白刺沙包浅层土壤水分动态及其对不同降雨量的响应

以乌兰布和沙漠典型白刺沙包为研究对象,使用EC-5土壤水分传感器对其浅层(0—50 cm)土壤水分进行长期连续监测,分析了白刺沙包不同深度土层对不同降雨量的响应及整个生长季的土壤水分动态特征。结果表明:降雨是乌兰布和沙漠白刺沙包土壤水分的最重要补给源,降雨量大小是影响浅层土壤水分补给深度的决定因素。小于10 mm的降雨完全被表层(0—10 cm)土壤吸收,无法补给10 cm以下土壤水分;10—20 mm的降雨对土壤水分的补给深度达到20 cm;20—30 mm的降雨对土壤水分的补给深度达到40 cm,大于30 mm的降雨补给深度可达到50 cm,甚至更深土层。在研究区降雨量以小于20 mm降雨为主的情况下,20 cm以下土层土壤水分逐步恶化,久之将有利于浅根系草本植物的生长,不利于白刺的生长繁殖。因此,这种降雨格局将对浅层土壤水分及植被演替产生重要影响。

Dynamics of shallow soil water content in Nitraria tangutorum nebkha and response to rainfall

This study examined typical Nitraria tangutorum nebkha in the UlanBuh desert. An EC-5 soil moisture sensor was used for long-term monitoring of the shallow (0-50 cm) soil water content. We analyzed the responses of different soil layers to different rainfall and soil water content dynamics in a Nitraria tangutorum nebkha during the growing seasons of 2015-2017. The results showed that rainfall was the most important supply source for soil water content. The amount of rainfall was the major factor affecting the depth of water supply in shallow soils. Rainfall < 10 mm was completely absorbed by the surface soil (0-10 cm), and was unable to replenish soil water content below the 10 cm soil layer. Rainfall between 10 and 20 mm replenished soil water content to the 20 cm soil layer; rainfall between 20 and 30 mm replenished soil water content to the 40 cm soil layer; and rainfall > 30 mm replenished soil water content to the 50 cm soil layer. In the case of rainfall < 20 mm, the soil water content of the study area below 20 cm could gradually deteriorate, which could promote the growth of shallow root herbaceous plants, leading to a decline of the Nitraria tangutorum community. Rainfall patterns have an important impact on shallow soil water content and vegetation succession.