黄土丘陵区林草恢复进程中土壤入渗特征研究

植被恢复可以改善土壤的入渗能力，植被恢复方式不同及恢复进程中其土壤性质的改善对土壤水文特征的影响程度也将影响到植被恢复的格局。为确定林地、草地植被恢复年限对土壤水分入渗特征的影响，以黄土丘陵区西部官山林场退耕后栽植的刺槐林地、撂荒草地为对象，选取退耕年限为9年、15年、25年的林地、草地。于2014年5月对各样地的原状土土柱进行定水头入渗，比较不同退耕年限林地、草地的入渗性能和湿润锋穿透60 cm土柱的时间，并分析影响入渗特性的因素。结果表明:退耕年限为25年林地的土壤稳定入渗率、平均入渗率、前120 min累积入渗量、湿润锋到达60 cm土柱的时间分别为1.86，2.60 mm/min，387.82 mm，23.00 min；退耕年限为15年林地分别为1.38，1.90 mm/min，288.88 mm，35.33 min；退耕年限为9年林地分别为0.35，1.03 mm/min，194.50 mm，40.00 min；退耕年限为25年草地分别为3.17，3.17 mm/min，386.43 mm，24.00 min；退耕年限为15年草地分别为1.86，2.60 mm/min，387.82 mm，34.33 min；退耕年限为9年草地分别为1.86，2.60 mm/min，387.82 mm，38.33 min。6种样地的土壤入渗过程均能用通用模型进行高精度拟合。各样地土壤入渗速率与土壤有机质、>0.25 mm水稳性团聚体含量呈正相关关系，与土壤密度呈负相关关系。土壤入渗能力随退耕年限增加而增强，退耕还草比退耕还林更有利于土壤入渗能力增强。因此建议在水资源有限的黄土区以退耕还草为主以促进更多的降雨就地入渗。 

Effects of forestland and grassland restoration process on soil infiltration characteristics in loess hilly region

Vegetation restoration can improve the soil infiltration capacity, the way and process of the vegetation restoration affect the soil properties in soil hydrological characteristics, and it will determine the distribution of vegetation restoration. In this paper, sites with different restoration types ( secondary acacia forestland, secondary grassland ) and the forestland and grassland whose vegetation restoration years were 9 , 15 and 25 located in Guanshan Forest Farm in the west of loess hilly region were chosen as research objects. We aimed to illustrate the effects of vegetation restoration types and years on the hydraulic conductivity, the wetting front penetration time of 60 cm column and analyze the factors affecting the infiltration characteristics in soil layer of 0--60 cm using the constant head infiltration of undisturbed soil columns in May 2014. The results showed that: 1) the stable infiltration rate, mean infiltration rate, accumulative infiltration amount in 120 minutes and the wetting front penetration time of 60 cm column in the site of 25 years vegetation restoration forestland were 1. 86,2. 60 mm/min,387. 82 mm,23. 00 min, respectively; in the 15 years vegetation restoration forestland, they were 1. 38,1. 90 mm/min,288. 88 mm,35. 33 min;in the 9 years vegetation restoration forestland, they were 0. 35,1. 03 mm/min,194. 50 mm,40. 00 min. Comparatively, these values were 3. 17,3. 17 mm/min,386. 43 mm, 24. 00 min in 25 years vegetation restoration grassland;1. 86,2. 60 mm/min,387. 82 mm,34. 33 min in the 15 years vegetation restoration grassland, and 1. 86,2. 60 mm/min,387. 82 mm,38. 33 min in 9 years vegetation restoration grassland. 2 ) Additionally, the universal empirical model was fitted to the undisturbed soil columns infiltration process of all the six experimental area. 3) The soil infiltration rate was positively correlated with the organic matter content and the >0. 25 mm water-stable aggregates content, while was negatively correlated with the bulk density. In conclusion, soil infiltration capacity was enhanced with the restoration years increased;at the same restoration year, soil infiltration capacity of the grassland performed better than that of the forestland, so it is recommended to increase the secondary grassland to improve the soil rainfall infiltration rate on the loess hilly region area, where the water resource is limited.