耕作方式对潮土土壤团聚体微生物群落结构的影响

为探究不同耕作方式对潮土土壤团聚体微生物群落结构和多样性的影响,采用磷脂脂肪酸(PLFA)法测定了土壤团聚体中微生物群落。试验设置4个耕作处理,分别为旋耕+秸秆还田(RT)、深耕+秸秆还田(DP)、深松+秸秆还田(SS)和免耕+秸秆还田(NT)。结果表明:与RT相比,DP处理显著提高了原状土壤和>5 mm粒级土壤团聚体中真菌PLFAs量和真菌/细菌,为真菌的繁殖提供了有利条件,有助于土壤有机质的贮存,提高了土壤生态系统的缓冲能力;提高了5～2 mm粒级土壤团聚体中细菌PLFAs量,降低了土壤革兰氏阳性菌/革兰氏阴性菌,改善了土壤营养状况;提高了<0.25 mm粒级土壤团聚体中微生物丰富度指数。总的来说,深耕+秸秆还田(DP)对土壤团聚体细菌和真菌生物量有一定的提高作用,并且在一定程度上改善了土壤团聚体微生物群落结构,有利于增加土壤固碳能力和保持土壤微生物多样性。冗余分析结果表明,土壤团聚体总PLFAs量、细菌、革兰氏阴性菌和放线菌PLFAs量与土壤有机碳相关性较强,革兰氏阳性菌PLFAs量与总氮相关性较强。各处理较大粒级土壤团聚体微生物群落主要受碳氮比、含水量、pH值和团聚体质量分数的影响,较小粒级土壤团聚体微生物群落则主要受土壤有机碳和总氮的影响。

Effects of tillage managements on soil microbial community structure in soil aggregates of fluvo-aquic soil

In order to explore the impacts of different tillage managements on the structure and diversity of microbial community in fluvo-aquic soil, the phospholipid fatty acid (PLFA) method was used to determine microbial community composition in soil aggregates. Four tillage treatments were set up in Qihe County, Shandong Province, including rotary tillage with straw return (RT), deep ploughing with straw return (DP), subsoiling with straw return (SS) and no-tillage with straw return (NT). Our results showed that DP treatment significantly increased the amount of fungal PLFAs and fungi/bacteria ratio in >5 mm soil aggregates compared with RT. DP could provide favorable conditions for fungi reproduction, facilitate soil organic matter storage and soil buffering capacity. DP increased the amount of PLFAs in 5-2 mm soil aggregates, reduced the gram-positive (G+) /gram-negative (G-) bacteria ratio in the soil, and improved soil nutritional status. In addition, DP improved the microbial abundance index in <0.25 mm soil aggregates. In general, DP could not only increase the abundance of bacteria and fungi in soil aggregates, but also improve the microbial community structure of soil aggregate, which help increase soil carbon sequestration capacity and keep soil microbial diversity to a certain extent. Results of the redundancy analysis showed that the total PLFAs, PLFAs of bacteria, G- bacteria and actinomycetes in soil aggregates are closely correlated with soil organic carbon, while PLFAs of G+ bacteria had a strong correlation with soil total nitrogen concentration. In each treatment, microbial communities in larger sizes of soil aggregates were mainly affected by the ratio of organic carbon to total nitrogen, soil moisture, pH, and mass fractions of soil aggregates, while the microbial communities in smaller sizes of soil aggregates were affected by the concentrations of organic carbon and total nitrogen.