Distance makes the difference in thermography for ecological studies

Faye, Émile; Dangles, Olivier; Pincebourde, Sylvain

doi:10.1016/j.jtherbio.2015.11.011

Cited by 54 publications

(45 citation statements)

References 35 publications

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“…Surface temperature might be underestimated at large shooting distances. We chose a 30 degree angle from photographer to the ground in order to minimize distortion in measurement accuracy of photographs from the front to back of the image (Faye et al 2016). The FLIR E40 thermal imaging camera, which captures 76,000 samples per photograph, can accurately measure the temperature of a 1 cm 2 spot from more than 120 cm away.…”

Section: Discussionmentioning

confidence: 99%

Extreme thermal heterogeneity in structurally complex tropical rain forests

et al. 2016

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Most terrestrial species on Earth are ectothermic and track temperature at small spatial scales, from sun flecks to cool shaded spots. Current assessments of thermal heterogeneity in complex environments are predominately characterized by ambient temperature. This omission of solar radiation may lead to inaccurate conclusions regarding thermoregulation and distribution of species. We use thermal cameras to gather data on temperature heterogeneity in structurally complex rain forest environments. Using thermographic photographs, we capture the multidimensionality of climate created by vegetation by collecting over 76,000 temperature samples within approximately 1 m2 quadrats. The method was tested against three standard methods that record air temperature to determine possible omissions in capturing thermal heterogeneity in four geographic locations—Colombia, Borneo, Madagascar, and Australia. Across all locations, there was greater thermal heterogeneity in surface temperature than captured from ambient temperature technologies. Spatial variability in surface temperature on 1 d was greater than temporal variability of ambient temperature across the entire month, with extreme deviation from ambient temperatures. Importantly, when compared to the lower bounds for optimal performance for five tropical Anolis species, this technology captured thermal regimes that support the thermoregulatory needs of these species, whereas ambient air temperature methods suggested that these species would be in thermal debt. Sampling surface temperature at high resolutions across space in combination with intensive sampling of ambient temperature and informed spatial modeling should improve our understanding of the distribution of ectothermic species living within thermally heterogeneous environments.

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Section: Discussionmentioning

confidence: 99%

Extreme thermal heterogeneity in structurally complex tropical rain forests

et al. 2016

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“…Furthermore, if several objects are of similar distances from the camera, the information on relative temperature differences should be accurate compared to their absolute temperatures (Faye et al. , see Kim et al. for further detail).…”

Section: Methodsmentioning

confidence: 99%

“…However, for emissivity values between 0.94 and 0.96, which is reasonable for most vegetation, the error is~1°C (Aubrecht et al 2016). Furthermore, if several objects are of similar distances from the camera, the information on relative temperature differences should be accurate compared to their absolute temperatures (Faye et al 2016, see Kim et al 2016 for further detail). Distances of canopy surface types selected for analyses (deciduous canopy, evergreen canopy, flowers, and bark), measured with a laser range finder, were 57 m, 51 m, 143 m, and 57 m, respectively.…”

Section: Study Site and Instrumentationmentioning

confidence: 99%

Tropical forest temperature thresholds for gross primary productivity

et al. 2018

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Tropical forests are hyper‐diverse and perform critical functions that regulate global climate, yet they are also threatened by rising temperatures. Canopy temperatures depart considerably from air temperatures, sometimes by as much as air temperatures are projected to increase by the end of this century; however, canopy temperatures are rarely measured or considered in climate change analyses. Our results from near‐continuous thermal imaging of a well‐studied tropical forest show that canopy temperatures reached a maximum of ~34°C, and exceeded maximum air temperatures by as much as 7°C. Comparing different canopy surfaces reveals that bark was the warmest, followed by a deciduous canopy, flowers, and coolest was an evergreen canopy. Differences among canopy surfaces were largest during afternoon hours, when the evergreen canopy cooled more rapidly than other canopy surfaces, presumably due to transpiration. Gross primary productivity (GPP), estimated from eddy covariance measurements, was more strongly associated with canopy temperatures than air temperatures or vapor pressure deficit. The rate of GPP increase with canopy temperatures slowed above ~28–29°C, but GPP continued to increase until ~31–32°C. Although future warming is projected to be greater in high‐latitude regions, we show that tropical forest productivity is highly sensitive to small changes in temperature. Important biophysical and physiological characteristics captured by canopy temperatures allow more accurate predictions of GPP compared to commonly used air temperatures. Results suggest that as air temperatures continue to warm with climate change, canopy temperatures will increase at a ~40% higher rate, with uncertain but potentially large impacts on tropical forest productivity.

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“…An infrared camera (FLIR Systems, B335, Wilsonville, OR, USA), equipped with a macro lens (FLIR Systems, IR Lens 10 mm), was used to acquire instantaneously the thermal images of several leaves either exposed to solar radiation or shaded in the canopy. The camera had a spatial resolution of 0.49 mm (at a distance of 20 cm) and a thermal resolution of 0.05 °C (Faye et al ). Four sessions of image acquisition were done in 2012, on 23 July around noon, 8 August around noon and 16:00 and 17 August around 09:30.…”

Section: Methodsmentioning

confidence: 99%

Temperature heterogeneity over leaf surfaces: the contribution of the lamina microtopography

Saudreau¹,

Ezanic

Adam³

et al. 2017

Plant Cell & Environment

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Temperature is spatially heterogeneous over leaf surfaces, yet the underlying mechanisms are not fully resolved. We hypothesized that the 3D leaf microtopography determines locally the amount of incoming irradiation flux at leaf surface, thereby driving the temperature gradient over the leaf surface. This hypothesis was tested by developing a model of leaf temperature heterogeneity that includes the development of the leaf boundary layer, the microtopography of the leaf surface and the physiological response of the leaf. Temperature distributions under various irradiation loads (1) over apple leaves based on their 3D microtopography, (2) over simulated flat (2D) apple leaves and (3) over 3D leaves with a transpiration rate distributed as in 2D leaves were simulated. Accuracy of the predictions was quantified by comparing model outputs and thermographic measurements of leaf surface temperature under controlled conditions. Only the model with 3D leaves predicted accurately the spatial heterogeneity of surface temperature over single leaves, whereas the mean temperature was well predicted by both 2D and 3D leaves. We suggest that in these conditions, the 3D leaf microtopography is the primary driver of leaf surface heterogeneity in temperature when the leaf is exposed to a light/heat source.

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Distance makes the difference in thermography for ecological studies

Cited by 54 publications

References 35 publications

Extreme thermal heterogeneity in structurally complex tropical rain forests

Extreme thermal heterogeneity in structurally complex tropical rain forests

Tropical forest temperature thresholds for gross primary productivity

Temperature heterogeneity over leaf surfaces: the contribution of the lamina microtopography

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