关键词: 土壤体积含水量, 森林演替, 时空异质性, 磨盘山, 中亚热带

Abstract:

Objective: Explore the heterogeneity characteristics of soil volumetric water content and spatial in different successional forest communities in typical mid-subtropical regions, including time (annual, wet and dry season) and spatial ( soil layer), and analyze the main factors causing the heterogeneity of soil volumetric water content in different soil layers during the succession process of forest communities, so as to provide data support for regional forest water resources management and forest ecosystem service function assessment. Method: The typical forests in Mopan Mountain, Yuxi, Yunnan, including the Pinus yunnanensis Franch forest (PF) in the pioneer stage of succession, P. yunnanensis broadleaf mixed forest (PBMF) in the mid-succession stage and the evergreen broadleaf forest (EBF) as climax community, the were selected by using time-domain reflectometry and classical statistical menthods. From May 2021 to April 2022, the soil volumetric moisture content for each 10 cm soil layer within 0?60 cm of the sample plot was measured to explore the spatio-temporal heterogeneity and influencing factors of forest soil moisture. Result: 1) In the mid-subtropical region with distinct climatic dry and wet and frequent droughts, the water storage of forest soil showed moderate variation in time and was consistent with the trend of precipitation. With the succession, the mean annual soil volumetric water storage was the highest in EBF, followed by PBMF, and the lowest in PF. The soil water storage of EBF and PBMF increased by an average of 31.24% and 15.22% respectively compared to PF throughout the year. 2) The soil volumetric water content of forests in three succession stages increases with the thickening of soil layers. The average soil volumetric water content in the 0?10 cm soil layer is 45.22% lower than that in the 50?60 cm soil layer. The coefficient of variation of soil volumetric water content is significantly negatively correlated with soil volumetric water content (P<0.05). 3) The soil volumetric water content is significantly negatively correlated with forest density, tree height, and soil sand content (P<0.01), there is a highly significant positive correlation with leaf area index, canopy density, soil porosity, clay content, silt content, organic matter content, and organic carbon content (P<0.01). The correlation between soil volumetric water content and leaf area index, soil porosity, silt content, organic matter content, and organic carbon content is the closest. Conclusion: The mean coefficients of variation of soil volumetric water content in the year, dry and wet seasons and 0?60 cm soil layers of forests at different succession stages in Yuxi Mopan Mountain, Yunnan Province were 19.86%, 17.31%, 14.06%, and 20.58%, respectively, showing moderate heterogeneity, and the water storage capacity of forest soil increased with succession, showing moderate heterogeneity, and the water storage capacity of forest soil increased with succession. Leaf area index, soil porosity, grit content, organic matter content, and origin carbon content were the dominant factors that contribute to the spatial heterogeneity of soil volumetric moisture content in different soil layers.

Key words: soil volumetric water content, forest succession, spatio-temporal heterogeneity, Mopan Mountain, the middle subtropics