多年冻土区退化湿地凋落物分解及其对鼠类入侵的响应机制

Litter Decomposition in Degraded Permafrost Wetlands and Its Response Mechanisms to Rodent Invasion

摘要: 湿地是连接陆地与水体的重要过渡带，在维持生物多样性、水文调节及区域气候缓冲等方面发挥关键作用，同时也是全球碳循环中的重要碳汇单元。大兴安岭多年冻土区广泛分布苔草草丘型湿地，具有水文波动显著、有机质积累深厚和凋落物分解缓慢等特征，是高寒地区重要的碳库。近年来，在气候变暖和人类活动共同作用下，该区域湿地出现不同程度退化，伴随鼠类入侵频率和强度的增加，原有苔草优势群落逐渐被小叶章和二歧银莲花等物种取代，地表微地形、土壤水热与养分格局也随之改变，从而可能重塑凋落物分解过程及湿地碳汇功能。本文系统梳理了湿地凋落物的来源与理化特征，综述了湿地凋落物分解及碳、氮、磷等养分释放的关键过程与主控因子，重点讨论了木质素、纤维素和半纤维素等结构性组分以及胞外酶活性在分解过程中的作用机制，并结合湿地退化及小型哺乳动物入侵的研究进展，分析了鼠类扰动可能通过改变植物群落组成、凋落物质量和土壤环境，进而影响凋落物分解速率和养分循环的潜在途径。最后，指出当前对不同鼠类入侵程度下凋落物分解与养分释放响应机制的定量研究仍然不足，未来应加强多年冻土区典型湿地的野外凋落物袋实验和微生物–胞外酶过程的联动监测，以期为退化湿地的生态修复与碳汇管理提供理论支撑和科学依据。

Abstract: Wetlands, as transitional ecosystems between terrestrial and aquatic environments, play crucial roles in maintaining biodiversity, regulating hydrology and buffering regional climate, and represent important carbon sinks in the global carbon cycle. In the permafrost region of the Da Xing’anling Mountains, Carex-dominated hummock wetlands around Arctic Village are characterized by pronounced hydrological fluctuations, substantial organic matter accumulation and slow litter decomposition, and thus constitute key carbon pools in cold regions. In recent decades, climate warming and human disturbances have led to various degrees of wetland degradation in this area, accompanied by increasing frequency and intensity of rodent invasion. Rodent activities not only disrupt hummock structures, but also alter microtopography and soil hydrothermal and nutrient conditions, thereby driving a community shift from Carex subpediformis to Calamagrostis angustifolia and Anemone dichotoma as dominant species, with potential impacts on litter decomposition dynamics and wetland carbon sink capacity. This review synthesizes current knowledge on the sources and biochemical characteristics of wetland plant litter, summarizes key processes and controlling factors of litter decomposition and C, N and P release in wetland ecosystems, and highlights the roles of structural compounds such as lignin, cellulose and hemicellulose, as well as extracellular enzyme activities, in regulating decomposition. By integrating studies on wetland degradation and small mammal invasion, we further discuss how rodent disturbance may affect litter mass loss and nutrient cycling through modifying plant community composition, litter quality and soil environment. Finally, we identify a lack of quantitative evidence on the responses of litter decomposition and nutrient release along gradients of rodent invasion, and propose that future work should combine field litterbag experiments with microbial and enzymatic measurements in typical permafrost wetlands, in order to support ecological restoration and carbon sink management in degraded wetlands.