民勤绿洲不同年限退耕地土壤物理性质与群落特征

Soil Physical Properties and Community Characteristics of Different Abandoned Land in the Minqin Oasis

通过对民勤绿洲1a、2a、3a、4a、5a、8a、15a、24a和31a退耕地的生境和植被群落特征的分析,研究了不同年限退耕地植被群落、土壤水分、容重、孔隙度和机械组成的变化.结果表明（1）民勤绿洲退耕地在31a自然恢复过程中共出现植物32种,14科,其中灌木6种,草本26种,分别占总物种数的18.75%、81.25%;其中藜科（6种）、菊科（4种）,禾本科（4种）、蒺藜科（3种）,4科植物占总物种数的53.13%.（2）不同年限退耕地0-40cm 范围内土壤含水量随土层深度增加经历了先增后减的一个变化过程,而土壤容重及孔隙度变化不太明显.（3）在退耕地0-40cm 土层范围内,各样地细沙粒的比例最大,粉粒和黏粒次之,粗沙粒的比例最小,但各粒径所占比例随退耕年限的变化不大.

The habitats &plant community characteristics in different abandoned lands were analyzed after abandon-ment for 1,2,3,4,5,8,15,24 & 31 a.The dynamic change of plant community,soil water content,bulk density,po-rosity and mechanical composition in the different abandoned lands were studied in the Minqin Oasis.Result shows that:(1)Plant of 32 species spread over 14 family live through fifty years appeared in abandoned lands in the study area;shrubs(6 species),herbs (26 species),which constitute 18.75%,81.25% of the total species respectively. Chenopodiaceae(6 species),Compositae(4 species),Gramineous (4 species),Zygophyllaceae(3 species),these four plant constitute 53.13% among them;(2)Within the range of 0-40 cm of different abandoned land,the soil moisture content showed a trend of first increase and then decrease with the increase of soil depth;the changes in soil bulk density and porosity are not significant;(3)In the range of 0-40 cm soil layer,the proportion of fine sand are the lar-gest,followed by silt and clay;the proportion of coarse sand is the smallest;the proportion of each particle size varies little with the restoration years.