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Background and aims: Understanding the variation of root hydraulic conductance (Lp) is critical for the simulation of the soil–plant-atmosphere continuum (SPAC), but its monitoring remains challenging. In this study, we introduce a new non-destructive method for characterizing Lp dynamics in woody species through the combination of simultaneous determinations of sap flow and xylem water potential. Recent studies indicate that modern microtensiometers provide robust estimates of xylem water potential, but it is unknown whether they allow tracking rapid changes in water potential without significant time lags, which may have implications for the proposed methodology.The impulse response of microtensiometers was measured in the lab, developing a procedure for correcting sensor data by deconvolution. Then, microtensiometers and compensation heat pulse sensors were used to evaluate the variations in Lp in two well-watered olive trees during the summer of 2022 in Cordoba, Spain.Correcting microtensiometer outputs was critical to analyze our field data as strong stomatal oscillations occurred, with microtensiometers damping xylem water potential variations. By contrast, our results suggest that correction procedures may not be required for many practical applications like irrigation scheduling. The daytime values of Lp were close to those obtained in previous studies, while nighttime values were extremely low. Therefore, a proportionality between Lp and sap flow rate was observed, which agrees with previous studies, although it does not prove a causal relationship.The methods proposed here could be applied to studying the temporal dynamics of root hydraulic conductance in other tree species.Methods: Understanding the variation of root hydraulic conductance (Lp) is critical for the simulation of the soil–plant-atmosphere continuum (SPAC), but its monitoring remains challenging. In this study, we introduce a new non-destructive method for characterizing Lp dynamics in woody species through the combination of simultaneous determinations of sap flow and xylem water potential. Recent studies indicate that modern microtensiometers provide robust estimates of xylem water potential, but it is unknown whether they allow tracking rapid changes in water potential without significant time lags, which may have implications for the proposed methodology.The impulse response of microtensiometers was measured in the lab, developing a procedure for correcting sensor data by deconvolution. Then, microtensiometers and compensation heat pulse sensors were used to evaluate the variations in Lp in two well-watered olive trees during the summer of 2022 in Cordoba, Spain.Correcting microtensiometer outputs was critical to analyze our field data as strong stomatal oscillations occurred, with microtensiometers damping xylem water potential variations. By contrast, our results suggest that correction procedures may not be required for many practical applications like irrigation scheduling. The daytime values of Lp were close to those obtained in previous studies, while nighttime values were extremely low. Therefore, a proportionality between Lp and sap flow rate was observed, which agrees with previous studies, although it does not prove a causal relationship.The methods proposed here could be applied to studying the temporal dynamics of root hydraulic conductance in other tree species.Results: Understanding the variation of root hydraulic conductance (Lp) is critical for the simulation of the soil–plant-atmosphere continuum (SPAC), but its monitoring remains challenging. In this study, we introduce a new non-destructive method for characterizing Lp dynamics in woody species through the combination of simultaneous determinations of sap flow and xylem water potential. Recent studies indicate that modern microtensiometers provide robust estimates of xylem water potential, but it is unknown whether they allow tracking rapid changes in water potential without significant time lags, which may have implications for the proposed methodology.The impulse response of microtensiometers was measured in the lab, developing a procedure for correcting sensor data by deconvolution. Then, microtensiometers and compensation heat pulse sensors were used to evaluate the variations in Lp in two well-watered olive trees during the summer of 2022 in Cordoba, Spain.Correcting microtensiometer outputs was critical to analyze our field data as strong stomatal oscillations occurred, with microtensiometers damping xylem water potential variations. By contrast, our results suggest that correction procedures may not be required for many practical applications like irrigation scheduling. The daytime values of Lp were close to those obtained in previous studies, while nighttime values were extremely low. Therefore, a proportionality between Lp and sap flow rate was observed, which agrees with previous studies, although it does not prove a causal relationship.The methods proposed here could be applied to studying the temporal dynamics of root hydraulic conductance in other tree species.Conclusions: Understanding the variation of root hydraulic conductance (Lp) is critical for the simulation of the soil–plant-atmosphere continuum (SPAC), but its monitoring remains challenging. In this study, we introduce a new non-destructive method for characterizing Lp dynamics in woody species through the combination of simultaneous determinations of sap flow and xylem water potential. Recent studies indicate that modern microtensiometers provide robust estimates of xylem water potential, but it is unknown whether they allow tracking rapid changes in water potential without significant time lags, which may have implications for the proposed methodology.The impulse response of microtensiometers was measured in the lab, developing a procedure for correcting sensor data by deconvolution. Then, microtensiometers and compensation heat pulse sensors were used to evaluate the variations in Lp in two well-watered olive trees during the summer of 2022 in Cordoba, Spain.Correcting microtensiometer outputs was critical to analyze our field data as strong stomatal oscillations occurred, with microtensiometers damping xylem water potential variations. By contrast, our results suggest that correction procedures may not be required for many practical applications like irrigation scheduling. The daytime values of Lp were close to those obtained in previous studies, while nighttime values were extremely low. Therefore, a proportionality between Lp and sap flow rate was observed, which agrees with previous studies, although it does not prove a causal relationship.The methods proposed here could be applied to studying the temporal dynamics of root hydraulic conductance in other tree species. [ABSTRACT FROM AUTHOR]

Several simulation models of the olive crop have been formulated so far, but none of them is capable of analyzing the impact of environmental conditions and management practices on water relations, growth and productivity under both wellirrigated and water-limiting irrigation strategies. This paper presents and tests OliveCan, a process-oriented model conceived for those purposes. In short, OliveCan is composed of three main model components simulating the principal elements of the water and carbon balances of olive orchards and the impacts of some management operations. To assess its predictive power, OliveCan was tested against independent data collected in two 3-year field experiments conducted in Córdoba, Spain, each of them applying different irrigation treatments. An acceptable level of agreement was found between measured and simulated values of seasonal evapotranspiration (ET, range 393 to 1016 mm year-1; RMSE of 89 mm year-1), daily transpiration (Ep, range 0.14-3.63 mm d-1; RMSE of 0.32 mm d-1) and oil yield (Yoil, range 13-357 g m-2; RMSE of 63 g m-2). Finally, knowledge gaps identified during the formulation of the model and further testing needs are discussed, highlighting that there is additional room for improving its robustness. It is concluded that OliveCan has a strong potential as a simulation platform for a variety of research applications. [ABSTRACT FROM AUTHOR]

Stomatal oscillations have long been disregarded in the literature despite the fact that the phenomenon has been described for a variety of plant species. This study aims to characterize the occurrence of oscillations in olive trees (Olea europaea L.) under different growing conditions and its methodological implications. Three experiments with young potted olives and one with large field-grown trees were performed. Sap flow measurements were always used to monitor the occurrence of oscillations, with additional determinations of trunk diameter variations and leaf-level stomatal conductance, photosynthesis and water potential also conducted in some cases. Strong oscillations with periods of 30-60 min were generally observed for young trees, while large field trees rarely showed significant oscillations. Severe water stress led to the disappearance of oscillations, but moderate water deficits occasionally promoted them. Simultaneous oscillations were also found for leaf stomatal conductance, leaf photosynthesis and trunk diameter, with the former presenting the highest amplitudes. The strong oscillations found in young potted olive trees preclude the use of infrequent measurements of stomatal conductance and related variables to characterize differences between trees of different cultivars or subjected to different experimental treatments. Under these circumstances, our results suggest that reliable estimates could be obtained using measurement intervals below 15 min. [ABSTRACT FROM AUTHOR]

In this paper, we analyse the combined effect of wetted area and irrigation volume and its impact on olive tree transpiration ( E ) after validating a multi-compartment SPAC model in a drip-irrigated hedgerow olive tree plantation. Modelled E is compared with 2 years of calibrated sap flow records under two different irrigation treatments: a control (C) that was watered using a crop coefficient ( K ) of 0.75 and a regulated deficit irrigation (RDI) in which applied irrigation was gradually reduced in relation to the K of the control (50, 25 and 20% from June to August). The simulated midday leaf water potential ( Ψ ) was also compared with measurements performed twice a month in each treatment and for both years. The model accurately predicted E in both years for the two treatments ( R = 0.81 and RMSE = 0.29 mm/day), while midday Ψ was slightly underestimated. Simulation analysis showed that (a) the use of drip irrigation systems always limits the maximum attainable E for a given environment; and (b) irrigation design should depend on available water. If irrigation water is limited, the wetted area should be minimized to reduce losses from soil evaporation, thus maximizing the water devoted to E ; by contrast, if water is available, the maximum E would be reached when wetting at least 30-40% of tree space. The model was accurate enough to capture the trends in E and Ψ of trees submitted to different irrigation regimes. [ABSTRACT FROM AUTHOR]

Aims: To evaluate the effects of changes in water stress and variable evaporative demand on water potential (Ψ), relative water content (RWC) and gas exchange during two consecutive years (2005 and 2006) providing insight into the mechanisms of stomatal control in the little-studied cultivar 'Cobrançosa'. Methods: Measurements of water potential, gas exchange in olive trees subjected to three irrigation treatments: rainfed (T0), continuous deficit irrigation (T1) and well irrigated (T2) that received 0, 30 and 100 % of estimated crop evapotranspiration. Results: Both the differences in irrigation amounts and the prolonged summer drought conditions characteristic of the study area (Northeast Portugal) resulted in considerable divergences among treatments, with T2 showing the highest values of both Ψ, RWC and gas exchange rates and T0 the lowest. Stomatal conductance exhibited a strong down-regulation under increasing vapor pressure deficit (VPD), with water stress leading to parallel reductions in stomatal conductance values at any given VPD and sensitivity to changes in VPD. These effects might be associated to the deduced drought-induced declines in leaf specific hydraulic conductance ( K). Conclusions: The results indicated that Cobrançosa olive trees have a near-isohydric behavior with a tendency to maintain a constant root-to-leaf water gradient (∆Ψ). [ABSTRACT FROM AUTHOR]

The effect of temperature on radial root hydraulic specific resistance (Rp) is a known phenomenon; however, the impact of Rp variations expected from soil temperature changes over the tree root system is unknown. The present article analyses the relations hip of Rp with temperature in olive 'Picual' and a hybrid rootstock, GF677, at five different temperatures, showing that a variation of 3- and 4.5-folds exists for olive 'Picual' and GF677 in the range from 10 to 20 °C. The functions obtained were scaled up to show the theoretical changes of total radial root system resistance in a common tree orchard in a Mediterranean climate at a daily and seasonal scale, using recorded soil temperature values: a difference between summer and winter of 3.5-fold for olive 'Picual' and 9-fold for GF677 was observed. Nevertheless, Rp changes are not only related to temperature, as cavitation or circadian rhythms in aquaporin expression may also play a role. The results obtained from an experiment with the two cultivars submitted to constant pressure and temperature during several hours exhibited a variation in Rp, but this was of lower magnitude than that observed due to temperature changes. Finally, a comparison of Rp at 25 °C between GF677 and GN15 (another rootstock obtained from the same parental as GF677) showed significant differences. According to our results, diurnal and seasonal changes in Rp due to temperature variations are of significant importance, and it would therefore be advisable to assess them explicitly into soil–plant–atmosphere continuum models. [ABSTRACT FROM AUTHOR]

The measurement of bulk net assimilation ( A) in fruit tree species is hindered by the need for sophisticated and complex instrumentation. The aim of this study is to present a simple alternative for estimating A from sap flow measurements and meteorological records. The proposed method was tested in a mature hedgerow olive orchard of 22.2 ha. Within the orchard, an irrigation experiment was established in a small plot including three treatments: a full irrigated control (CI), regulated deficit irrigation (DI) and a treatment mimicking customary orchard irrigation management (FI). Determinations of sap flow, water potential ( Ψ) and trunk diameter variations (TDV) were conducted in the three treatments for 3 years. Also, measurements of net ecosystem exchange (NEE) were performed with an eddy covariance system in the centre of the orchard for the first season. The validity of the method was supported by the fact that estimates of A were consistent with both the measured values of NEE and published data regarding the same species under similar environmental and management conditions. Also, differences in A between irrigation treatments were generally in agreement with irrigation applied, transpiration ( E), Ψ and TDV. It is concluded that the proposed sap flow-based method represents a user-friendly approach to estimate A at the canopy level with potential to study the effects of DI on biomass accumulation. [ABSTRACT FROM AUTHOR]

The accurate assessment of respiration by woody vegetation, still a challenge in plant productivity models, is generally a problem of correctly scaling-up the process from organs to the whole plant. We used a large (41.6 m), canopy chamber to enclose mature olive trees and to measure aboveground respiration ( R) under natural environmental conditions in an irrigated olive orchard in Córdoba (Spain). The 3-year study assessed nocturnal and seasonal R patterns in terms of temperature ( T), plant dry matter composition, and phenology. The relative contributions of maintenance and growth respiration to R were determined empirically via an independent experiment. Although short-term variations in R rates were explained mainly by T variations, over seasonal time-scales this relationship was modulated by the vegetative composition of the olive trees and the contribution of growth respiration to R when the plants, in different seasons, allocated most of the new assimilates to actively growing shoots, flowers or fruits. Leaf mass and fruit load were the main determinants of R, which was weakly affected by differences in woody biomass since woody tissue respiration accounted for just 15 % of R. Respiration in olive trees during fruit setting periods is composed of approximately 30 % growth and 70 % maintenance. This study provides an independent evaluation of how, and to what degree, seasonally varying plant organ composition determines total respiration. Improved modelling of ecosystem respiration can be achieved by accounting for plant biological patterns characterising energy-requiring growth and maintenance processes, since biochemical kinetics alone cannot explain the observed seasonal variability. [ABSTRACT FROM AUTHOR]

Abstract: Improving current approaches to quantify the transpiration of fruit trees is needed for water allocation purposes and to enhance the precision of water applications under full and deficit irrigation. Given that transpiration of tree crops is mainly modulated by canopy conductance (G c) and vapour pressure deficits, we developed a functional model of tree transpiration by quantifying an average daily G c based on radiation use efficiency and CO2 assimilation. For model calibration, an extensive experimental dataset of tree transpiration (E p) was collected in many of the main temperate fruit tree species, namely, apricot, apple, citrus, olive, peach, pistachio, and walnut, all under non-limiting water conditions, in different orchards in Spain and California (USA). In all species, E p was assessed by measuring sap flux with the Compensation Heat Pulse method for several months, and a transpiration coefficient (K t) was calculated as the ratio of measured E p to the reference evapotranspiration. For three deciduous species (apricot, peach and walnut) K t showed maximum values close to 1, a value which stayed more or less constant throughout the summer in peach and walnut. The maximum K t values were measured in pistachio (1.14) while they only reached 0.35 in olive and citrus trees. In the latter two species, K t varied seasonally between 0.2 and 0.6 depending on the weather. The average G c in July was high for apple, walnut, peach and pistachio (range 0.240–0.365molm−2 s−1) and low for olive and orange (range 0.074–0.100molm−2 s−1). The calibrated model outputs were compared against measured E p data, suggesting the satisfactory performance of a functional model for E p calculation that should improve the precision of current empirical approaches followed to compute fruit tree water requirements. [Copyright &y& Elsevier]

Studying the dynamics of stem water content (θ ) in living trees has an outstanding physiological interest but all the available techniques to measure θ exhibit major drawbacks. In this work, we present a new methodology to estimate variations in θ along with sap velocity using the compensated heat pulse (CHP) technique. One lab experiment was performed on several wooden blocks obtained from three different tree species. Samples were slowly dried and their moisture loss was monitored by both gravimetric approaches and time-domain reflectometry (TDR) or CHP probes in order to contrast the validity of our methodology (volumetric specific heat (VSH)-CHP) over a range of water contents. In addition, a field experiment was conducted to monitor θ fluctuations in standing olive trees (Olea europaea L. cv. ‘Arbequina’) growing under three different irrigation regimes. In the lab test, the actual θ values deduced gravimetrically differed from the estimates yielded by the VSH-CHP method. However, it could successfully track relative changes in the water stored for the range of θ expected in living wood. Furthermore, the field experiment showed a seasonal change in θ, which was similar in shape and magnitude to those reported in the literature for olive and other Mediterranean tree species. On the other hand, differences in the seasonal patterns of θ between irrigation treatments strongly corresponded with those of sap flow and some leaf water potential measurements. The results of this work suggest that the CHP technique could be employed to monitor the dynamics of both θ and sap flow simultaneously in standing trees and evidence that seasonal changes in θ might be used as a long-term water status indicator. [ABSTRACT FROM AUTHOR]

The compensation heat pulse (CHP) method is widely used to estimate sap flow and transpiration in conducting organs of woody plants. Previous studies have reported a natural azimuthal variability in sap flow, which could have practical implications in locating the CHP probes and integrating their output. Sap flow of several olive trees (Olea europaea L. cv. ‘Arbequina’) previously grown under different irrigation treatments were monitored by the CHP method, and their xylem anatomical characteristics were analyzed from wood samples taken at the same location in which the probes were installed. A significant azimuthal variability in the sap flow was found in a well-irrigated olive tree monitored by eight CHP probes. The azimuthal variability was well related to crown architecture, but poorly to azimuthal differences in the xylem anatomical characteristics. Well-irrigated and deficit-irrigated olive trees showed similar xylem anatomical characteristics, but they differed in xylem growth and in the ratio of nocturnal-to-diurnal sap flow (N/D index). The results of this work indicate that transpiration cannot be accurately estimated by the CHP method in olive trees if a small number of sensors are employed and that the N/D index could be used as a sensitive water status indicator. [ABSTRACT FROM AUTHOR]

Abstract: The compensation heat-pulse method (CHPM) for measuring sap velocity in tree stems shows a poor performance for low velocities. Here we present a new procedure, that extends the validity of the technique down to zero and even for small negative values of the corrected heat-pulse velocity . A simulation model of heat transport for the sensor inserted in the tree showed that is linearly related to the average temperature difference (ΔT a ) between the 2 needles from negative up to 30cmh−1. The relation was confirmed for olives and pistachio trees in the field with no apparent variation for very long periods (months). The procedure, named “calibrated average gradient” (CAG), consists in averaging the ΔT a measurements after the pulse, then obtaining empirically the function in its linear domain, when is still measurable with the traditional CHPM. The calibrated function can then be used to calculate below the minimum velocity measurable by the CHPM as determined by the measuring system resolution. The function is sensor-specific and depends only on sensor characteristics and thermal properties; its empirical fit allows not only estimating for low transpiration conditions, but may also serve to check possible variations in sensor performance or changes in thermal properties of xylem tissue caused by wounding, advocating the need to re-install sensors in a new position. [Copyright &y& Elsevier]

In olive ( Olea europaea L), deficit irrigation (DI) has proven to be an effective management strategy to improve water productivity (WP, yield per unit of water used), particularly under localized irrigation. However, despite the significant research efforts made to adapt irrigation programs to each particular cropping environment, little has been done to study the response of tree root systems to DI. The present paper analyzes the effect of water stress on olive root morphology and studies olive ideotypes best suited to DI. To do so, the results of a two-year field experiment using two irrigation treatments, a well-watered control irrigation (CI) and a regulated deficit irrigation (RDI), are combined with simulations using a soil-plant-atmosphere continuum (SPAC) model. Results of the field experiment show that olive root systems forage for water resources when RDI is imposed, i.e. they try to maximize the soil area explored. However, simulations indicate that under DI, foraging might not be the best strategy. Instead, a root system that tends to concentrate new growth inside the wet bulb will increase daily net assimilation ( A n ) by up to 16%. The present analysis shows that tree performance under DI could be optimized to trigger a new leap in WP. [ABSTRACT FROM AUTHOR]

Abstract: A transient-state chamber was developed to measure canopy gas exchange of single trees in the field. The chamber, with a volume of 41.6m3, is designed to enclose a medium-size orchard tree; chamber top and windows can be left open, causing minimum disturbance to the tree environment. Transitory closures allow simultaneous measurement of CO2 exchange and transpiration of the enclosed tree. The chamber was tested during a 2-year study in an olive orchard submitted to different irrigation treatments: control with no water stress (CI) and regulated deficit irrigation (RDI). Leakage had a minimal impact on flux calculations (0.8%min−1); adsorption was not detectable. Maximum increases in canopy temperature of 0.58°Cmin−1 for CI and 1.3°Cmin−1 for RDI generated very small effects on fluxes. Changes in the transpiration rate induced by the chamber''s modification of the canopy environment were evaluated by continuous sap flow measurements with heat pulse gauges inserted in the trunk of two trees enclosed by chambers. Results showed a sap flow decrease of about 8% after 180s of chamber closure. The artificial turbulence generated by fans into the chamber to facilitate air mixing did not alter the transpiration rate. The enclosure had a very small impact on the tree canopy conductance (G c ). The initial lag and mixing time was estimated as 30s; the optimal duration of the calculation window was 70s. Hourly carbon assimilation (A), transpiration (E), and water use efficiency (WUE) for two olive trees in the field subjected to different levels of water stress were measured. [Copyright &y& Elsevier]

• Oil accumulation rate in olive is proportional to the increase in fruit dry weight. • This proportionality remains rather independent of crop load or water status. • A simple model predicts oil accumulation dynamics with minor input requirements. • The model can help in the definition of rational criteria for setting harvest date. Harvest timing in olive orchards has a strong effect on the quality and quantity of oil yield, but many farmers still lack simple and affordable quantitative tools for rationally deciding appropriate harvest dates. This study presents and tests a conceptual model for predicting fruit oil content (O f , g oil fruit−1) from inexpensive measurements of fruit dry weight (w f). The model presents two physiologically relevant parameters, the fruit dry weight at the onset of the oil accumulation phase (w f0) and the ratio of accumulated oil per unit of fruit dry weight increase during the oil accumulation period (β), the latter assumed invariable throughout ripening. A compilation of data on w f and O f dynamics collected from four experiments including six olive cultivars and contrasting conditions of water supply and crop load was used to test the model. Our results suggest that β could be fairly independent of crop load or watering regime and, probably, genetically controlled. By contrast, w f0 is clearly affected by both the cultivar and the availability of assimilates for fruit growth preceding oil accumulation, which makes it orchard- and year-specific. According to those premises, once cultivar-specific β values are available w f0 could be easily calibrated by either a single determination of O f and w f at any time during the oil accumulation phase (Approach A) or by directly measuring w f0 if the date for the onset of oil accumulation can be estimated (Approach B). Validation tests with an independently calibrated β showed an excellent performance for reproducing O f patterns from w f data using Approach A. Approach B satisfactory predicted oil accumulation rates, but absolute estimates of O f were less reliable. Regardless of the calibration approach, the model is easy to implement and has a minimal cost, which satisfies the demand for inexpensive tools for monitoring oil accumulation dynamics. [ABSTRACT FROM AUTHOR]

Olive (Olea europaea L.) is a widely spread tree species in the Mediterranean. In the last decades, olive farming has known major management changes with high economic and environmental impacts. The fast track expansion of this modern olive farming in these recent years casts doubts on the sustainability of such important tree plantation across the Mediterranean. In this work, we performed a spatial modelling analysis to investigate the implications of climate variability and farming management on the productivity and environmental performances of olive orchards around the Mediterranean. Implementation of this research is based on the use of OliveCan; a process-based model able to illustrate responses of water and carbon balances to weather variables, soil characteristics and management techniques enabling the comprehension of olive orchard dynamics under heterogeneous conditions of climate and agricultural practices. Four main intensification levels were adopted to reflect the main olive grove types from traditional to new intensive plantations: low density LD (100 trees ha−1), medium density MD (200 trees ha−1), high density HD (400 trees ha−1) and super high density SHD (1650 trees ha−1). Managements tested were intensification, water supply (rainfed, deficit and full irrigated) and the fate of pruning residues (exported or left on the soil). Two cases studies in two of the main Mediterranean olive-growing regions with contrasting environmental conditions, Tuscany and Jaen regions, focused on mitigation alternative managements for carbon sequestration. Results showed that olive orchards responses in terms of yield and Net Ecosystem Productivity (NEP) vary along with climatic conditions. Water supply was the main driver with a production function that varies for different atmospheric demands. Application of deficit irrigation proved to boost water use efficiency. Besides, intensification from LD to SHD, presented the greatest improvements, 28–73% for yield and 50–100% for NEP. The C sequestration potential of olive orchards was confirmed. In fact, soil organic carbon (SOC) increased continuously over 400 years of simulation, reaching a state of equilibrium. Moreover, intensification and irrigation improved total carbon sequestration. Management of incorporating pruning residues in the soil increased SOC of 10.5 t C ha−1 for Tuscany and 10.8 t C ha−1 for Jaen. Findings of this research enabled the identification of the main drivers influencing the productive and environmental performance of olive groves in the different Mediterranean sub-climates. Impacts of management innovations on olive farming sustainability were also quantified which may help improve production systems for a more sustainable olive cultivation. Unlabelled Image • Impacts of management innovations on olive farming sustainability are quantified • Productive and environmental performances of olive groves are responsive to climate • Water supply is the main driver for olive productivity and carbon sequestration • Intensification improves carbon sequestration potential of olive orchards [ABSTRACT FROM AUTHOR]

• Low autumn temperatures induce growth cessation in shoot apical meristems of olive. • The subsequent dormant state is easily reversed after the exposure to warm conditions. • Growth rate upon budbreak is related to the length of the preceding dormant period. • Cultivar differences in the onset of winter dormancy are small. • Two simple models for predicting the onset of dormancy are presented and tested. The abundance of scientific papers dealing with olive reproductive phenology contrasts with the scarce information available in relation to the winter dormant state of olive vegetative structures. In this study, three experiments with young olive trees were performed in Southern Spain, aiming to provide insight into some features of the winter rest period in this evergreen species. Experiment 1 evaluated the environmental cues triggering dormancy induction by measuring leaf appearance rates in trees subjected to different conditions of temperature and daylength over the course of the 2012 autumn. In Experiment 2, several sets of plants were placed into a greenhouse at different dates along the 2013/2014 winter, testing the ability of dormant plants to resume growth upon the return of favourable temperatures. Finally, Experiment 3 was carried out during the autumns of 2016 and 2017 in two locations, and was devoted to assess differences between five cultivars in the onset of dormancy under natural conditions. Our findings revealed that dormancy induction is not controlled by photoperiod, but by low temperatures. The subsequent winter rest state seems to be easily reversed after 1–2 weeks of exposure to warm conditions, irrespective of the initial date of exposure. With regard to cultivar variability, differences in the timing of growth cessation was found to be rather small. Finally, two simple models for predicting the onset of dormancy based on the accumulation of a certain amount of chilling (either considering or not a reversal of chilling by warm temperatures) are presented. Calibration and validation was performed with independent datasets from Experiments 1, 2 and 3. Validation tests highlighted the reliability of both models in reproducing the date of growth cessation. [ABSTRACT FROM AUTHOR]