宁夏东部荒漠草原向灌丛地转变过程土壤微生物响应

为探究荒漠草原向灌丛地人为转变过程中土壤微生物及其酶活性的响应特征,选取宁夏东部荒漠草原近30年典型草地-灌丛地镶嵌体区域的荒漠草地、草地边缘、灌丛边缘、灌丛地为研究样地,开展各样地不同微生境(植丛和空斑)下的0～20 cm土层土壤理化性质、微生物数量、微生物生物量及其酶活性特征研究.结果显示:随转变过程各样地土壤水分...

Responses of soil microbes across an anthropogenic transition from desert steppe grassland to shrubland in eastern Ningxia

This research investigated the impacts on soil microbes and their enzyme activities,of the anthropogenic transition process from desert steppe to shrubland vegetation.Four site categories:desert grassland(DG),grassland edge(GE),shrubland edge(SE)and shrubland(SL)in grassland-shrubland mosaic were selected to represent the transition process,and soil properties,microbial population counts,microbial biomass and enzyme activity in the 0-20 cm soil layer under vegetation patches(VP)and bare interspaces(BI)at each site were measured.It was found that soil moisture,soil organic carbon,total carbon,total nitrogen and total phosphorus decreased from 6.84%,8.54 g·kg^-1,22.67 g·kg^-1,0.85 g·kg^-1,0.32 g·kg^-1 in DG to 1.78%,5.85 g·kg^-1,6.63 g·kg^-1,0.16 g·kg^-1,0.23 g·kg^-1 in SL,respectively(P<0.05),while pH was not significantly changed.Across the transition,bacteria numbers were lowest at GE and SE sites,and slightly lower in SL than DG.Fungi showed a"decrease-rise-decrease"trend,with slightly higher population numbers in SL than in DG.Actinomycete population numbers decreased significantly in SL,compared to DG.The amount of microbial biomass carbon and nitrogen decreased from 87.66 and 5.94 mg·kg^-1 in DG,to 9.94 and 1.85 mg·kg^-1 in SL,respectively(P<0.05).The activities of catalase,alkaline phosphatase and sucrase showed a significant"decrease-rise-decrease"decline trend in the transition from DG to SL,and urease activity was significantly lower in DG than in SL(P<0.05).The soil microbe characteristics and enzyme activities were significantly higher under VP than in BI(P<0.05).Across the vegetation transition,soil moisture,total carbon and total nitrogen were positively correlated with soil microbe-related parameters(actinomycete numbers,soil microbial biomass carbon and nitrogen,and catalase,urease,alkaline phosphatase activities)(P<0.01),and soil organic carbon and total phosphorus were significantly correlated with soil microbial biomass carbon and urease activity(P<0.05),while pH was not significantly correlated with soil microbe-related parameters(P>0.05).Actinomycete numbers,and the enzymatic activities of catalase,alkaline phosphatase and urease were positively correlated with microbial biomass carbon and nitrogen(P<0.01).However,the numbers of bacteria and fungi and sucrase activities were not significantly correlated with microbial biomass carbon and nitrogen.Across the DG-SL ecological boundary transition(established nearly 30 years),the indexes observed differed between DG and SL,with SL being significantly lower than DG in most cases,showing that the soil microbial activity of DG is significantly decreased after 30 years as shrubland.