吉林西部不同土地利用类型的土壤有机碳垂向分布和碳密度

土壤碳库在陆地生态系统碳循环中起着关键性的作用。在对吉林西部进行为期6年（2004－2009年）的环境调查基础上，采集了217个土壤剖面，获取了2 170个土壤样品的平均容重、含水率和有机碳含量，分析了不同土地利用类型下土壤有机碳（SOC）的垂向分布特征、原因和机理。结果表明：不同土地利用类型的土壤有机碳垂向分布表现出截然不同的特征，大致可分为“下降型”、“上升型”和“不变型”3种。呈下降型的草地、农田、湿地等SOC含量主要富集在0~30 cm耕作层，并随深度增加而快速下降；滩地为上升型，良好的水文条件和相对茂盛的植物为有机质提供了有利条件；不变型包括盐碱地、林地和沙地，SOC含量处于全区最低水平。不同土地利用类型的土壤有机碳密度差异很大，从大到小依次为水田、草地、旱田、湿地、退化草地、滩地、林地、沙地、盐碱地，其中水田为（169.25±17.70） t/hm²，盐碱地为 （26.50±10.00） t/hm²。植被生物量和土壤理化性质是影响土壤有机碳含量的主要因素。

Vertical Distribution of Soil Organic Carbon and Carbon Density Under Different Land Use Types in Western Jilin Province

The soil carbon pool plays a key role in terrestrial ecosystem carbon
cycle. A toal of 217 soil profiles has been collected, a total of 2 170 soil samples were obtained for measuring the average bulk density, moisture content and organic carbon content based on the six-year（2004-2009） environmental investigation implemented in western Jilin Province. The vertical distribution characteristics, reasons and mechanism of soil organic carbon（SOC） under different land use/cover types were analized. The result shows that the vertical distribution of SOC under different land use types has sharply different characteristics, and they can be divided into three types. The decreasing type including grassland, farmland and wetland, SOC of them mostly enriched in the planting layer (0-30 cm), and decreases with depth. Bottomland is under the increasing type, according to the appropriate hydrological conditions and lush vegetation. Meanwhile, SOC of saline and sandy land belongs to the stable type, stay at the lowest standard. The soil organic carbon density of different land use types varies a lot, the general trend from high to low is paddy field, grassland, upland field, wetland, degraded grassland, bottomland, woodland, sandy land and saline land. The soil organic carbon density of paddy field is (169.25±17.70) t/hm²; while, saline land is (26.50±10.00) t/hm². Therefore, the main factors that influence soil organic carbon contents are vegetation biomass, and soil physical and chemical properties.