Thermal imagery of woodland tree canopies provides new insights into drought-induced tree mortality

Our understanding of how water dynamics determines the probability of tree mortality during drought is incomplete. Here we help address this shortcoming by coupling approaches from the disciplines of ecophysiology, geophysics and remote sensing in a woodland ecosystem undergoing protracted drying. W...

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Bibliographic Details
Published in:The Science of the total environment 2022-08, Vol.834, p.155395-155395, Article 155395
Main Authors: Drake, Paul L., Callow, Nikolaus J., Leopold, Matthias, Pires, Rodrigo N., Veneklaas, Erik J.
Format: Article
Language:English
Subjects:
Banksia
Leaf temperature
Mediterranean
Transpiration
Water stress
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Summary:Our understanding of how water dynamics determines the probability of tree mortality during drought is incomplete. Here we help address this shortcoming by coupling approaches from the disciplines of ecophysiology, geophysics and remote sensing in a woodland ecosystem undergoing protracted drying. Water uptake and use strategies varied between the dominant canopy species of the ecosystem. At one extreme were species that tightly regulate their water status, which is broadly consistent with the definition of isohydry. The higher leaf temperatures revealed by thermal imagery of these isohydric species are likely a reflection of reduced latent cooling owing to a stringent control of transpiration rate. Where silty sediments occur in the root zone, this strategy may have the effect of limiting the water sources available to these species during prolonged drought because of an insufficient hydraulic gradient for water uptake. In contrast were species that allowed their water status to fluctuate, operating in a fashion more consistent with anisohydry. For these species, latent cooling owing to relatively high transpiration rates maintained leaf temperatures near, or below, the ambient air temperature. The resulting drawdown in leaf water potential between soil and leaves in these anisohydric species may generate a sufficient hydraulic gradient to enable water uptake from silty soil during seasonal or prolonged droughts. In this way the spatial distribution of fine textured soil could indicate areas where the isohydric hydraulic control strategy is disadvantageous during prolonged droughts or where annual soil water recharge has fallen below a critical threshold. [Display omitted] •The relationship between water dynamics and tree mortality is not fully resolved.•Thermal imagery confers specific stomatal control strategies.•Access to water during drought hinges on a sufficient hydraulic gradient.•Incomplete rehydration due to a drying climate will disadvantage isohydric species.
ISSN:0048-9697
1879-1026
DOI:10.1016/j.scitotenv.2022.155395