Objective:To investigate the effect of planting Rheum tanguticum on soil micro-ecology.Methods:Use routine determination methods to study the changes of microbial biomass and enzyme ac-tivity in the root soil of R.tanguticum in different growth years.Results:The results showed that the contents of soil microbial biomass carbon(MBC),microbial biomass nitrogen(MBN)and microbial biomass phosphorus(MBP)showed a"saddle type"trend with the increase of the planting year of R.tanguticum.There was a very significant negative correlation between soil microbial biomass and soil depth of R.tanguticum with the same growth period(P<0.01);The values of MBC/MBN varied from 8.85%to 18.94%,indicating that the number of fungi in the root soil of R.tanguticum increased signifi-cantly.Values of MBC/SOC,MBN/TN and MBP/TP were lower than those in areas with good vegeta-tion coverage.The enzyme activity in the root soil of R.tanguticum with the same growth period de-creased with increasing soil depth.As the increase of the planting year of R.tanguticum,the cellulase activity decreased and the activities of protease and nitrate reductase also showed a"saddle type"trend,and the catalase activity increased.Conclusion:Continuous planting of R.tanguticum could affect the soil microbial community structure,increase the number of fungi in the root soil,and promote the ac-cumulation of hydrogen peroxide substances in the root soil,which may lead to the susceptibility of R.tanguticum root system to diseases or damage.Therefore,it was believed that the optimal planting peri-od of R.tanguticum in northeast edge of Qinghai-Tibet Plateau was 4 years.
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