Impacts of mining on landscape pattern and primary productivity in the grassland of Inner Mongolia: A case study of Heidaigou open pit coal mining

Abstract

Coal has been the primary energy resource that made rapid economic and social development in China possible. Yet, its extraction in the form of open-field mining operations changed landscape patterns considerably and created a suite of environmental and ecological problems. Therefore, it is very important to understand these landscape pattern dynamics and their effects on ecosystem processes. While open pit coal mining is one of the fast growing human modifications of the Earth's surface which transforms landscapes and ecological functioning, studies in applied ecology and restoration ecology examining the effects of this human activities have been lacking. We conducted a field study in the 10 km buffer around the landscape of ZhunggerHeidaigou ecosystem in Inner Mongolia where large open mine operations are presently underway. Within this landscape land use/ land cover changed substantially between 1987 and 2010. We related these human transformed landscape patterns to primary productivity and found the relationship to be highly scale dependent. Our results are summarized as follows. First, the 10 km buffer was found to be the optimum size of this study area, although we seek expanding the scale domain of our study because the size of the mining area is expected to increase. Second, grassland andagricultural areas, the two main land uses that preceded coal mining, have both decreased in the past 20 years. Grassland area decreased from 71.18% (45 199.73 hm2) in 1987 to 60.71% (38 550.76 hm2) in 2010,while agricultural area decreased from 25.76% (16 360.24 hm2) in 1987 to 20.48% (13 002.40 hm2) in 2010. On the other hand, industrial and residentialareas increased between 1987 and 2010. Particularly, mining operations occupied only 0.01% (3.12 hm2) in 1987, but increased to3.16% (2 007.04 hm2) in 2000, which corresponds to 10.05% (6 385.04 hm2) in 2010, respectively. Third, although landscape structure in the area has experienced overall consistent trend of change dynamics of landscape pattern at later stages were very different at two spatial scales-the scale of the mining area and the whole landscape. The number of introduced and disturbance patches increased at the expense of dominant resource patches, which resulted in severe landscape fragmentation. At the fine scale, previously dominant grassland patches characterized by higher pattern complexity and irregular shapes were replaced by simpler and more regular patches of coal mining operations and accompanying infrastructures. Fourth, primary productivity in the landscape as a whole and mining area in particular decreased with time since mining operations started. Areas affected by mining experienced more significant decrease of primary productivity. Partial correlation analysis of landscape patterns and primary productivity, with growing season precipitation as the controlling factor, showed that primary productivity was positively correlated with landscape configuration landscape pattern indices(perimeter-area ratio average, PARA; landscape shape index, LSI), especially at the whole landscape level. Primary productivity was negatively correlated with landscape composition indices (patch density, PD; shannon -weaver diversity index, SHDI; and shannon evenness index, SHEI) in the mining area. We conclude that vegetation restoration cannot change the relationship between landscape patterns and primary productivity at the large scale because of current limitations of available areas and long term successions. We believe the success of restoration of damaged ecosystems in the study area is heavily dependent upon the realization of the importance of natural ecosystems.