Effects Of Plant Root Exudates And Their Organic Acids On Soil Microbes And Nutrients In Desert Steppe

In this study,we collected the roots of Stipa breviflora,Cleistogenes songorica,Artemisia frigida,Heteropappus altaicus and Convolvulus ammannii,which the edificator or constructive species,dominant species and associated species of desert steppe of siziwang banner,Inner Mongolia.The root exudates of 12 hours,24 hours and 48 hours were collected respectively,and the organic acid components in the root exudates were analyzed by ultra-high performance liquid chromatography-quadrupole Rod(unit)time-of-flight tandem mass spectrometry(UPLC-QTof/MS).The collected stock solution of 5 plant root exudates and 4 organic acid components were returned to the soil for cultivation,and their effects on the number of microorganisms and nutrients in the soil were analyzed.The main results are as follows:1.Palmitic acid and oleic acid were detected in root exudates of Stipa breviflora and Heteropappus altaicus at different collection times.Phthalate,oleic acid and palmitic acid were detected in root exudates collected at different times by Cleistogenes songorica.Only one organic acid phthalate was detected in root exudates of Artemisia frigida at different collection times.Succinic acid,palmitic acid,oleic acid and phthalic acid were detected in root exudates of Convolvulus ammannii at different collection times.2.Root exudate stock solutions of Stipa breviflora,Cleistogenes songorica and Artemisia frigida at different collection times significantly promoted the number of bacteria,fungi and actinomycetes in soil.Convolvulus ammannii's collection of root exudates for 12 hours promoted the number of bacteria and actinomycetes in soil and significantly inhibited the number of fungi.Collection of root exudates for 24 hours and 48 hours promoted all three microorganisms.The root exudates collected for 12 hours from Heteropappus altaicus promoted the number of three kinds of microorganisms in the soil,while the root exudates collected for 24 hours and 48 hours promoted the number of bacteria and actinomycetes in the soil and inhibited the number of fungi.The root exudates of the five plants could increase the contents of available phosphorus(AP),available nitrogen(AN)and soil organic matter(SOM).Root exudates from all five species could reduce the soil pH value.3.Among the four organic acid components,palmitic acid and oleic acid with different concentrations could increase the number of bacteria,fungi and actinomycetes in the soil,which than also increase the content of soil organic matter,available phosphorus and available nitrogen.When the concentration of phthalic acid in soil is 5 ?L/g,the number of bacteria and fungi increases while the number of actinomycetes decreases.When the concentration is 10 ?L/g and 15 ?L/g,the number of fungi increases while the number of bacteria and actinomycetes decreases.Phthalate of different concentrations can reduce the content of soil organic matter and available nitrogen and increase the content of soil available phosphorus.When the concentration of succinic acid in soil is 5 ?L/g,the number of three kinds of microorganisms all increase.When the concentration was 10 ?L/g,the number of fungi and actinomycetes increased significantly while the number of bacteria decreased.When the concentration is 10 ?L/g,the number of fungi increases while the number of bacteria and actinomycetes decreases.Succinic acid with different concentrations can significantly increase the contents of soil organic matter,available nitrogen and available phosphorus.Four kinds of organic acids with different concentrations can reduce soil pH value,and have no significant effect on soil water content.