Effects of Underground Coal Mining on Soil Spatial Water Content Distribution and Plant Growth Type in Northwest China

The Synergistic Effect of Topographic Factors and Vegetation Indices on the Underground Coal Mine Utilizing Unmanned Aerial Vehicle Remote Sensing

Understanding the synergistic effect between topography and vegetation in the underground coal mine is of great significance for the ecological restoration and sustainable development of mining areas. This paper took advantage of unmanned aerial vehicle (UAV) remote sensing to obtain high-precision topographic factors (i.e., digital elevation model (DEM), slope, and aspect) in the Shangwan Coal Mine. Then, a normalized difference vegetation index (NDVI) was calculated utilizing Landsat images from 2017 to 2021, and the NDVI with the same spatial resolution as the slope and aspect was acquired by down-sampling. Finally, the synergistic effect of topography and vegetation in the underground mining area was revealed by dividing the topography obtained using high-precision data into 21 types. The results show that: (1) the vegetation cover was dominated by "slightly low-VC", "medium-VC", and "slightly high-VC" in the study area, and there was a positive correlation between the slope and NDVI when the slope was more than 5°. (2) When the slope was slight, the aspect had less influence on the vegetation growth. When the slope was larger, the influence of the aspect increased in the study area. (3) "Rapidly steep-semi-sunny slope" was the most suitable combination for the vegetation growth in the study area. This paper revealed the relationship between the topography and vegetation. In addition, it provided a scientific and effective foundation for decision-making of ecological restoration in the underground coal mine.

Coal-mining subsidence changed distribution of the microbiomes and their functional genes in a farmland

Land subsidence is a serious geological event, and can trigger severe environmental and ecological issues. In this study, the influences of coal-mining subsidence on distribution of farmland microbiomes and their functional genes were investigated by 16 S ribosomal RNA (rRNA) gene and metagenome sequencing. The results showed the existence of a core microbiome, which determined the community compositions across the subsidence farmland. Subsidence decreased the relative abundances of dominant Streptomyces, Nocardioides, and Rhizophagus, but increased the relative abundances of dominant Bradyrhizobium, Rhizobium, and Trichoderma. Subsidence also decreased the relative abundances of genes related to carbon metabolism, Quorum sensing, aminoacyl-transfer RNA (tRNA) biosynthesis, and oxidative phosphorylation, and increased the relative abundances of genes related to two-component system and bacterial chemotaxis. Furthermore, subsidence weakened the biosynthesis of organic carbons by decreasing the relative abundances of genes encoding glycosyl transferases, and strengthened decomposition of degradable organic carbons of the microbiomes and auxiliary activities by increasing the relative abundances of genes encoding glycoside hydrolases and polysaccharide lyases. The concentrations of total phosphorus, Mg²⁺ , and Ca²⁺ at the lower areas were significantly higher than those at the upper areas, indicating an associated loss of soil nutrients. Canonical correspondence analysis showed that soil moisture, pH, and the concentrations of NH₄ ⁺ and Ca²⁺ were the main factors affecting the distribution of the microbiomes and their functional genes. Collectively, this study shows that coal-mining subsidence alters soil physicochemical properties and distribution of farmland microbiomes and their functional genes.

Spatiotemporal Variation and Influencing Factors of Vegetation Growth in Mining Areas: A Case Study in a Colliery in Northern China

Based on MODIS EVI data of August collected from 2010 to 2021, and taking the Yingpanhao coal mine as an example, the spatiotemporal variation features of vegetation are analyzed using time series analysis, trend analysis and correlation analysis methods in the eco-geo-environment of the phreatic water desert shallows oasis. A significant increase trend is found for vegetation variation, and its development has improved generally in most areas. There is an obvious positive correlation between precipitation and vegetation growth, and a negative correlation between coal mining intensity and vegetation growth, but the influence of atmospheric precipitation on vegetation growth is stronger than that of coal mining intensity in the eco-geo-environment. The research results effectively reflect that atmospheric precipitation is the primary factor advancing the vegetation growth status in the coal mining regions. Vegetation development response to coal mining would be degraded first, then improved, and finally restored in areas with a deeply buried phreatic water level; that would promote the transformation of vegetation species from hydrophilous plants to xerophyte plants in areas with a shallowly buried phreatic water level. Therefore, it is necessary to carry out reasonable mine field planning according to the phreatic water level and the vegetation type distribution and to adopt different coal mining methods or corresponding engineering and technical measures to realize water conservation to avoid damaging the original hydrogeological conditions as far as possible. This information is helpful for promoting the eco-geo-environmental protection and further establishing the need for the dynamic monitoring of the eco-environment in the coal mining regions in the arid and semi-arid ecologically vulnerable areas of Northern China, which play a significant role in the long-term protection and rehabilitation of the eco-geo-environment and in the promotion of sustainable development.