Preliminary Study On Migration Mechanism Of Calcium In Soil, Karst Dynamics System

Karst Dynamics System is an important part in earth surface system.The soil is not only the product of interaction between the spheres,but also the supporter of spheres in earth surface system.The circulation of substances be distinguished by the carbon circulation,water circulation and calcium circulation in Karst Dynamics System. In the previous study, the carbon circulation and water circulation have a in-depth understanding, but calcium circulation work is in its infancy.Based on the field observations and the experiment of the soil from the typical subtropical karst watershed in Southwest China, the key elements of calcium is studied in Spatial and temporal scales. To reveal the fractionsof the soil calcium and migration factors of soil calcium,the fractions of limestone soil calcium were analyzed with the modified BCR three-step sequential extraction procedure.The results are intended for the scientific basis to soil improvement in comprehensive management of karst rocky desertification area and theoretical basis for the Karst Dynamics System theory.The main results were briefly summarized as follows:According the Pearson correlation analysis, it is concluded that the content of organic matter in soil has influences upon the the total content of N,P, K,Ca and the weights of calcium fractions.The total content of soil nutrient elements from different landforms had little changes,the available of nutrient elements changed a lot during the seasons, especially in the good moisture and temperature conditions. There is a certain regular change of the content of soil nutrient elements from different landforms. On the whole,the contents of soil organic matter in depression and the gentle slope in the good moisture and vegetation conditions.were higher.There are less seasonal changes of the soil physical and chemical characters in depression than the slope's. There is a certain regular change of the content of soil nutrient elements during the seasons.On the whole, the content of soil nutrient elements during the summer ,in the good moisture and temperature conditions ,is higher. In winter and spring, the situation is just the opposite. Therefore, the organic matter and nitrogen of farmland must to be complemented in spring ploughing season.Overall, among landforms, the content of soil calcium from high to low is abrupt slope> gentle slope > depression>saddle>plain. Among seasons, the content of soil calcium from high to low is spring> winter>summer>autumn.In the fractions of calcium, the content of acid extractable fraction is higher in winter and autumn, the weigh of acid extractable fraction is higher in the depression and saddle.The content and the weigh of reducible fractions are higher in the winter and spring from the slope. The content of oxidable fractions aer higher in winter and autumn from the depression.There are close relationships among the total content of soil calcium and the fractions of calcium,the content of soil nutrient elements and the landforms,climate.Generally speaking,the soil with rich soil organic matter has the higher total content of soil calcium and the oxidable fraction.The soil with the high pH value and high oxidation-reduction potential has the high content of the reducible fraction.Among Soil types, the content of soil calcium from high to low is Rendzina> brown rendzina > yellow limestone soil.The content of soil calcium from high to low is limestone soil> Dolomite soil > Impure limestone soil.The limestone soil has the highest migration capability of calcium...