引黄灌区苹果树液流规律及与微气象因子响应关系

Dynamics of sap flow of apple trees in Yellow River irrigation areas and their responses to micrometeorological factors

为研究果树蒸腾耗水规律,揭示苹果树干液流与气象因子之间响应关系和评估当地灌溉制度对土壤水分保持作用,利用热扩散探针式茎流计监测引黄灌区苹果树干液流变化规律,分析在不同天气条件下红富士苹果日液流密度活动特征,以及液流密度变化特征与各气象因子之间的相关性和响应关系。结果表明:引黄灌区苹果年蒸腾量为685.8 mm,7、8、9月蒸腾耗水量均较大;苹果液流规律呈单峰变化,在夜间保持一定的液流速率,约为日间的30%,同生长季阴天苹果树的液流速率为晴天的2/3;液流与气象因子相关性高度排序为水汽压亏缺>气温>光照>相对湿度>风速。该地区苹果应在7、8、9月视降雨量及时补充灌溉,目前的灌溉制度下,不会造成土壤干化,可使土壤保持较好水分适宜性;白天树干液流主要驱动为水汽压亏缺、温度、光照等环境因素导致的蒸腾活动,而夜晚主要为白天消耗后的夜间补水活动;液流密度的变化与气象因子之间存在时滞性,且液流密度与水汽压亏缺和气温因素的非对称响应较大。

[Background]China’s agricultural water occupies a significant proportion of total water,but the utilization coefficient of irrigation water is low. At the same time,apple is a widely grown fruit tree in northern China,the study of its water consumption rule can guide irrigation effectively,improve the utilization coefficient of irrigation water,and assess the effects of local irrigation systems on soil water use. Transpiration is one of the ways plants consume water,there are some differences in the conclusions about the variation regularity of the sap flow of apple trunk transpiration and the relationship between it and meteorological factors. [Methods]The water consumption rule of apple tree transpiration in irrigation area of the Yellow River was studied in this paper. The experiment was carried out in Fuji apple orchards irrigated by local farmers in Zuncun irrigation area in Shanxi province from February 20 to September 30 in 2016. The thermal diffusion probe stem flowmeter was used to monitor the changes of apple trunk sap flow. At the same time,the weather data were obtained from a small local weather station near the apple orchard. The law of apple tree sap flow during the whole growth period was analyzed,the characteristics of apple daily sap flow density under different weather conditions were analyzed, SPSS bivariate correlation analysis was used for analyzing the correlation between the characteristics of sap flow density and various meteorological factors. Finally,the hysteresis effect between sap flow and meteorological factors were analyzed. [Results]1) The annual transpiration of apple trees in Yellow River irrigation areas was 685. 8 mm,and more water was consumed by transpiration in July,August,and September.2) There was a single peak variation rule for the apple trunk sap flow,apple trees maintained a certain sap flow at night,which was about 30% of the daytime sap flow rate. Apple tree’s sap flow rate on cloudy days was 2/3 on sunny days during the same growing season. 3) The degree of correlation between sap flow rate and meteorological factors was ranked as water vapor pressure deficit > air temperature >illumination > relative humidity > wind speed. [Conclusions] Apple orchards in this area should be timely replenished in July,August and September depending on rainfall and under the current irrigation system,there was no soil drying effect,and the soil can maintain better water suitability. During the day,the trunk sap flow was mainly driven by transpiration activities caused by water pressure deficit,temperature,light,and other environmental factors,while the liquid flow driving factor was mainly the nighttime water replenishment activities at night,after consumption in the day. And there was a time delay between the change of sap flow density and meteorological factors,and the asymmetric response between sap flow density and vapor pressure deficit and air temperature factors was large.