摘要:柠条（Caragana korshinskii Kom.）种植是黄土高原地区生态环境建设中重要的人工植被恢复措施。选择黄土丘陵区条带种植15、25和35年的柠条坡地，以荒草坡地为对照，运用Le Bissonnais法分析柠条种植不同年限和坡位对0-40 cm土层团聚体分布及其稳定性的影响。结果表明：长时间柠条种植对土壤团聚体稳定性的影响主要在0-20 cm土层；不同处理下土壤大团聚体（>0.25 mm）含量总体表现为柠条35年 > 柠条25年 > 柠条15年 > 荒草地，表明柠条种植年限增加促进了大团聚体的形成。从坡面尺度看，柠条平均重量直径整体表现为坡下 > 坡上 > 坡中；在上坡的柠条35年样地具有最大值（3.08 mm），但在下坡荒草地显著高于柠条林地（P<0.05）。基于相对消散指数和相对机械破碎指数，上中坡土壤团聚体均对消散作用和机械破碎作用较敏感，而下坡的下层土壤团聚体对破碎作用更敏感。冗余分析表明，土壤有机碳和粘粒含量与柠条平均重量直径呈显著正相关关系（P<0.05）。种植年限是影响土壤团聚体稳定性的主要因素，解释了30.4%的变异；其次是土层（2.75%）和坡位（0.61%）。总体而言，柠条种植年限增加有利于促进黄土丘陵区土壤团聚体稳定性提升，但这种影响在不同坡位具有差异：在上中坡团聚体稳定性均随种植年限增加而增强，在下坡则先降后增。



Abstract:Planting shrubs such as Caragana korshinskii Kom. is one of the main components of the ecological rehabilitation project implemented on the Loess Plateau of China. However, the effects of C. korshinskii plantations on soil aggregate stability in the loess hilly region remain unclear. The objectives of the present study were to investigate the distribution and stability of soil aggregates in C. korshinskii stands of different ages (15, 25, and 35 years of strip planting) in the loess hilly region, with natural grassland as the control (> 40 years). Soil samples were collected from four depths (0-10, 10-20, 20-30, and 30-40 cm) at three slope positions (upper, middle, and lower). Soil aggregate stability was determined using the Le Bissonnais method. The results showed that long-term planting of C. korshinskii mainly affected soil aggregate stability at the shallower depths (0-20 cm). In all cases, the proportion of soil macro-aggregates (> 0.25 mm) increased with increasing stand age, indicating that older stands better facilitated the formation of soil macro-aggregates. Mean weight diameter (MWD) of soil aggregates at different slope positions followed the order: lower slope > upper slope > middle slope. On the upper slope, the highest MWD was found in 35-year stands (3.08 mm), whereas on the lower slope, the MWD in 35-year stands was significantly lower than that of the control (P<0.05). Based on the relative slaking index and relative mechanical breakdown index, soil aggregates were sensitive to both slaking and mechanical breakdown on the middle and upper slopes, whereas soil aggregates at the deeper depths (20-40 cm) were more sensitive to mechanical breakdown on the lower slope. Redundancy analysis indicated that MWD was significantly correlated with soil organic carbon and clay contents (P<0.05). Soil aggregate stability was primarily affected by stand age, which explained 30.4% of the observed variation; soil depth and slope position were less influential, accounting for 2.75% and 0.61% of the variation, respectively. In conclusion, soil aggregate stability improved with increasing stand age of C. korshinskii in the loess hilly region; however, this effect varied with slope position. On the upper and middle slopes, soil aggregate stability increased with increasing stand age, whereas on the lower slope it first decreased and then increased.





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