北京海坨山典型林分土壤有机碳含量及有机碳密度垂直分布特征

Vertical Distribution Characteristics of Soil Organic Carbon Content and Organic Carbon Density of Typical Forest Stands at Haituo Mountain,Beijing

[目的]探讨海坨山不同林分类型下土壤有机碳含量和有机碳密度的垂直分布特征及其与土壤性质相关关系,为华北地区森林土壤碳库准确评价及森林生态服务功能评估提供科学依据。[方法]选择不同5种典型林分(油松林、核桃秋林、蒙古栎林、针阔混交林、山杨林)分别设置3块标准样地,采集0~100 cm不同土层土样,并分析相关土壤理化性质,分析不同土壤理化因子对土壤有机碳含量的影响,研究该林区不同林分土壤碳含量及密度的分配特征。[结果]不同林分类型下土壤各层次有机碳含量为9.35~50.25 g·kg^−1,均值为27.42 g·kg^−1。林分类型对不同土层土壤有机碳含量影响显著(p<0.05),不同林分类型土壤有机碳平均含量由小到大排序:山杨林<针阔混交林<核桃楸林<蒙古栎林<油松林。不同林分类型土壤有机碳含量垂直变化趋势相同:从表层向下逐渐降低,表聚性明显,表层(A+AB)占土壤总有机碳含量约57%。不同林分类型100 cm深度土壤有机碳密度为21.4~76.6 t·hm^−2,均值为45.7 t·hm^−2。各林分间土壤总有机碳密度大小为:山杨林>核桃楸林>针阔混交林>蒙古栎林>油松林。单位cm厚度土壤有机碳密度的垂直变化规律与土壤有机碳含量相同,从表层向下逐渐降低,表层(A+AB)土壤有机碳密度占土壤总有机碳密度的35%~40%。不同林分土壤有机碳含量与全氮含量呈极显著正相关(r=0.923~0.985),与土壤密度呈极显著负相关(r=−0.971~−0.996)。[结论]林分类型是影响土壤有机碳垂直分配的重要因素之一,且其影响程度随土壤深度的增加而下降;仅山杨林下土壤有机碳含量与土壤黏粒含量呈极显著正相关,其它林分与黏粒含量相关性不显著。

[Objective]To evaluate the forest soil carbon pools and provide references for the assessment of forest ecosystem services function in North China by exploring the vertical distribution of soil organic carbon(SOC)content and density in different typical forest stands in Haituo Mountain,Beijing.[Method]Three replicates of soil profiles from each plot were selected from five typical forest stands(Chinese pine,walnut tyurin,oak,coniferousbroadleave mixed stand,and aspen).One-Way ANOVA was employed to study the effects of stand types on SOC content and density in different horizons.Correlation analysis was conducted to analyze the relationship between the SOC content and different soil physical-chemical factors.[Result]The soil organic carbon content was between 9.35-50.25 g·kg^−1(mean=27.42).Stand types had significant effect on SOC content(p<0.05).The mean SOC content of the stands studied followed the ascending order of aspen,coniferous-broadleave mixed stand,walnut tyurin,oak,Chinese pine.The SOC content in all these stands showed similar vertical distribution tendency,i.e.decreasing from top horizon to bottom,with a higher concentration on the top horizon(A+AB horizon accounted 57%).The SOC density ranged from 21.4 t·hm^−2 to 76.6 t·hm^−2 within 100 cm in these stands,with the mean of 45.7 t·hm^−2.The mean SOC density of these stands followed the following descending order of aspen,walnut tyurin,coniferousbroadleave mixed stand,oak,Chinese pine.The vertical distribution pattern of SOC density in unit volume was similar with that of the SOC content:decreasing from top horizon to bottom,with a higher density on the top horizon(A+AB horizon accounted 35%-40%).The SOC content in these stands had significant positive correlation to total nitrogen content(r=0.923−0.985),and significant negative correlation to bulk density(−r=0.971−0.996).With the increase of soil depth,the relative carbon density per centimeter decreased successively.[Conclusion]Stand type is one of the main factors controlling the vertical distribution of SOC,and its effect tends to decrease with the depth of soil profile.The result of correlation analysis suggests that there is significant positive correlations between aspen and clay content,but there may be no significant correlations between other stands and clay content.