宁夏南部半干旱黄土区3种土地利用类型的土壤水分时空变化特征

Temporal and Spatial Variation Characteristics of Soil Moisture Under Three Land Use Types in the Semi-arid Loess Region of Southern Ningxia

选择宁南黄土区贾新庄组的3种土地利用类型(川地农田、阴坡梯田、阳坡人工林),在2021年生长季使用土钻监测土壤含水量(SMC),同时利用自动气象站监测气象数据,分析土地利用、坡位、作物种类影响下的土壤水分时空变化特征。结果表明:3种土地利用类型的SMC大小为川地农田(16.32%)>阴坡梯田(12.66%)>阳坡人工林(10.82%);随着研究时段推进,SMC呈先降后升的变化,SMC与降水量存在较好的时间协同性,气温、太阳辐射、饱和水汽压差与阳坡人工林SMC显著相关;随土层深度增加,川地农田、阴坡梯田、阳坡人工林的SMC分别呈升高、降低、先降后升的变化,0—100 cm土层的土壤水分变异系数大于100—200 cm土层。SMC季节变化分为相对稳定期(4—5月)、消退期(6—8月)和恢复期(9—10月);SMC土层变化分为活跃层(0—40 cm)、相对活跃层(40—140 cm)、相对稳定层(140—200 cm)。土壤水分的补给时间滞后于降水,下层土壤水分补给滞后于上层土壤。阴坡梯田和阳坡人工林SMC随坡位降低均先降后升,最小值分别在坡上和中下坡位。土地利用、坡位差异、作物种类、气象因子均是影响SMC的因素;从SMC的变异程度看,各因子对SMC的作用大小依次为气象>土地利用>坡位>作物种类。研究结果有利于指导半干旱黄土区的植被重建与生态产业发展,确定不同立地环境下的合理植被配置。

In this study, three land use types(flat field farmland, shady slope terrace and sunny slope plantation) of Jiaxinzhuang Formation in the loess region of southern Ningxia were selected. Soil water content(SMC) was observed by soil drill in the growing season of 2021. At the same time, meteorological data were monitored by an automatic weather station. The spatio-temporal variation characteristics of SMC under the influence of land use, slope position and crop species were analyzed. The results showed that the order of SMC of the three land use types was flat field farmland(16.32%)>shady slope terrace(12.66%)>sunny slope plantation(10.82%). With the advance of the study period, SMC decreased first and then increased. There was excellent temporal synergy between SMC and precipitation. Temperature, solar radiation and saturation vapor pressure deficit were significantly related to the SMC of sunny slope plantations. With the increase of soil depth, SMC increased in flat field farmland, decreased in shady slope terrace, first decreased and then increased in sunny slope plantation. The variation coefficient of SMC in the 0—100 cm soil layer was greater than that in the 100—200 cm soil layer. Seasonal variation of SMC were divided into a relatively stable period(April-May), regression period(June-August) and recovery period(September-October). The change of SMC in different soil layers was divided into the active layer(0—40 cm), the relatively active layer(40—140 cm) and the relatively stable layer(140—200 cm). The replenishment time of soil moisture lagged behind precipitation, and the replenishment of lower soil moisture lagged behind that of upper soil. SMC of shady slope terrace and sunny slope plantation decreased first and then increased with the decreasing of slope position, and the minimum values were at the upper and middle-down slope position, respectively. Land use, slope position, crop species and meteorological elements were all factors that affected SMC. In terms of the variation degree of SMC, the effect of each factor on SMC followed the order of meteorological>land use>slope position>crop species. The results of this study were conducive to guiding the vegetation reconstruction and ecological industry development in semi-arid loess area, and determining the reasonable vegetation allocation under different site environments.