Terroir 2010 banner
IVES 9 IVES Conference Series 9 Diurnal cycles of grapevine leaf water potential under field conditions

Diurnal cycles of grapevine leaf water potential under field conditions

Abstract

[English version below]

Les cycles journaliers du potentiel hydrique foliaire (Ψl) ont été établis toutes les heures, pour différents stades phénologiques, sur deux localités et en fonction de différentes mesures de la température de l’air et du déficit en pression de vapeur (VPD). De faibles valeurs pour ces 2 paramètres ont été enregistrées tout au long de la saison à l’endroit le plus frais. Les mesures du potentiel hydrique foliaire obtenues au stade floraison montrent que les vignes de Sauvignon blanc à l’endroit le plus frais, ont subi un stress hydrique plus important au cours de la journée par rapport aux vignes situées à l’endroit plus chaud. De plus le potentiel hydrique du sol (Ψm) obtenu sur les sols bien drainés de la localité plus fraîche, à ce même stade, était d’environ -0.03 MPa comparés au -0.01 MPa de la localité plus chaude. Ceci laisse à penser que le statut hydrique de la vigne durant la journée est d’abord contrôlé par la teneur en eau du sol. Les différences de statut hydrique entre les deux endroits diminuent progressivement durant la phase de croissance végétative et ce, jusqu’à la période suivant les vendanges durant laquelle le potentiel foliaire obtenu à l’endroit plus frais devenait supérieur à celui obtenu à l’endroit plus chaud. Les valeurs relativement faibles du potentiel hydrique obtenues à l’aube à l’endroit plus frais, indiquent que les vignes étaient exposées à un important stress hydrique comme le montre la faible teneur en eau du sol (Ψm= -0.77 MPa). La fermeture stomatique partielle observée sur les vignes de l’endroit plus frais, ont permis d’éviter de trop sévères stress hydriques (Ψl < -1.2 MPa) durant les plus chaudes heures de la journée. Cependant ce mécanisme de résistance fut à peine observé à l’endroit plus chaud.
On peut donc conclure sur ces résultats, qu’un faible potentiel hydrique obtenu à l’aube, ne conduira pas forcément à un stress hydrique plus important durant les plus chaudes heures de la journée, et vice versa. La détermination des cycles hydriques journaliers, ainsi que le stress hydrique observés sur une journée entière à différents stades phénologiques sont donc indispensables si l’on veut comprendre et quantifier l’effet du terroir sur le statut hydrique de la vigne.

Diurnal cycles of leaf water potential (Ψl) were established on an hourly basis at various phenological stages at two localities with different air temperature and vapour pressure deficit (VPD). Lower air temperature and VPD values were recorded consistently throughout the season at the cooler locality. Leaf water potential measurements at flowering showed that Sauvignon blanc grapevines at this cooler locality were subjected to a higher degree of water stress throughout the day compared to grapevines at the warmer locality. At this phenological stage, soil water matric potential (Ψm) of the well-drained soil at the cooler locality was ca -0.03 MPa compared to ca -0.01 MPa at the warmer locality. This suggested that diurnal grapevine water status was primarily controlled by soil water content. The difference in grapevine water status between the two localities gradually diminished as the growth season progressed until the post harvest period when Ψl in grapevines at the cooler locality tended to be higher compared to those at the warmer one. The relatively low pre-dawn Ψl at the cooler locality during this measurement cycle indicated that the grapevines were exposed to excessive water stress as a result of the low soil water content (i.e. Ψm = -0.77 MPa). Partial stomatal closure in grapevines at the cooler locality, however, prevented excessive water stress (i.e. Ψl < -1.2 MPa) during the warmest part of the day compared to grapevines at the warmer terroir where almost no stomatal control occurred.
It appears from these results that low pre-dawn Ψl values do not necessarily imply that grapevines will experience more water stress during the warmest part of the day, or vice versa. Hence, determination of daily water status cycles, as well as the accumulated water stress over the full diurnal cycle at various phenological stages is invaluable in order to understand and quantify terroir effects on grapevine water status.

DOI:

Publication date: January 12, 2022

Issue: Terroir 2004

Type: Article

Authors

M. Laker (1), P.A. Myburgh (1) and E. Archer (2)

(1) ARC Infruitec-Nietvoorbij, Private Bag X5026, 7599 Stellenbosch, Republic of South Africa
(2) LUSAN Premium Wines, Private Bag 104, 7599 Stellenbosch, Republic of South Africa

Contact the author

Keywords

Soil water matric potential, diurnal cycles, leaf water potential, accumulated water stress

Tags

IVES Conference Series | Terroir 2004

Citation

Related articles…

austrianvineyards.com: online viewer of all designations of Austrian wine

To digitally record and present all the origins of Austrian wines in the same perfect and clear way was the motivation for the Austrian Wine Marketing Board (Austrian Wine) to start with the project in 2018. In June 2021 the results were presented to the public in an online viewer showing all the designations of Austrian wine, available at https://austrianvineyards.com in a largely barrier-free manner. The online viewer provides tailored individual maps fitted to the respective zoom level. The smallest unit of wine-origins in Austria is called Ried and is displayed in a plot-specific manner highlighting areas under vine. Information on the Ried include administrative district, winegrowing municipality, cadastral municipality, large collective vineyard site, specific winegrowing region, generic winegrowing region, winegrowing area and, in many cases, an illustrative picture. Complementary data on the size, elevation (minimum-maximum), orientation (in 8 sectors plus flat) and gradient (minimum, maximum, average) are based on the area under vine according to the EU’s Integrated Administration and Control System. Additional information covers climate data. The diagrams are taken from the monthly breakdown of data in the annals of the Central Institute for Meteorology and Geodynamics, Austria provide a display of values for air temperature, precipitation, and sunshine hours for the reference year and the long-term average. Seasonal aggregated data on temperature, precipitation, and sunshine hours complete the display. Short descriptions with emphasis on geology and soil, field name in historical maps, etymology of the denomination, and main planted variety complements the available information for the main designations in the online viewer. These descriptions are compiled by winegrowers, geologists, historians, and journalists. All the information and data can be extracted to a pdf-file. Printed vineyard maps are also available. Missing content regarding wine origins in Styria will be completed in winter 2021/22.

A multidisciplinary approach to evaluate the effects of the training system on the performance of “Aglianico del Vulture” vineyards

Vineyards are complex agro-ecosystems with high spatial and temporal variability. An efficient training system may counteract the adverse effects of this variability. Moreover, considering the climate change issues, choosing an efficient training system that enhances water use and protects the vines from radiative thermal stress has become a priority for the farmers. A multidisciplinary approach that assesses the soil-crop-yield-wine relationships of vineyards in a distributed and holistic way could bring added knowledge on the behavior of the different training systems. This ongoing research aimed to implement a multidisciplinary approach to study the behavior of “Aglianico del Vulture” grapevines trained with two different systems: a spurred cordon (SC) and an “Alberello in parete” (AL), grown in a high-quality wine production area of Basilicata region (Italy). The approach merged several methods and scales of soil, ecophysiology, must/wine quality, and spectral data collection to assess the influence of the training system. Homogeneous zones (HZs) in both training systems were defined through a procedure based on geomorphological classification, unmanned aerial vehicles (UAV) images analysis, and a traditional soil survey supported by geophysical scanning. During the 2021 season, TDR probes monitored soil water content, while grapevine health status was assessed using eco-physiological measurements (LWP, chlorophyll content, PSII photosynthetic efficiency, LAI, and point-based field spectroscopy). These grapevine in-vivo measurements validated the spectral vegetation indexes (NDVI, RENDVI, CVI, and TVI) derived from the UAV multispectral imagery, which monitored the grapevine status in a distributed and non-invasive way. Grape yield, quality of berries, must and wine were measured to assess the effects of the training systems. The first experimental year results showed the variability of the vineyards and revealed relationships among soil parameters, crop characteristics, and vegetation indices of the SC and AL training systems. This multidisciplinary study could bring new insights into the vineyard training system’s effects on grape yield and wine quality.

Climate ethnography and wine environmental futures

Globalisation and climate change have radically transformed world wine production upsetting the established order of wine ecologies. Ecological risks and the future of traditional agricultural systems are widely debated in anthropology, but very little is understood of the particular challenges posed by climate change to viticulture which is seen by many as the canary in the coalmine of global agriculture. Moreover, wine as a globalised embedded commodity provides a particularly telling example for the study of climate change having already attracted early scientific attention. Studies of climate change in viticulture have focused primarily on the production of systematic models of adaptation and vulnerability, while the human and cultural factors, which are key to adaptation and sustainable futures, are largely missing. Climate experts have been unanimous in recognising the urgent need for a better understanding of the complex dynamics that shape how climate change is experienced and responded to by human systems. Yet this call has not yet been addressed. Climate ethnography, coined by the anthropologist Susan Crate (2011), aims to bridge this growing disjuncture between climate science and everyday life through the exploration of the social meaning of climate change. It seeks to investigate the confrontation of its social salience in different locations and under different environmental guises (Goodman 2018: 340). By understanding how wine producers make sense of the world (and the environment) and act in it, it proposes to focus on the co-production of interdisciplinary knowledge by identifying and foreshadowing problems (Goodman 2018: 342; Goodman & Marshall 2018). It seeks to offer an original, transformative and contrasted perspective to climate change scenarios by investigating human agency -individual or collective- in all its social, political and cultural diversity. An anthropological approach founded on detailed ethnographies of wine production is ideally placed to address economic, social and cultural disruptions caused by the emergence of these new environmental challenges. Indeed, the community of experts in environmental change have recently called for research that will encompass the human dimension and for more broad-based, integrated through interdisciplinarity, useful knowledge (Castree & al 2014). My paper seeks to engage with climate ethnography and discuss what it brings to the study of wine environmental futures while exploring the limitations of the anthropological environmental approach.

VINIoT: Precision viticulture service for SMEs based on IoT sensors network

The main innovation in the VINIoT service is the joint use of two technologies that are currently used separately: vineyard monitoring using multispectral imaging and deployed terrain sensors. One part of the system is based on the development of artificial intelligence algorithms that are feed on the images of the multispectral camera and IoT sensors, high-level information on water stress, grape ripening status and the presence of diseases. In order to obtain algorithms to determine the state of ripening of the grapes and avoid losing information due to the diversity of the grape berries, it was decided to work along the first year 2020 at berry scale in the laboratory, during the second year at the cluster scale and on the last year at plot scale. Different varieties of white and red grapes were used; in the case of Galicia we worked with the white grape variety Treixadura and the red variety Mencía. During the 2020 and 2021 campaigns, multispectral images were taken in the visible and infrared range of: 1) sets of 100 grapes classifying them by means of densimetric baths, 2) individual bunches. The images taken with the laboratory analysis of the ripening stage were correlated. Technological maturity, pH, probable degree, malic acid content, tartaric acid content and parameters for assessing phenolic maturity, IPT, anthocyanin content were determined. It has been calculated for each single image the mean value of each spectral band (only taking into account the pixels of interest) and a correlation study of these values with laboratory data has been carried out. These studies are still provisional and it will be necessary to continue with them, jointly with the training of the machine learning algorithms. Processed data will allow to determine the sensitivity of the multispectral images and select bands of interest in maturation.

Heatwaves and grapevine yield in the Douro region, crop model simulations

Heatwaves or extreme heat events can be particularly harmful to agriculture. Grapevines grown in the Douro winemaking region are particularly exposed to this threat, due to the specificities of the already warm and dry climatic conditions. Furthermore, climate change simulations point to an increase in the frequency of occurrence of these extreme heat events, therefore posing a major challenge to winegrowers in the Mediterranean type climates. The current study focuses on the application of the STICS crop model to assess the potential impacts of heatwaves in grapevine yields over the Douro valley winemaking region. For this purpose, STICS was applied to grapevines using high-resolution weather, soil and terrain datasets over the Douro. To assess the impact of heatwaves, the weather dataset (1989-2005) was artificially modified, generating periods with anomalously high temperatures (+5 ºC), at certain onset dates and with specific durations (from 5 to 9 days). The model was run with this modified weather dataset and results were compared to the original unmodified runs. The results show that heatwaves can have a very strong impact on grapevine yields, strongly depending on the onset dates and duration of the heatwaves. The highest negative impacts may result in a decrease in the yield by up to -35% in some regions. Despite some uncertainties inherent to the current modelling assessment, the present study highlights the negative impacts of heatwaves on viticultural yields in the Douro region, which is critical information for stakeholders within the winemaking sector for planning suitable adaptation measures.