晋西黄土区土地利用类型对阳坡土壤水分特征的影响

How land-use types affect the soil moisture characteristics of sunny slopes in the loess area of western Shanxi Province

土壤水分是黄土区植被恢复建设过程中的主要限制因素,但不同土地利用下阳坡坡面土壤水分变化研究较少.以晋西黄土区土桥沟小流域为研究区,选取刺槐林、油松林、荒草地和梯田退耕地4种不同土地利用类型阳坡坡面为研究对象,用TDR土壤水分测量仪,以20 cm为间隔,测量阳坡各监测点0-200 cm土层土壤水分,并进行数理统计分析.结果表明:(1)观测期内,同一月份不同土地利用和同一土地利用不同月份阳坡土壤含水量差异显著(P<0.05),梯田退耕地各月土壤含水量较高,各土地利用类型10月份土壤平均含水量最高,6月份最低.(2)不同土地利用下阳坡土壤含水量均在0-100 cm土层变化较大,60 cm附近土壤含水量最高,随深度增加,变化趋势逐渐减弱,最终达到稳定状态,在观测范围内呈"S"状分布.(3)不同土地利用下阳坡坡面土壤水分活动层划分范围不同,刺槐林活跃层为0-80 cm,其深度范围大于其他3种土地利用类型,荒草地次活跃层深度范围最大为0-100 cm,此外,4种土地利用类型下,100-200 cm土层均为相对稳定层.(4)阳坡不同土地利用下土壤水分季节变异系数随土层深度增加先变大后减小,其中土壤水分季节变异系数均在土层40 cm处最大,140 cm左右开始趋于稳定.综上所述,阳坡不同土地利用类型下,土壤水分时空变化、土壤剖面活动层划分和土壤水分季节变异特征均呈现不同变化特征,结果可为黄土区阳坡植被恢复建设,土地与水资源有效利用提供理论依据.

Soil moisture(SM)is one of the main limiting factors in the vegetation restoration in loess areas.Few research has been conducted on the change in SM of sunny slopes under different land-use types.This paper mainly examined the dynamics of monthly and vertical SM profiles;as well as the division of soil water activity layers and the stratification characteristics of seasonal variation coefficients in different slopes and land-use types.The study site was in the Tuqiaogou small watershed in the Loess Plateau of Shanxi Province.Four different land-use slopes from a Robinia pseudoacacia forest,Pinius tabulaeformis forest,barren grass field,and terraced field were selected as research objects.The TDR soil moisture meter was used to measure SM to a depth of 0-200 cm,at 20 cm intervals for each monitoring point of the sunny slope,and results were analyzed using mathematical statistics.The results show that(1)during the observation period,the SM of different slopes in different months and different land uses in the same month were significantly different(P<0.05),and the SM content of the terraced field was higher in each month.The average SM of each land-use type was highest in October,but lowest in June.(2)The SM in sunny slopes under different land uses varied greatly in the 0-100 cm soil layer,with the SM being highest near 60 cm.This trend gradually weakened as the depth increased,and finally reached a stable state showing“S”in the observation range.(3)The soil water activity layers of the different slopes were different for each land use.The active layer of the R.pseudoacacia forest was 0-80 cm,and its depth range was wider than that of the other land-use types.The depth of the sub-active layer in the grassland was 0-100 cm.Additionally,the 100-200 cm soil layers were relatively stable under the four land use types.(4)The seasonal variation coefficients of SM in the sunny slopes of different land uses decreased first,and then decreased as soil depth increased.The coefficient was largest at the 40 cm soil layer,and began to stabilize at around 140 cm.The spatio-temporal changes in SM,the division of the soil profile,and the seasonal variation showed different characteristics in the sunny slopes of each land-use type.These results can provide a theoretical basis to effectively utilize land and water resources in the loess area of western Shanxi Province.