Abstract: Vegetation succession is an important way to increase carbon sequestration in terrestrial ecosystems. However, few studies have been conducted to evaluate the impact of vegetation succession on CH₄ fluxes. In this study, soil CH₄ fluxes were measured with the static box method in five different ecosystems in the karst mountains of southwest China, including a grassland, a shrubland, a 15-year-old secondary forest, a 25-year-old secondary forest, and a 50-year-old secondary forest. The results showed that the annual flux of soil CH₄ uptake first increased and then decreased with the succession process, and the annual flux of soil CH₄ uptake was 1.23±0.23, 1.63±0.09, 1.95±0.29, 2.35±0.26, and 1.88±0.20 kg C·hm^-2·a^-1 in the five ecosystems, respectively. Soil CH₄ uptake flux was significantly positively correlated with soil organic carbon, total nitrogen, nitrate nitrogen, microbial biomass carbon, soluble carbon, exchangeable Ca²⁺ and Mg²⁺ (P<0.05), while significantly negatively correlated with soil bulk density and soil temperature (P<0.05). Our results indicated that soil properties (higher soil organic carbon, total nitrogen, nitrate nitrogen, microbial biomass carbon, soluble carbon, exchangeable Ca²⁺ and Mg²⁺) were the key driving factors for CH₄ uptake fluxes during vegetation succession, which is beneficial to quantitative evaluation of CH₄ reservoir in karst ecosystems in southwest China.

Key words: vegetation succession, soil CH₄ uptake flux, soil property