Photosynthetic temperature responses in leaves and canopies: why temperature optima may disagree at different scales

作者：Dushan Kumarathunge, Belinda E. Medlyn, John E. Drake, Martin G. De Kauwe, Mark G. Tjoelker, Michael J. Aspinwall, Craig V. M. Barton, Courtney Campany, Kristine Y. Crous, Jinyan Yang, Mingkai Jiang · 发表于：Tree Physiology · 年份：2024 · DOI：10.1093/treephys/tpae135 · 被引用次数：16 · 研究领域：Plant Ecology and Soil Science、Plant Water Relations and Carbon Dynamics、Greenhouse Technology and Climate Control

Understanding how canopy-scale photosynthesis responds to temperature is of paramount importance for realistic prediction of the likely impact of climate change on forest growth. The effects of temperature on leaf-scale photosynthesis have been extensively documented but data demonstrating the temperature response of canopy-scale photosynthesis are relatively rare, and the mechanisms that determine the response are not well quantified. Here, we compared leaf- and canopy-scale photosynthesis responses to temperature measured in a whole-tree chamber experiment and tested mechanisms that could explain the difference between leaf and crown scale temperature optima for photosynthesis. We hypothesized that (i) there is a large contribution of non-light saturated leaves to total crown photosynthesis, (ii) photosynthetic component processes vary vertically through the canopy following the gradient in incident light and (iii) seasonal temperature acclimation of photosynthetic biochemistry has a significant role in determining the overall temperature response of canopy photosynthesis. We tested these hypotheses using three models of canopy radiation interception and photosynthesis parameterized with leaf-level physiological data and estimates of canopy leaf area. Our results identified the influence of non-light saturated leaves as a key determinant of the lower temperature optimum of canopy photosynthesis, which reduced the temperature optimum of canopy photosynthesis by 6-8 °C compar...