Effects of Groundwater Level Decline on Soil-Vegetation System in
Semi-Arid Grassland Influenced by Coal Mining
Abstract
Although it is well known that groundwater significantly influences
plant communities, there have been few studies on how the soil and plant
communities respond to groundwater level decline in a short time
affected by coal mining. This paper examined the changes in groundwater
depth before and after coal mining and the soil-vegetation response in a
typical semi-arid grassland coal mine area of Hulunbuir Steppe,
Northeastern China. The IsoSource model, based on the dual stable
isotopes of δ D and δ 18O, was employed to estimate
groundwater contributions to shallow soil (0-100cm) water under
different groundwater depths. The results revealed that groundwater was
the dominant water source (75.7±17.1%) for shallow soil water when the
groundwater depth is less than 4 meters, indicating that 4m is a
threshold in groundwater depth, separating groundwater-dependent, and
precipitation-driven vegetation system in the study area. Secondly, a
strong non-linear response between vegetation species, height, coverage,
and groundwater decline was identified in the coal mine area. The
vegetation properties were found to be lowest in the areas where
groundwater depth increased from 1.5~4 m to
4~28 m before and after coal mining. Finally, the
groundwater level decline in the mining area significantly influenced
the groundwater-dependent vegetation ecosystem, with the soil CEC and
organic matter reduced, and the plant community degraded, succeeding
from mesophytic to xerophytic. Whereas, the soil-vegetation system in
the non-groundwater-dependent area has no obvious response to the
groundwater decline. These results suggest that caution should be
exercised when mining in groundwater-dependent ecosystem regions.