干旱区绿洲化过程土壤有机碳库与盐基离子变化及其对团聚体结构的响应

The expansion of oasification in arid regions has changed the characteristic of soil organic carbon reservoir, and also posed new risks on the soil salinization. The research on soil aggregates and dynamic changes in soil organic carbon with the oasification process is carried out with a focus on the Manas River Valley using time series data. This involves field investigation, field location test, micro zone control test and laboratory analysis, etc and a series of measures. With the increasing planting time, it disclosed the accumulation of soil organic carbon after abandoned salinized field reclaimed in different recovery modes. The distribution, accumulation and the contribution to total organic carbon of soil active organic carbon in the various components of aggregate will be analysed, and soil aggregate stability and changes of active organic carbon reservoir in oasification process will be examined. It also involves studies on the response relationship between the composition and accumulation of soil exchangeable cations and soil aggregate structure, the influence mechanism of soil aggregate composition to cations distribution and immobilization. Finally, the soil aggregate stability and carbon management index will be analysed so as to determind the ideal reclamation mode of abandoned farmland and the reasonable time of continuous cultivation. The results would enrich the theory of arid soil carbon reservoir, it also has important theoretical and practical significance to develop sustainable utilization of farmland management practices and measures in arid land.

随着干旱区绿洲化规模的扩大，改变了土壤有机碳库特征，也对土壤盐渍化产生新的风险。本研究选择新疆玛纳斯河流域为例，应用野外调查、田间定位试验、微区控制试验、室内测试分析等方法，开展时间序列下绿洲化过程有机碳动态变化及土壤团聚体稳定性的研究，阐明随着种植年限的增加土壤有机碳库积累特征；研究盐渍化弃耕地不同复垦模式下土壤活性有机碳在团聚体中的分布、储量及对总有机碳的贡献率，阐明垦殖模式对土壤团聚体稳定性与活性有机碳库动态过程的影响；研究土壤交换性盐基离子分布与积累对土壤团聚体结构的响应关系，揭示土壤团聚体组分对盐基离子分布及固持的影响机理。最后，进行绿洲化过程土壤团聚体稳定性及土壤碳库管理指数的分析，确定盐渍化弃耕地复垦的理想模式及合理的种植年限。研究结果丰富了干旱区农业土壤碳库理论，对制订绿洲农田持续利用的管理措施具有重要的理论与实践意义。

随着干旱区绿洲化规模的扩大，改变了土壤有机碳库特征与团聚体组成。本研究选择新疆玛纳斯河流域为例，开展绿洲化过程有机碳变化及土壤团聚体稳定性研究，取得结果如下：. 1、绿洲化过程土壤有机碳含量显著提高，呈现碳汇现象；土壤养分在恢复10年后有所降低；弃耕地开垦后增加了土壤大团聚体数量，且随着恢复年限的增加，微团聚体（<0.25mm）比例呈先增加后下降的趋势。恢复5年土壤团聚体中微生物碳代谢活性（AWCD）、Shannon指数（H） 和McIntosh指数（U） 最高。. 2、绿洲化过程各恢复模式土壤以大团聚体（R>0.25mm）为主，所占比例依次为人工草地>林地模式>单作农田>间作模式>轮作农田，较原始弃耕地增加了18.91 %、14.45%、11.98 %、11.53 %、10.19 %；土壤团聚体有机碳以轮作农田最高，人工草地、单作农田、间作模式和林地模式次之，原始弃耕地最低。人工草地、间作模式、轮作农田、单作农田、林地模式土壤团聚体微生物量碳分别是弃耕地的2.27、2.23、2.03、1.98和1.74倍，而易氧化有机碳含量较原始弃耕地分别增加4.08，1.77，2.02，2.87和2.21 g/kg。. 3、绿洲化过程土壤团聚体中Na+、 K+含量较弃耕地均有显著的下降，且随着恢复年限的增加呈现出递减的趋势。Mg2+、 Ca2+含量呈现出先增加后下降的趋势，且随着团聚体粒径的减小呈现出增加的趋势；Na+、 K+含量在表现为弃耕地>单作农田>间作模式>轮作农田，Mg2+、 Ca2+含量在间作模式与轮作农田中显著低于弃耕地。. 4、绿洲化过程土壤团聚体的比例（R0.25）、平均重量直径（MWD）和几何平均直径（GMD）较弃耕地增加明显，且随着恢复年限的增加呈现递增趋势，土壤团聚体分形维数（D）呈现出递减趋势；不同恢复模式提高了土壤大团聚体含量，以人工草地，单作农田，林地模式含量较高。不同恢复模式土壤团聚体平均重量直径，团聚体几何平均直径显著增大。绿洲化过程有利用提高土壤团聚体的稳定性。