The Distribution Character Is Tics Of Jujube Root System In Loess Hilly Under Different Water Environment

Mountain close planting dwarf jujube forest has become the leading model of developingthe loess hilly ecological economic forest in recent years because good characteristics of itsearly fruit and fertility. In addition, water production efficiency has already increased from0.50kg/m~3to4.2kg/m~3. However, researches involving forest stand root within the model arevery little. In order to guide the tasks of Shaanbei jujube cultivation scientifically and improveproductivity and stability of jujube forest in the area, to prevent soils in the loess plateau fromforming the dry layer and also maintain the sustainable development after returning the grainplots to forestry, the space distribution of jujube root system with different tree-age anddifferent terrain has been conducted under the same water environment but different waterregulation. The key research conclusions are as follows:（1）Vertical distribution of accumulated root biomass of different diameter dwarf closeplanting jujube from0to9m for nine ages under dry conditions accord with Y=1-βdof rootvertical distribution models. And there is no root system distribution below7m. Therelationships among jujube root spatial biomass density1m away from the surface andvertical soil depth as well as horizontal distance from soil thickness can be fitted accuratelyusing binomial expression function, which can also be utilized to fit the distributionrelationship among dry weight, surface area and soil depth. In the vertical direction, thedistribution of dry weight and accumulative length of root system for dwarf close plantingjujube of nine ages reduced with the increase of soil depth while the root surface areaincreased and then decreased. The root biomass density is maximum between0and60cm.The corresponding mean is667g/m~3、627g/m~3、534g/m~3respectively.(2) For the same water environment, studying on spatial distribution features of rootsystem for different ages indicates: root biomass has an ascending trend along with theincrease of jujube tree-age. Meanwhile, the root systems gradually deep into the soil andextend outward in the horizontal direction. Biomass intensity of jujube root systems fordifferent tree-age and different diameter falls both in vertical and horizontal direction withsoil depth and horizontal distance from the trunk increases. More importantly, biomassdensity appears superposition in the place of root crisscross (90~110cm). (3) The growth rate of jujube root also increases gradually along with the rise of annualtemperature. And the root growth peak appears in July and August. However, root growth rateis also different in different water environment. From the distance of different trunk position(35cm,65cm,100cm), root biomass density maximum is1050g/m~3、550g/m~3、775g/m~3forhumid regions and624g/m~3、417g/m~3、500g/m~3for no humid regions, respectively. Besides,root growth rate falls slowly when the temperature decreases in no humid regions. By contrast,the counterparts in humid areas hardly changes thereby improving the increase scope of rootbiomass in humid areas.(4) Spatial distribution of root biomass density also has many differences as soil watercontent is different for the same soil depth but different terrain in the case of no irrigation.Slope root distribution along the slope downward is greater than that of upward and rootbiomass density in the soil depth of ranging from20to40cm is larger than the counterpartsof0to20cm soil depth. As for the flat ground, it is exactly opposite compared with slope. Inaddition, horizontal distribution is relatively even, which has a guiding significance forirrigation equipment layout or fertilizer plant in different terrain situation.(5) The effect of different water regulation measures on the density of root amount invertical direction and horizontal are shown as: fish-scale pits and drip irrigationcomprehensive measures（Y+D）> drip irrigation zone of artificial increased water content（D）> fish-scale pits having natural water storage capacity（Y）>natural state growth（CK）.The density of jujube root amount can grow to2284strips/m~2and2031strips/m~2afterwater regulation measures namely fish-scale pits and drip irrigation comprehensive measures（Y+D） in comparison with1302strips/m~2和973strips/m~2in the natural state in verticaland horizontal direction respectively.