‘寒富’苹果树茎流特征及其对环境因子的响应

The Characteristics of Sap Flow of Hanfu Apple Trees and Its Response to Environmental Factors

【目的】果树蒸腾规律集中体现在其茎流特征上,研究东北地区‘寒富’苹果Malus pumila Mill(‘Hanfu’)树蒸腾耗水规律,为制定适宜的灌溉制度提供理论依据。【方法】采用热扩散式茎流计(TDP)于2017年5—10月连续监测‘寒富’苹果树幼果期至落叶期的茎流速率,用果园内自动气象站获取气象数据;分析‘寒富’苹果树茎流特征及其与环境因子间的关系,建立树干茎流速率与环境因子的关系模型。【结果】‘寒富’苹果树单日茎流速率呈现昼高夜低的单峰"几"字型变化,夜间茎流速率变化稳定,零点到日出的时间段内茎流速率变化平缓且接近于0,日落后到次日零点的时间段内仍然保持较高的茎流速率水平。果树生长周期中,茎流启动时间和下降时间较集中,到达峰值的时间较分散。夜间茎流量占比为10月>9月>5月>6月>8月>7月,10月夜间茎流量占比达到33.69%,7月夜间茎流量占比仅为4.57%。瞬时尺度下环境因子与‘寒富’果树茎流相关性程度大小为:太阳辐射>大气温度>风速>水汽压差>相对湿度>30 cm土层温度;‘寒富’苹果树茎流速率和各环境因子的多元回归方程为:V=6.441+0.012Rn+1.874T-0.577Ts,5cm+1.915Ws-9.766VPD-0.362RH,方程的相关系数R^2为0.842。茎流与10 cm土层含水率在日尺度下显著正相关,相关性系数为0.521,与其他土层含水率相关性不显著。【结论】东北冷凉地区‘寒富’苹果树在6—9月蒸腾量较大,蒸腾受太阳辐射、风速等环境因子影响程度高,应注意在果实膨大期,尤其7、8月及时补充灌水,灌水时间宜避开太阳辐射最强的时间段,选在日出前或在日落后,以减少蒸发造成的水分损耗。

【Objective】The law of transpiration of fruit trees is embodied in the characteristics of sap flow. The objective of this paper was to study the transpiration and water consumption laws of Malus pumila Mill(‘Hanfu’) in Northeast China, so as to provide a theoretical basis for the development of suitable irrigation system.【Method】In this experiment, the sap flow rates from young fruit stage to the deciduous stage of Hanfu apple trees were continuously monitored by the thermal dissipation probes(TDP) from May to October in 2017, and the meteorological data were continuously recorded by automatic weather station in this orchard. The characteristics of sap flow in Hanfu apple trees and their relationship with environmental factors were analyzed, and then a regression model between sap flow rate and environmental factors was established.【Result】The results showed that the rates of sap flow in Hanfu apple trees were higher in the daytime than that at night. The sap flow rates of Hanfu apple trees at night were stable, the change of sap flow rate was gentle and closed to zero between 0 o’clock and the sunrise, and the high sap flow rate level was still maintained in the period from the sunset to 0 o’clock of the next day. During the growth periods of fruit trees, the start-up and fall time of sap flow was concentrated, and the time of reaching the peak value was dispersive. The proportion of nocturnal sap flow was October > September > May > June > August > July. The proportion of nocturnal sap flow in October was 33.69%, but only 4.57% in July. The correlation degree between environmental factors and sap flow of Hanfu fruit trees was as follows: solar radiation >atmospheric temperature > wind speed > water vapor pressure difference > relative humidity > 30 cm soil layer temperature. The multivariate regression equation of sap flow rate and environmental factors of Hanfu fruit tree was: V=6.441+0.012 Rn+1.874 T-0.577 Ts,5 cm+1.915 Ws-9.766 VPD-0.362 RH, and the correlation coefficient of R^2 was 0.842. The correlation coefficient between daily sap flow and 10 cm soil moisture content was 0.521, which was not significantly correlated with the other layers soil moisture content. 【Conclusion】 The results showed that in the cold area of Northeast China, the transpiration of Hanfu apple trees was large from June to September, and the transpiration was affected by solar radiation, wind speed and other environmental factors. It should be noticed that in the fruit expansion period, especially in July and August, the irrigation should be carried out timely. Irrigation time should avoid the strongest solar radiation time, and be arranged before sunrise or after sunset to reduce water loss caused by evaporation.