Spatiotemporal dynamics of leaf transpiration quantified with time-series thermal imaging

Page, Gerald; Liénard, Jean‐Sylvain; Pruett, Matthew J.; Moffett, Kevan B.

doi:10.1016/j.agrformet.2018.02.023

Cited by 22 publications

(23 citation statements)

References 37 publications

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“…Thermography has been used to estimate Esoil (Haghighi and Or, 2015;Nachshon et al, 2011;Shahraeeni and Or, 2010) and T from plant canopies (Jones, 1999;Jones et al, 2002), often in agricultural settings (Ishimwe et al, 2014;Vadivambal and Jayas, 2010). Researchers are increasingly using tower and UAV-mounted thermal cameras to measure the temperatures of different ecosystem 10 components at high temporal and spatial resolution (Hoffmann et al, 2016;Pau et al, 2018), which could revolutionize the measurement of T from plant canopies (Aubrecht et al, 2016) or even individual leaves in a field setting (Page et al, 2018).…”

Section: Advances In Thermal Imaging 30mentioning

confidence: 99%

Reviews and syntheses: Turning the challenges of partitioning ecosystem evaporation and transpiration into opportunities

Stoy¹,

El‐Madany²,

Fisher³

et al. 2019

Preprint

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Evaporation (E) and transpiration (T) respond differently to ongoing changes in climate, atmospheric composition, and land use. Our ability to partition evapotranspiration (ET) into E and T is limited at the ecosystem scale, which renders the validation of satellite data and land surface models incomplete. Here, we review current progress in partitioning E and T, and provide a prospectus for how to improve theory and observations going forward. Recent advancements in analytical techniques provide additional opportunities for partitioning E and T at the ecosystem scale, but their assumptions have yet to be fully 35 tested. Many approaches to partition E and T rely on the notion that plant canopy conductance and ecosystem water use efficiency (EWUE) exhibit optimal responses to atmospheric vapor pressure deficit (D). We use observations from 240 eddy covariance flux towers to demonstrate that optimal ecosystem response to D is a reasonable assumption, in agreement with recent studies, but the conditions under which this assumption holds require further analysis. Another critical assumption for many ET partitioning approaches is that ET can be approximated as T during ideal transpiring conditions, which has been 40 Biogeosciences Discuss., https://doi.

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Section: Advances In Thermal Imaging 30mentioning

confidence: 99%

Reviews and syntheses: Turning the challenges of partitioning ecosystem evaporation and transpiration into opportunities

Stoy¹,

El‐Madany²,

Fisher³

et al. 2019

Preprint

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“…To simplify this equation, the number of parameters was reduced by introducing the following assumptions; (i) Net radiation (R n ) is equal to the absorbed short-wave radiation (R s ), and H is much smaller than λE when transpiration occurs (Moncrieff et al, 1997;Page, Liénard, Pruett & Moffett, 2018). Therefore, the term R n -H is proportional to R s .…”

Section: Indicator Of Stomatal Conductancementioning

confidence: 99%

A new indicator of leaf stomatal conductance based on thermal imaging for field grown cowpea

Iseki

Olaleye

2019

Plant Production Science

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Compared with a porometer, a thermal camera can be easily applied to large plant populations comprising a set of varieties, treatments, and replications, whereby, leaf temperature-based indicators are widely used to estimate stomatal conductance (g s); however, a major difficulty in applying these indicators is their vulnerability to meteorological conditions. In this study, a new indicator of g s (GsI) was developed with a modified theoretical equation of g s that was highly simplified by means of several assumptions. GsI calculation uses leaf and air temperature, relative humidity, and solar radiation measurements. To validate and compare GsI values with other thermal indicators as leaf-air temperature difference and crop water stress index, glasshouse and field experiments were conducted. Leaf temperature of cowpea plants was measured using a low-cost thermal camera to ensure a cost-friendly method. GsI proved to be more stable than other indicators, relative to the measured g s , irrespective of solar radiation, air temperature, and relative humidity conditions. As no reference temperature is needed for the calculation of GsI, it easily applies to large plant populations, although the GsI is most accurate in the range from moderate to high g s values (approximately, >0.2 mol m −2 s −1). We used GsI to evaluate a cowpea germplasm collection consisting of 248 accessions, and elucidated that most accessions with higher GsI, which expected to have higher g s , are originated in West-Africa. As GsI is available regardless of varying meteorological conditions, it is a useful indicator of g s , especially in field studies involving multilocation and time-course evaluations.

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“…During the severe drought experiment (2018), thermal and color (RGB) images were captured using a FLIR 420T camera (FLIR Systems Inc., Wilsonville, OR, United States) with a 35 mm lens. The senor had an accuracy of ±1% for measurements within the range of 5-120 • C in ambient temperatures lower than 35 • C. Thermal images were post-processed using FLIRTools, correcting for long-wave radiation attenuation effects using target distances, ambient vapor pressures, and ambient temperatures from meteorological data collected in the greenhouse (Page et al, 2018). Images were not corrected for greenhouse long-wave emissions, as corrections were less than the sensitivity of the instrument (Page et al, 2018).…”

Section: Thermal and Rgb Measurementsmentioning

confidence: 99%

“…The senor had an accuracy of ±1% for measurements within the range of 5-120 • C in ambient temperatures lower than 35 • C. Thermal images were post-processed using FLIRTools, correcting for long-wave radiation attenuation effects using target distances, ambient vapor pressures, and ambient temperatures from meteorological data collected in the greenhouse (Page et al, 2018). Images were not corrected for greenhouse long-wave emissions, as corrections were less than the sensitivity of the instrument (Page et al, 2018). Corrections of leaf emissivity (ε) were standardized at 0.97 because previous studies have shown no difference in droughted and watered leaves (Buitrago et al, 2016).…”

Section: Thermal and Rgb Measurementsmentioning

confidence: 99%

Biophysically Informed Imaging Acquisition of Plant Water Status

Beverly

Ewers

2020

Front. For. Glob. Change

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Vegetation controls carbon and water fluxes because of the fundamental tradeoff between carbon dioxide uptake and water loss occurring when stomata are open. Quantifying the rates of this exchange typically requires either intensive gas exchange or destructive harvesting of tissues and mass spectrometry analyses. Recent developments in high-throughput methods have enhanced our capacity to empirically test plant-environmental interactions. The vast integration characterizing satellite remote sensing methods masks organ-level physiological mechanisms limiting the predictive capability of current process models. Hence, more ground truth studies are necessary to determine the amount of mechanistic information needed to improve our understanding of forest, crop, and land management. Imaging methodologies, such as thermal and chlorophyll a fluorescence, are currently used to collect information for relevant traits such as water use, growth, and stress response. We tested these techniques during progressive drought across species with different susceptibility in controlled greenhouse conditions. We chose two highly represented tree species in North America: the gymnosperm Pinus ponderosa and the angiosperm Populus tremuloides. To better explore the whole drought response parameter space, we also tested a crop (Brassica rapa) and desert shrub (Artemisia tridentata). Thermal and fluorescence images of the canopy were coupled with leaf-level measurements as we performed three tests to predict drought response using (1) leaf temperature, (2) chlorophyll a fluorescence, and (3) the combination of the two. At 5 days of drought, leaf temperature increased 7 and 10%, accounting for 63 and 73% of the variation in stomatal conductance for both tree species, respectively. The fluorescence signal from images decreased ∼12% and ∼83% in moderately and severely droughted leaves respectively, reaching zero at mortality. Leaf water status was then predicted using a Bayesian approach that incorporated measurements' uncertainty and parsimony in the analysis of the parameters. Changes in canopy temperature provided confident predictions for the reductions of daily evapotranspiration at the onset of drought. Empirically combining thermal and fluorescence measurements improved predictions (R 2 = 0.81) of midday leaf water potential compared to univariate models. Our results represent an important step toward quantifying plant water status during drought using first principles that do not require species-specific information.

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Spatiotemporal dynamics of leaf transpiration quantified with time-series thermal imaging

Cited by 22 publications

References 37 publications

Reviews and syntheses: Turning the challenges of partitioning ecosystem evaporation and transpiration into opportunities

Reviews and syntheses: Turning the challenges of partitioning ecosystem evaporation and transpiration into opportunities

A new indicator of leaf stomatal conductance based on thermal imaging for field grown cowpea

Biophysically Informed Imaging Acquisition of Plant Water Status

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