三峡库区重庆段土壤保持服务时空分布格局研究

土壤保持是生态系统服务与功能的重要组成,在防止土壤侵蚀、减少径流泥沙与农业面源污染等方面具有至关重要的作用。以对国家生态安全具有重要作用的土壤保持生态功能区——三峡库区重庆段为研究区域,研究得到了2000~2013年时间序列区域土壤保持服务"流量"结果,结果表明:(1)三峡库区重庆段多年平均土壤保持量为604.39 t/hm~2·a,沿长江干流自西向东逐渐增强,区域差异显著;(2)三峡库区的土壤保持服务存在明显的垂直分异特征,随着高程的增加,以300 m与900 m为节点,出现递减-递增-递减的分段规律,与人类活动存在明显的相关关系;(3)增加森林覆被面积是改善区域土壤保持、减少水土流失的重要举措。同时,在三峡库区开展坡改梯工程,减少坡耕地的数量能够有效控制区域水土流失;

SPATIO-TEMPORAL VARIATIONS OF SOIL CONSERVATION SERVICES IN THREE GORGES RESERVOIR AREA OF CHONGQING

Soil conservation is considered to be an important part of ecosystem services, and is by far the greatest factor for reducing soil erosion, surface sediment and agricultural non-point source pollution. The aim of this study is to investigate the spatio-temporal variations of soil conservation in Three Gorges Reservoir Area of Chongqing, which is of great significance to national ecological security. Evaluation results of soil conservation services during 2000–2013 were analyzed by using the InVEST(Integrate Valuation of Ecosystem Sevices and Tradeoffs tool) model. We find that: (1) the annual average of soil conservation was 604.39 t/hm²·a with a remarkable variation, increasing gradually along the Yangtze River from west to east. Six counties in the eastern hinterland were the dominant area for soil conservation in Three Gorges Reservoir (about 56%), which was accord with the target of the ecological conservation and development areas of the Chongqing's five major functional areas. (2) For the past 14 years, the annual soil conservation changed significantly, and presented a downward trend overall. As national key ecological function areas and crucial ecological barrier of Yangtze basin, the eastern hinterland found remarkable declines in the average soil conservation. (3) The soil conservation services structured a clear pattern of vertical differentiation, followed a decrease-increase-decrease law along with the increase of elevation. Anthropogenic activities, especially the agricultural activity was the primary cause for the formation tendency. Meanwhile, the soil conservation services rose gradually with increasing gradient, yet the trend decreased. (4) Forest is absolutely one of the most important land cover for soil conservation, while the shrub forest achieved 675.01 t/hm²·a, slightly stronger than the arbor forest with 608.37 t/hm²·a. The terrace fields reached up to 741.97 t/hm²·a, which were much stronger than dry land with 504.84 t/hm²·a. Combining with the fact that soil conservation services were improved during the Grain for Green Project (2002–2008), The results show that it can significantly improve the soil conservation services and reduce soil loss by increasing the forest cover area. On the other hand, the implement of the terracing engineering can effectively prevent soil erosion and improve the ecological environment and agricultural conditions.