Study On Soil Moisture Of Economic Forest Land In Southeast Of Yulin

The climate and soil of the Southeast of Yulin are suitable for planting fruit. But less precipitation and soil moisture deficient have become the main factors that restrict fruit industry to develop. Therefore, there are important value on the study of soil moisture of apple, jujube and apricot tree in Jiaxiang, Mizhi and Suide, which in the southeast of Yulin. Though the investigation and analysis of soil moisture and particle size of economical forest land in the depths of0～4.0m at southeast Yulin, the paper studied the variation characteristics of soil moisture, formation of soil moisture, dried soil layer, soil reservoir and the influence of climate for soil moisture. The main conclusions were described as follows:(1) The soil moisture of economical forest land was low in early June. When the tree age is similar, average soil moisture content of jujube tree land was the highest, apricot tree land was second, and apple tree land was lowest. The water consuming intensity of apple tree was higher than jujube tree and apricot tree. The soil moisture content was found to decrease with tree age. The vertical variation characteristic of soil moisture of Jiaxiang was consistent with variation of Mizhi. It was divided into3layers,0～1.0m,1.1～2.3m, and2.4～4.0m. The soil moisture content of the second layer was the highest, the third layer was second, and the first layer was lowest. The soil moisture of apple trees and jujube trees in Suide also was divided into3layers. The soil moisture content of the second layer was the highest, the frist layer was second, and the third layer was lowest. There was abundant precipitation in2011, the precipitation in2012was normal. Because the precipitation was not completely consumed, the soil moisture content of the second layer was high. The soil moisture in the depths of0～4.0m was mainly existed in the form of film water in June, the gravity water did not appear.(2) The compartment model could reflect the process of the vertical changes of soil moisture content of jujube tree in Suide. The goodness of fit was0.74. The quintic polynomial could well reflect soil moisture content varied with depth, which below1.0m. The goodness of fit reached0.9.(3) Different land use patterns effected soil moisture content. The soil moisture content of the farmland was highest, the undisturbed grassland was second, and the economical forest land was lowest. It was due to the biomass of farmland and undisturbed grassland was lower than economic forest land.(4) The grain composition was similarity in the study area. There was mianly coarse silt and fine sand, which the sum of the content more than70%. The grain composition in the study area had certain regularity. From north to south, the content of coarse silt increased, very fine sand and fine sand decreased, colloidal particle, clay sand and fine silt increased correspondingly.(5) Each economic forest in the1.5～4.0m soil layer existed dried soil lay. The jujube tree land (13years old) and apricot tree land (14years old) in Jiaxiang and apricot tree land (13years old) in Mizhi had developed mild dried soil layer. Others had mainly developed moderate dried soil layer. Only it developed severe dried soil layer in apple tree land (30years old) in Mizhi, which thickness was about0.5-1.0m.(6) The common development of dried soil layer in the study area indicated had negative balance of soil moisture, which expenditure of soil water was higher than income. The dried soil layer cut off the infiltration of the precipitation. Underground water cycle did not exist. It was abnormal water level, which was incomplete.(7) The soil water of apple, jujube and apricot tree land was difficult available water. Apple tree land and jujube tree land (30years old) belonged to medium water deficiency, the others were light water deficiency. The effectiveness of soil reservoir was poor, which had limited regulating capacity.