黄土高原苹果树各生育期需水特征研究

【目的】准确界定苹果树在各个生育期的需水量及需水特征的季节性变化是指导果园节水灌溉的重要依据。【方法】利用热扩散树干液流测定技术,连续2年监测了旱作果园苹果树(盛果期)的树干液流速率,计算了单株的耗水强度,并与同步观测的叶面积指数、物候特征进行关联分析。【结果】2017、2018年苹果树年耗水量分别为295.5 mm、215.3 mm,分别占同期降水量的88%和58%。在整个年生育周期中,果实膨大期耗水量最多,占果树整个生育期耗水总量的51%(2017年)和41%(2018年),其次依次为果实成熟期、幼果形成期、花期、萌芽期、落叶期和休眠期,不同生育期果树的耗水量与同期降水量具有相似的季节变化趋势。在萌芽期,果树耗水强度快速上升,到果实膨大期时最高可达2.17 mm·d^-1;之后逐渐下降,在落叶期时耗水强度最高值为1.19 mm·d^-1;休眠期树液仍有流动,此阶段的耗水量占年蒸腾总量的5%,日蒸腾强度最高为0.53 mm·d^-1。冠层叶面积指数(LAI)的季节变化表现为从4月初展叶开始快速增加,到5月上旬达到3.2,日增速平均为0.07;之后LAI基本维持不变,日增速仅为前期的1%,最高值为3.4。在11月中旬左右遇到大风天气后快速落叶,LAI在数天内降至零。【结论】苹果树在不同生育期的需水特征有明显的差异,且与叶面积指数的季节变化并不完全同步,需结合不同生育期的水分需求特征开展合理的灌溉、控水等管理措施。

A study on water demand characteristics of apple trees in different growing stages in the Loess Plateau Area

【Objective】Accurately determining the water demand and seasonal changes of water demand characteristics of apple trees in each growing stage is an important basis for guiding water-saving irrigation in orchards.【Methods】In this study, the trunk sap flow rates(Js) of sample trees in dry orchard in full productive age was monitored for successive two years by means of thermal dissipation method, and the water consumption intensity of each tree was calculated. Correlation analysises were performed between the Jsand the leaf area index(LAI) and the phenological characteristics of apples trees.【Results】The total water consumption of apple trees in 2017 and 2018 was 295.5 and 215.3 mm,respectively, accounting for 88% and 58% of the precipitation in the same period. Specifically, the water consumption of apple trees in fruit expansion stage was the greatest with the proportion of 51% in2017 and 41% in 2018, of the total transpiration during the entire growing seasons each year. The water consumption in different stages decreased in the order of the fruit ripening stage, fruit formation stage,flowering stage, germination stage, defoliation stage, and the dormancy stage. The seasonal variation in water consumption of the trees was similar to that in precipitation. In the germination stage, the water consumption intensity of the trees increased rapidly and reached up to 2.17 mm · d^-1 in the fruit expansion stage. After that, it gradually decreased, and the maximum water consumption intensity in the defoliation stage was 1.19 mm · d^-1. In the dormancy stage, the sap flow in apple trees ran at lower level. The water consumption in this stage accounted for 5% of the total annual transpiration. The maximum daily transpiration intensity was 0.53 mm · d^-1. The seasonal variation of LAI in apple orchard showed a rapid increase from the early April to the mid May with an average rate of 0.07(dimensionless) per day and reaching 3.2. After that, however, LAI increased slowly with the rate accounted for only 1% of that in the previous period and up to 3.4 before defoliation. In the mid November, the leaves began to fall rapidly and the LAI dropped nearly to zero within few days in the windy weather.【Conclusion】The water demand of apple trees in different growing stages showed great differences, which was not synchronized with the changes of LAI. It is necessary to carry out precise irrigation based on both water demand and soil moisture in each growing period.