Abstract
The microtopographic changes induced by coal mining subsidence caused a series of environmental problems such as soil erosion, and vegetation degradation in the mining area. However, the corresponding influence on surface vegetation and soil characteristic in different parts of the slope was completely different. To understand soil and vegetation degradation in coal mines and their future ecological restoration, it was crucial to investigate the origin. The relationship between soil microbial community diversity, structure, and taxa in the slope of subsidence area of different topographic locations in Daliuta coal mine, Shannxi, China, was determined by high throughput sequencing and molecular ecological network analysis. The relationship between the bacterial communities, environmental factors, and soil physicochemical properties was also investigated. We found a new topographic trait formed by surface subsidence to deteriorate the living environment of vegetation and the bacterial community. The vegetation coverage, soil water content, organic matter, and urease and dehydrogenase activities decreased significantly (p < 0.05). Although soil bacterial community diversity in the subsidence area did not differ significantly, the dominant taxa in different topographic locations varied. The molecular ecological networks representing bacterial community structure and function were also totally different. The networks in the middle and the top of the slope tend to be more complicated, and the interaction between species is obviously stronger than that of the bottom. However, the network in the bottom slope approached simplicity, and weak interaction, predominantly cooperative, was observed within and between modules. Meanwhile, the double stress of aridity and the lack of carbon source induced by subsidence also enhanced the capacity of the soil bacterial community to metabolize complex carbon sources at the bottom of the slope.
Highlights
Fossil fuels are used globally and are the dominant source of energy
With the increase in the intensity of topographic change, there was no significant loss of main nutritional elements such as N, P, and K, the soil environment in the middle and bottom slope deteriorated dramatically
In the prediction of functional genes, it was found that the genes related to metabolism of terpenoids and polyketides were significantly improved as well in the bottom slope bacteria (Figure 8). These findings suggest that in response to the extreme lack of carbon sources, the metabolic relationship of the bacterial community in the bottom of the slope was reshaped by the availability of carbon sources, so autotrophic bacteria and bacteria with strong secondary metabolism became the key species of community
Summary
The exploitation of fossil energy, especially that of coal, usually introduces super-incumbent topographic changes such as surface subsidence, fracture, and land sliding, which aggravate soil erosion and degradation. The productivity of coal mines in China reached 3.6 billion tons in 2018 (Wang et al, 2019), amounting to half of the global production. A few years ago, the damaged mine land scale was so huge that its artificial ecological restoration was nearly impossible. Many large-scale coal production bases of China are distributed in the semiarid and arid sandy grassland, whose ecological environment, once destroyed by mining, was degraded. It is essential to understand the influence of mining-induced change in topographic traits on the soil microbial community succession and interaction, and the potential of sandy grassland to restore the damaged ecological system of mine land
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