大桥水库消落带不同水位高程柳树林地土壤团聚体组成与分形特征

为研究植被恢复对水库消落带土壤团聚体组成及稳定性的影响,利用干筛和湿筛法,测定了大桥水库消落带不同水位高程下柳树林地土壤团聚体组成分布,并基于分形理论分析了土壤团聚体分形特征。结果表明:(1)消落带柳树林地土壤0.25 mm非水稳定性团聚体和水稳性团聚体分别为73.13%～93.69%和47.62%～82.06%,较对照无植被样地土壤均有所增加,但两者差异不明显;消落带土壤大团聚体含量随水位高程升高而降低,随土层深度增加而减少,但在不同水位高程和不同土层间均无显著性差异(p0.05)。(2)消落带柳树林地土壤水稳性团聚体分形维数(D)为2.51～2.82,平均值为2.67,低于对照的2.75;土壤水稳性团聚体分形维数(D)在不同水位高程和不同土层间均无显著性差异(p0.05),整体呈现出随水位高程升高而降低的趋势,且0—10 cm土层D值低于10—20 cm土层。(3)消落带柳树林地土壤MWD、GMD平均值分别为0.81,0.24 mm,高于对照的0.71,0.15 mm,柳树林地土壤团聚体稳定性高于对照;土壤团聚体稳定性在消落带内部具有一定空间差异,MWD与GMD均表现为高水位(2 016～2 019 m)中水位(2 010～2 013 m)低水位(2 007 m),且0—10 cm土层MWD与GMD大于10—20 cm土层的,但不同水位高程和不同土层间均无显著性差异(p0.05)。综上,大桥水库消落带植被恢复对土壤团粒结构有一定程度改善,且随淹水深度的增加,消落带柳树林地土壤团聚体稳定性降低。

Composition and Fractal Features of Soil Aggregates inWillow Forest Lands at Different Elevations in the Water Level Fluctuation Zone of the Daqiao Reservoir

In order to study the effects of vegetation restoration on the composition and stability of soil aggregates in the water-level-fluctuation zone, dry screening and wet screening methods were used to determine the composition and distribution of soil aggregates in willow forest under different water levels and elevations in the water-level-fluctuation zone of Daqiao Reservoir, and fractal characteristics of soil aggregates were analyzed based on fractal theory. The results showed as follows:(1) The contents of non-water-stable aggregates and water-stable aggregates that greater than 0.25 mm in willow forest land in the water-fluctuation zone were 73.13%~93.69% and 47.62%~82.06%, respectively, which were higher than those of control plots without vegetation, but the difference between them was not significant. The content of macro-aggregates in water-level-fluctuation zone decreased with the increasing of water level elevation and depth of soil layer, however, there was no significant difference between different water levels and soil layers (p>0.05). (2) The fractal dimension (D) of soil water-stable aggregates in willow forest in the water-level-fluctuation zone ranged from 2.51 to 2.82, with an average of 2.67, which was lower than that of the control (2.75). The fractal dimension (D) of soil water-stable aggregates showed no significant difference between different water level elevations and different soil layers (p>0.05), and it decreased with the increasing of water level, and the D value of 0-10 cm soil layer was lower than that of 10-20 cm soil layer. (3) The average values of soil MWD and GMD of willow forest in water-level-fluctuation zone were 0.81 and 0.24 mm, respectively, which were higher than those of the control (0.71 and 0.15 mm). The stability of soil aggregates in willow forest was higher than control. The stability of soil aggregates had a certain spatial difference in the water-level fluctuation zone. Both MWD and GMD followed the order of high water level (2 016~2 019 m) > medium water level (2 010~2 013 m) > low water level (2 007 m), and the MWD and GMD in the 0-10 cm soil layer were both greater than those in the 10-20 cm soil layer. However, there was no significant difference between different water levels and different soil layers (p>0.05). In conclusion, vegetation restoration in the water-level-fluctuation zone of Daqiao Reservoir could improve soil aggregate structure to a certain extent, and the stability of soil aggregate in willow forest land in the water-level-fluctuation zone decreased with the increasing of flooding depth.