东北丘陵区林地转型耕地对土壤编码碱性磷酸酶基因的细菌群落的影响

Effect of conversion of forest to arable land in the hilly region, Northeast China on soil alkaline phosphatase gene encoding bacterial community

摘要:

[目的] 通过研究林地转型耕地对土壤编码碱性磷酸酶基因的细菌群落丰度、多样性和结构的影响，为丘陵区耕地长期施肥下农田土壤微生物多样性丧失的影响机制以及未来的退耕还林过程中土壤微生物多样性的提升和土地可持续利用研究提供一些基础数据和技术支撑。[方法] 采用实时荧光定量PCR（real-time quantitative PCR，qPCR）和高通量测序技术解析土壤编码碱性磷酸酶基因的细菌群落的丰度、多样性和结构变化，并耦合土壤化学性质分析，明确土壤编码碱性磷酸酶基因的细菌群落丰度和多样性与土壤化学性质的关系以及关键的驱动因子。[结果] 林地垦殖为农田后，长期施肥导致土壤酸化，pH从5.58降至4.72，而土壤速效磷则从2.49 mg/kg增至49.3 mg/kg。相应地，耕地土壤编码碱性磷酸酶基因的细菌群落的丰度和Shannon指数均显著低于林地。基于编码碱性磷酸酶的phoD基因（alkaline phosphatase-encoding gene）序列的物种分类表明，丘陵区土壤编码碱性磷酸酶基因的细菌群落的优势门为变形菌门（Proteobacteria）、蓝藻门（Cyanobacteria）、浮霉菌门（Planctomycetes）、放线菌门（Actinobacteria）、厚壁菌门（Firmicutes）和疣微菌门（Verrucomicrobia），其中林地土壤的蓝藻门的相对丰度显著高于耕地。耕地土壤的慢生根瘤菌属（Bradyrhizobium）和芽孢杆菌属（Bacillus）的相对丰度显著高于林地，而中慢生根瘤菌属（Mesorhizobium）、假单胞菌属（Pseudomonas）、Chlorogloea属、Gemmata属、Phormidesmis属和Pseudolabrys属的相对丰度显著低于林地。土壤编码碱性磷酸酶基因的细菌群落结构因林地转型耕地而发生显著改变。phoD基因丰度和Shannon指数与pH显著正相关，而与总磷、速效磷、硝态氮和铵态氮均显著负相关，其中土壤速效磷是这些影响因素中影响最强烈的，长期施用无机磷肥导致含碱性磷酸酶的土壤细菌群落对有机磷分解的能力退化。[结论] 林地转型耕地加之长期施肥改变了土壤pH和速效磷，并在其他理化因子的协同驱动下，导致土壤编码碱性磷酸酶基因的细菌群落丰度、多样性和结构的显著变化。

关键词:林地;耕地;丘陵区;phoD基因;实时定量PCR;高通量测序

Abstract:

[Objective] By studying the effect of conversion of forest to arable land on the abundance, diversity and structure of soil alkaline phosphatase gene encoding bacterial community, to provide basic data of soil microbial diversity, for sustainable land use. [Methods] The abundance, diversity and structure of soil alkaline phosphatase gene encoding bacterial community were investigated using real-time fluorescence quantitative PCR (qPCR) and high-throughput sequencing. Combining the determination and statistical analysis of soil chemical properties, relationships among the soil alkaline phosphatase gene encoding bacterial community abundance, Shannon diversity and soil chemical properties were also evaluated, as well as the key driving factors affecting community structure. [Results] After the forest land was reclaimed as arable land, long-term fertilization led to acidification of the soil, the pH dropped from 5.58 to 4.72, and the soil available phosphorus increased from 2.49 mg/kg to 49.3 mg/kg. Correspondingly, the soil alkaline phosphatase gene encoding bacterial community abundance and diversity significantly decreased with the conversion of forest to arable land. Based on species classification of alkaline phosphatase-encoding gene sequence, Proteobacteria, Cyanobacteria, Planctomycetes, Actinobacteria, Firmicutes and Verrucomicrobia were the dominant phyla, and the relative abundance of Cyanobacteria in forest significantly higher than that in arable land. The relative abundance of Bradyrhizobium and Bacillus in arable land were significantly higher than that in forest, while significantly higher relative abundance of Mesorhizobium, Pseudomonas, Chlorogloea, Gemmata, Phormidesmis and Pseudolabrys was found in forest. The structure of soil alkaline phosphatase gene encoding bacterial community was significantly affected by the land-use change. The abundance and Shannon diversity of soil alkaline phosphatase gene encoding bacterial community were significantly positively correlated with pH, but significantly negatively correlated with the soil available phosphorus, total phosphorus, nitrate nitrogen (NO₃^-) and ammonium nitrogen (NH₄⁺), the soil available phosphorus is the most affected among these factors. The application of inorganic phosphate fertilizer caused the degradation of organophosphorus decomposition ability of soil bacterial community containing alkaline phosphatase. [Conclusion] The soil available phosphorus and pH changed by land-use change and long-term fertilization cause the alteration of the abundance, diversity and structure of the soil alkaline phosphatase gene encoding bacterial community under the coordinated driving of other physical and chemical factors.

Key words:forest;arable land;hilly region;phoD gene;qPCR;high-throughput sequencing