荒漠草原两种类型土壤的水分动态对比

基于2017—2018年的定位监测数据,分析了宁夏东部的盐池荒漠草原2种不同类型土壤(灰钙土和风沙土)的水分时空动态特征。结果表明: 2017和2018年生长季(5—10月),研究区降雨量分别为208.2和274.8 mm,降雨在各月份的分配差异较大。2018年除5月存在极端降雨事件(129.6 mm)外,其余各月降雨量均低于2017年。土壤水分变化的季节动态规律大致可以分为两个阶段:土壤水分补偿期(5月初至6月初)和土壤水分波动期(6月中旬至9月底)。0～20 cm土层土壤含水量在降雨后呈骤增骤减的脉冲式特点,深层土壤含水量较稳定。灰钙土土壤含水量随土层加深表现为“升-降-升”的变化,风沙土土壤含水量在0～60 cm土层出现井喷式增加,而后增加缓慢,但随着土层深度的增加土壤含水量逐渐增大。2017年,灰钙土全剖面(0～100 cm)土壤水分表现为积累型,风沙土表现为消耗型;2018年,两种类型的土壤水分在全剖面均表现为消耗型。两种土壤类型土壤水分的时间稳定性随土壤深度的增加而增强,灰钙土和风沙土全剖面的平均土壤含水量代表性土层分别为80～100和40～60 cm。2种类型土壤的土壤水分时空分布不同,风沙土受降水的影响高于灰钙土。降水会降低土壤水分的变异性,改变土壤水分的时间稳定性。

Comparison on moisture dynamics of two different soil types in desert steppe

Based on the positioning monitoring data from 2017 to 2018, we analyzed the spatial-temporal dynamic characteristics of moisture in two different soil types (sierozem and aeolian sandy soil) in the Yanchi desert steppe in the eastern Ningxia. The results showed that the rainfall in the study area was 208.2 and 274.8 mm in the growing season of 2017 and 2018 (May-October), respectively. The distribution of rainfall varied across different months. Except for the extreme rainfall event (129.6 mm) in May in 2018, rainfall in other months was lower than that in 2017. The seasonal dynamics of soil water content was roughly divided into two phases: compensation period (early May to early June) and fluctuation period (mid June to late September). The soil moisture of 0-20 cm layer had a pulse characteristic of rapid increase and decrease after rainfall, while that of the deep soil was relatively stable. The soil water content of sierozem showed a “rise-fall-liter” change with increasing soil depth. The saeolian sandy soil increased sharply from 0 to 60 cm then increased slowly, whereas soil water content gradually increased with increasing soil depth. In 2017, soil moisture in the soil profile (0-100 cm) of the sierozem was accumulated, and the aeo-lian sand soil was in the consumption type. In 2018, both soil water across the full profile in both soil types were the consumption type. The temporal stability of soil moisture of two soil types increased with increasing soil depth. The average soil water content of the whole sections of sierozem and aeolian sandy soil were 80-100 and 40-60 cm, respectively. The two soil types had different spatial and temporal distributions of soil moisture. Aeolian sandy soil was more affected by precipitation than sierozem. Precipitation would reduce the variability of soil moisture and change its temporal stability.