ABSTRACT There is growing interest in the use of canopy temperature to evaluate the water status of crops for irrigation water management. One of the main indicators currently used is the Crop Water Stress Index (CWSI). In this index, the canopy temperature is normalized by the environmental conditions to account for the evaporative demand of the atmosphere. The theoretical framework, based on the Penman-Monteith equation, defined the CWSI as one minus the ratio between actual and potential water use (Jackson et al., 1981). For the first time in tree crops, we have related the actual transpiration of almond trees measured with heat-pulse sap flow probes with the CWSI, calculated using an empirical Non-Water Stress Baseline. The relationship obtained between the CWSI and the relative transpiration fitted the theoretical relationship, although it showed a large scatter (R2=0.69; RMSE=0.13). The variability in micrometeorological conditions among different parts of the canopy, the scatter of the NWSB, or inherent measurement errors are identified as probable causes of this scatter. Finally, the effect of this scatter on the accurate assessment of actual transpiration from canopy temperature is analyzed for practical irrigation management purposes. We found an error of about 10% in the relative transpiration, which seems acceptable for irrigation management applications.

中文翻译：

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杏树作物水分胁迫指数与相对蒸腾量关系的实证验证

摘要人们越来越关注使用冠层温度来评估灌溉水管理作物的水分状况。目前使用的主要指标之一是作物水分压力指数（CWSI）。在该指数中，冠层温度由环境条件标准化，以说明大气的蒸发需求。基于 Penman-Monteith 方程的理论框架将 CWSI 定义为 1 减去实际用水和潜在用水之间的比率（Jackson 等，1981）。我们第一次在树木作物中将使用热脉冲树液流探头测量的杏仁树的实际蒸腾作用与 CWSI 相关联，使用经验性非水分胁迫基线计算。得到的 CWSI 与相对蒸腾量的关系符合理论关系，尽管它显示出很大的分散（R2=0.69；RMSE=0.13）。冠层不同部分微气象条件的变化、NWSB 的分散或固有的测量误差被确定为这种分散的可能原因。最后，为了实际灌溉管理目的，分析了这种散射对根据冠层温度准确评估实际蒸腾作用的影响。我们发现相对蒸腾量的误差约为 10%，这对于灌溉管理应用来说似乎是可以接受的。出于实际灌溉管理的目的，分析了这种散射对根据冠层温度准确评估实际蒸腾作用的影响。我们发现相对蒸腾量的误差约为 10%，这对于灌溉管理应用来说似乎是可以接受的。出于实际灌溉管理的目的，分析了这种散射对根据冠层温度准确评估实际蒸腾作用的影响。我们发现相对蒸腾量的误差约为 10%，这对于灌溉管理应用来说似乎是可以接受的。