三江源区不同建植年限人工草地土壤微生物群落结构特征

Soil microbial community structure characteristics in artificial grassland with Soil microbial community structure characteristics in arti different cultivation years in the headwater region of Three Rivers, China

近年来,对退化生态系统恢复的研究逐渐由地上向地下部分转移,地下部分特别是土壤微生物群落对土壤的恢复机理和过程已倍受关注.运用常规实验室分析法和磷脂脂肪酸法,研究三江源区不同建植年限人工草地土壤养分和微生物群落结构及其分布特征.结果显示:土壤总磷脂脂肪酸(总PLFAs)、真菌PLFAs(F PLFAs)、细菌PLFAs(B PLFAs)、革兰氏阳性菌PLFAs(G+PLFAs)、革兰氏阴性菌PLFAs(G-PLFAs)含量与PLFA类型随建植年限的增加呈先降低后升高的变化趋势,随土层深度的增加而降低.土壤全量、速效养分含量均随建植年限的增加呈现同样的变化规律.主成分分析表明,在0-10 cm、10-20 cm土层中,4年和16年人工草地土壤微生物群落PLFA类型丰富多样,群落结构更加复杂稳定,而7年和9年的土壤微生物群落结构较为单一.相关分析表明,总PLFAs、B PLFAs、F PLFA s、G+PLFAs和G-PLFAs含量与土壤全量和速效养分含量(除速效氮、速效磷)均呈极显著或显著正相关(P<0.01;P<0.05).综上,在合理放牧条件下,人工草地的建植有利于土壤微生物生物量的提高和群落结构的改变.利用微生物PLFA含量和类型的多样性作为监测土壤环境的指标,能及时有效地判别土壤养分的变化情况,有利于及时管理人工草地.

Recent studies of restoration mechanisms and processes are concentrated more and more on belowground systems,especially the soil microbial community. In this study, soil microbial community structure and distribution characteristics were evaluated in artificial grassland with different cultivation years in the headwater region of Three Rivers, China. Soil nutrients were investigated by conventional laboratory analysis; the soil microbial composition was analyzed by phospholipid fatty acid （PLFA） method. The results showed that the PLFAs decreased with soil depth, with PLFA abundance and contents of total PLFAs, including fungal PLFAs （F PLFAs）, bacterial PLFAs （B PLFAs）, Gram-positive PLFAs （G PLFAs） as well as Gram- negative PLFAs （G- PLFAs） initially decreasing but subsequently increasing with the cultivation year. Contents of soil organic matter （SOM）, total nitrogen （TN）, total phosphorus （TP）, available nitrogen （AN） and available phosphorus （AP） followed the same trend as the contents of PLFAs. Soil microbial communities at 0-20 cm soil were abundant and diverse in 4-year and 16- year artificial grasslands, but less so in 7-year and 9-year cultivations. Correlation analysis showed that the contents of total PLFAs, B PLFAs, F PLFAs G PLFAs and G- PLFAs were significantly and positively correlated to the concentrations of SOM, TN, TP, AN and AP （P 〈 0.01）; fungal contents were significantly and positively correlated with TN and TP （P 〈 0.01） besides with organic matter （P 〈 0.05）, and also positively, though not significantly, related to AN and AP. Therefore, under reasonable grazing conditions, artificial grasslands can be planted to increase soil microbial biomass and change microbial community structure. Soil microbial biomass and types as monitoring indicators of soil environment can help to timely identify changes of soil nutrients, which is beneficial for efficient management of artificial grasslands.