The Distribution Characters Of Main Nutrient In Karst Calcareous Soil-scrub System

The author selects the scrub community and soil of the special karst terrain in Yangzhong, Huaxi, Guiyang city, Guizhou province as the sample analyzed. From the research, the writer tries to find the distributions of the Ca, Mg, K and P, the regulation of the changeable content and the relationship among the four elements in the soil-vegetation ecological system. And here the author has paid more attention to the pretreatment of the Ca isotope, and that is the first important step and the essential basis on the research of the biogeochemistry cycling on the Ca, Mg, K and P in the soil-vegetation system in Karst district. At the same time, the research is useful evidence from the plant themselves for the vegetation succession, substance cycling and man-made restoration of the grass and woods from the plantation. The conclusions we get from this research are as follows:1. The property of the elements of the sample soil (CaO>MgO>K₂O >P2O5 ) is the same as that in basement rock. There are some relationships between the element and the altitude changing, such as: with the increase of the altitude, the content of CaO rises, whilst the contents of MgO, K2O, Na20 all decrease; with the deepen of the soil section, PH tends to go down. From the surface to the bottom in section 1, both CaO, MgO decrease. The content of Ca shows the definite trend of the changing in soil sections, in that aqueous solutions or cavern waters which are rich in calcium ion pour. In addition, potassium oxide and sodium oxides present a positive correlation in the content variety, while calcium oxide and kalium oxide are in the opposite.2. The abundant calcium in Karst seriously affects the floristic compositions and the proportion of the nutrition elements in the bush wood in Karst. Based on the research, it is natural to conclude that the calcicole takes a great percentage in the whole bush woods, and at the same time, the Ca is the richest element among the four elements, followed by Mg, K and P in that order in this kind of plant. In addition, Ca and P show a negative correlation whilst Mg and P show a positive correlation. The average contents of K and P reflect the relationship between the vegetation type and...