湘东丘陵区4种林地深层土壤溶解性有机碳的数量和光谱特征

Dissolved Organic Carbon in Deep Forest Soil Horizon in Eastern Hunan Province:Amount and Ultraviolet-visible Spectroscopic Features

选取湘东丘陵4种典型母质发育的林地土壤,挖掘土壤剖面并分层采集土壤样品至母质层/母岩,研究深层土壤有机碳（SOC）和溶解性有机碳（DOC）的数量和分布规律,采用紫外-可见光谱技术分析深层土壤DOC的宏观化学结构特征。结果表明,土壤DOC含量（2.33~185.26 mg·kg^-1）在板岩红壤和酸性紫色土剖面上某些深层土层出现升高现象。DOC/SOC除第四纪红土红壤在浅层表土最高（1.5%）外,其他3种土壤均在60~80 cm深层土层达到最高峰值（1.0%~2.5%）。SOC数量是控制不同母质土壤DOC数量的重要因素。但光谱分析显示,随着土壤剖面的加深,DOC的宏观化学组成、结构趋于复杂,化学稳定性升高。尽管一些深层土层中DOC/SOC升高,但其DOC化学结构更为复杂,评价深层土壤SOC和DOC稳定性还应考虑其化学结构特性。

Four types of upland forest soils derived from various parent materials in hilly region of eastern Hunan were sampled vertically to parent material / rock horizon to investigate their content and storage of soil organic carbon（SOC） and dissolved organic carbon（DOC）,the proportion of DOC to SOC（DOC/SOC） and whole-profile ultraviolet-visible（UV-Vis） spectroscopic features of DOC,in order to evaluate DOC quantity and quality and their controls in deep soil horizons.Results showed that the content of DOC ranged from 2.33 mg·kg^-1to 185.26 mg·kg^-1,first decreased and then increased along soil profile in acidic purple soil and red soil derived from slate.The DOC / SOC peaked at 60 ~ 80 cm soil depth,except for the red soil derived from quaternary red clay which peaked at 0 ~ 20 cm soil depth.SOC amount was the primary control of DOC storage.Spectroscopic analysis showed that,with the deepening of soil profile,macroscopic chemical structure of DOC became complex and the chemical resistance of DOC increased.Although the DOC / SOC was higher in some deep soil horizons,thechemical structure of DOC tended to be more complex,which should be considered in the evaluation of soil DOC and SOC stability.