黄土丘陵区红枣经济林根系分布与土壤水分关系研究

Root Distribution and Soil Water Dynamics of Jujube Plantations in Loess Hilly Regions

为明确半干旱黄土丘陵区不同年龄无灌溉旱作矮化修剪密植枣林的根系分布范围与其土壤水分的空间关系,利用根钻法测定枣林株间不同深度的根系分布、枣树主干就近位置的根系量,并采用土钻取土和中子仪定位测定结合了解不同年龄的枣林10 m深度的土壤水分。结果表明：随着树龄增加,1、3、5、12 a枣树根系最大深度年平均增值在减小,12 a枣林垂直根系达520 cm。枣树株间100 cm处向下的根系深度较浅,枣林的垂直根系最大和最小值之差先增加后减小,12 a枣林垂直根系之差只有180 cm。研究区枣树株间水平根系在枣林3 a时开始交汇,枣树水平根系延伸无法确定,所得到的水平方向根系实际是枣林多株树汇集的根系。枣林垂直根系对土壤水分的垂直变化作用显著,但矮化修剪密植枣林株间根系深度差异并没有造成土壤水分因此而波动。随着枣树树龄的增加根系深度和土壤水分干层均增加,0～2 m土层的土壤水分年内变化幅度也增加,而且根层范围的土壤水分随着树龄增加在降低,但是土壤干层深度稍大于测得的根系深度。

The spatial correlation between soil water content and root distribution in non-irrigation dense- dwarf jujube plantations was analyzed in semiarid hilly loess region of China. The soil coring method was used to sample roots at different depths within the 0 - 1 000 em soil profile under different-aged jujube plants （1, 3, 5 and 12 a）. The results showed that the increment of average annual root depth decreased with the increase of jujube stand age. The maximum root depth of 12-year-old jujube was 520 em and the minimum root depth was 100 cm from the tree base, which was half-way between two trees planted 2 m apart. The difference between maximum and minimum root depths of 12-year-old jujube trees was 180 em. Lateral roots started developing intersection networks after three years of planting. Soil water fluctuation was not induced by vertical root systems of dense-dwarf jujube plants. Root depth, dry soil layer depth and annual soil water variance within top 0 - 200 em soil layer increased with increase of .jujube stand age. However, root-zone soil water content decreased with increase of stand age, while dry soil layer depth was slightly larger than root depth. The results can provide vital technical support for jujube cultivation especially under semiarid conditions.