关键词: 碳循环, 甲烷通量, 凋落物输入, 森林类型, 亚高山地区, 土壤

Abstract: [Aims] Forest soil is an important biological sink for atmospheric methane (CH4), and its CH4 oxidation function plays a key role in regulating global carbon cycling and climate change. Aboveground litter serves as a critical link between vegetation and soil, and changes in its input can affect the CH4 oxidation process by altering soil microenvironments, nutrient cycling and microbial activity. However, whether this process varies with forest type remains unclear, particularly in subalpine forests that are sensitive to climate change, where relevant research is especially limited. [Methods] This study selected typical coniferous and broad-leaved forests on the southern of Yulong Snow Mountain and established three treatments: double litter (DL), control (CK), and no litter (NL). Through continuous monitoring of soil CH4 flux dynamics, combined with data on soil physicochemical properties, microbial biomass and extracellular enzyme activities, this study systematically analyzed the combined effects of litter quantity and quality on soil CH4 flux and identified the key driving pathways. [Important findings] The results showed that: (1) forest type significantly affected soil CH4 uptake rates (P<0.001), with annual CH4 uptake in coniferous forests significantly higher than in broad-leaved forests; (2) the effect of litter input quantity on CH4 fluxes differed between forest types: DL significantly reduced CH4 uptake in broad-leaved forests (P<0.05), whereas no significant differences were observed among treatments in coniferous forests (P>0.05); (3) soil CH4 uptake was synergistically regulated by soil physicochemical properties and microbial extracellular enzymes, with soil pH and total nitrogen showing higher relative importance in coniferous forests, while soil moisture and β-glucosidase activity were more important in broad-leaved forests. This study demonstrates that subalpine forest soil CH4 sink function is primarily controlled by forest type divergence, with the effect of litter input quantity being more pronounced in broad-leaved forests, and the regulatory pathways varying with forests. These findings provide important theoretical basis and data support for accurately assessing forest C sequestration potential and optimizing parameters in Earth system models.

Key words: Carbon cycle, Methane flux, Litter input, Forest types, Subalpine area, Soil