第七届青年地学论坛

The subsurface critical zone structure and water storage play an important role in ecological restoration and sustainable development of alpine zone under the background of climate change. However, there are few studies on the subsurface critical zone structure in the alpine and cold region, as well as the spatiotemporal differentiation characteristics of the deeper soil moisture. This study selected six typical ecosystems (alpine desert, alpine meadow, alpine meadow and steppe transition ecosystem, alpine steppe, sandy land and A. splendens steppe ecosystem) along the elevation gradient (4221~3205 m) in Qinghai Lake Basin (QLB). A series of field profile survey, observation experiments, Ground Penetrating Radar (GPR) and Electrical Resistivity Tomography (ERT) were conducted. The results reveal that the total thicknesses of organic layer (A)-leaching deposit layer (B) -parent material layer (C) of the typical ecosystems along the decreasing elevation was 1.41, 1.82, 3.96, 4.23, 43.23 and 6.65 m, respectively. The average total thickness of the A-B-C layer in the critical zones of each typical ecosystem except sandy land was 3.61 m. The average seasonal frozen soil thickness increased first and then decreased with the decrease of elevation, with an average thickness 1.04 m. The maximum and minimum thickness were 1.46 m and 0.33 m in alpine meadow and steppe transition ecosystem and sandy land, respectively. The C layer was the main soil water storage layer. The process of thawing to freezing mainly consumed the soil water storage of A-B layer and increased in the C layer. On the vertical layer, both soil water content and soil water storage were A-B layer < C layer during freezing periods, but were opposite during freezing and non-freezing periods, as well as freezing and thawing periods < non-freezing periods in time. The average soil water storage of the A-B-C layer of the ecosystem was sandy land (697.82±957.53 mm) > A. splendens steppe ecosystem (324.34±262.34 mm) > alpine steppe (176.40±222.98 mm) > alpine meadow and steppe transition ecosystem (173.15±144.21 mm) > alpine desert (105.22±73.11 mm) > alpine meadow (87.99±41.65 mm). Soil water storage was controlled by type of soil layer, elevation, capillary moisture capacity, silt and saturated water conductivity during the non-freezing period. The thickness of frozen soil was negatively correlated with soil water storage during freezing and thawing periods. The study of the subsurface critical zone structure and soil moisture characteristics in this basin plays an important role in understanding the interaction between its structure and water storage function, perfecting the theory of water conservation function and improving the ecological and hydrological model.
 

Subsurface critical zone structure; Soil water storage; Geophysical technologies; Typical ecosystems; Cold regions; Qinghai Lake Basin