典型黑土酸化对主要微生物类群的影响规律

Effects of typical black soil acidification on major microbial groups

摘要:

目的 黑土酸化将加剧土壤退化过程，导致微生物功能下降，威胁东北黑土区粮食产能的发挥。厘清土壤酸化过程对微生物群落的影响及其控制机理，能明确土壤有机碳稳定化和酸化阻控的效应关系。方法 采集玉米带典型黑土区不同酸化程度的土壤样品，应用磷脂脂肪酸分析技术从细胞生物学角度探究微生物类群对黑土酸化的响应；分析不同酸化程度土壤基本理化性质变化与微生物群落的关系。结果 玉米带黑土酸化对土壤有机碳的影响存在阈值效应，适度酸化并未引起有机碳含量的显著变化，但当pH下降至某一阈值(6.75)时，酸化则会造成有机碳的损失。土壤酸化的不同阶段阳离子缓冲机制存在明显差异，钙离子在黑土酸化的不同阶段均起到重要的缓冲作用，但当pH<6.00时，钙离子和镁离子共同起到酸化缓冲作用。黑土酸化对微生物产生了明显的胁迫，随着酸化程度的加剧，各类群PLFA含量呈现先下降，随后在pH为5.25-6.25范围保持相对稳定，随后又显著下降的“S”型变化规律。然而，不同微生物类群对土壤酸化的敏感性不同，相对来说，革兰氏阴性细菌对土壤酸化最为敏感，其次是革兰氏阳性细菌和丛枝菌根真菌。真菌，尤其是丛枝菌根真菌，在土壤酸化过程中对有机碳稳定可能起到了尤为重要的作用。结论 土壤酸化过程中，阳离子的交换能力和底物可利用性的变化显著改变了活体微生物群落结构，进而影响土壤有机碳的积累。本研究结果为制定合理的控酸培肥措施提供了依据。

Abstract:

Objective Black soil acidification may exacerbate the soil degradation processes and reduce microbial functions, thus threatening the crucial role of the northeast region in guaranteeing the food security of China. Unraveling the impacts of soil acidification on the soil microbial community and its underlying mechanisms can help clarify the relationship between soil organic carbon (SOC) stabilization and soil acidification.Methods Soil samples with different acidification degrees were collected from the corn belts of black soil regions. The changes of living microbial groups in the soil samples with different pH were investigated by the phospholipid fatty acid (PLFA) analysis. Additionally, the relationship between changes in the soil physicochemical properties and microbial community composition was analyzed.Results A threshold effect of black soil acidification on SOC was identified in the corn belts. Moderate acidification did not cause significant changes in SOC. However, when pH dropped below a certain threshold (6.75), further acidification resulted in a significant loss of SOC. The cation buffering effect in soil changed significantly with different acidification degrees. Calcium ion was primarily responsible for buffering black soil acidification, while when the pH fell below 6.00, both calcium and magnesium ions buffered the acidification. Soil acidification imposed noticeable stress on soil microorganism growth. Different microbial groups exhibited an S-shaped response pattern, with PLFA content initially decreasing, remaining stable within the range of pH 5.25-6.25, and subsequently declining as acidification progressed. However, different microbial groups exhibited varying sensitivities to soil acidification. Gram-negative bacteria were the most sensitive, followed by Gram-positive bacteria and arbuscular mycorrhizal fungi. Fungi, particularly arbuscular mycorrhizal fungi, may play a crucial role in stabilizing SOC during soil acidification.Conclusion Soil acidification significantly alters the structure of the living microbial community, primarily through changes in cation exchange capacity and substrate availability, which further affect SOC accumulation. These findings provide scientific support for developing management strategies to alleviate black soil degradation and acidification.