SOME SOIL FEATURES IN KARST ECOSYSTEM
CAO Jianhua1, YUAN Daoxian1, PAN Genxing2(1.Institute of Karst Geology, Chinese Geological Academy, Guilin 541004,China; 2.Resource and Environmental College, Nanjing Agricultural University, Nanjing 210095,China)
Many features of limestone soil are controlled by the carbonate rock with rich calcium:①the rate of limestone soil formation is very slow, and the formation of 1m thickness soil last 0.25～7.88 million years. However, the rate of soil erosion in karst area is from several decade to hundred times than that of the soil formation. Therefore, the damage of the soil erosion is more serious than we think;②the high concentration and good immobility of soil humus closely related with the high concentration and activity of calcium in soil, mainly, the humin acid could be combined with the calcium in the soil to form stable humin calcium, however, the nutrient elements are slowly provided for vegetation; ③ the content and validity of trace elements in limestone soil are unstable, the validity of trace elements would become more effective as the concentration of calcium and magnesium decreasing. By the way, the behavior of zinc in limestone soil is in particularity,because of zinc in alkaline soil usually depositing;④ limestone soil has more clay component than other soils, because its parent material is carbonate rock which precipitated in clean sea environment. So when the soil in high humus, it might have good aggregate structure and effectively to support water and fertilizer for vegetation growing; by contraries, when the soil in low humus, its aggregate stability is weak and the available water for vegetation become short, therefore, the ability of the soil to resist soil erosion become low; ⑤ the limestone soil types and their distribution controlled by karst geomorphology, the black limestone soil usually scatters in the upper hillside with 10～30 cm thick, the brown and yellow limestone soils are covered the foot of the hill, depression and valley, and they usually are used to cultivated land, and the red limestone soil can be found in the peak forest plain area. During the limestone soil development and evolvement, the losing and taking calcium action are the key factors. In other word, the rich calcium in karst environment postpones the limestone soil to approach to zone soil. Therefore the effective landuse planning should be designed taking use of karstology, soil science and botanic nutrion.
【CateGory Index】： X144
【CateGory Index】： X144