长武塬边坡不同植被下土壤团聚体及入渗特征

黄土塬塬坡的水土流失一直是一个重要热点问题而得到广泛关注。本文以长武塬边坡的刺槐、侧柏和草地3种植被类型为研究对象，于2016年5月测定了3类样地0~30 cm土壤的水稳性团聚体组成、有机碳含量(SOC)及土壤稳定入渗率(SIR)等土壤物理性质，探讨不同植被类型下土壤团聚体和入渗特征的差异性。结果表明:刺槐林地表层0~30 cm土壤水稳性团聚体的平均质量直径(MWD)、分形维数(D)、SOC及SIR的测定结果为:2.63 mm、2.60、5.62 g/kg和10.40 mm/min；侧柏林地分别为3.67 mm、2.60、4.87 g/kg和5.41 mm/min；草地分别为2.44 mm、2.58、6.07 g/kg和12.45 mm/min。结果表明:草地和刺槐林地的土壤结构性状相对优良，SOC高且入渗能力强，有利于长武塬边坡地区的水土保持，侧柏林地虽具有一定的大团聚体塑造能力，但其土壤SOC和入渗能力相对较低，不利于降水的就地入渗。因此，建议适度种植常绿性(侧柏)树种，合理配置该地区退耕还林还草植被类型。 

Soil aggregates and infiltration characteristics under different vegetations in Changwu tableland slope of northwestern China

Soil and water loss in loess tableland slope had been widely concerned as a hot issue. In this paper, sites with three vegetation types ( Robinia pseudoacacia, Platycladus orientalis and grassland) located in Changwu tableland slope of northwestern China were chosen as research objects. Our aim is to explore the effects of different vegetation types on soil aggregates and infiltration capacity, the mean weight diameter ( MWD) and fractal dimension ( D) of soil water-stable aggregates in layer of 0--30 cm, the soil organic carbon content (SOC) and the steady infiltration rate (SIR) were measured on May 2016. The results showed that:the MWD and D of soil water-stable aggregates in layer of 0--30 cm, SOC and SIR in the site of R. pseudoacacia land were 2. 63 mm, 2. 60, 5. 62 g/kg and 10. 40 mm/min, respectively;in P. orientalis land, they were 3. 67 mm, 2. 60, 4. 87 g/kg and 5. 41 mm/min; in the grassland, they were 2. 44 mm, 2. 58, 6. 07 g/kg and 12. 45 mm/min. Results showed that soil structure, organic carbon content and infiltration capacity of grassland and R. pseudoacacia land performed better than that of P. orientalis land, and were beneficial to the conservation of soil and water in Changwu tableland slope. P. orientalis land showed the advantage of shaping large aggregates, while its soil organic carbon content and water infiltration capacity were relatively low and not advantaged for rainfall infiltration. So it is recommended to plant evergreen tree ( Platycladus orientalis) moderately, and design rational distribution of different vegetation types in this area.