沙化草地恢复过程中土壤有机碳物理组分和全氮含量的变化

Change of Soil Organic Carbon Fraction and Total Nitrogen in the Process of Restoration in Desertification Grassland

以宁夏中北部盐池县不同恢复阶段的沙化草地(流动沙地、半固定沙地、固定沙地和荒漠草地)土壤为研究对象,分析土壤粗砂粒有机碳、细砂粒有机碳、粘粉粒有机碳、重组有机碳、轻组有机碳和土壤全氮的变异特征,探讨沙化草地恢复过程中土壤有机碳变化机制。结果显示:(1)荒漠草地、固定沙地、半固定沙地0~30cm土层土壤,粗砂粒有机碳、细砂粒有机碳和粘粉粒有机碳含量分别比流动沙地增加了67.7%、69.8%、212.1%和48.8%、35.3%、99.9%以及33.6%、23.0%、48.9%。(2)随着沙化草地不同程度的恢复,轻组有机碳含量、分配比例和重组有机碳含量均表现为流动沙地<半固定沙地<固定沙地<荒漠草地;重组有机碳分配比例随沙化草地恢复程度的升高呈降低趋势。(3)土壤细砂粒、粘粉粒、重组有机碳、轻组有机碳、粗砂粒有机碳、细砂粒有机碳、粘粉粒有机碳含量与土壤有机碳、土壤全氮含量均呈显著正相关关系,与粗砂粒含量均呈显著负相关关系。研究表明,轻组有机碳和粘粉粒有机碳含量对土壤有机碳的影响最大,轻组有机碳、重组有机碳、粗砂粒有机碳和粘粉粒有机碳对土壤全氮的影响最大,表明沙化草地的恢复有利于减小土壤侵蚀,改善土壤结构与质量。

In order to discuss the change mechanism of soil organic carbon during the recovery of desertifica-tion grassland, we studied the soil organic carbon of coarse sand, soil organic carbon of fine sand,soil or-ganic carbon of clay and silt, heavy-fraction organic carbon （ H F O C ）, light-fraction organic carbon （LFOC ） and total nitrogen under different restoration of desertification grassland in Yanchi Country, north and middle region of Ningxia （mobile dunes, semi-fixed dunes, fixed dunes and grasslands）. T he re-sults showed that： （1） to compare with mobile dunes, soil organic carbon of coarse sand, soil organic car-bon of fine sand, soil organic carbon of clay and silt in grassland, fixed dunes and semi-fixed dunes wereincreased by 67.7%, 69.8% and 212.1 %; 4 8 .8% , 35 .3% and 9 9 .9 %; 3 3 .6% , 23 .0% and 48. 9 % , re -spectively. （2） The content of LFOC, the proportion of LFOC and the content of HFOC showed that mo-bile dunes〈C semi-fixed dunes〈C fixed dunes〈C grassland; the proportion of HFOC decreased gradually in the process of grassland restoration in desertification grassland. （3） The content of fine sand, clay and silt, HFOC, LFOC, soil organic carbon of coarse sand, soil organic carbon of fine sand and soil organic carbon of clay and silt were significantly positively correlated to the content of SOC and soil total nitrogen （TN）,were significantly negatively correlated to the content of coarse sand. The content of LFOC and soil organic carbon of clay and silt have significantly effected on SOC, and the content of LFOC, HFOC, soil organic carbon of coarse sand, soil organic carbon of clay and silt have significantly effected on soil total ni-trogen, which indicated that the restoration of desertification grassland is beneficial to reduce soil erosion and improved soil structure and quality.