The Study Of Physical Properties In Different Degeneration Of Semi-desert Soil

The studied area is located in the nature conservation area in West Ordos. West Ordos is either a relatively independent nature union in arid and semi-arid area or a comprehensive nature conservation area which take protecting ancient extinct plants(Tetrana,Ammopiptanthas mongolicus,Helianthemum,Dotaninina etc) as well as the plant-belt glassland transist to desert and various ecosystem as primary object, it is a very special and sensitive ecological transitional zone.This paper takes the brown calcic soil and the light brown calcic soil of the nature conservation area in West Ordos as study object, analyzing the character of physical and chemical of brown calcic soil and light brown calcic soil at three different degradation grades.Which provide theoretical foundation for science management of grassland resource. The result indicated as follows:(1) For the brown calcic soil and the light brown calcic soil in semi-desert area. With increased steppe degradation grades, the water content of soil showed a decreasing trend,and soil water vertical variation tendency is more complex;With increased steppe degradation grades, surface soil bulk density increased,soil compactibility also increased (except for moderate degradation of the brown calcic soil );With increased steppe degradation grades,soil particles in the 0～30cm layer has the tendency of coarsen, in the soil layer rock fragments and fine sand increase as the aggravation of degeneration , while powder and clay decrease; The vertical distribution regulation of soil particle is with deepening of soil layer , physical powder and physical clay increase;A positive correlation between soil bulk density and compactibility,fine sand,a negative correlation between soil bulk density and clay ; A negative correlation between soil water content and fine sand , a positive correlation between soil water content and powder , clay .(2) With increased steppe degradation grades, the content of soil organic matter, the content of total nitrogen, total phosphorus, available nitrogen and available phosphorus decrease. The relationship between the changes of total potassium, available potassium and degradation grades are not obvious.(3) Total nutrient vertical variation tendency of light brown calcic soil of different degeneration in 0～30 cm soil layer as follows : the distribution of the content of organic matter and total nitrogen is 20～30 cm > 0～10 cm > 10～20 cm ; Vertical distribution tendency of total phosphorus is not obvious ; With deepening of soil layer , total potassium content showed a decreasing trend .(4) Total nutrient vertical variation tendency of brown calcic soil of different degeneration grades in 0～30 cm soil layer as follows :the distribution of the content of organic matter and total nitrogen is 20～30 cm > 0～10 cm > 10～20 cm ; For different degradation gradient , with deepening of soil layer , total phosphorus content gradually decrease , while total potassium content gradually increase .(5) The character of vertical variation of soil available nutrient of light brown calcic soil of different degeneration grades as follows : with deepening of soil layer , the change theory of the content of available nitrogen and available phosphorus is not obvious, while available potassium content gradually decrease.(6) The character of vertical variation of soil available nutrient of brown calcic soil of different degeneration grades as follows:in slightly and seriously degraded area, the vertical distribution of available nitrogen content is 20～30 cm > 0～10 cm > 10～20 cm ; In moderately degraded area , with deepening of soil layer , available nitrogen content gradually increase , available phosphorus and available potassium content showed a decreasing trend .(7) There were significantly positive relationships between soil organic matter , total nitrogen , total phosphorus , available nitrogen and available phosphorus content; A positive correlation between soil moisture and total phosphorus , available phosphorus ; A negative correlation between soil bulk density and organic matter,total nitrogen ; A negative correlation between fine sand and organic matter , total nitrogen ; A positive correlation between powder , clay and organic matter , total nitrogen , soil available nutrient .