Soil Microbial Community Diversity Of Karst Rocky Desertification Ecosystem Based On Phospholipid Fatty Acid(PLFA) Method

The structure and activity of soil microbial community are important limiting factors in soil biological processes,and to a large extent determine the biogeochemical cycle,soil fertility,soil quality and soil organic carbon cycling process.In order to study the effect of different land use patterns on the diversity structure of soil microbial communities.Based on the method of space instead of time,In the small areas,forest lands,agricultural lands and abandoned lands with obvious relevance were selected as research objects,Phospholipid fatty acid(PLFA)analysis was used to investigate the effect of land-use change on microbial population and community structure,and soil microbial PLFA content and diversity in different depths(0~20cm?20~60cm?60~100cm).The results are as follows:(1)A total of 26 PLFAs were detected in the soil under three different land use patterns,of which 24 were detected in the agricultural land in June.22 species were detected in forest lands,abandoned lands,and agricultural lands in September;21 species were detected in forest lands and abandoned lands in December,and 22 species were detected in agricultural lands.PLFA species in June and September were richer than those in December.PLFA species in forest lands were higher than agricultural lands and abandoned lands.(2)In the 3 different land use patterns,the total PLFAs which is 16:0,16:1,18:0,18:2n6c in soil was significantly higher than other PLFAs,14:1 was only found in woodland,but agricultural land and abandoned land were relatively undetected.Abandoned land in June was not detected C17:0,C22:0,C22:2,C24:1;Neither C15:1,C17:1,24:1,22:6n3 were detected in forest land,agricultural land,or abandoned land in September;Neither C15:1,C17:1,C20:4n6,C24:1,C22:6n3 were detected in forest land,agricultural land and abandoned land in December.(3)The PLFA species detected from 0~20 cm is more abundant than that from 20~60 cm and 60~100 cm,and the content of PLFA16:0 is the highest at all depths.In June and December,the single PLFA from 0~20 cm was higher than 20~60 cm and 60~100 cm,while the majority of single PLFAs from 20~60 cm and 60~100 cm were similar.In September,a single PLFA of 0~20cm was higher than 20~60cm,60~100cm,and 20~60cm was higher than 60~100cm.Looking at the content of each PLFA in a comprehensive way,it can be found that the four PLFAs C16:0,C16:1,C18:0,C18:2n6c have the highest content in different depths.In June,September and December,there was a very significant positive correlation with pH,organic matter,total nitrogen,and carbon-nitrogen ratio,and there was no correlation with pH and organic matter only in June.(4)In the process of land use transformation,the microbial community structure still has certain similarities;and with the increase of the depth of the soil profile,PLFA shows a decreasing trend.The total contents of PLFAs and content of single PLFA in the soil will change slightly with seasonal changes,and the bacteria content will gradually decrease,and the fungal content will gradually increase.The PLFA content of bacteria and fungi is dominant in soil microorganisms and is one of the main components affecting soil biota.In June,September and December,there was a significant positive correlation with pH,organic matter,total nitrogen,carbon and nitrogen ratio,but no correlation between pH and organic matter in June.