贵州山区石灰土侵蚀及石漠化的地质原因分析

石灰土是广泛分布于亚热带喀斯特山区的一种非地带性土壤，近几十年来，位于西南喀斯特分布中心的贵州石灰土地区石漠化扩张速度明显加快，已经对该地区数千万群众的基本生存条件构成严重威胁。从地质学角度详细分析这一地区石灰土土壤侵蚀和土地石漠化的形成原因，分析结果表明：石灰土本身的矿物学特征和基本理化性质较好，并不是造成土壤侵蚀和石漠化的主要原因。石灰土成土速率慢，土壤允许流失量小；作为土壤营养库的富含有机质和矿质养分的表土层一旦被剥蚀，土壤结构迅速退化，土壤侵蚀愈演愈烈；喀斯特独特的二元结构和地形地貌是石灰土侵蚀的主要影响因子；石灰土与基岩之间缺少风化母质的过渡，岩土界面的土壤侵蚀是石灰土侵蚀的重要特征；这些因素才是导致石灰土地区土地石漠化的主要原因。

GEOLOGICAL CAUSE OF CALCAREOUS SOIL EROSION AND LAND ROCKY DESERTIFICATION IN KARST AREA,GUIZHOU PROVINCE

Calcareous soil is a kind of non-zonal soil,distributed in mountainous karst area in subtropical region of China. Guizhou province is located in the center of karst area of Southwest China, and is the largest karst unit in the world. Over last one or two decades soil erosion and land rocky desertification have become more and more serious in the karst area,resulting in great difficulties for the survival of several ten million inhabitants in these regions. This paper analyzed the geological causes of calcareous soil erosion and land rocky desertification.The analytic results show that the mineralogical and basic physical chemistry characteristic of the soil is not the main factor. The main factors include: (1)the low soil-forming velocity, and thus the small amount of endurable soil losses is the direct cause of land rocky desertification;(2) in the other hand, the unique dualistic structure, fragmentized terrain and physiognomy in karst area provide the potential energy of erosion and leave space for erosion material deposition;(3)The surface soil contains a majority of organic matter and nutrient of soil body. If erosion happened and surface soil was eroded, soil structure and characteristic would degrade quickly. (4) The absence of weathering mother-soil between soil and rocks makes calcareous soil unstable. Soil erosion at the rock-soil interface is a distinct character. These are the main geological causes of calcareous soil erosion and land rocky desertification.