| The "plants-soil-lithosphere" is an important part of the karst ecological system, the plants play an important role in the karst ecological system,it can influent the physical and chemical properties of soil, thus indirectly affect rock envelops. The main performance is the circulation process of the material,namely the biogeochemic-alcycle. Karst dynamic system of the karst ecological system is an important part of the earth surface system.The main circulation of material is carbon,water,calcium as the basic characteristics.So far,the research of the cycle of calcium in different vegetation use type is still in the primary stage.This paper to southwest China subtropical in karst area as the study area. In the wet and dry conditions,the concent of the total calcium and different form calcium,and the basic physical and chemical properties in the depth of soil were determined under the grass ground of low-lying land,bush of contoured land,2years Castanea mollissima trees,5years Castanea mollissima trees,10years Castanea mollissima trees,Show the changes of the basic physical and chemical properties and the concent of the total calcium and different form calcium after planting castanea mollissima trees.provide the scientific basis and theoretical support for rocky desertification comprehensive control the soil and water and soil conservation in the karst region of southwest. The main research results are as follows:(1) The soil of bush of contoured land and grass ground of low-lying land is partial alkaline,and the soil of Castanea mollissima trees show weakly acidic.And along with the growth of the age mollissima trees increase soil pH more lower.The pH value from small to large for:10years Castanea mollissima trees<5years Castanea mollissima trees <2years Castanea mollissima trees<grass ground of low-lying land<bush of contoured land. In contrast,has highlighted the land for planting mollissima trees and make the soil pH become low.Along with the increase of age Castanea mollissima trees pH value gradually become low, further proof that soil pH was changed after planting the molliss-ima trees.(2)The soil BS(from large to small)is:bush of contoured land>grass ground of low-lying land>2years Castanea mollissima trees>5years Castanea mollissima trees>10years Castanea mollissima trees.It is positively related between the soil pH and the BS,and the soil BS of mollissima trees is lower,with the age increase of the mollissima trees,BS is lower. The root of the secretion of several common extract the analysis and comparison. Whether the dry season or rainy season:10years Castanea mol-lissima trees>5years Castanea mollissima trees>2years Castanea mollissima trees>bush of contoured land>grass ground of low-lying land.(3)The content of total calcium under Grass ground of low-lying land and bush of contoured land is higher than the Castanea mollissima trees.its value is much higher than Castanea mollissima trees.the physical and chemical properties of soil was changed by Castanea mollissima trees,show it is different the content of total calcium from other soil under vegetation types.Along with the Castanea mollissima trees ages increased,the content of acid soluble calcium gradually decreased,but also the content of reduction state calcium and oxidation state calcium was increased.the soil was influenced by castanea mollissima trees,the influence more longer,the influence more greater.(4)The soil of grass ground of low-lying land and bush of contoured land,along with the depth of soil increased,the content of acid soluble calcium and reduction state calcium was gradually decreased.The content of acid soluble calcium was gradually decreased.but the content of oxidation state and residualform was gradually increased under the castanea mollissima trees.The percent of acid soluble calcium was decrease-d,the percent of reduction state calcium, xidation state and residualform was increased.Along with the increase of castanea mollissima trees age,the content of acid soluble calcium and the acid soluble calcium was gradually decreased.Along with the depth of soil increased the content of effective state calcium is bigger fluctuation range than the quantity calcium.In the soil profile,the effective state are more sensitive.(5)Grass ground of low-lying land,bush of contoured land,2years castanea molliss-ima trees of low-lying land,Whether it rain or dry seasons, the content of organic matter,total phosphorus, alkali solution nitrogen, total nitrogen in the soil under castanea mollissima trees is low.Comparison of the total potassium and rapidly-availa--ble potassium content in the soil,the total potassium and rapidly-available potassium content in the soil under castanea mollissima trees is high. In addition,The soil pH,rain--fall, and many kinds of factors have an impact on the content of total potassium and rapidly-available potassium in the soil under castanea mollissima trees,show it is complexity.(6)With castanea mollissima trees growth,content of Organic matter,total nitrogen,total phosphorus,Alkali solution nitrogen is gradually decreased,but the castanea mollissima trees growth to a certain age,the basic content of nutrient elements have a rising trend.The content of total potassium and rapidly-available potassium in the soil along with the increase of castanea mollissima trees age showed gradually increased, castanea mollissima trees have an effect on the soil lead to the basic nutrient elements in the soil is different from other vegetation types.(7) The content of nutrient elements in the soil was influenced by many kinds of factors.the rainfall,temperature,vegetation type,soil texture,topography,depth,etc,to influ-ence the content of nutrient elements in the soil.Generally the content of nutrient elements in the soil at the dry season is lower than the rainy season.Through do the correlation analysis,the organic matter and some nutrition elements have a significantly positive correlation,show a good cooperative.(8)The soil pH and the soil organic matter,total nitrogen,total potassium,etc all affect the content of the total calcium and different forms calcium in the soil.The soil pH value more higher,the content of the amount of calcium more higher,the acid soluble calcium more higher,but the reduction state and the oxidation state calcium more reduced.the content of organic matter in the soil and the total calcium,the content of acid soluble and reduction state calcium have a moderate linear positive correlation,and the relationship for the oxidation state is not big.it is positively correlated between the content of total nitrogen and the total calcium,the content of acid soluble calcium. And it is a negative correlation for the content of reduction state calcium and oxidation state calcium,but the correlation is not big.it is a positive correlation for total potassium and the content of the amount of calcium,acid soluble calcium, and the correlation of reduction state and oxidation state is not clear. |
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