贵州喀斯特区域土壤有机质的分布与演化特征

中国西南喀斯特区域是全球最大的喀斯特生态区域之一,该区生态环境脆弱,水土流失严重,石漠化趋势严峻。土壤有机质是极为重要的保持土壤结构与质量的物质,深刻认识喀斯特区域土壤有机质的特征与演化是防治和改善我国西南喀斯特区域石漠化现状的迫切需求。本文以贵州省为例,总结归纳前人的研究成果,阐述了该区土壤有机质的分布规律与演化特征,探讨了影响该区土壤有机质分布的因素,以期提出更好的石漠化防治策略。中国西南喀斯特区域土壤受该区多山地形的限制,具有水平地带性以及垂直地带性特征,同时受到喀斯特地质地貌的控制,发育各种非地带性土壤,本区土壤类型多、成因复杂;土壤有机质的分布、演化特征与土壤类型密切相关,具有明显的区域特点。贵州省分布广泛的主要土壤有黄壤、石灰土、红壤、紫色土、黄棕壤、棕壤以及水稻土等。其中,棕壤有机质含量最高,原因可能是棕壤存在区域海拔高,气温低,抑制微生物活动,土壤有机质分解过程比较缓慢;石灰土有机质含量高,原因可能是土壤中钙的含量较高,有机质的保存可能受益于腐殖酸钙及碳酸盐沉淀的包裹保护;而黄壤和红壤等酸性土壤有机质主要是与R_2O_3结合,有机质的活性高于石灰土;黄棕壤有机质含量介于棕壤和黄壤之间;紫色土由于土壤质地的原因,有机质含量最低。

The Distribution and Evolution of Soil Organic Matter in the Karst Region, Guizhou Province, Southwestern China

The karst region in Southwestern China is one of the famous karst regions in the world. This region is considered to be an extremely fragile ecological environment due to its thin and coarse texture of soil, and how to protect the soil resource in this region has become an urgent concern for the local government and public. Soil organic matter (SOM) plays an important role in stabilizing the structure, and is considered to be a key factor for soil rehabilitation in karst areas. In this paper, we reviewed the recent literature studies on SOM in the study region, especially in Guizhou Province, China, summarized the characteristics and distribution of SOM in this area, and discussed the evolution regulations and their controlling factors. Many types of soil are found in the karst region of Guizhou Province, and both of climate condition and karst landform play the important role in the soil development. The broadly distributed soils in Guizhou Province include yellow soil, limestone soil, red soil, purple soil, yellow-brown soil, brown soil, and paddy soil. Brown soil owns the highest SOM content among seven soils, which may due to suppressed microbial activities caused by low temperature and high altitude. The high content of Ca²⁺ plays an important role in the evolution of SOM in limestone soil. It has been suggested that forming of calcium humus and secondary calcium carbonate coating are the favor mechanisms for SOM conserving in limestone soil. SOMs in yellow and red soils may associate to R₂O₃ minerals, and these SOMs are more labile compared with that of limestone soil. The SOM content of yellow-brown soil falls between that of brown soil and yellow soil. The SOM content in purple soil is the lowest due to its sandy texture.