TY - JOUR

T1 - Thermal sensitivity across forest vertical profiles: patterns, mechanisms, and ecological implications

AU - Vinod, Nidhi

AU - Slot, Martijn

AU - McGregor, Ian

AU - Ordway, Elsa

AU - Smith, Marielle

AU - Taylor, Tyeen C.

AU - Sack, Lawren

AU - Buckley, Thomas

AU - Anderson-Teixeira, Kristina

PY - 2023/1/1

Y1 - 2023/1/1

N2 - Rising temperatures are influencing forests on many scales, with potentially strong variation vertically across forest strata. Using published research and new analyses, we evaluate how microclimate and leaf temperatures, traits, and gas exchange vary vertically in forests, shaping tree, and ecosystem ecology. In closed-canopy forests, upper canopy leaves are exposed to the highest solar radiation and evaporative demand, which can elevate leaf temperature (Tleaf), particularly when transpirational cooling is curtailed by limited stomatal conductance. However, foliar traits also vary across height or light gradients, partially mitigating and protecting against the elevation of upper canopy Tleaf. Leaf metabolism generally increases with height across the vertical gradient, yet differences in thermal sensitivity across the gradient appear modest. Scaling from leaves to trees, canopy trees have higher absolute metabolic capacity and growth, yet are more vulnerable to drought and damaging Tleaf than their smaller counterparts, particularly under climate change. By contrast, understory trees experience fewer extreme high Tleaf's but have fewer cooling mechanisms and thus may be strongly impacted by warming under some conditions, particularly when exposed to a harsher microenvironment through canopy disturbance. As the climate changes, integrating the patterns and mechanisms reviewed here into models will be critical to forecasting forest–climate feedback.

AB - Rising temperatures are influencing forests on many scales, with potentially strong variation vertically across forest strata. Using published research and new analyses, we evaluate how microclimate and leaf temperatures, traits, and gas exchange vary vertically in forests, shaping tree, and ecosystem ecology. In closed-canopy forests, upper canopy leaves are exposed to the highest solar radiation and evaporative demand, which can elevate leaf temperature (Tleaf), particularly when transpirational cooling is curtailed by limited stomatal conductance. However, foliar traits also vary across height or light gradients, partially mitigating and protecting against the elevation of upper canopy Tleaf. Leaf metabolism generally increases with height across the vertical gradient, yet differences in thermal sensitivity across the gradient appear modest. Scaling from leaves to trees, canopy trees have higher absolute metabolic capacity and growth, yet are more vulnerable to drought and damaging Tleaf than their smaller counterparts, particularly under climate change. By contrast, understory trees experience fewer extreme high Tleaf's but have fewer cooling mechanisms and thus may be strongly impacted by warming under some conditions, particularly when exposed to a harsher microenvironment through canopy disturbance. As the climate changes, integrating the patterns and mechanisms reviewed here into models will be critical to forecasting forest–climate feedback.

KW - climate change

KW - ecosystem

KW - forest

KW - gas exchange

KW - leaf temperature

KW - leaf traits

KW - microclimate

KW - vertical gradients

U2 - 10.1111/nph.18539

DO - 10.1111/nph.18539

M3 - Review article

VL - 237

SP - 22

EP - 47

JO - New Phytologist

JF - New Phytologist

SN - 0028-646X

IS - 1

ER -