不同类型地膜覆盖对拉萨市农田土壤微生物多样性的影响

Effects of different types of plastic film mulching on soil microbial diversity in farmland of Lhasa City

摘要:

目的 随着地膜在青藏高原的使用与推广，地膜应用所引发的一系列问题接踵而至。鉴于青藏高原生态环境脆弱，有必要探究不同类型地膜覆盖对青藏高原农田土壤微生物群落结构的影响。方法 本研究设置了3个处理：种植前土壤(ZQ)、传统聚乙烯地膜覆盖土壤(CMPs)和可降解生物地膜覆盖土壤(BMPs)。通过测定土壤理化性质，并结合16S rRNA基因及ITS区高通量测序技术，解析不同处理下微生物群落的多样性、结构及其与环境因子的关联，以此评估地膜类型对土壤微生物的影响。结果 不同处理组间的各理化因子存在显著差异(P<0.05)。各处理组间细菌与真菌的α多样性指数均无显著差异，表明短期地膜覆盖并未显著改变微生物群落的丰富度与多样性。细菌优势门为假单胞菌门(Pseudomonadota)、放线菌门(Actinomycetota)、酸杆菌门(Acidobacteriota)和绿屈挠菌门(Chloroflexota)，优势属多为未分类类群；而真菌的优势菌门则是子囊菌门(Ascomycota)、担子菌门(Basidiomycota)和被孢霉门(Mortierellomycota)，优势属有Mortierella、Solicoccozyma等。网络分析表明，细菌与真菌群落结构的主要驱动因子分别为pH和微塑料(microplastics, MPs)含量，这可能反映了二者生态功能的差异：作为主要分解者的真菌对MPs污染更为敏感，而细菌群落结构则与土壤酸碱度关系更为密切。功能预测分析显示，细菌中仅KEGG level 1分类中的“代谢”通路与覆膜处理呈正相关，且COG功能在组间未发现显著差异；真菌中腐生营养型功能占主导，且其相对丰度在处理间变化显著。结论 短期地膜覆盖虽未显著影响微生物α多样性，但改变了群落结构。相较于传统PE地膜，可降解地膜在提升土壤氮素及有机碳库方面更具潜力，但也导致更严重的短期微塑料富集，且存在病原真菌富集的风险。因此，其长期生态效应需进一步评估。

Abstract:

Objective With the widespread use and promotion of plastic film mulching on the Qinghai-Xizang Plateau, a series of issues caused by its application have also emerged. Given the fragile eco-environment of the plateau, it is necessary to investigate the effects of different types of plastic film mulching on the soil microbial community structures in farmland ecosystems.Methods Three treatments—pre-planting soil (ZQ), soil covered with conventional polyethylene mulch (CMPs), and soil covered with biodegradable mulch (BMPs)—were established. Soil physicochemical properties were measured, and high-throughput sequencing of the 16S rRNA gene and ITS region was employed to analyze microbial diversity, community structure, and their associations with environmental factors, on the basis of which the impacts of mulch types on soil microorganisms were evaluated.Results Differences in soil physicochemical factors were observed among different treatments (P<0.05). There were no significant differences in alpha diversity indices for both bacteria and fungi among the treatments, indicating that short-term plastic film mulching did not significantly alter the richness and diversity of microbial communities. The dominant bacterial phyla were Pseudomonadota, Actinomycetota, Acidobacteriota, and Chloroflexota, with most dominant genera being unclassified. The dominant fungal phyla were Ascomycota, Basidiomycota, Mortierellomycota, with dominant genera including Mortierella and Solicoccozyma. Network analysis revealed that the main drivers of bacterial and fungal community structures were pH and microplastic (MP) content, respectively. This result reflected functional differences of fungi and bacteria. Fungi, as primary decomposers, were more sensitive to MP pollution, whereas bacterial community structure was more closely related to soil pH. Functional prediction showed that, in bacteria, only the metabolism pathway within the KEGG level 1 showed a positive correlation with the mulching treatment, and no significant differences in COG functions were observed between treatments. In fungi, saprotrophic functions predominated, and their relative abundance changed significantly among treatments.Conclusion Short-term plastic mulching does not significantly affect microbial alpha diversity, but alters the community structure. Compared with conventional PE mulch, biodegradable mulch shows greater potential in enhancing soil nitrogen and organic carbon pools. However, it leads to more severe short-term MP accumulation, accompanied by the risk of pathogenic fungal enrichment. Therefore, its long-term ecological effects require further assessment.