The Ecological Relationship of Groundwater–Soil–Vegetation in the Oasis–Desert Transition Zone of the Shiyang River Basin

Abstract

Groundwater is an important ecological water source in arid areas. Groundwater depth (GWD) is an important indicator that affects vegetation growth and soil salinization. Clarifying the coupling relationship between vegetation, groundwater, and soil in arid areas is beneficial to the prevention of environmental problems such as desertification and salinization. Existing studies lack research on the water–soil–vegetation relationship in typical areas, especially in shallow groundwater areas. In this study, the shallow groundwater area in Minqin, northwest China, was taken as study area, and vegetation surveys and soil samples collection were conducted. The relationships between vegetation fractional coverage (VFC) and GWD, soil salinity, soil moisture, and precipitation were comprehensively analyzed. The results showed low soil salinity in the riparian zone and high soil salinity in other shallow-buried areas with salinization problems. Soil salinity was negatively correlated with VFC (R = −0.4). When soil salinity >3 g/kg, VFC was less than 20%. Meanwhile, when GWD >10 m, VFC was usually less than 15%. In the areas with soil salinity <3 g/kg, when GWD was in the range of 4–10 m, VFC was positively correlated with soil moisture content (R = 0.99), and vegetation growth mainly depended on surface soil water, which was significantly affected by precipitation. When GWD was less than 4 m, VFC was negatively correlated with GWD (R = −0.78), and vegetation growth mainly relied on groundwater and soil water. There are obvious ecological differences in the shallow-buried areas in Minqin. Hence, it is reasonable to consider zoning and grading policies for ecological protection.

Effects of Groundwater Depth and Salt Content on Vegetation in Dry Lake Basins: A Case Study of Chahan Lake, Northern China

“…Qi et al [49] identified the ecological thresholds of the groundwater depth and TDS content (groundwater depth: 4.8-6.1 m, TDS: 0.37-1.25 g/ L) in Qian'an County by combining indoor tests with remote sensing technology. Cao et al [50] suggested that the groundwater depth should be maintained at 4-10 m and the TDS at <3 g/L to alleviate salinization and desertification in the Shiyang River Basin. These studies suggest that studying the ecological thresholds of the groundwater depth and TDS can provide scientific support for groundwater management in oasis areas to prevent salinization and desertification.…”

Study on Index of Groundwater Ecological Function Crisis Classification and Early Warning in Northwest China

“…; a value of 0 tends to represent rock or bare soil; a positive value represents different degrees of vegetation coverage, and the larger the value, the higher the vegetation coverage. Remote sensing data were collected from Landsat satellite data during 2000-2017, with a temporal resolution of 16 days and a spatial resolution of 30 m. Based on the annual mean value of NDVI calculated by 30 m spatial resolution Landsat satellite data [56] and long-term observation data of groundwater depth in the Minqin Basin that were collected from 2000 to 2017, the relationship curve between groundwater depth and NDVI value was established to determine the index of GEF degeneration classification and early warning in the natural vegetation oasis area. Qingtu Lake wetland is a seasonal water area, which needs artificial water conveyance to maintain a certain water area after agricultural irrigation in August every year.…”

Spatial and temporal groundwater dynamics in extreme arid basins

“…Groundwater is not only an essential guarantee of water for human production and life (Huang et al, 2022; Shi et al, 2021) but also has an irreplaceable role in the oasis (Lozano et al, 2013). In the arid zone of northwest China, vegetation in artificial and natural oases is strongly dependent on groundwater (Gries et al, 2003; Martinetti et al, 2021; Tamea et al, 2009), providing vegetation water demand (Wang, Wang, et al, 2018; Wang, Yu, et al, 2018), regulating soil water content (Cao et al, 2021), salinity (Wang et al, 2013), and balancing water use in abundant and dry years (Gao et al, 2020; Wada et al, 2012; Wang et al, 2023). However, climate change (Devkota & Gyawali, 2015; Shrestha et al, 2017; Tan et al, 2017) enhanced the impacts of human activities (Riley et al, 2019; Scanlon et al, 2005), turning groundwater evolution more complex.…”