不同种植方式对亚热带红壤微生物多样性的影响

土壤微生物在推动土壤碳循环过程方面发挥着重要作用,然而种植方式的改变对土壤微生物多样性的影响机制还不十分清楚.本研究采集湖南省盘塘县长期定位试验站红壤稻田(PR)、旱地(UC)及水旱轮作(PR)这3种不同种植方式的土壤样品,采用末端限制性酶切片段长度多态性分析(T-RFLP)技术和实时荧光定量(RT-PCR)技术分析了土壤细菌16S rRNA基因的多样性和丰度,研究种植方式改变对土壤微生物数量、群落结构及其多样性的影响.结果表明,3种种植方式的土壤细菌16S rRNA基因数量(以干土计)为2.5×109~1.5×1010拷贝·g-1,与PR相比,UP和UC处理16S rRNA基因丰度显著下降(P0.05).同时,3种种植方式下土壤细菌的优势类群为变形菌(76、90和327 bp;相对丰度47%~53%)和绿弯菌(65 bp;相对丰度10%~12%).冗余分析表明种植方式改变了土壤理化性质,导致土壤细菌群落结构特征的显著变化,而土壤理化性质中有机碳和全氮含量是影响土壤细菌群落结构的主要因子.多样性指数分析(香农指数和均匀度指数)显示种植水稻的土壤细菌多样性最高,显著高于水旱轮作和旱地土壤.可见,种植方式的改变对土壤群落组成和数量造成了深刻的影响,而水稻种植是亚热带红壤可持续利用的一种有效方式,其更有利于土壤有机质的累积,土壤肥力及微生物多样性均较高.

Effects of Different Plantation Type on the Abundance and Diversity of Soil Microbes in Subtropical Red Soils

Soil microbe plays an important role in carbon cycling, however, the effect of land use on soil microbe remain unclear.In present study, soil samples were collected from a long-term field experiment (Pantang Agroecosystem) in subtropical China (established in 1989), including paddy-rice (PR), upland-crop (UC), and paddy rice-upland crop rotation (PU) on soil bacterial (bacteria and Archaea) community structures.The effects of long-term different land uses were determined using terminal restriction fragment length polymorphism(T-RFLP)and quantitative PCR(RT-PCR)of the 16S rRNA gene.The abundance of soil microbial 16S rRNA genes ranged from 2.5×10⁹-1.5×10¹⁰ copies·g^-1 dry soil.Compared with the PR, UP and UC led to a significant reduction in 16S rRNA genes abundance (P<0.05).The soil microbial communities were dominated by bacteria such as Proteobacteria (76 and 90 and 327 bp;relative abundance of 47%-53%) and Chloroflexi (65 bp;relative abundance of 10%-12%).RDA statistical analyses demonstrated that there were significant differences in the microbial community composition in PR, UC, and PU treated soils.Soil organic carbon and total nitrogen content were the most highly statistically significant factors which positively influenced the soil microbial population.Taken together, our findings prove the long-term different land uses significantly influence the microbial diversity and community structure.The rice planting is an effective way of sustainable utilization of subtropical red soil, and it is more advantageous to the accumulation of soil organic matter, soil fertility and microbial diversity.