黄土山地苹果树树体不同方位液流速率分析

精准确定果园蒸腾耗水规律是进行果园水肥管理的基础.论文采用热扩散式边材液流茎流探针和微型自动气象站组成的测定系统,对陕北黄土山地苹果树树干液流及相关指标进行了连续观测,分析了不同方位探针树干液流速率的测定结果.结果表明:果树不同生长阶段,液流速率变化较大,白天蒸腾速率较大,蒸腾量占全天蒸腾量均在86.29％以上；不同方位探针测定结果差异明显,东、西向探针测定结果较为接近,南、北向测定结果差异较大；不同方位探针测定边材液流量与参考作物蒸散量的线性模型表明,东、西向探针测定液流量与参考作物蒸散量关系密切,决定系数分别达0.74和0.83,方差分析均方比分别为78.21和137.85,其相关性明显优于南、北方向；比较以水量平衡计算得出的苹果树耗水量,东、西向探针测定的苹果树蒸腾量与水量平衡计算结果较为接近,均方比分别达到14.11和14.57,显著性水平分别达到0.020和0.019,明显高于南北方向探针测定结果.测定苹果树液流量时,选择东面或西面安装液流计探针,可有效减小试验误差.

Directional flow rate determination in trunks of apple trees in China's Loess Mountain

Accurately measuring plant transpiration and water consumption is essential for regulating water and fertilizer use in traditional apple-fruit orchards. In this study, we combine thermal dissipation probes (TDP) and micro miniature automatic weather stations to evaluate the sap flow rate of apple-fruit trees planted in the north of Shaanxi on China's Loess Plateau, with the aim of improving accuracy of measurements to assist better decision making by orchard managers. TDP probes were inserted in different directions into the trunks of apple trees in their whole growth stages, and related factors were compared and analyzed. The results demonstrate that: 1) Sap flow rate (SFR) varies across the different growth stages of apple trees in a year; transpiration is lower during dormancy and maturity stages, and higher during periods of initial growth, rapid development and the Middle Growing Stage. However, SFR is higher during the day than at night, with average daytime transpiration accounting for over 86.29% of total transpiration. 2) SFR also varies depending on the direction of the TDP probe; determined SFR values were largest in the south, smallest in the north, and east and west values were approximately equal in the middle of the range. 3) The linear model built between SFR and transpiration indicates that both factors are closely correlated with east/west measurements. For east and west, the coefficients of determination are 0.74 and 0.83 and the square ratios are 78.21 and 137.85, respectively. Their correlation in the direction of both east and west is significantly better than in the north and south. 4) When water consumption is calculated according to the water balance equation, it is safe to draw the conclusion that transpiration approximately equals consumption when measured in the east/west direction. For east/west measurements, respective values for the mean square are 14.11 and 14.57, and significance levels are 0.020 and 0.019, which are both significantly better than values obtained from the north/south direction. Results from this study indicate that TDP probes should be inserted either in the east or west direction to effectively minimize error in the measurement of the sap flow.