## 3 Results and Discussion  
### Meteorological Conditions  
As mentioned in Section 2.1, both almond orchards are located and develop under a semi-arid climate. Specifically, the average annual precipitation was 314 mm, mainly concentrated during the spring and autumn months. The average interannual mean, maximum, and minimum air temperatures were 14.1 \({}^{\circ}\)C, 21.5 \({}^{\circ}\)C, and 7.2 \({}^{\circ}\)C. Seasonal weather patterns were similar throughout the 6 years of study (Figure 2). However, we conducted an in-depth analysis of the data points on some climatic events that could have affected the normal development of the almond trees during the six-season experiment. In this sense, within the 2017-2022 time series, 2022 was the warmest year, with maximum temperatures above 35 \({}^{\circ}\)C for 45 days (Table S1), which is the maximum threshold temperature for proper almond physiological activity [26; 78]. Additionally, in June 2022, we found the highest values of VPD and VPDmax (Figure 2B and Table S1). Moreover, during this year, there were 10 days with temperatures below 0 \({}^{\circ}\)C, which affected almond blossoming in Spain [79]. These extreme temperatures, such as late frosts during flowering, can lead to frost damage, which can, in turn, result in substantial yield losses and impaired physiological performance [78; 79; 80; 81]. Furthermore, in the years 2019 and 2022, there was a nearly rain-free period between May and August but preceded by notable rains in April. The impact of unfavorable weather conditions, such as those observed here in 2022, have previously been reported in other studies on GPP and NEE performance [17; 82]. In this sense, other studies have reported that high evaporative demand contributes to constrained photosynthesis and higher respiration, affecting NEE and GPP [17], while low precipitation combined with high atmospheric temperature can increase WUE to a certain point [82]. This effect, where low rainfall and high temperatures influence the carbon sequestration capacity of almond trees, may be key in the short to medium term in a scenario where climate change may aggravate these impacts in the coming years. Interannual, Interlocation and Interseasonal Patterns in Net Ecosystem Exchange (NEE), Gross Primary Productivity (GPP) and Ecosystem Water Use Efficiency (eWUE)  
Figure 3 lists the accumulated values of monthly NEE and GPP obtained in the experiment. Several studies have shown that natural ecosystems act as net carbon sinks, thus contributing to climate change mitigation, absorbing more CO\({}_{2}\) than they release [83; 84; 85; 86]. Estimations of terrestrial GPP are consistently influenced by a number of environmental variables, the methods used to measure it, and the unique response characteristics of diverse vegetation types [87]. In this sense, when comparing our results with other natural and agricultural ecosystems, various aspects should be carefully considered to ensure fair comparisons. Figure 2: Evolution of the meteorological variables during the experiment in Las Tiesas (2017–2019) and Tarazona (2020–2022): Tair (**A**), VPD (**B**), global radiation (**C**), ETo and precipitation (**D**). In the experiment, positive GPP and negative NEE monthly values were found during the almond growing season (Figure 3). Obtaining a complete year of data from eddy covariance flux towers is challenging due to a number of factors, including instrument malfunctions, maintenance, power outages, and data quality issues. These interruptions often lead to significant gaps in the data, with some studies reporting gaps in 30-60% of the annual data [88; 89; 90]. Despite ground measurements not covering the entire year, with temporal gaps due to maintenance and calibration of the instrument, our dataset (from April to September) coincides with the vegetative phase of almond trees in Spain. We can state that, during the vegetative phase, the almond tree captured more CO\({}_{2}\) than it released.