No abstract

Regional land use changes are an important part of global changes. The research on land use changes in the Three Gorges Reservoir Area of China attracts a lot of attention owing to the Three Gorges Dam building. The Three Gorges Reservoir Area becomes one of the important research areas.This study analyzed the transforming processes and traits of each land use type and the regional differences of land use changes during the past 30 years, summarized the distribution of different land use types in different buffer zones and regresses the equation areas and different buffer distances based on buffer analyses and regression analyses, and then analyzed the transforming rules in different buffer distances, got the optimal influence distances. The research results indicate that, (1) cultivated land lies at the northwest of the reservoir and was decreasing, however, the construction land was increasing, especially the urban construction land, a large number of land was flooded because of the reservoir water level rise; (2) urban area was sprawling quickly in developed and neighboring areas, and a great deal of cultivated land and a considerable amount of grassland were occupied; in the earlier time, rural settlements occupied lots of cultivated land and a sum of forestry land in the later time; (3) the optimum influenced distances for cultivated land and forestry land were 10-35 km, and for urban and rural settlements were in 5-20 km. Overall, this research can reflect the spatial-temporal characteristics of land use changes during the 30 years, and it is helpful for urban planning and land use planning in the reservoir area.

Opencast coal mining causes serious damage to the natural landscape, resulting in the depletion of the carbon sequestration capacity in the mining activity. There are few studies on the variation of carbon sequestration capabilities caused by land use changes in opencast mining areas. This paper uses six images were used to quantify the changes in land use types from 1986 to 2015 in the Pingshuo mining area in northwest China. At the same time, used statistical analysis and mathematical models to study soil and vegetation carbon sequestration. Results indicate that the total carbon sequestration exhibits a significant downward trend from 4.58 × 106 Mg in 1986 to 3.78 × 106 Mg in 2015, with the decrease of soil carbon sequestration accounting for the largest proportion. The carbon sequestration of arable land accounted for 51% of the total carbon sequestration in the mining area, followed by grassland (31%) and forestland (18%). Land reclamation contributed to the greatest increase in carbon sequestration of arable land from 17,890.15 Mg (1986) to 27,837.95 Mg (2015). Additionally, the downward trend in the carbon sequestration capacity of the mining ecosystem was mitigated after 2010 as the positive effects of land reclamation gradually amplified over time and as the mining techniques were greatly optimized in recent years in the Pingshuo mining area. Thus, terrestrial carbon sequestration can be improved through land reclamation projects and optimized mining activities. These results can help guide the utilization of reclaimed land in the future.