黄土高原降水年内分布差异对旱作果园蒸散特征的影响

天然降水是雨养农业区水文循环的主要驱动因子,在一定程度上决定着土壤水分生态环境,从而影响作物的蒸散特征。本研究通过分析静宁地区历年降水年内分布特征,明确了降水的集中趋势,在2018和2019年田间定位试验基础上,探究土壤水分随降水发生的变化过程以及果园蒸散特征对降水年内分布差异的响应规律。结果表明: 试验区历年降水集中度较高,集中期多分布在7和8月,8月所占比例达75%,且各年降水集中期出现的早晚变化较大。土壤水分对降水的响应主要集中在0～40 cm土层,深层水分只有在大雨量和连续性降水出现时才会发生明显变化。同为丰水年的情况下,2018年降水集中度高,集中期早,时间短,果树日耗水强度呈单峰结构,变幅较大;2019年降水分布均匀,集中期滞后,日耗水强度呈双峰结构,变幅小,大峰靠后。果树最大需水期历时长,2018年大雨的集中分布无法满足后期果树生理需水,果实产量受损,降水利用效率较2019年下降30.2%。黄土高原地区在苹果树幼果生长期往往会出现短暂干旱,影响果实品质,需加强该时段的水分管控。

Effects of annual distribution difference of precipitation on evapotranspiration characteristics of dry orchard in Loess Plateau,China

Precipitation is the main driving factor for hydrological cycle in rain-fed agricultural areas, which determines the water-related ecological environment and affects the evapotranspiration characteristics of crops. By analyzing the annual distribution characteristics of precipitation across different years, this study clarified the concentrated trend of precipitation in Jingning County. Based on a field experiment in 2018 and 2019, the changes of soil moisture with precipitation and the response process of orchard evapotranspiration characteristics to the annual distribution differences of precipitation were explored. The results showed that the concentration degree of precipitation was high in the study area over the years. The concentration period was mainly distributed in July and August, with the proportion of August being up to 75%. Moreover, the time of precipitation concentration period varied greatly among years. The response of soil moisture to precipitation was mainly concentrated in the 0-40 cm layer, while moisture in deep soil layer would change significantly only in response to heavy and continuous rain. Both 2018 and 2019 were water-rich years. The precipitation concentration degree in 2018 was high, and the concentration period was earlier and shorter, with the diurnal water consumption of apple trees showing a single peak with large amplitude. In 2019, the distribution of precipitation was uniform, the concentration period was late, and the diurnal water consumption showed double-peak with a small amplitude and a lagged large peak. The maximum water demand period of apple trees lasted a long time. The concentrated distribution of heavy rain in 2018 could not meet the physiological water demands of apple trees in the later period, which damaged the yield, and the utilization efficiency of precipitation decreased by 30.2% compared with 2019. In the Loess Plateau region, there is often a brief drought during the young fruit growth period, which would affect fruit quality. Therefore, water management during this period should be strengthened.