川东平行岭谷区典型县农田土壤碳库演变特征

Evolution of Soil Organic Carbon Pool in the Cropland of a Typical County Located in Paralleled Ridge-Valley of Eastern Sichuan

选取川东平行岭谷区典型县域垫江县为研究区,依据第二次土壤普查数据(1980年)和2007年的测土配方施肥项目监测数据,考察了该区域农田耕层土壤碳库现状与演变特征.结果表明,垫江县境内,紫色土和水稻土是最重要的农田耕层碳库,其中红棕紫泥土、灰棕紫泥土、红棕紫色水稻土和灰棕紫色水稻土是面积分布最广、耕层碳储量最高的4个土属,其耕层碳储量之和占全县耕层有机碳总储量的68.34%;对于绝大部分土属来说,水耕稻作在促进其耕层土壤碳累积方面要明显优于旱作.1980-2007年期间,长期人为扰动对垫江县农田耕层有机碳累积的影响是正面的,全县农田耕层土壤一直发挥着"碳汇"效应;近30年来,全县农田耕层碳储量的增加主要得益于紫色土耕层碳储量的提高,而耕层土壤有机碳亏损则主要出现在灰棕紫色水稻土中,有效减少其耕层有机碳亏损是提高全县耕层碳储量的一个重要切入点.目前,垫江县农田耕层仍具有巨大的增碳潜力,主要存在于紫色土和水稻土中;就土属而言,灰棕紫泥土、红棕紫泥土、灰棕紫色水稻土、红棕紫色水稻土等4个土属的耕层增碳潜力较高,是垫江县农田管理调查与增碳策略实施的重点.

Dianjiang ,a typical county in the paralleled ridge-valley region of eastern Sichuan ,was selected as the study area .According to data from soil testing and fertilizer recommendation in 2007 and the second general survey of soil in 1980 ,the storage and evolution of soil organic carbon （SOC） in the cropland in Dianjiang County were investigated .Most of SOC storage in the cultivated horizon was found to be stocked in purple soils and paddy soils ,of w hich four soil genera （red-brow n purple soil ,gray-brow n purple soil ,redbrown purple paddy soil and gray-brown purple paddy soil） were distributed most extensively and had higher SOC storage in the cultivated horizon than other soil genera ,the sum of their SOC storage in the cultivated horizon accounting for 68 .34% of total SOC storage in the cultivated horizon of croplands .In increasing SOC accumulation in the cultivated horizon ,water culture and rice planting were obviously better than dry farming for most soil genera in the county .From 1980 to 2007 ,the effect of long-term artificial disturbance on organic carbon accumulation in the cultivated horizon was positive ,and the topsoil of croplands always functioned as a carbon sink .In the last 30 years ,total SOC storage increase in the cultivated horizon of croplands was benefited from purple soils .The main SOC loss in the cultivated horizon was found in grey-brown purple paddy soil ,and reducing the subsoil organic carbon loss in grey-brown purple paddy field should be an important way to increase total SOC storage in the cultivated horizon .The above study showed that the cultivated horizon of croplands ,especially purple soils and paddy soils ,in Dianjiang County maintains great carbon sequestration potential ,and that the genera of gray-brow n purple soil ,redbrown purple soil ,gray-brown purple paddy soil and redbrown purple paddy soil have higher carbon se-questration potential in the cultivated horizon than other soil genera and ,therefore ,should be the most important soil types in surveying cropland management and enforcing measures to increase carbon storage of cropland in Dianjiang County .