed obviously.The indexes of Simpson and Shannon Wiener species diversity were decreased with the increase of fenced time,whereas the Pielou evenness was increased at firstly,and then decreased with the increase of fenced period; (2) Nutrient content in topsoil (0-10 cm) in the fenced grassland was increased,but the electric conductivity was decreased at firstly,and then increased with the vegetation regeneration process.Soil moisture content was decreased with fenced time; (3) Effects of topsoil factors on the plant species diversity were different.There was a significant negative correlation (P<0.05) between total N and the pH value and Pielou diversity index,but a positive one between total N and richness index.The correlations between soil factors and diversity indices were not so significant.Therefore,fencing in sandy grassland was disadvantageous for maintaining the species diversity but advantageous for accumulating soil nutrient.