湘东丘陵区不同类型土壤活性碳组分的剖面分布与差异

土壤活性碳组分是土壤健康变化的指示器。选取湘东丘陵区3种不同母质发育的林地土壤（紫色土、板岩红壤和花岗岩红壤），研究土壤颗粒有机碳（POC）和溶解性有机碳（DOC）的剖面分布规律，并分析POC、DOC与土壤有机碳（SOC）、土壤质地的关系。结果表明：土壤剖面POC、DOC质量分数分别介于0．29～3．87g·kg。和15．01～311．34mg·kg^-1，随剖面加深而大幅降低。土壤剖面POC储量介于8．61一16．54t·hm^-2，以花岗岩红壤最高，板岩红壤最低；而DOC储量介于380．76～1184．83kg·hm^-2，以板岩红壤最高，紫色土最低。POC占SOC的比例（POC／SOC）介于6．42％～46．25％，其中紫色土和板岩红壤POC／SOC随土层加深而降低，而花岗岩红壤则完全相反。DOC占SOC的比例（DOC／SOC）介于O．35％～3．02％，其中紫色土DOC／SOC随土层加深而降低，板岩红壤与花岗岩红壤DOC／SOC则以B层最高。由此可见，不同母质发育的土壤类型，碳库质量和脆弱程度不一。从维持地力和环境健康的角度，应对不同母质发育的土壤制定不同的开发利用方案。

Soil profile distribution of labile organic carbon fractions in three types of hilly woodland soils in eastern Hunan province

The labile fractions of soil organic carbon （SOC） are sensitive indicators of soil health. In the present study, two labile fractions of SOC, such as particulate organic carbon （POC） and dissolved organic carbon （DOC） were selected from three woodland soils derived from different parent materials （purple soil, red soil derived from granite and red soil derived from slate） in the hilly region, eastern Hunan Province. The purpose is to analysis the soil profile distributions of POC and DOC, and their correlations to SOC and soil texture in the three selected soils. Results showed that the content of POC and DOC in the soil profile ranged from 0.29 g＇kg1 to 3.87 g＇kg1 and from 15.01 mg.kg1 to 311.34 mg-kgl, respectively, and both decreased markedly with increasing soil depth. POC stock in the soil profile ranged from 8.61 t＇hrn2 to 16.54 t.hm2, with the highest one in the red soil derived from granite and the lowest one in the red soil derived from slate. While DOC stock in the soil profile, ranging from 380.76 kg＇hrn2 to 1184.83 kg.hm-2, was the highest in red soil derived from slate and the lowest in purple soil. The proportion of POC to SOC （POC/SOC） in the three soils ranged from 6.42% to 46.25%. It decreased with increasing soil depth in purple soil and red soil derived from slate, but increased with increasing soil depth in red soil derived from granite. The proportion of DOC to SOC （DOC/SOC） ranged from 0.21% to 1.31%, and it showed similar profile distribution to POC/SOC in purple soil, but peaked in the B horizon in red soils. This study suggests that soil carbon quality and vulnerability differed between soils developed from different parent materials. It is necessary to implement individual land use policy according to the development of different soils, in order to maintain soil fertility and environmental health.