贵州石漠化空间分布与喀斯特地貌、岩性、降水和人口密度的关系

本次研究从地貌发育的角度揭示了贵州省石漠化景观及其等级的空间分布与下垫面的物质组成和气候(降雨量)的空间变化存在着密切的联系,而与现今人类活动强度(人口密度)的空间分布不存在关联性。具体体现为:(1)贵州溶蚀为主地貌类型区和纯碳酸盐岩分布区基本一致,区内的峰丛(林)地貌主要分布于年降水量≥1200mm的威宁-毕节-贵阳-凯里一线以南的溶蚀为主地貌类型区,随着降水量由北向南逐渐增加,塔状峰丘增多;溶丘,峰丛(林)不发育地貌主要分布于年降水量≤1100mm的威宁-毕节以北的黔西北溶蚀为主地貌类型区和毕节-贵阳-凯里一线以北的溶蚀侵蚀地貌类型区,(2)贵州石漠化程度与喀斯特地貌类型空间分布的耦合关系较好,与人口密度空间分布的耦合关系不好。峰丛(林)地貌发育的威宁-毕节-贵阳-凯里一线以南的溶蚀为主地貌区,黔中地区人口密度为300～400/km2,该区一些县的石漠化,远不如黔西南地区人口密度为200～300/km2或黔南地区人口密度为100～200/km2的严重。历史时期森林植被的全面破坏是贵州喀斯特地区石漠化的主要驱动力,除荔波茂兰喀斯特森林保护区等少数地区,贵州喀斯特地区的原始森林无论是现在人口密度高的地区,还是低的地区,历史时期均已遭受全面的破坏。喀斯特坡地次生植被的恢复状况在很大程度上取决于坡地的岩土组成,现代石漠化严重程度的区域差异,主要受下垫面地面物质组成的控制,也就是"石山"的多寡。

Relationships Between the Spatial Distribution of Karst Land Desertification and Geomorphology, Lithology, Precipitation, and Population Density in Guizhou Province

This study reveals the spatial distribution of degraded karst landscape in Guizhou and concludes that it is well related to ground substance and climate(precipitation) conditions,but not well to current human activities(population densities).It is expressed as follows:(1) The spatial distribution of the geomorphologic type,dominated by chemical erosion,is well related to pure carbonate rocks in Guizhou,where peak cluster landforms are mostly distributed in the area south of the Weining-Bijie-Guiyang-Kaili line with the annual precipitation of ≥1200 mm and more tower karst hills appear as precipitation increases.In the northwest of Guizhou with the annual precipitation of ≤1100 mm,dominated by chemical erosion,north of the Weining-Bijie line,and in the area,dominated by chemical-fluvial erosion,north of the Bijie-Guiyang-Kaili line,there are mostly normal hills with few peak clusters.(2) The karst land desertification severities are well related to karst landform types,but not to population densities,in Guizhou.In the area south of the Weining-Bijie-Guiyang-Kaili line,where peak cluster landforms develop well,karst land desertification in the counties of central Guizhou with population densities of 300~400/km2 is not severer as in the counties of Southwest Guizhou with population densities of 200~300/km2 and in the counties of South Guizhou with population densities of 100~200/km2.Destruction of forests is the main driving force to karst land desertification in Guizhou.Except for a few natural karst forests,such as the Maolan Park in Libo County,the original natural forests were massively destroyed during the history,either in the areas with high population densities or in the areas with relatively low population densities.As the restored extent of secondary vegetation depends largely on the soil conditions on hill slopes,the spatial variation of karst land desertification severities is mainly controlled by soil and rock compositions on the ground,frankly speaking,by the proportion of bared rock hill land.