水位脉动条件下三峡水库消落带土壤团聚体演变规律及其稳定特征

Degradation of ecological functions for water-fluctuation-zone (WFLZ) attracted intensive concerns in the Three-Gorges Reservior (TGR). Soil aggregate stability is the material basis for the restoration and reconstruction of ecological function for WFLZ. Affected by Water level fluctuation, WFLZ periodically experienced soaking and exposing, along with the decomposition and accumulation of plant debris, which may have far-reaching influence on size distribution and stability of soil aggregates. However, the detailed information on its dynamics and mechanisms were unknown yet. In this study, we mainly focused on the temporal and spatial dynamics of size distribution of soil aggragates for WFLZ in the TGR, using the method of on-site tracing and sampling, and lab determination. The stability of soil aggregates were quauntified by Mean weight diameter (MWD), Geomitric mean diameter (GMD) and fractal dimension (D). Path analysis and principal component analysis were used to reveal the key factors influencing the transformation and stability of soil aggregates. This investigation could be conducive to improve our knowledge on the formation and stability of soil aggregates under the condition of special changing disturbance, reveal the distribution and existing forms of exogenous organic carbon and its role in stabilizing soil aggregates, provide guidance for vegetation restoration, pollutants reduction and prevention of soil and water loss in the WFLZ of TGR.

三峡水库消落带生态功能退化一直备受关注，而稳定的土壤团聚体是消落带生态功能恢复和重建的物质基础。受独特的水位脉动节律影响，三峡水库消落带周期性浸泡和出露，以及消落带植物凋亡与残体累积，都可能对土壤团聚体数量、分布和稳定性产生重要影响，然而其变化规律和稳定特征目前尚不明确。本项目拟通过连续3年动态追踪、原位采样和室内分析相结合的方法，研究三峡水库消落带土壤团聚体粒径分布及其时空演变规律；通过MWD、GMD、分形维数等评价消落带土壤团聚体稳定特征；采用通径系数和主成分分析法揭示消落带土壤团聚体变化与稳定的关键影响因素。本研究有助于认识特殊变化环境条件下土壤团聚体形成与演变规律，揭示外源有机碳输入后在土壤团聚体中的分配和赋存形态，及其对土壤团聚体稳定性的影响；对三峡水库消落带植被恢复、污染物消减，以及水土流失防治等具有现实的指导意义。

三峡水库正式蓄水以来，消落带生态功能退化备受关注，而稳定的土壤团聚体是消落带生态功能恢复和重建的物质基础。受独特的水位脉动节律影响，三峡水库消落带周期性浸泡和出露，以及消落带植物凋亡与残体累积，都可能对土壤团聚体数量、分布和稳定性产生重要影响，然而其变化规律和稳定特征目前尚不明确。本项目通过连续3年动态追踪、原位采样和室内分析相结合的方法，研究三峡水库消落带土壤团聚体粒径分布及其时空演变规律；通过MWD、GMD、分形维数等评价消落带土壤团聚体稳定特征；采用通径系数和主成分分析法揭示消落带土壤团聚体变化与稳定的关键影响因素。结果发现，消落带土壤团聚体稳定性随高程的增加而升高，而且土壤结构稳定性与团聚体粒径分布具有极显著的相关关系；表层土壤大团聚体比例随着高程降低（淹水时间增加）而呈减小的趋势，而且经历多个淹水周期后，大团聚体（>2000 μm）崩解更明显，小团聚体比例增加；表层土壤有机碳随着高程降低有增加的趋势，而其在不同粒径团聚体上的分配及存在形态也呈现相似的规律。本研究结果有助于认识独特水位波动影响下土壤团聚体形成与演变规律，揭示外源有机碳输入后在土壤团聚体中的分配和赋存形态，及其对土壤团聚体稳定性的影响；对三峡水库消落带生境恢复、污染物消减，以及水土流失防治等具有现实的指导意义。