Hydraulic Characteristics of Mountain Ash (Eucalyptus regnans F. Muell.) Derived From in situ Measurements of Stem Water Potential

1985 ◽  
Vol 12 (1) ◽  
pp. 77 ◽  
Author(s):  
NJ Legge ◽  
DJ Connor
Keyword(s):  
Water Potential ◽  
Time Lag ◽  
Vapour Pressure Deficit ◽  
Early Summer ◽  
In Situ Measurements ◽  
Stem Water Potential ◽  
Transfer Resistance ◽  
Mountain Ash ◽  
Stem Water

An osmotic tensiometer has been successfully used for in situ measurements of stem water potential, Ψst, in mountain ash. During spring and early summer when soils were saturated, fluctuations in Ψst, at a given height in different trees were very similar. When Ψst, values were measured at different positions around the circumference of individual trees during late summer, considerable variation between the different positions was recorded. The data at this time also suggest that night temperatures above 17°C can lead to stomatal opening, but this was not confirmed by direct measurement. Possible reasons for apparent discrepancies between leaf and stem water potential measurements are discussed. The time lag between vapour pressure deficit and Ψst was around 2 h whenΨst values were high, but fell to 10 min or less for Ψst values below about - 1.2 MPa. Analysing this time lag in terms of a resistance-capacitance model of water flow made it possible to estimate the storage-to-vessel transfer resistance as 1.7 × 107 Pa s m3 kg-1.

Relating Water Potential Gradients in Mountain Ash (Eucalyptus regnans F. Muell.) To Transpiration Rate

1985 ◽  
Vol 12 (1) ◽  
pp. 89 ◽  
Author(s):  
NJ Legge
Keyword(s):  
Water Potential ◽  
Transpiration Rate ◽  
Vapour Pressure Deficit ◽  
Stem Water Potential ◽  
Sapwood Area ◽  
Eucalyptus Regnans ◽  
Tree Transpiration ◽  
Mountain Ash ◽  
Simple Tree

Osmotic tensiometers recording in situ stem water potential, Ψst, were implanted at two heights in the trunks of mountain ash (Eucalyptus regnans) in mature and 1939 regrowth forests. Measurements over one summer showed that Ψst gradients, obtained from the mean Ψst values at each height, reached over 50 kPa/m, with the diurnal maxima generally occurring between 1500 and 1600 h. When Ψst gradients were averaged over 24 h it was found that, unless temperatures were extremely high or the foliage was wet, the average diurnal gradient was linearly related to the average vapour pressure deficit. From this relationship the average diurnal gradient during two earlier summers was estimated to be 23 kPa/m. The forest transpiration rate during this time was estimated to be 4.1 mm/day and when these data, together with sapwood area data, were put into a simple tree transpiration model, the relative conductivity of the sapwood was found to be approximately 7.9 × 10-12 m2.

Simultaneous measurements of tomato fruit and stem water potentials using in situ stem hygrometers

1989 ◽  
Vol 67 (8) ◽  
pp. 2352-2355 ◽  
Author(s):  
D. R. Lee ◽  
M. A. Dixon ◽  
R. W. Johnson
Keyword(s):  
Water Potential ◽  
Tomato Fruit ◽  
Potential Gradient ◽  
Diurnal Changes ◽  
Stem Water Potential ◽  
Simultaneous Measurements ◽  
Water Potentials ◽  
Stem Water ◽  
Water Potential Gradient

Simultaneous measurements were made of the water potentials of the stem and fruit of intact tomato plants (Lycopersicon esculentum Mill. var. Heinz 2653) using in situ temperature-corrected stem psychrometers. Water potential of the fruit remained consistently lower than the water potential of the stem except when the plant had been subjected to prolonged water stress. Stem water potential recovered quickly with rewatering, increasing by approximately 0.5 MPa in 1 h, but the water potential of the fruit remained consistently near −1.0 MPa. The results indicate a significant resistance to water flow between the stem and the fruit and a substantial hydraulic capacitance represented by the volume of the fruit. Diurnal changes in dimensions of tomato fruit were also measured. Fruit diameter expanded at night and contracted during the day even when the water potential gradient favoured flow towards the fruit. This indicates that bidirectional flow (to and from the fruit) is not responsible for the observed diurnal changes in the fruit dimensions.

scholarly journals The Effect of Irrigation Rate on the Water Relations of Young Citrus Trees in High-Density Planting

2021 ◽  
Vol 13 (4) ◽  
pp. 1759
Author(s):  
Said A. Hamido ◽  
Kelly T. Morgan
Keyword(s):  
Water Potential ◽  
Soil Water ◽  
Soil Salinity ◽  
Planting Density ◽  
Stem Water Potential ◽  
Irrigation Rate ◽  
Biological Stress ◽  
Stem Water ◽  
Water Contents ◽  
Soil Water Contents

The availability and proper irrigation scheduling of water are some of the most significant limitations on citrus production in Florida. The proper volume of citrus water demand is vital in evaluating sustainable irrigation approaches. The current study aims to determine the amount of irrigation required to grow citrus trees at higher planting densities without detrimental impacts on trees’ water relation parameters. The study was conducted between November 2017 and September 2020 on young sweet orange (Citrus sinensis) trees budded on the ‘US-897’ (Cleopatra mandarin x Flying Dragon trifoliate orange) citrus rootstock transplanted in sandy soil at the Southwest Florida Research and Education Center (SWFREC) demonstration grove, near Immokalee, Florida. The experiment contained six planting densities, including 447, 598, and 745 trees per ha replicated four times, and 512, 717, and 897 trees per ha replicated six times. Each density treatment was irrigated at 62% or 100% during the first 15 months between 2017 and 2019 or one of the four irrigation rates (26.5, 40.5, 53, or 81%) based on the calculated crop water supplied (ETc) during the last 17 months of 2019–2020. Tree water relations, including soil moisture, stem water potential, and water supplied, were collected periodically. In addition, soil salinity was determined. During the first year (2018), a higher irrigation rate (100% ETc) represented higher soil water contents; however, the soil water content for the lower irrigation rate (62% ETc) did not represent biological stress. One emitter per tree regardless of planting density supported stem water potential (Ψstem) values between −0.80 and −0.79 MPa for lower and full irrigation rates, respectively. However, when treatments were adjusted from April 2019 through September 2020, the results substantially changed. The higher irrigation rate (81% ETc) represented higher soil water contents during the remainder of the study, the lower irrigation rate (26.5% ETc) represents biological stress as a result of stem water potential (Ψstem) values between −1.05 and −0.91 MPa for lower and higher irrigation rates, respectively. Besides this, increasing the irrigation rate from 26.5% to 81%ETc decreased the soil salinity by 33%. Although increasing the planting density from 717 to 897 trees per hectare reduced the water supplied on average by 37% when one irrigation emitter was used to irrigate two trees instead of one, applying an 81% ETc irrigation rate in citrus is more efficient and could be managed in commercial groves.

scholarly journals Towards Vine Water Status Monitoring on a Large Scale Using Sentinel-2 Images

2021 ◽  
Vol 13 (9) ◽  
pp. 1837
Author(s):  
Eve Laroche-Pinel ◽  
Sylvie Duthoit ◽  
Mohanad Albughdadi ◽  
Anne D. Costard ◽  
Jacques Rousseau ◽  
...  
Keyword(s):  
Climate Change ◽  
Water Potential ◽  
Large Scale ◽  
Water Status ◽  
Vegetation Indices ◽  
Machine Learning Algorithms ◽  
Severe Drought ◽  
Stem Water Potential ◽  
Stem Water ◽  
Sentinel 2

Wine growing needs to adapt to confront climate change. In fact, the lack of water becomes more and more important in many regions. Whereas vineyards have been located in dry areas for decades, so they need special resilient varieties and/or a sufficient water supply at key development stages in case of severe drought. With climate change and the decrease of water availability, some vineyard regions face difficulties because of unsuitable variety, wrong vine management or due to the limited water access. Decision support tools are therefore required to optimize water use or to adapt agronomic practices. This study aimed at monitoring vine water status at a large scale with Sentinel-2 images. The goal was to provide a solution that would give spatialized and temporal information throughout the season on the water status of the vines. For this purpose, thirty six plots were monitored in total over three years (2018, 2019 and 2020). Vine water status was measured with stem water potential in field measurements from pea size to ripening stage. Simultaneously Sentinel-2 images were downloaded and processed to extract band reflectance values and compute vegetation indices. In our study, we tested five supervised regression machine learning algorithms to find possible relationships between stem water potential and data acquired from Sentinel-2 images (bands reflectance values and vegetation indices). Regression model using Red, NIR, Red-Edge and SWIR bands gave promising result to predict stem water potential (R2=0.40, RMSE=0.26).

Estimation water status of the vineyard by calculating multispectral index from satellite images

2021 ◽  
Author(s):  
Marta Rodríguez-Fernández ◽  
María Fandiño ◽  
Xesús Pablo González ◽  
Javier J. Cancela
Keyword(s):  
Water Stress ◽  
Water Potential ◽  
Spectral Index ◽  
Satellite Images ◽  
Irrigation System ◽  
Water Status ◽  
Stress Index ◽  
Stem Water Potential ◽  
Stem Water ◽  
Water Potential Measurements

<p>The estimation of the water status in the vineyard, is a very important factor, in which every day the winegrowers show more interest since it directly affects the quality and production in the vineyards. The situation generated by COVID-19 in viticulture, adds importance to tools that provide information of the hydric status of vineyard plants in a telematic way.</p><p>In the present study, the stem water potential in the 2018 and 2019 seasons, is analysed in a vineyard belonging to the Rias Baixas wine-growing area (Vilagarcia de Arousa, Spain), with 32 sampling points distributed throughout the plot, which allows the contrast and validation with the remote sensing methodology to estimate the water status of the vineyard using satellite images.</p><p>The satellite images have been downloaded from the Sentinel-2 satellite, on the closets available dates regarding the stem water potential measurements, carried out in the months of June to September, because this dates are considered the months in which vine plants have higher water requirements.</p><p>With satellite images, two spectral index related to the detection of water stress have been calculated: NDWI (Normalized Difference Water Index) and MSI (Moisture Stress Index). Stem water potential measurements, have allowed a linear regression with both index, to validate the use of these multispectral index to determine water stress in the vineyard.</p><p>Determination coefficients of r<sup>2</sup>=0.62 and 0.67, have been obtained in July and August 2018 and 0.54 in June of 2019 for the NDWI index, as well as values of 0.53 and 0.63 in July 2018 and June 2019 respectively, when it has been analysed the MSI index.</p><p>Between both seasons, the difference observed, that implies slightly greater water stress in 2019, is reflected in the climate conditions during the summer months, with an average accumulated rainfall that doesn’t exceed 46 mm of water. Although, the NDWI index has allowed to establish better relationships in the 2018 season respect to the MSI index and the 2019 season, (r<sup>2</sup>=0.60 NDWI in 2018), as well as greater differences in terms of water stress presented in the vineyard.</p><p>With the spectral index calculated, it has been possible to validate the use of these index for the determination of the water stress of the vineyard plants, as an efficient, fast and less expensive method, which allows the application of an efficient irrigation system in the vineyard.</p>

Estimation of water stress in olive orchards through remote sensing data analysis

2021 ◽  
Author(s):  
Luz Karime Atencia ◽  
María Gómez del Campo ◽  
Gema Camacho ◽  
Antonio Hueso ◽  
Ana M. Tarquis
Keyword(s):  
Remote Sensing ◽  
Water Stress ◽  
Water Potential ◽  
Statistical Tests ◽  
Remote Sensing Data ◽  
Olive Tree ◽  
Fruit Trees ◽  
Data Sets ◽  
Stem Water Potential ◽  
Stem Water

<p>Olive is the main fruit tree in Spain representing 50% of the fruit trees surface, around 2,751,255 ha. Due to its adaptation to arid conditions and the scarcity of water, regulated deficit irrigation (RDI) strategy is normally applied in traditional olive orchards and recently to high density orchards. The application of RDI is one of the most important technique used in the olive hedgerow orchard. An investigation of the detection of water stress in nonhomogeneous olive tree canopies such as orchards using remote sensing imagery is presented.</p><p>In 2018 and 2019 seasons, data on stem water potential were collected to characterize tree water state in a hedgerow olive orchard cv. Arbequina located in Chozas de Canales (Toledo). Close to the measurement’s dates, remote sensing images with spectral and thermal sensors were acquired. Several vegetation indexes (VI) using both or one type of sensors were estimated from the areas selected that correspond to the olive crown avoiding the canopy shadows.</p><p>Nonparametric statistical tests between the VIs and the stem water potential were carried out to reveal the most significant correlation. The results will be discussing in the context of robustness and sensitivity between both data sets at different phenological olive state.</p><p><strong>ACKNOWLODGEMENTS</strong></p><p>Financial support provided by the Spanish Research Agency co-financed with European Union FEDER funds (AEI/FEDER, UE, AGL2016-77282-C3-2R project) and Comunidad de Madrid through calls for grants for the completion of Industrial Doctorates, is greatly appreciated.</p>

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