黄土丘陵区坡面整地和植被耦合下的土壤水分特征

水分是干旱半干旱地区植被恢复的主要环境制约因子。在黄土高原小流域,合理整地能够有效截留降雨补给土壤水,进而促进植被恢复。选择地处甘肃定西的半干旱黄土小流域为研究区,基于野外实测数据,分析不同植被和整地方式(柠条水平阶、山杏水平沟、侧柏反坡台,油松反坡台)综合影响下的土壤水分特征。采用最优分割法将不同整地方式土壤水分垂直层次划分为活跃层,次活跃层和相对稳定层。结果表明:生长季不同整地方式土壤水分的变化与降水量的变化密切相关,不同月份以及不同深度各整地方式土壤水分之间差异显著(P0.05)。根据土壤水分垂直变化特征,山杏水平沟水分活跃层与次活跃层为0—80cm,其深度范围均大于其他3种整地方式,而柠条水平阶土壤水分均在30 cm以下较为稳定,其深度范围均小于其他3种整地方式。不同整地方式土壤水分含量具体表现为:山杏水平沟侧柏反坡台柠条水平阶油松反坡台。

Coupling effects of different land preparation and vegetation on soil moisture characteristics in a semi-arid loess hilly region

Soil moisture is the main environmental factor affecting vegetation restoration in the arid and semi-arid regions. In the small watershed of the Loess Plateau, reasonable land preparation methods can be utilized the surface runoff effectively and thus supply for the soil moisture during the vegetation restoration processes. In the present study, a small watershed located in Dingxi City Gansu Province was selected, based on the field survey data in the growing season. Different land preparation methods combined with various vegetation types (Level bench-Caragana korshinskii, Level ditch-Prunus armeniaca, Adverse grade tableland-Platycladus orientalis, Adverse grade tableland-Pinus tabulaeformis) were used to investigate the soil moisture dynamics during the re-vegetation. Time domain reflectometry was applied to record volumetric soil moisture in the research plots at 12 different soil depths below the ground surface (0-5, 5-10, 10-20, 20-30, 30-40, 40-60, 60-80, 80-100, 100-120, 120-140, 140-160, 160-180 cm) during the growing season of 2014. Meanwhile, the vertical soil moisture layer could be divided into the active layer, the second active layer and the stable layer according to the optimal segmentation method. The results indicated that: soil moisture variation exhibited closed relationship with the changes of precipitation, the rainfall events were scattered during the growing season, the precipitation with a small amount with more frequency and large amount with small frequency can led to different effects to different vegetation types. In addition, soil moisture content was relative lower from May to June, whereas higher soil moisture content exhibited from September to October. Moreover, soil moisture showed significant differences between different months and soil depths (P < 0.05). Different land preparations showed different hierarchy partition. The depth of the active layer and second active layer can reach 80 cm of the level ditch with Prunus armeniaca, which was higher than the other land preparation types, while the stable layer was below 30 cm of the level bench-Caragana korshinskii, which was lower than the other land preparation types. The active layer, second active layer and stable layer of the Level bench-Caragana korshinskii were 0-10, 10-30 and 30-180 cm, of the Level ditch-Prunus armeniaca were 0-40, 40-80 and 80-180 cm, of the adverse grade tableland-Platycladus orientalis were 0-30, 30-60 and 60-180 cm, and of the adverse grade tableland-Pinus tabulaeformis were 0-10, 10-60 and 60-180 cm, respectively. In conclusion, during the growing season, different soil moisture variation showed as the followed order, Level ditch-Prunus armeniaca > Adverse grade tableland-Platycladus orientalis > Level bench-Caragana korshinskii > Adverse grade tableland-Pinus tabulaeformis.