不同生长年限唐古特大黄根部土壤中微生物量及酶活性变化规律研究

Study on the Changes of Microbial Biomass and Enzyme Activity in the Root Soil of Rheum tanguticum in Different Growth Years

目的:明晰种植唐古特大黄对土壤微生态的影响。方法:利用常规测定方法研究不同生长年限唐古特大黄根部土壤中微生物量和酶活性的变化规律。结果:土壤微生物量碳(MBC)、微生物量氮(MBN)和微生物量磷(MBP)含量随着唐古特大黄生长年限的增加而表现出“马鞍型”变化趋势,同一生长年限的唐古特大黄根部土壤微生物量与土壤深度呈极显著负相关(P <0.01);MBC/MBN值在8.85%~18.94%之间,说明唐古特大黄根部土壤已向“真菌型”转变。MBC/SOC、MBN/TN和MBP/TP值均低于植被覆盖良好区域。同一生长年限的唐古特大黄根部土壤酶活性随土壤深度增加而降低;在不同生长年限的唐古特大黄间,纤维素酶活性随着唐古特大黄生长年限的增加而降低;蛋白酶和硝酸还原酶活性随唐古特大黄生长年限增加也呈“马鞍型”变化趋势;过氧化氢酶活性随唐古特大黄生长年份增加而增高。结论:连续种植唐古特大黄能够对土壤微生物群落结构产生影响,一方面增加了根部土壤真菌数量,另一方面根部土壤积累过氧化氢类物质,可能导致唐古特大黄根系易发生病害或损伤。因此,研究认为唐古特大黄在青藏高原东北缘最适生长年限为4年。

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 activity 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 significantly.Values of MBC/SOC,MBN/TN and MBP/TP were lower than those in areas with good vegetation coverage.The enzyme activity in the root soil of R.tanguticum with the same growth period decreased 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 accumulation 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 period of R.tanguticum in northeast edge of Qinghai-Tibet Plateau was 4 years.