岩溶槽谷区耕地涨落时空特征与驱动机制

研究岩溶槽谷区耕地的涨落时空演变规律,对揭示岩溶山地乡村人地关系演变具有重要意义。以印江县为例,基于地貌特征把全县划分为槽谷区、低山河谷区、梵净中山区、丘陵谷地区,利用多源数据对印江县1958-2016年的耕地数量变化及其在不同高程、坡度上的分布演变进行了探讨。研究表明:(1)全县及各分区耕地都表现为先增加后减少、林灌地先减少后增加的变化趋势。1990年之前林灌地向耕地转移,之后耕地向林灌地转移,但各分区转移程度有所不同。(2)耕地的涨落高程界限为700 m,低于700 m时,1990年之前扩张,之后萎缩;涨落幅度随着高程增加而递减;高于700 m时,涨落不明显。(3)以1990年为界,各坡度范围耕地1990年之前扩张,1990年之后萎缩;在小于25°的坡度范围内,随坡度增加,耕地涨落幅度递增;在大于25°的坡度范围内,随坡度增加,耕地涨落幅度递减。(4)研究区耕地的涨落变化与当地农户对土地依赖程度相关,依赖程度高,耕地扩张;依赖程度低,耕地萎缩。研究结果可以为优化岩溶区人地关系发展提供参考依据。

The transition of karst valley area farmland and its dynamic mechanism

It is of significance to analyze the temporal and spatial evolution of karst valley of farmland so as to reveal the law of human-environmental relationship in the karst valley rural area, with Yinjiang county as an example, which was divided into trough valley region, low mountain valley region, Fanjing mountain region and hilly valley region. Based on the landform, multi-source data are used to discuss the change of cultivated land quantity and its distribution evolution at different elevations and on different slope scopes from 1958 to 2016 in the county. The results show: (1) Farmland increased first and then declined; woodland increased after decreases. Before 1990, woodland was transferred to farmland, but after 1990, cultivated land was transferred to forest, and the degree of transfer of each subregion was different. (2) The fluctuation elevation level of cultivated land is 700 m. When it is lower than 700 m, it expanded before 1990 and then shrank, the range of change decreased as the elevation increased. Above 700 m, the fluctuation was not obvious. (3) Taking 1990 as the boundary, the cultivated land expanded before 1990 and shrank after 1990 on all slopes. If the slope is less than 25° slope, the farmland increased with the increase of slope. Within the slope greater than 25°, the cultivated land decreased with the increase of slope. (4) The fluctuation of cultivated land in the study area was closely with the land dependence of local farmers. Cultivated land will expand, if farmers are highly dependent on land. On the contrary, the cultivated land will shrink.