中亚热带不同演替阶段森林土壤水分时空异质性

Spatial and Temporal Heterogeneity of Soil Moisture in Forests at Different Successional Stages in the Middle Subtropics of China

【目的】探究典型中亚热带区不同演替阶段森林群落土壤体积含水量的时间(年、干湿季)与空间(土层)异质性特征,分析森林群落演替进程中引起土壤不同土层体积含水量异质性的主要因素,为区域林水资源管理及森林生态系统服务功能评估提供基础数据。【方法】选取云南玉溪磨盘山的典型森林,包括演替初期的云南松林(PF)、演替中期的云南松阔叶混交林(PBMF)和顶级群落常绿阔叶林(EBF),应用时域反射法与经典统计学分析法,于2021年5月至2022年4月测量样地0~60 cm土层内每10 cm土层的土壤体积含水量,探析森林土壤水分的时空异质性及影响因素。【结果】1)在气候干湿分明、干旱频繁的中亚热带地区,森林土壤储水量在时间上呈中等变异且与降水变化趋势一致。随演替进行,年均土壤储水量为EBF最大,MPBF次之,PF最小。EBF与PBMF全年土壤储水量较PF分别平均增加31.24%和15.22%。2)3种演替阶段森林的土壤体积含水量均随土层加深而增大,0~10 cm土层土壤体积含水量平均比50~60 cm土层低45.22%,土壤体积含水量变异系数与土壤体积含水量呈显著负相关(P<0.05)。3)土壤体积含水量与林分密度、树高、胸径、土壤密度、土壤砂粒含量均极显著负相关(P<0.01),与叶面积指数、郁闭度、土壤孔隙度、黏粒含量、粉粒含量、有机质含量和有机碳含量均极显著正相关(P<0.01),叶面积指数、土壤孔隙度、粉粒含量、有机质含量和有机碳含量与土壤含水量的关联程度最高。【结论】云南玉溪磨盘山不同演替阶段森林的年、干湿季和0~60 cm土层的土壤体积含水量变异系数均值分别为19.86%、17.31%、14.06%和20.58%,均表现出中等强度异质性,随演替进行森林土壤储水能力不断增强。叶面积指数、土壤孔隙度、砂粒含量、有机质含量和有机碳含量是土壤不同土层体积含水量产生空间异质性的主导因素。

【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.