断陷盆地区不同土地利用方式土壤钙形态分布特征

选择云南省蒙自市西北勒乡碧色寨村具有典型岩溶地貌特征的草地、人工林地、玉米地（由草地开垦种植玉米2年）和火龙果地（由草地开垦种植火龙果5年）作为研究对象，采用连续浸提（BCR）提取方法测定不同形态钙含量，以探讨岩溶区不同土地利用方式下石灰性土壤钙形态特征及其影响因素。结果表明:土地利用方式显著影响了土壤全钙含量及其形态分布；草地土壤全钙和各形态钙含量均高于其他土地利用类型，玉米地最低；４种土地利用方式土壤钙的赋存形态主要为交换态（占总量的59.4%~74.8%），有机结合态钙含量最低（占总量的0.5%~1.0%）；全钙和各形态钙与有机碳、全氮、全镁、阳离子交换量（CEC）、pH呈显著正相关，说明全钙和各形态钙与土壤物理化学性质是互相影响的。 

Characteristics of calcium fraction distribution in soil under different land use types in karst fault-depression basins

Limestone soil in karst regions is characterized by high pH and calcium (Ca) content, which is one of the key elements in determining the structure and function of karst ecosystems, and is significantly affected by land use types. However, so far there are few studies on soil Ca fraction distribution under different land use types in karst fault-depression basins. This study chose four land use types including grassland, plantation, cornfield and dragon fruit landing the Bisezhai village, Xibeile country in Mengzi City, Yunnan Province as objectives, all of which are characterized by typical karst landforms. The BCR three-step sequential extraction method was used to determine the content of different Ca forms under different land use types in karst areas and influence factors. The results show land use types significantly influence soil total Ca content and its fraction distribution. Total Ca and various Ca forms in grassland soil are greatly higher than other land use types, and the lowest values appear in cornfield. The exchangeable Ca form is dominant in all soils, accounting for 59.4%-74.8% of total Ca, while the content of bound to organic matter-Ca is the lowest, accounting for 0.5%-1.0% of total Ca. The contents of total Ca and various Ca forms are significantly positively correlated with organic carbon, total N, total Mg, CEC, and pH. These data indicate that total Ca and various Ca forms interact with the physical and chemical properties of the soil to some extent.