林地转型耕地对东北丘陵区白浆土cbbL细菌群落丰度和结构的影响

土壤固碳细菌的CO_2同化作用能够将CO_2转化成有机质,是土壤碳循环的重要过程,然而对土地利用方式转变下土壤固碳细菌群落丰度和结构变化的了解却非常有限.在此,采用q PCR和高通量测序技术研究了东北丘陵区林地转型耕地后白浆土cbb L细菌群落丰度和结构变化,并探讨了土壤理化因子在群落丰度和结构变化中的作用.结果表明,耕地土壤细菌的cbb L基因丰度为2. 57×108copies·g~(-1),显著低于林地土壤的7. 30×108copies·g~(-1),但林地与耕地间cbb L/16S r RNA基因拷贝数比无显著差异.与林地相比,耕地土壤cbb L细菌群落的Shannon和Chao1指数显著降低,而Simpson指数显著升高.系统发育树分析和主坐标分析(principal co-ordinates analysis,PCo A)均表明林地转型耕地改变了土壤cbb L细菌群落组成.Pearson相关分析表明,cbb L基因丰度和Shannon指数均与pH极显著正相关,而与AP和NO_3-显著负相关,证明了施肥导致的土壤pH和速效养分改变是造成土壤cbb L细菌群落丰度和多样性变化的主要原因.典范对应分析(canonical correspondence analysis,CCA)显示,pH、NO_3-、AP和NH_4+与土壤cbb L细菌群落结构变化显著相关.综上所述,了解土壤cbb L细菌群落对土地利用方式转变的响应及其微生物学机制将为加强我国东北丘陵区白浆土的可持续利用及生态环境重建提供新的见解.

Effects of Conversion of Forest to Arable Land on the Abundance and Structure of the cbbL-Harboring Bacterial Community in Albic Soil of the Hilly Region of Northeast China

Soil CO₂ fixer, which plays an important role in soil carbon cycling, can convert CO₂ into organic matter. However, the effect of land-use change on the abundance and community structure of soil CO₂ fixer is poorly understood. Examining the community of functional microbes that encode the large subunit of ribulose-1, 5-bisphosphate carboxylase/oxygenase under the conversion of land-use patterns may provide valuable information for promoting soil carbon sequestration ability and sustainable use. In this study, we investigated how the abundance and community diversity of the CO₂-fixing bacteria responded to conversion of forest to arable land in the hilly region of Northeast China. We found that the abundance of soil cbbL-harboring bacteria was substantially lower in arable land (2.57×10⁸ copies·g^-1, soil) compared to forest (7.30×10⁸ copies·g^-1, soil), while the cbbL/16S rRNA gene ratio did not differ significantly between the two treatments. The values of the Shannon and Chao1 index decreased significantly with the conversion of forest to arable land, but the Simpson index was in contrast to these results. Neighbor-joining phylogenetic tree and principal coordinates analysis (PCoA) both demonstrated that the composition of the cbbL-harboring bacterial community was significantly affected by land-use change. Soil cbbL gene abundance and Shannon diversity significantly positively correlated with pH, and significantly negatively correlated with AP and NO₃^-, indicating that the changes in soil pH and available nutrients caused by land-use change greatly affected soil cbbL abundance and diversity. Meanwhile, pH, NO₃^-, available phosphorus (AP) and NH₄⁺ significantly correlated with soil cbbL-harboring bacterial community structure. In conclusion, a 25-year long-term conversion of forest to arable land changed the community structure of soil cbbL-harboring bacteria, and soil pH, AP and available N played crucial roles in controlling the ecological properties of soil cbbL-harboring bacteria.