scholarly journals Sap flow in trembling aspen: implications for stomatal responses to vapor pressure deficit

1997 ◽  
Vol 17 (8-9) ◽  
pp. 501-509 ◽  
Author(s):  
E. H. Hogg ◽  
P. A. Hurdle
Keyword(s):  
Vapor Pressure ◽  
Sap Flow ◽  
Vapor Pressure Deficit ◽  
Trembling Aspen ◽  
Stomatal Responses

Wood anatomy constrains stomatal responses to atmospheric vapor pressure deficit in irrigated, urban trees

Oecologia ◽  
2008 ◽  
Vol 156 (1) ◽  
pp. 13-20 ◽  
Author(s):  
Susan E. Bush ◽  
Diane E. Pataki ◽  
Kevin R. Hultine ◽  
Adam G. West ◽  
John S. Sperry ◽  
...  
Keyword(s):  
Vapor Pressure ◽  
Wood Anatomy ◽  
Vapor Pressure Deficit ◽  
Urban Trees ◽  
Stomatal Responses

Assessing reliability of HRM sap-flow sensors under large range of vapor pressure deficit

2020 ◽  
Author(s):  
Rémy Schoppach ◽  
Daniella Ekwalla Hangue ◽  
Julian Klaus
Keyword(s):  
Vapor Pressure ◽  
Sap Flow ◽  
Vapor Pressure Deficit ◽  
Heat Waves ◽  
Linear Trend ◽  
Water Flux ◽  
Gravimetric Method ◽  
Flow Sensors ◽  
Tree Transpiration ◽  
Sap Flow Sensors

<p>Evapotranspiration (ET) is a major water flux of ecosystems and represents globally 60-80% of the incoming precipitation lost by terrestrial environments. In forested lands, tree transpiration (TR) is the dominant component of ET, yet remains challenging to measure. Over the years, sap-flow sensors have become the standard tool for quantifying tree TR and different methods based on thermal approaches have been developed. Heat ratio methods (HRM) are considered as the most reliable and accurate method to quantify absolute flows. Leading commercial brands ensure an accurate measurement of positive flows up to 100 cm hr<sup>-1</sup> but different studies have highlighted a saturation effect at high flows with threshold for accuracy remaining elusive[RS1] . Due to climate change, the occurrence, the severity and the duration of extreme events like heat waves and dry periods are expected to increase in future, so the potential for high TR rate periods will also increase. Therefore, it is crucial to determine the species-specific environmental conditions allowing a reliable measurement of TR in order to improve or understanding of eco-hydrological and physiological processes during high potential TR periods that can be crucial for vegetation survival. In this study, we tested the accuracy of HRM sap-flow sensors for beech (Fagus sylvatica) and oak (Quercus robur) tree species under extreme vapor pressure deficit (VPD) conditions in order to determine threshold for reliable measurements. In greenhouse conditions, we collected a complete and dense series of TR response to VPD between 0.7 to 8.3 kPa for potted beech and oak trees using three different methods: infrared gas analyser, gravimetric method, and HRM sap-flow sensors. Responses shown a linear trend at the low-canopy leaf level (41.5 and 45.1 mg H<sub>2</sub>O m<sup>-2</sup> s<sup>-1</sup> kPa<sup>-1</sup> respectively for beech and oak) but a bi-linear conformation at the whole plant level (1<sup>st</sup> slope = 12.04 ± 0.7 mg H<sub>2</sub>O m<sup>-2</sup> s<sup>-1</sup> kPa<sup>-1</sup> and break-point at 3.9 ± 0.07 kPa for beech trees). Sap-flow sensors using the HRM method displayed a clear inability to reliably measure flows under high VPD conditions. Thresholds of 2.25 ± 0.04 and 2.87 ± 0.14 kPa were identified as the maximum limit of method reliability for beech and oak respectively. In highly demanding environments, we suggest a bi-linear extrapolation beyond VPD threshold for better quantifying tree TR. Further experiments aiming at characterizing TR responses to VPD for a broad range of species and in different water deficit conditions are certainly needed for better understanding tree transpiration at the whole stand level.</p>

scholarly journals Responses of trembling aspen and hazelnut to vapor pressure deficit in a boreal deciduous forest

2000 ◽  
Vol 20 (11) ◽  
pp. 725-734 ◽  
Author(s):  
E. H. Hogg ◽  
B. Saugier ◽  
J.-Y. Pontailler ◽  
T. A. Black ◽  
W. Chen ◽  
...  
Keyword(s):  
Vapor Pressure ◽  
Vapor Pressure Deficit ◽  
Deciduous Forest ◽  
Trembling Aspen

scholarly journals Responses of petiole sap flow to light and vapor pressure deficit in the tropical tree Tabebuia rosea (Bignoniaceae)

2015 ◽  
Author(s):  
Adam Roddy ◽  
Klaus Winter ◽  
Todd Dawson
Keyword(s):  
Vapor Pressure ◽  
Sap Flow ◽  
Vapor Pressure Deficit ◽  
Water Flux ◽  
Tropical Tree ◽  
Environmental Drivers ◽  
Ratio Method ◽  
Flow Rates ◽  
Leaf Level ◽  
Tabebuia Rosea

Continuous measurements of sap flow have been widely used to estimate water flux through tree stems and branches. However, stem-level measurements lack the resolution necessary for accurately determining fine-scale, leaf-level responses to environmental variables. We used the heat ratio method to measure sap flow rates through leaf petioles and leaflet petiolules of saplings of the tropical tree Tabebuia rosea (Bignoniaceae) to determine how leaf and leaflet sap flow responds to variation in photosynthetically active radiation (PAR) and vapor pressure deficit (VPD). In the morning sap flow rates to east-facing leaves increased 26 minutes before adjacent west-facing leaves. Integrated daily sap flow was negatively correlated with daily mean VPD, and sap flow declined when VPD exceeded 2.2 kPa whether this occurred in the morning or afternoon, consistent with a feedforward response to humidity. Indeed, changes in VPD lagged behind changes in sap flow. In contrast, changes in PAR often preceded changes in sap flow. The sap flow-VPD relationship was characterized by two distinct patterns of hysteresis, while the sap flow-PAR relationship displayed three types of hysteresis, and the type of VPD hysteresis that occurred on a given day was correlated with the type of PAR hysteresis occurring on that day. These patterns highlight how multiple environmental drivers interact to control leaf sap flux and that the development of sap flow sensors capable of measuring individual leaves could drastically influence the amount of data recordable for these structures.

scholarly journals Sap flow through petioles and petioles reveals leaf-level responses to light and vapor pressure deficit in the tropical tree Tabebuia rosea (Bignoniaceae)

2013 ◽  
Author(s):  
Adam Roddy ◽  
Klaus Winter ◽  
Todd Dawson
Keyword(s):  
Vapor Pressure ◽  
Sap Flow ◽  
Vapor Pressure Deficit ◽  
Water Flux ◽  
Tropical Tree ◽  
Ratio Method ◽  
Flow Rates ◽  
Leaf Level ◽  
The Difference ◽  
Tabebuia Rosea

Continuous measurements of sap flow have been widely used to measure water flux through tree stems and branches. However, these measurements lack the resolution necessary for determining fine-scale, leaf-level responses to environmental variables. We used the heat ratio method to measure sap flow rates through leaf petioles and leaflet petiolules of saplings of the tropical tree Tabebuia rosea (Bignoniaceae) to determine how leaf and leaflet sap flow responds to variation in light and vapor pressure deficit (VPD). We found that in the morning sap flow rates to east-facing leaves increased 26 minutes before adjacent west-facing leaves. Although leaves had higher integrated sap flow than their largest leaflet, this difference was not proportional to the difference in leaf area, which could be due to lower conduit area in petiolules than in petioles. In contrast to measurements on main stems, integrated daily sap flow was negatively correlated with daily mean VPD. Furthermore, leaves exhibited previously undescribed patterns of hysteresis in the sap flow-VPD and sap flow-PAR relationships. When hysteresis in the sap flow-PAR relationship was clockwise, the sap flow-VPD relationship was also clockwise; however, when hysteresis in the sap flow-PAR relationship was counterclockwise, the sap flow-VPD relationship displayed an intersected loop. These pattern differences highlight how substantially leaf-level processes may vary within a canopy and how leaf-level processes may not scale predictably to the stem level.

scholarly journals Sap Flow Dynamics and Responses to Grazing and Seasonal Changes in Soil Moisture for Acacia Ancistroclada and Comberatum Molle in a Kenyan Savanna

2020 ◽  
Author(s):  
Joseph Ondier ◽  
Dennis Otieno ◽  
Daniel Okach ◽  
John Onyango
Keyword(s):  
Soil Moisture ◽  
Vapor Pressure ◽  
Flux Density ◽  
Sap Flow ◽  
Seasonal Changes ◽  
Vapor Pressure Deficit ◽  
Livestock Grazing ◽  
Sap Flux ◽  
Sap Flux Density ◽  
Rainfall Patterns

Abstract The Kenyan savanna, which is dominated by Acacia ancistroclada and Comberatum molle, has experienced notable changes in rainfall patterns and increased livestock grazing. A significant decrease in trees spread from 5 % to less than 1 % has been documented for the ecosystem and could be linked to the increased livestock grazing and changes in rainfall patterns, however, scientific evidence is lacking. We utilized sap flow to analyze the hydraulic responses of the prevailing trees to livestock grazing and seasonal changes in soil moisture. Environmental factors including precipitation, air temperature, soil moisture at - 0.3 m, and vapor pressure deficit were simultaneously measured. The results showed that the diurnal variation in sap flux density exhibited a single peak curve at around midday and correlated strongly with vapor pressure deficit and air temperature. Sap flux density was higher in the grazed (27.47 ± 8.65 g m-2s-1) than the fenced plots (20.17 ± 7.27 g m-2s-1). In all the plots, sap flux density followed seasonality in rainfall patterns, increasing and decreasing in wet and dry seasons respectively. The higher crown projected area was responsible for higher sap flow in the grazed plots. The diurnal variation in sap flux density showed that sap flow was coupled to the atmosphere with relatively low boundary layer resistance and the seasonal variation in sap flow was controlled by stomatal regulation. These findings point to the possibility that the dominant tree species in Lambwe are isohydric species. However, additional measurements need to be conducted on the eligibility of the species to confirm the conclusion.

scholarly journals Effect of canopy management in the water status of cacao (Theobroma cacao) and the microclimate within the crop area

2019 ◽  
Vol 97 (4) ◽  
pp. 701-710
Author(s):  
Alfredo Jiménez-Pérez ◽  
Manuel J. Cach-Pérez ◽  
Mirna Valdez-Hernández ◽  
Edilia De la Rosa-Manzano
Keyword(s):  
Vapor Pressure ◽  
Water Potential ◽  
Sap Flow ◽  
Theobroma Cacao ◽  
Vapor Pressure Deficit ◽  
Soil Water Potential ◽  
Flow Density ◽  
Closed Canopy ◽  
Sap Flow Density ◽  
Crop Area

Background: Cacao is an umbrophile species and therefore the handling of shade by producers can cause a microclimatic modification that influences the physiology of the plant. Questions: Can canopy management influence the microclimate of the crop area and the water content of cacao? Species of study: Theobroma cacao L. (Malvaceae). Study site: Comalcalco, Tabasco, Mexico; dry and rainy season 2018. Methods: Three sites were selected with an open canopy (OC) and three with a closed canopy (CC), where we determined air temperature and humidity, soil temperature, vapor pressure deficit, photosynthetically active radiation, soil water potential and leaf water potential in 15 cacao trees and the sap flow density in 12 trees, by canopy condition and by season. Results: Higher values of solar radiation, air and soil temperature, vapor pressure deficit and lower relative humidity were recorded under OC compared to CC, in both seasons. Differences in soil water potential between 10 and 60 cm depth in CC were recorded during the dry season. There was a lower sap flow density and daily water use in OC. The leaf water potential was similar between canopy conditions, in both seasons. Conclusions: Changes in canopy coverage significantly modify the microclimate of the crop area, a less stressful environment being generated under closed canopy conditions, influencing the sap flow density of cacao trees.

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