Convergence in the temperature response of leaf respiration across biomes and plant functional types

Abstract

Plant respiration constitutes a massive carbon flux to the atmosphere, and a major control on the evolution of the global carbon cycle. It therefore has the potential to modulate levels of climate change due to the human burning of fossil fuels. Neither current physiological nor terrestrial biosphere models adequately describe its short-term temperature response, and even minor differences in the shape of the response curve can significantly impact estimates of ecosystem carbon release and/or storage. Given this, it is critical to establish whether there are predictable patterns in the shape of the respiration-temperature response curve, and thus in the intrinsic temperature sensitivity of respiration across the globe. Analyzing measurements in a comprehensive database for 231 species spanning 7 biomes, we demonstrate that temperature-dependent increases in leaf respiration do not follow a commonly used exponential function. Instead, we find a decelerating function as leaves warm, reflecting a declining sensitivity to higher temperatures that is remarkably uniform across all biomes and plant functional types. Such convergence in the temperature sensitivity of leaf respiration suggests that there are universally applicable controls on the temperature response of plant energy metabolism, such that a single new function can predict the temperature dependence of leaf respiration for global vegetation. This simple function enables straightforward description of plant respiration in the land-surface components of coupled earth system models. Our cross-biome analyses shows significant implications for such fluxes in cold climates, generally projecting lower values compared with previous estimates.temperature sensitivity | climate models | carbon exchange | Q 10 | thermal response P lant respiration provides continuous metabolic support for growth and maintenance of all tissues and contributes ∼60 Pg C y −1 to the atmosphere (1, 2), with ∼50% of the carbon (C) released by whole-plant respiration from leaves (3). As rates of leaf respiration (R) vary substantially with changes in temperature (T) (4, 5), even slight increases in ambient T can lead to increases in the flux of carbon dioxide (CO 2 ) from leaves to the atmosphere. This has the potential to create concomitant decreases in net primary productivity, and affect the implications of fossil fuel burning by contributing additionally to atmospheric CO 2 levels due to any imposed surface-level global warming. Hence, quantification of the T response of leaf R, and how this response may vary across diverse ecosystems and plant species, is critical to current estimations and future projections of the global carbon cycle (6-8). Evaluating how leaf R relates to T in terrestrial plants will clarify fundamental controls on energy metabolism and enable more accurate parameterization, as leaf R, in addition to photosynthesis (9, 10), has been identified as a major source of uncertainty in models of the global carbon cycle (8, 11). The response of leaf R to T differs in both ma...

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