民勤退耕区次生草地土壤特性研究

为探讨不同年限对退耕区次生草地土壤理化及土壤微生物特性的影响，以民勤绿洲退耕区不同退耕年限次生草地（1、2、8、13、20年）为研究对象，并将耕地作为对照，采用时空互代法测定和分析土壤理化性质（pH、含水率、砂粒含量、全氮、速效钾、速效磷）、土壤三大类微生物（细菌、放线菌、真菌）数量、土壤微生物生物量（碳、氮、磷）变化特征及其三者的相关性。结果表明：不同年限退耕地土壤微生物数量均以细菌最高，放线菌次之，真菌最低。随着退耕年限的增加，土壤砂粒含量、全氮、速效钾、土壤微生物量碳、土壤微生物量氮、土壤微生物量磷等指标均呈现先上升后下降趋势；土壤含水率、速效磷、细菌数量、放线菌数量均表现出不同程度的下降趋势；不同退耕年限对土壤pH值及真菌含量影响不显著。土壤理化性质与土壤微生物学特性间存在一定的相关性。土壤肥力质量综合评价结果表明退耕8年之前是民勤退耕区次生草地治理过程中的关键时期。

A study of change in soil characteristics with recovery time in degraded grassland in Minqin

This research investigated soil physical and chemical properties and soil microorganism presence for five sites forming a time series(1,2,8,13,20 years since cessation of farming)for recovery of degraded grassland in Minqin County,Gansu Province.Soil physical and chemical properties measured included pH,moisture content,sand content,total nitrogen,available potassium and available phosphorus.Soil microbial determinations included comparative abundance of the three main taxonomic groups(bacteria,actinomycetes and fungi),and soil microbial biomass(carbon,nitrogen,phosphorus)and their correlation.It was found that bacteria were the most abundant soil microorganism,while actinomycetes and fungi were less abundant.With increase in years of recovery,soil sand content,total nitrogen,available potassium,soil microbial biomass carbon,soil microbial biomass nitrogen,soil microbial biomass phosphorus and other indicators showed an initial rise and then a decline trend.For soil moisture content,available phosphorus,bacterial population count,and actinomycete abundance showed a decreasing trend in different degrees.Difference in recovery time did not significantly affect the soil pH or the soil fungal content.There is a certain correlation between soil physical and chemical properties and soil microorganism properties.The results of multivariate evaluation of soil fertility data show that eight years was the time by which key changes were achieved in the recovery of degraded grassland in abandoned farmland areas in Minqin.