丹江口水源涵养区退耕还草对土壤微生物和线虫群落的影响

Effects of the conversion of cropland to grassland on soil microbial and nematode communities in the Danjiangkou water source conservation area

研究丹江口水源涵养区退耕还草土壤微生物和线虫群落变化特征及相互作用机制,为全面分析和评估退耕还草土壤生态效应提供基础数据,也为库区生态环境保护和土地可持续利用提供科学的依据。2017年9月,在丹江口水源涵养区上游选取退耕种植3年紫花苜蓿(Medicago sativa)草地作为退耕还草的代表样地,以相邻未退耕的玉米(Zea mays)田为对照,比较分析退耕还草土壤微生物和线虫群落变化及其相互作用。结果表明,退耕还草改变了土壤微生物群落结构和多样性,0–10和10–20 cm土层中微生物群落磷脂脂肪酸总量分别显著提高了59.13%和62.58%(P<0.05)。土壤微生物与土壤有机碳、全氮和硝态氮极显著正相关(P<0.01),与土壤pH和C/N显著负相关(P<0.05)。土壤微生物和土壤线虫相互作用,土壤革兰氏阴性菌与土壤食细菌线虫显著负相关(P<0.05),与食真菌线虫显著正相关(P<0.05),土壤食微线虫结构改变。土壤微生物中革兰氏阴性菌与土壤线虫富集指数和结构指数显著正相关(P<0.05)。退耕还草土壤微食物网结构发生分异,土壤线虫对土壤微食物网结构稳定性贡献更大。

Studying the changes in characteristics and mechanisms of interaction between the soil microbial and nematode communities resulting from the conversion of cropland to grassland in the Danjiangkou water conservation area can provide primary data for comprehensive analysis and evaluation of the ecological effect of soil.Additionally,this can offer a scientific basis for the regional ecological environmental protection and sustainable land use.In September 2017,we chose three representative Alfalfa(Medicago sativa)grasslands(three years)for the conversion of cropland to grassland.The plots are located upstream of the Danjiangkou water conservation area.We also chose an uncultivated maize(Zea mays)field as the control.In this study,we examined the effects of the conversion of farmland to grassland on the microbial organisms present in the soil and the interactions between the soil microbial and nematode communities.The results showed that the soil microbial community structure changed greatly after the cropland was converted into grassland in the Danjiangkou water source conservation area.The amount of total microbial phospholipid fatty acids in the 0–10 and 10–20 cm soil layers increased significantly by 59.13%and 62.58%,respectively(P<0.05).The soil organic carbon,total nitrogen,and nitrate nitrogen contents had a positive correlation with the total phospholipid fatty acids(PLFAs)(P<0.01),whereas,the soil pH and C/N negatively correlated with the total PLFAs(P<0.05).As the main components of the soil micro-food web,there is an interaction between the nematodes and the microbial community.The soil G–bacteria had a negative relationship with the abundance of bacterivores(P<0.05),and a positive correlation with the abundance of fungivores(P<0.05).Moreover,a significant positive correlation was observed between the G–bacteria and nematode ecological index(EI and SI)(P<0.05).This study indicated that the conversion of cropland to grassland changed the micro-food web structure,and soil nematode contributed more to the stability of the soil micro-food web.