黄土高原子午岭退耕地土壤物理性质与群落特征

通过对子午岭北部黄土丘陵沟壑区4、9、15和20a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的植被群落、土壤水分、容重和生物量的变化。结果表明：随退耕年限的增加，杂草群落中物种分布较均匀，物种丰富度明显增加，植物种数和个体数增加，其优势种和亚优势种分属于6科9属；根系在土层中分布增多，在一定深度范围内土壤结构逐渐疏松，致使土壤容重随退耕年限的增加而减小；在0～80cm土层内土壤含水量从高至低依次为4a、20a、15a和9a退耕地；80～300cm土层的土壤含水量得到明显改善，土壤含水量从高至低依次为20a、4a、15a和9a退耕地；地面生物量随退耕年限的延长而增加，但增加幅度逐渐趋于缓慢。

Study of soil physical properties and community characteristics of different abandoned lands in Ziwuling area of Loess Plateau

The evolution of environments and plant community characteristics in different abandoned lands were analyzed after abandonment for 4, 9,15 and 20 a,and the plant community characteristics,bulk density,water content and biomass of the different abandoned lands were also researched in the course of succession in hilly-gully regions in north Ziwuling of Loess Plateau.Results showed that in the progress of slow succession,plant species were distributed equally in weed community and the number of species and individuals was increased prominently;dominant and sub-dominant species belonged to 9 genera and 6 families.The distribution of root systems was increased in soil and soil configuration got loosen.As a result,the bulk density was decreased in certain depth.Soil moisture was ordered from large to small: 4 a,20 a,15 a,9 a and 20 a,4 a,5 a,9 a abandoned lands in 0-80 cm and 80-300 cm depth soil respectively.Above-ground biomass was increased with abandoned time,but the trend was slow.