水土保持研究

为探究三峡水库消落带水位周期性涨落对土壤团聚体组成及稳定性的影响,采集消落带不同水位高程150 m,155 m,160 m,165 m,170 m和175 m的表层土壤,以未淹水高程180 m的表层土壤为对照,采用干筛法与湿筛法对土壤团聚体组成和稳定性进行了分析。结果表明:(1)7个水位高程土壤中>0.25 mm的非水稳性和水稳性团聚体含量分别占95%以上和63.60%以上; >5 mm的非水稳性和水稳性团聚体含量均随水位高程降低显著降低,最大降幅分别为19.71%和85.20%; <0.25 mm的非水稳性和水稳性团聚体含量均随水位高程的降低呈增加的趋势,最大增幅分别为289.97%和402.97%。(2)>0.25 mm水稳性团聚体含量随着水位高程的降低显著降低,由180 m的92.75%逐渐降低到150 m的63.60%; 平均重量直径和几何平均直径均随着水位高程的降低显著降低,降幅分别为3.31%～66.43%和5.81%～81.35%; 分形维数介于2.41～2.73,随着水位高程的降低而增加; 与180 m土壤相比,消落带内土壤团聚体破碎率随着水位高程的降低而增加,增幅分别为4.73%,24.49%,54.22%,78.55%,169.26%和463.51%。(3)团聚体稳定性指标与土壤颗粒组成、容重和有机碳含量均显著或极显著相关,其中>0.25 mm水稳性团聚体含量、平均重量直径和几何平均直径与有机碳具有极显著正相关关系,分形维数和团聚体破碎率与有机碳极显著负相关。三峡水库消落带水位周期性涨落显著改变了团聚体的组成和稳定性,随水位高程的降低,团聚体稳定性显著降低,研究结果可为三峡水库消落带土壤侵蚀研究提供科学依据。

In order to study the effects of the periodic water-level fluctuation on soil aggregate composition and stability in the Three Gorges Reservoir, the topsoil samples were collected at different water levels of 150 m, 155 m, 160 m, 165 m, 170 m and 175 m in the water-level fluctuation zone and at the elevation of 180 m from the bank uplands where soil was used as a control since it was not subjected to inundation. The present study used dry and wet sieving methods to analyze the composition and stability of soil aggregate. The results showed that:(1)the content of >0.25 mm air-dried aggregates and water-stable aggregates at seven water levels accounted for more than 95% and 63.60%, respectively; the content of >5 mm air-dried aggregates and water-stable aggregates significantly decreased with the decrease of water levels, and the maximum reductions were 19.71% and 85.20%, respectively; the content of <0.25 mm air-dried aggregates and water-stable aggregates significantly increased with the decrease of water levels, and the maximum increases were 289.97% and 402.97%, respectively;(2)the content of >0.25 mm water-stable aggregates decreased significantly with the decrease of water levels, decreasing gradually from 92.75% of 180 m to 63.60% of 150 m; mean weight diameter and geometric mean diameter decreased significantly with the decrease of water levels, and the decreased ranges were 3.31%～66.43% and 5.81%～81.35%, respectively; fractal dimension was between 2.41～2.73, which increased with the decrease of water levels; compared with soil at 180 m, the percentage of aggregate destruction in the water-level fluctuation zone increased by 4.73%, 24.49%, 54.22%, 78.55%, 169.26% and 463.51% with the decrease of water levels, respectively;(3)the aggregate stability indexes were significantly or extremely significantly related to soil particle composition, bulk density, and soil organic carbon; >0.25 mm water-stable aggregate content, mean weight diameter, and geometric mean diameter had the significantly positive correlation with soil organic carbon, while fractal dimension and the percentage of aggregate destruction were significantly negatively correlated with organic carbon. It can thus be deduced that the periodic water-level fluctuation of the Three Gorges Reservoir significantly changed aggregate composition and stability. With the decrease of water levels, soil aggregate stability decreased significantly. This research can provide a basis for the study of soil erosion in the water-level fluctuation zone of the Three Gorges Reservoir.