哈尼梯田遗产核心区土地利用信息图谱及地形梯度效应

    Land use change geo-spectrum and its topographic gradient effect in the core areas of Hani Terraces, a World Heritage Site

    • 摘要: 地形因子深刻制约山地型遗产区土地利用时空变化和资源配置。基于Google Earth 0.55m×0.55m 高精度历史影像,目视解译更新和野外验证得到哈尼梯田遗产核心区2005、2010、2015、2020年4期土地利用数据,通过计算转移矩阵、信息图谱、分布指数、地形位指数(TI)、面积-高程积分指数(HI)、坡长坡度指数(LS)、地形湿度指数(TWI),以期从较长时间尺度和完整空间范围揭示区内土地利用时空变化特征及地形梯度效应。结果表明:1)研究区土地利用类型以乔木林和水田为主,平均占比分别为33.79%、25.28%,从2005-2020年,园地、水域、道路、人工林、房屋建筑、乔木林面积持续增加,增长率分别为148.32%、147.27%、138.76%、118.68%、70.58%、12.73%,减少最多的是裸地,其次是草地、旱地、水田和灌木林地,减少率分别为-54.01%、-29.58%、-28.56%,-16.56%、-10.87%。2)土地利用信息图谱类型以稳定型、持续变化型和反复变化型为主,占比分别为37.43%、25.36%、18.41%,对应的最大图谱类型分别为水田→水田→水田→水田、草地→草地→灌木林→乔木林、水田→旱地→水田→水田。3)研究区土地利用图谱在表征地表演化动力、侵蚀强度和潜在土壤水分空间分异的HI、LS、TWI指数上具有显著地形梯度效应,有效揭示了地形梯度影响土地利用信息图谱的动力机制。结合土地利用信息图谱的地形梯度效应特征,未来应进一步引导遗产区土地利用类型向增强"点(村寨)-轴(水系、沟渠)-面(森林和梯田)"的主体联系和不同地形梯度区差异发展、互为补充的方向转变,进而提升梯田系统景观完整性和生态服务功能,维系民族文化传统和实现可持续发展。

       

      Abstract: Topographic factors have been confined to the temporal and spatial changes of land use and resource allocation in mountainous heritage areas. Taking the Core Area of Hani rice Terraces as the study area, this study aims to explore the geo-spectrum of land use and topographic gradient, thereby enchancing the landscape integrity and ecological service function of terraced fields for sustainable development. The land-use types were first classified as grassland, road, construction, shrub, dry land, bare land, tree, plantation, paddy field, river, and garden using Google Earth 0.55m×0.55m high-precision historical images in 2005, 2010, 2015, and 2020. After that, the transfer matrix was calculated to determine the geo-spectrum, distribution index, topographic index (TI), hypsometric index (HI), slope length factor, slope steepness factor (LS), topographic wetness index (TWI), the temporal and spatial variation of land use and topographic gradient in the study area from a long time scale and a complete spatial range. A field test was finally conducted to verify the data using visual interpretation. The results showed that: 1) The main types of land use in the study area were the arbor woodland and paddy field, followed by the dry land and shrub land from 2005 to 2020. Specifically, there was an annual increase in the arbor forest, garden land, plantation land, road, and house building, where the comprehensive growth rates were 12.73%, 148.32%, 118.68%, 138.76%, and 70.58%, respectively. The reduction rates of the paddy field and dry land were -16.56% and -28.56%, respectively. The water areas fluctuated from 0.28 km2 in 2005 to 0.69 km2 in 2020, where the overall growth rate was 147.27%. By contrast, there was a fluctuated reducing trend in the shrub land and grassland with the comprehensive decreasing rates of -10.87% and -29.58%, respectively. 2) The information maps illustrated the stable, continuous, and repeated types of land use, accounting for 37.43%, 25.36%, and 18.41%, respectively. The stable type was the paddy field and arbor forest land, concentrating mainly on the low LS gradient and high TWI gradient. The continuous change type was from the grassland to the arbor forest, and from the paddy field to the plantation, focusing on the low TI gradient and high LS gradient. The recurrent variations were mainly in the paddy-dry land and arbor-shrub forest, concentrating on the low HI, high LS, and low TWI gradient. The land use map in the study area presented a significant effect of terrain gradient on the HI, LS, and TWI indices, indicating the dynamic characteristics of the terrain, erosion intensity, and potential spatial variation of soil moisture. Consequently, the dynamic mechanism of terrain gradient was effectively interpreted using the information maps of land use. 3) Some recommendations were addressed: (1) To strengthen the main connection of "point (village) - axis (water system, ditch) - surface (forest and terraced fields)", as the tourism developed; (2) To implement the differential development and complementarity of different terraced gradient areas; (3) To maintain the current characteristics of the stable areas in the geo-spectrum, while optimizing the spatial structure of the pre-change and intermediate change areas, and slow down the expansion of the late-change type; (4) To promote the continuously and repeatedly changing areas to the stable type in the heritage areas.

       

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