松嫩平原苏打盐碱地土壤团聚体对秸秆生物炭的响应机制

Saline–sodic soils are degraded both by the negative effects of salinity on plant growth and of sodicity on soil structure deterioration. Biochar application as a potential new approach plays an important role in increasing the C content and improving soil properties. The effects of biochar application on physiochemical properties of saline–sodic soils have been well studied. However, little is known about the effects of biochar application on soil aggregates, especially in soil aggregation and its mechanism, which is drived by microorganisms in saline-sodic soils. Changes in soil microbial properties with respect to microbial biomass, activity, and community structure will influence the stability of soil aggregation, which is critical to soil fertility. In this study, saline-sodic soils in the Songnen Plain are subjected to different amounts of biochar application, and changes in soil aggregates were monitored. The objectives of this study are to identify the stability of soil aggregation, to analyze the characteristics of soil properties and microbial community structure, and finally to clarify the critical factors that influence the stability of soil aggregation and its mechanism. The knowledge will provide certain guiding significance for saline-sodic soils ecosystem management.

盐碱地退化主要表现在盐分胁迫植物生长及碱性破坏土壤结构，生物炭施用作为一种潜在可行的新方法，对提高土壤碳含量以及改善土壤性状具有重要作用。目前，生物炭施用对盐碱地影响的研究主要集中在土壤理化性状方面，而对盐碱地土壤团聚体影响的认识非常有限，特别是对土壤微生物参与的土壤团聚过程及机制缺乏理解和认识。微生物数量、活性及群落组成变化将会对土壤团聚体稳定性产生影响，这对土壤肥力变化起着至关重要的作用。本项目以松嫩平原苏打盐碱地为对象，在研究揭示土壤团聚体对不同秸秆生物炭施用量响应规律的基础上，以土壤团聚体稳定性为切入点，结合分析土壤主要性质及微生物群落特征变化，阐明苏打盐碱地土壤团聚体对秸秆生物炭添加响应的关键因素及内在机制。本研究成果对改良盐碱地土壤生态系统具有一定指导意义。

东北苏打盐碱地是我国重要的后备耕地资源，合理改良苏打盐碱地对提高作物生产力具有重要意义，也是应对国家粮食安全挑战的关键因素。面向“藏粮于地，藏粮于计”的国家重大战略需求，以及培育土壤永续生产力和提高土壤碳汇的生态安全需求，有机含碳改良剂成为盐碱地改良的研究热点。生物炭因其自身特性而具备巨大的应用潜力，可显著改善土壤物理结构，并降低盐分危害。本项目以松嫩平原苏打盐碱地为对象，在研究揭示土壤团聚体对不同秸秆生物炭施用量响应规律的基础上，以土壤团聚体稳定性为切入点，结合分析土壤主要理化性质及微生物群落特征变化，阐明苏打盐碱地土壤团聚体对秸秆生物炭添加响应的关键因素及内在机制。本项目研究结果表明，针对东北苏打盐碱地改良，过量施用秸秆生物炭（如50 t ha-1）有降低土壤团聚体稳定性的风险，且会降低土壤微生物群落间的相互作用；适量施用秸秆生物炭（如10-30 t ha-1）可以增强微生物群落间的相互作用，特别在ME粒级（＞2mm）中；施用30 t ha-1秸秆生物炭后，微生物组核心功能发生改变，从难降解聚合物分解转变为碳氮循环转化。此外，适量施用秸秆生物炭可以提高土壤微生物数量，特别是施用10 t ha-1秸秆生物炭，其增幅最大；过量施用秸秆生物炭会减少土壤细菌数量，进而影响微生物群落功能与代谢。土壤容重（物理结构）和速效磷含量（养分有效性）与土壤微生物群落结构均有较高相关性，而土壤CO32-含量（盐碱胁迫）与细菌群落相关性最高，土壤碳库管理指数与真菌群落相关性最高。相较于团聚体粒级分布，生物炭施用对土壤微生物群落影响更大，且对土壤细菌群落影响作用大于真菌群落。本项目研究成果可为苏打盐碱地治理和生态建设提供理论依据和技术支撑，进一步提升苏打盐碱地治理水平和植被恢复，未来在增加农民收入和保障社会协调可持续发展，建设环境友好和生态文明社会等方面发挥重要作用。