三峡库区景观格局粒度效应及其对土地利用变化过程的响应

1992—2012年,受大型水利工程建设影响,三峡库区土地利用/覆被发生剧烈变化,论文选取工程建设重要时点1992、2002、2006和2012年的土地利用覆被图,探讨景观格局指数在30~1 000 m粒度范围内的粒度效应及其对土地利用变化过程的响应。结果表明：1）所选取的27个景观指数中,有14个对空间粒度变化高度敏感、3个中度敏感、7个低敏感、3个不敏感;不同类型景观（除裸地外）粒度效应规律相似。2）景观格局指数随粒度变粗呈5种变化规律：单调下降、单调上升、阶梯状上升、无明显变化、先增大后迅速下降。形状指数粒度效应对土地利用变化过程的响应明显,聚集度指数、面积-边缘指数、多样性指数随土地利用变化的特征不受粒度粗细影响。因此,景观格局分析最适宜粒度范围为30~60 m。3）1992—2012年三峡库区整体景观异质性增大、优势度降低、呈小斑块密集格局;耕地面积急剧下降、破碎化加剧,林地面积稳步提升,连通性提高。

Grain Size Effect of Landscape Pattern and Its Response to Land Use Change in the Three Gorges Reservoir Area

Affected by the Three Gorges Reservoir Project, land use/cover in this area dramatically changed during 1992-2012. Based on the land use map in 1992, 2002, 2006 and 2012 (representing important stages of the Project’s construction), we selected a suite of metrics to characterize the grain size effect of landscape pattern within 30-1 000 m grain size range and its dynamic response to land use change. The results reveal: 1) Among the selected 27 metrics, there are 14 metrics showing high sensitivity, 3 metrics showing medium sensitivity, 7 metrics showing low sensitivity and 3 metrics showing insensitivity to the change of grain size. The metrics of different landscape types (except bare land) showed similar trends. 2) The behaviors of the metrics in response to change of grain size can be grouped into five types: monotonous decrease, monotonous increase, staircase increase, no obvious change, and slow increase followed by rapidly decrease. Grain size effect of shape metric showed obvious response to land use change, while the responses of aggregation metric, area-edge metric and diversity index were not affected by the grain size. The optimal grain size for landscape pattern analysis is 30-60 m. 3) Landscape pattern of the Three Gorges Reservoir area became more fragmentary and heterogeneous during 1992-2012. There was a sharp decline and more fragment of cropland while a gradual rise and more connectivity of forest.