皖江自然湿地土壤碳密度及其开垦为农田后的变化

于2005年分别采集了安徽沿江4个淡水湖泊的自然湿地及其周边围垦农田的代表性土壤剖面样品，测定了总有机碳含量，讨论了天然淡水湿地有机碳密度与深度分布特征及其开垦为农田后的变化。结果显示，湿地表层（0～30cm）和全剖面（0～100cm）中的碳密度分别为42．5～57．4t／hm^2和81．5～91．6t／hm^2；而农田则分别为22．4～48．4t／hm^2和41．4～76．5t／hm^2。湿地开垦为农田后，土壤表层和全剖面的土壤有机碳含量明显降低，且有机碳含量的变异性增大。表明湿地开垦为农田后，其碳库失去稳定性。但是，开垦的旱地土壤的有机碳含量和碳密度显著低于开垦的稻田，故湿地开垦为旱地更不利于湿地碳库保护。因而，将湿地垦殖为水田是相对较有利于湿地碳库保护的人为土地利用方式。湿地开垦的碳库损失可能是土壤的大气CO2源效应的主要途径。

Organic Carbon Density of Soil of Wetland and Its Change after Cultivation along the Yangtze River in Anhui Province, China

Samples of topsoil and soil profile to depth of 100 cm were collected both natural wetlands and the cultivated croplands around them of 4 fresh water lakes along the Yangtze River reaches in Anhui Province,China during a field reconnaissance in 2005.Soil organic carbon(SOC)contents were measured by a wet combustion procedure and the SOC storage calculated both of topsoil at 0-30 cm and of whole profile.The changes in SOC distribution and storage after cultivation and the difference between cultivated dry croplands and paddy fields were discussed focusing the impact of human utilization on wetland carbon stock.SOC storage of topsoil and the whole profile were shown in a range of 42.5-57.4 t/ha and of 81.5-91.6 t/ha for undisturbed wetlands and of 22.4-48.4 t/ha and 41.4-76.5 t/ha for the cultivated croplands respectively,indicating a great decline of SOC storage after cultivation.A decline in SOC content and a rise in SOC variability among the sites implicated instability of wetland SOC under human utilization.Nevertheless,a higher(by 15%-25%)SOC storage found of paddy fields than dry croplands revealed a relatively preserving effect for SOC pool of cultivated wetlands.The rapid and significant loss of SOC storage within 35 years may demonstrate the potential impact of the wetland cultivation on C source effect from terrestrial soils to atmosphere.