Lysimeter assessment of the Simplified Two-Source Energy Balance model and eddy covariance system to estimate vineyard evapotranspiration
Introduction
Monitoring the land surface energy balance (EB) from remote sensing techniques has become essential in hydrology, agriculture, climatology, and weather forecasting (Baldocchi et al., 2000; Wilson et al., 2002; Anderson et al., 2012; Colaizzi et al., 2012; Evett et al., 2012a). In particular, the new challenges in the current climate change context require improvements in the accuracy of actual crop evapotranspiration (ETa) estimation to achieve more effective irrigation scheduling of croplands (Howell et al., 1995; Chávez et al., 2009; Anderson et al., 2012; Evett et al., 2012a; Kustas et al., 2012; López-Urrea et al., 2012; Xia et al., 2016). This becomes particularly important in arid and semi-arid areas where ETa plays a significant role, and fields are rather small size and sparse crops dominate. Also, a better knowledge of the partition of ETa into soil evaporation (E) and canopy transpiration (T) would contribute to this task of determining the water-use efficiency of crops, especially under these environmental conditions (López-Urrea et al., 2012; Kustas et al., 2018), but also to a better understanding of biomass production (Pinter et al., 2003) or carbon sequestration (Scott et al., 2006) due to the strong correlation between them.
The interest of this work focuses on vine crops. Vineyards occupy large areas in the Mediterranean basin and in other regions under predominant semi-arid conditions. Spain occupies the first position in planted surface area in the world with near 1 million ha in 2016 (˜13% of the total world extension) (MAPAMA, 2018). In terms of wine production, Spain is the third in the ranking with a production of 3300.5 Ml in 2017 (˜14% of the total world production). In terms of value, Spain exported in 2017 more than 2200 Ml of production, and 2700 million euros (data from the Global Trade Atlas, GTA 2017). Castilla-La Mancha is the main wine production area with 63% of the total Spanish production, with almost 50% of the planted vines in the national territory. This makes Castilla-La Mancha the geographical area with the greatest concentration of vineyards for wine production in the world.
It is well known that water management is a critical aspect to improve vine performance, and grape, and wine composition (Intrigliolo and Castel, 2008). In order to follow the correct irrigation strategy, vineyard water requirements should be known. Irrigation needs to be carefully managed to prevent severe water stress and ensure economic yields in regions with scarce water resources (Sipiora and Lissarrague, 1999), whereas in regions where vineyards have access to a reliable and unlimited source of water, irrigation can be scheduled so that water stress is imposed during certain periods of time to control canopy growth and to increase fruit quality (Intrigliolo and Castel, 2008). Thus, an accurate estimation of vineyard evapotranspiration in semi-arid regions, such as Castilla-La Mancha, becomes crucial (Li et al., 2008; Campos et al., 2010; Ortega-Farias et al., 2010; Balbontín et al., 2011; Carrasco-Benavides et al., 2012; López-Urrea et al., 2012; Er-Raki et al., 2013).
Different methods and techniques have been applied and tested to derive actual water use or evapotranspiration in vineyards from surface heat flux estimates (Ortega-Farias et al., 2007, 2008; 2010; González-Dugo et al., 2010; Zhang et al., 2010; Shapland et al., 2012; Andreu et al., 2015; Xia et al., 2016; Kustas et al., 2018; Nieto et al., 2018). Sánchez et al. (2008) proposed a Simplified version of the Two-Source Energy Balance (STSEB) model based on the parallel approach introduced by Norman et al. (1995). The STSEB model uses the measured temperature of both soil (Ts) and canopy (Tc) sources to calculate the different terms of the energy balance equation. Feasibility of STSEB was early assessed in a variety of crops at a field scale: maize (Sánchez et al., 2008), sorghum (Sánchez et al., 2011), sunflower and canola (Sánchez et al., 2014), or winter wheat (Sánchez et al., 2015). One of the goals of this work is to further assess the performance of STSEB model in a vine crop.
Validation of surface energy balance model estimates in row crops such as vineyards requires additional experimental efforts (Ortega-Farias et al., 2007 and 2010; Li et al., 2008; Poblete-Echeverría and Ortega-Farias, 2014). Allen et al. (2011) alerted the need for a sufficient description of the procedures used when reporting ET measurements so that the reader can be aware of potential flaws or shortcomings that may question representativeness of ET presentations.
Eddy covariance (EC) is the prevalent technique for ground measuring ET. However, EC instrumentation has some experimental limitations because of the measurement footprint or the spatial variability in atmospheric and surface conditions. Turbulent fluxes are usually underestimated when using EC technique, producing a lack of closure in the surface EB long reported in the literature (Twine et al., 2000; Wilson et al., 2002; Foken, 2008; Sánchez et al., 2010). Vineyard fields are usually small in size, in many cases occupying just a few hectares, and interspersed among other crops and dryland areas. As a consequence, the effect of advection may become significant. Thus, feasibility of EC technique needs to be tested under these challenging conditions.
Although they are quite scarce, the weighing lysimeter is the best direct ETa measurement method. ETa measurements from weighing lysimeters are considered the standard (Howell et al., 1995; López-Urrea et al., 2006; Chávez et al., 2009; Allen et al., 2011; Evett et al., 2012b). However, weighing lysimeters are expensive compared with EC instruments, and therefore not economically feasible for studies of ET over large areas (Evett et al., 2012b).
Several authors have dealt with the comparison of the estimated ET by EC and lysimeter under different conditions on cotton (Chávez et al., 2009; Alfieri et al., 2012; Kustas et al., 2015), maize (Ding et al., 2010) or grassland (Gebler et al., 2015). Also, some authors compared EC to Bowen Ratio Energy Balance (BREB) or Water Balance (WB) techniques in vineyards (Li et al., 2008; Balbontín et al., 2011). But, to the best of our knowledge, a comprehensive comparison between EC and lysimeter measurements has not been attempted for vineyards before. Another objective of this work is to explore the feasibility of the EC data under the conditions of our study site by comparing, for the first time, ETa measurements by a weighing lysimeter available in a vineyard plot with ETa estimates from an EC flux tower.
To achieve these goals, an experiment was carried out during the growing seasons of 2014 and 2015 in a ˜4 ha Tempranillo vineyard located in “Las Tiesas” experimental farm, Castilla-La Mancha, Spain. As a novelty, data from a large weighing lysimeter were used for the assessment of both EC measurements and STSEB results of hourly, daily and full season crop evapotranspiration.
Section snippets
Study site and measurements
The experiments were carried out during the growing seasons of 2014 and 2015 in a vineyard located in “Las Tiesas” experimental farm (39° 3´N, 2° 5´W, 695 m a.s.l) close to Albacete (Castilla-La Mancha, Spain) (Fig. 1). Climate is semi-arid, continental, with 320 mm of annual rainfall, mostly concentrated in spring and fall. Average mean, maximum, and minimum temperatures are: 13.7, 24.0 and 4.5 °C, respectively. The ˜4 ha vineyard (Vitis vinifera L., cv. Tempranillo) was planted in 1999. The
Results and discussion
Overall, both growing seasons at “Las Tiesas” farm (Albacete) were typical of the long-term average weather conditions in Central Spain. Dry and hot atmospheric conditions prevailed during the experiment, with clear days predominant for both years. Daily averages of air temperature ranged between 15–30 °C, with maximum and minimum Ta values near 40 °C and 5 °C, respectively (Fig. 3). Air temperature patterns remained quite stable in 2014 whereas a clear decreasing trend can be observed for
Conclusions
An assessment of the feasibility of the eddy-covariance systems to estimate ETa in vineyards is addressed, for the first time in this paper, by comparison with measurements from a weighing lysimeter. Good agreement between both techniques was observed with RMSE values of ±0.09 mm h−1 and ±0.5 mm d−1 at hourly and daily scales, respectively. Results in this paper give confidence to the use of the EC technique to monitor accurate ETa in vineyards, but advising that some discrepancies may appear
Acknowledgements
This work was funded by the Spanish Ministry of Economy and Competitiveness, together with FEDER funds (projects AGL2017‐83738‐C3‐3‐R and CGL2016-80609-R, and Juan de la Cierva research grant of Dr. Galve, FJCI-2015-24876), the Instituto Nacional de Investigaciones Agrarias (INIA) (project RTA 2014-00049-C05-03) and the Education and Science Council (JCCM, Spain) (project SBPLY/17/180501/000357). The authors would like to thank the logistic support in the instrumentation maintenance of
References (66)
- et al.
Evapotranspiration information reporting: I. Factors governing measurement accuracy
Agr. Water Manage.
(2011) - et al.
Use of Landsat thermal imagery in monitoring evapotranspiration and managing water resources
Remote Sens. Environ.
(2012) - et al.
On measuring and modeling energy fluxes above the floor of a homogeneous and heterogeneous conifer forest
Agric. Forest Meteorol.
(2000) - et al.
Assessing satellite-based basal crop coefficients for irrigated grapes (Vitis vinífera L.)
Agric. Water Manage.
(2010) - et al.
Combining a water balance model with evapotranspiration measurements to estimate total available soil water in irrigated and rainfed vineyards
Agric. Water Manage.
(2016) - et al.
Analysis of an empirical model for soil heat flux under a growing wheat crop for estimating evaporation by an infrared-temperature based energy balance equation
Agric. Forest Meteorol.
(1987) - et al.
Two-source energy balance model estimates of evapotranspiration using component and composite surface temperatures
Adv. Water Resour.
(2012) - et al.
Evaluating eddy covariance method by large-scale weighing lysimeter in a maize field of norhwest China
Agric. Water Manage.
(2010) - et al.
Determination of crop evapotranspiration of table grapes in a semi-arid region of Northwest Mexico using multi-spectral vegetation index
Agric. Water Manage.
(2013) - et al.
Overview of the Bushland Evapotranspiration and Agricultural Remote Sensing Experiment 2008 (BEAREX08): a field experiment evaluating methods for quantifying ET at multiple scales
Adv. Water Resour.
(2012)