猫儿山不同海拔土壤有机碳组分构成及含量特征

Fraction and Content of Soil Organic Carbon at Different Elevations in Maoer Mountain

土壤有机碳(SOC)的组成和存在形态影响土壤碳库稳定性,揭示SOC组分构成及含量特征,对发挥土壤碳库功能具有重要意义。本研究以华南第一高峰-广西猫儿山为对象,采集不同海拔(460~2120 m)的土壤剖面发生层的土壤,分别测定基于化学组成、密度和粒径区分的胡敏酸碳(HAC)、富里酸碳(FAC)和胡敏素碳(HC)、轻组有机碳(LFOC)和重组有机碳(HFOC)、颗粒有机碳(POC)和矿物结合态有机碳(MOC)含量,分析不同海拔SOC组分特征及其生态意义。结果表明:(1)土壤HAC、FAC、HC、LFOC、HFOC、POC、MOC含量分别为0.10~8.56 g kg^-1、0.33~25.62 g kg^-1、1.38~70.46 g kg^-1、0.01~41.94 g kg^-1、1.95~72.73 g kg^-1、0.41~21.37 g kg^-1、1.38~104.74 g kg^-1;(2)在海拔460~1400 m的常绿阔叶林植被下,土壤HC、HAC、FAC、POC、HFOC、MOC含量随海拔升高总体上呈增加趋势,而土壤LFOC含量随海拔升高总体上呈先增加后降低趋势;在海拔1400~1580 m的常绿落叶阔叶混交林植被下,土壤HAC、FAC含量随海拔升高保持平稳趋势,而HC、LFOC、POC、HFOC、MOC呈增加趋势;在海拔1580~2005 m的针阔混交林植被条件下,土壤HC、HAC、LFOC、POC、HFOC、MOC含量明显低于其相邻植被类型;在海拔2005~2120 m的山顶矮林和灌草丛植被下,HC、FAC、HAC、LFOC、HFOC、MOC含量均随海拔升高呈陡峭上升趋势,而POC呈略微的下降趋势;(3)HFOC/SOC和MOC/SOC均随土壤深度增加呈增大趋势,随海拔升高呈减小趋势,而LFOC/SOC和POC/SOC则与之相反;惰性态有机碳(MOC、HFOC)占SOC比例分别为63.44%~99.71%和68.41%~93.89%,是土壤有机碳的主要组成部分;(4)LFOC对海拔和土壤深度变化的平均敏感性指数均显著高于其他碳组分,能够敏感反映土壤碳库随海拔和土壤深度的变化。

The fractions of soil organic carbon(SOC)affect the stability of soil C pool.It is of great significance of studying the characteristics of SOC in mountainous areas to maintain soil C balance and stability.In this study,soil samples at the genetic horizons were collected from different altitudes(460-2120 m)in Maoer Mountain,Guangxi,the highest mountain in South China.SOC fractions,including humic acid C(HAC),fulvic acid C(FAC),humin C(HC),light fraction organic C(LFOC),heavy fraction organic C(HFOC),particulate organic C(POC)and mineral associated organic C(MOC),were determined based on chemical composition,density and particle size fractionation,and their distribution characteristics and ecological significance with altitudes were analyzed.The results showed that the contents of HAC,FAC,HC,LFOC,HFOC,POC,and MOC were 0.10-18.56 g kg^-1,0.33-25.62 g kg^-1,1.38-70.46 g kg^-1,0.01-41.94 g kg^-1,1.95-72.73 g kg^-1,0.41-21.37 g kg^-1,and 1.38-104.74 g kg^-1,respectively.The contents of soil HC,HAC,FAC,POC,HFOC,and MOC were generally increased with elevations,while soil LFOC content was firstly increased and then decreased with elevations under evergreen broad-leaved forests at the altitude of 460-1400 m.The contents of soil HAC and FAC kept a steady trend,while the contents of HC,LFOC,POC,HFOC,and MOC were increased with elevations under the mixed evergreen deciduous broad-leaved forest at the altitude of 1400-1580 m.The contents of soil HC,HAC,LFOC,POC,HFOC,and MOC under mixed coniferous and broad-leaved forests were significantly lower than those under the adjacent vegetation types at the altitude of 1580-2005 m.The contents of soil HC,FAC,HAC,LFOC,HFOC,and MOC were increased sharply with elevation,while the content of POC was decreased slightly with elevation under the hilltop shrub and grass vegetation at the altitude of2005-2120 m.The ratios of HFOC to SOC(LFOC/SOC)and MOC to SOC were increased with the increase of soil depth and were decreased with altitude increase,while LFOC/SOC and ratio of POC to SOC showed the contrary results.The percentages of MOC and HFOC(inert organic C fractions)in total SOC were 63.44%-99.71%and68.41%-93.89%,respectively.The average sensitivity index of LFOC to altitude and soil depth was significantly higher than that of the other C fractions,which could sensitively reflect the change of soil C pool with altitude and soil depth.