黄土丘陵半干旱区密植枣林随树龄变化的根系空间分布特征

Spatial pattern of root systems of dense jujube plantation with jujube age in the semiarid loess hilly region of China

该文研究了黄土丘陵半干旱区密植枣(Ziziphus jujuba‘Lizao’)林群体根系随树龄变化的空间分布特征。对1年生、4年生、8年生和11年生4种树龄的密植枣林采用剖面法,获得0-1m土壤剖面上直径>3mm、1-3mm及<1mm的根系数量和空间位置信息。利用方差分析,评价了山地密植枣林林分根系随树龄变化的水平和垂直分布特征。结果表明:3种直径的根系数量均随着树龄的增长而增加,直径<1mm的根系增长速度最快;随着土层加深,根系数量递减,1年生枣林的根系主要聚集在0-40cm土层中,4年生及以上树龄的根系主要分布在0-60cm土层中;0-1m土层内,1年生枣林(株距1.2m)及4年以上树龄(株距2m),同树龄枣林中直径<1mm的根系水平分布无差异;同一土层中(0-20cm,20-40cm,40-60cm),无论树龄大小及离树干的水平位置如何,不同直径根系的数量都无差异。研究表明:在有水肥管理措施的条件下,枣林根系垂直方向形成浅层型的适应模式;在密植环境下,枣林细根形成根网型的适应模式。

Aims Dense jujube （Ziziphus jujuba ＇Lizao＇） plantations with a spacing of 2 m between trees and 3 m between rows have been established in the semiarid hilly region of the Chinese Loess Plateau.Our objective was to study characteristics of vertical and horizontal root distribution with different tree ages.Methods Four stands formed a chronosequence 1,4,8 and 11 years old.We used the trench profile method to study root distribution.We excavated four trenches 6 m long × 1 m deep × 0.8 m wide for each stand age and measured root intersects as fine （ 1 mm）,medium-sized （1-3 mm） and coarse （ 3 mm） roots.Important findings The number of root intersects increased by tree age （especially fine roots） and decreased with soil depth.1-year-old tree root intersects were concentrated at 0-40 cm depth,and the other three older tree root intersects were mainly at 0-60 cm depth.There was no significant difference with the fine-root intersects along the horizontal distance from the trunk regardless of tree age.Different diameter root intersects showed no significant difference in the same soil layer （0-20,20-40 and 40-60 cm） regardless of tree age and horizontal dis-tance from trunk.The efficiency of root distribution under the densely planted pattern was determined to ensure a sustainably high fruit yield.We suggest that jujube roots formed shallow patterns vertically under the water and nutrient management measures,while it formed net patterns when densely planted.Our findings can provide a theoretical basis for efficient root management in this region.