极度干旱区不同灌水量下沙枣防护林根系分布特征

研究滴灌条件下极端干旱区防护林的根系生长,对研究制定科学的防护林灌溉制度和维护绿洲防护林稳定性有重要意义。以塔里木河下游尾间绿洲——喀拉米吉绿洲滴灌沙枣防护林体系为研究对象,设置了3个滴灌量梯度（18 L、30 L、48 L）,分析了极端干旱区沙枣防护林在不同灌水量处理下的根系分布特征。结果表明：①长期采用滴灌后,沙枣根系大部分分布在较浅的土层（以地下0～40 cm为主）,越往下分枝能力越小,沙枣根系生物量在0～60cm土层中累计百分比达86%。②灌水量梯度不断增加后,导致了根系总生物量随之增加,但不会导致深层土壤根系持续增加,因此,即使用48 L的灌水量形成更深的土壤湿润层,林木根系下扎能力与深度没有表现出随之增加的趋势。48 L滴灌量处理下,土层根系含量20～40cm/0～20cm的比值较小（仅为0.6）,生物量主要集中在表层;30 L处理下,土层根系含量20～40cm/0～20cm的比值较大（0.75）。③粗根（φ≥5 mm）数量随着滴灌量的增大而增多,30 L滴灌量处理下,5 mm〉φ〉2 mm的根最多;18 L滴灌量处理下,φ≥5 mm的根与φ≤2 mm的根系数量均最少。建议大规模防护林的灌溉中应采取多样化的灌溉制度,才可达到极端干旱区防护林体系的可持续发展：棉林争水季节（5-7月）适当亏缺灌溉,8月以后可增加灌水量或1～2次灌水。

Characteristics of the Root of Drip Irrigated Elaeagnus angustifolia with Different Irrigation Amounts in Extremely Arid Areas

Distribution of the roots of drip irrigated Elaeagnus angustifolia with different irrigation amounts were investigated and the influence of root on soil water content was analyzed in extremely arid areas on Kalamiji oasis in the lower reaches of the Tarim River. Three treatments were: 18 L, 30 L and 48 L each time one tree. This paper conducted a study on root biomass density and roots quantity. The results are shown as follows.(1) After long-term use of drip irrigation, most of Elaeagnus angustifolia root is distributed in the shallow soil layer (0～40 cm), and root branching ability reduces with the increase of soil depth. The root biomass of Elaeagnus angustifolia in the 0-60 cm soil is up to 86% in the cumulative percentage. (2) The higher amount of irrigation resulted in enhancement in the total root biomass, but did not lead to the development of the root system in the deep layer. Therefore, by using the irrigation quota of 48 L formed a deeper layer of soil moisture, the ability of striking-root did not show an increasing trend with the larger irrigation amount, namely, the capacity of deepening and depth of the roots did not increase with the increased irrigation amounts. In treatment 48 L, the ratio of soil root content in the layers of 20～40 cm/0～20 cm is small (only 0.6), and biomass is mainly concentrated in the surface; in treatment 30 L, the ratio of soil root content in the layers of 20-40 cm/0-20 cm is larger (0.75).(3) Roots of ≥ 5 mm increases with the increase in the amount of drip irrigation. In treatment 30 L, roots of 5 mm ≥φ≥2 mm occupy the largest part of all. In treatment 18 L, there are the smallest numbers of thick roots (φ≥5 mm) and fine roots (φ≤2 mm). It is proposed that, to achieve the sustainable development of shelterbelt system in the extreme arid areas, large-scale irrigation of shelterbelt system should be taken in a variety of irrigation measures: to take the appropriate deficit irrigation in the season of competition for water between cotton and shelterbelt (from May to July), and the irrigation quota can be increased or the irrigation can be done 1-2 times after August.