Abstract
We excavated soil to study root distribution in Haloxylon ammodendron seedlings grown with different amounts of irrigation (35, 24.5 and 14 kg water for each plant each time) in the hinterland of the Taklimakan Desert.The results indicated that: 1) With decreasing irrigation amounts, the root biomass tended to be distributed in deeper soil layers. Underground biomass had a signifi-cantly negative logarithmic relationship with soil depth under different irrigation amounts. 2) Maximum horizontal spread of roots was twice that of vertical root spread, and horizontal distribution of root biomass was similar under all irrigation amounts. 3) Vertical distribution of fine roots was nearly consistent with vertical changes in soil moisture, and all had a unimodal curve; but peak values of fine root biomass in different soil layers varied with different irrigation amounts. The smaller the amount of irrigation, the deeper were the fine roots concentrated in soil layers. 4) Root length, root surface area and root volume all exhibited a unimodal curve under different irrigation amounts; the less the irrigation amount, the deeper the peak values appeared in soil layers. 5) Root- shoot ratio and ratio of vertical root depth to plant height both increased as irrigation amounts decreased.
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