Identifying The Influence Of Soil Parameters To Vegetation Restoration In An Open-Pit Mining Area In China

Mining is one of the most distinct human activities in the Anthropocene Epoch. At present, there are more than 9,000 large and medium-sized mines in China, and mineral exploitation has made positive contributions to the rapid development of China’s economy.

However, mineral exploitation has also brought a series of damage to the ecological environment of the region (Hu et al., 2015). Mining methods are mainly divided into open-pit mining and underground mining. Among them, open-pit mining is more destructive to the land, about 2-11 times as destructive as underground mining. From the sky, open-pit mining surface looks just like a scar of a terrestrial land ecosystem, and the landscape could be greatly altered. 

Open-pit mining and other related activities will cause serious damage to the vegetation, soil, microorganisms, animals, water quality, and air quality of the region, and the restoration of vegetation can alleviate these damages (Peng et al., 2017). Therefore, vegetation restoration is the primary task after open-pit mining. 

Identifying the key environmental factors (climate, topography, and soil) that affect vegetation restoration is critical to selecting the appropriate species for restoration. Previous studies have shown that soil is the most important parameter affecting vegetation restoration in mining areas (Ahirwal et al., 2017). Abandoned mines are often extreme environments, often accompanied by a shortage or surplus of nutrients in the mining area, where high rock content and harmful element content, low nutrient content and moisture content will inhibit the plant growth. Therefore, it is necessary to analyze the influence of soil characteristics on vegetation restoration and find out the limiting factors that play a key role in the process of vegetation restoration.

The Kunyang phosphate mine (24°43′ N, 102°34′ E), located in Kunming, Yunnan Province, China, is the largest open-pit phosphate mine in China and has been exploited for more than 50 years. It is the first phosphate recovery area for vegetation restoration and the first batch of national green mine pilot units in China. The area of vegetation restoration has exceeded 1000 acres. We conducted vegetation surveys and soil sampling on the restoration area of the Kunyang phosphate mine in order to analyze which environmental factors affect the restoration quality of the plant community during the vegetation restoration process. In this study, we used a comprehensive index, the Floristic Quality Index, to represent the restoration quality of plant communities.

Fig.1 Location of the Restoration area in the Kunyang phosphate rock mine. Credit: Shiliang Liu

Based on some statistical analysis methods, we know that in the process of vegetation restoration, the distance from the mining area, the distance from the road, altitude, soil heavy metal content, and soil fertility content will all have an impact on this process. But the effects of different factors vary greatly. For example, the distance from the mine and the distance from the road will not have a direct impact on vegetation restoration but will have an indirect impact by affecting the physical and chemical properties of soil. The physical and chemical properties of soil are still the most important influencing factors, which is similar to previous studies (Ahirwal et al., 2017).

However, unlike previous studies, some soil heavy metal elements such as copper, which are often thought to inhibit plant growth in other mining-type areas, have contributed to plant growth in this study. Some soil fertility elements, such as potassium, which are often considered to promote plant growth in other mining-type areas, inhibit plant growth (Cross and Lambers, 2017). This result confirms the limiting factors law in ecology that too much or too little of certain elements will become the limiting factors affecting plant growth. Our research results can provide a theoretical basis for vegetation restoration in mining areas.

These findings are described in a paper entitled Interaction mechanism between floristic quality and soil parameters during ecological restoration in a mine area based on structural equation modeling, recently published in the journal Ecological Engineering (Hou et al., 2018). This work was conducted by Xiaoyun Hou and Shiliang Liu et al. from the Beijing Normal University in China.

References:

1. Ahirwal, J., Maiti, S.K., Reddy, M.S., 2017. Development of carbon, nitrogen and phosphate stocks of reclaimed coal mine soil within 8 years after forestation with Prosopis juliflora (Sw.) Dc. Catena 156, 42–50. https://linkinghub.elsevier.com/retrieve/pii/S0341816217301145
2. Cross, A.T., Lambers, H., 2017. Young calcareous soil chronosequences as a model for ecological restoration on alkaline mine tailings. Sci. Total Environ. 607–608, 168–175. https://linkinghub.elsevier.com/retrieve/pii/S0048969717317084.
3. Hu, Y.L., Niu, Z.X., Zeng, D.H., Wang, C.Y., 2015. Soil amendment improves tree growth and soil carbon and nitrogen pools in Mongolian pine plantations on post-mining land in northeast China. Land Degrad. Dev. 26, 807–812. https://onlinelibrary.wiley.com/action/cookieAbsent.
4. Peng, X.D., Dai, Q.H., Ding, G.J., Zhu, C., Li, C.L., 2017. Distribution and accumulation of trace elements in rhizosphere and non-rhizosphere soils on a karst plateau after vegetation restoration. Plant Soil 420, 49–60. https://doi.org/10.1007/s11104-017-3363-1
5. Hou, X.Y., Liu, S.L. Liu, Zhao, S. Zhang, Y.Q. Wu, X. Cheng, F.Y. Dong, S.K. 2018. Interaction mechanism between floristic quality and environmental factors during ecological restoration in a mine area based on structural equation modeling. Ecological Engineering, 124, 23-30. https://linkinghub.elsevier.com/retrieve/pii/S0925857418303598.