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Isoprene emissions track the seasonal cycle of canopy temperature, not primary production: evidence from remote sensing

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Title: Isoprene emissions track the seasonal cycle of canopy temperature, not primary production: evidence from remote sensing
Authors: Foster, PN
Prentice, IC
Morfopoulos, C
Siddall, M
Van Weele, M
Item Type: Journal Article
Abstract: Isoprene is important in atmospheric chemistry, but its seasonal emission pattern – especially in the tropics, where most isoprene is emitted – is incompletely understood. We set out to discover generalized relationships applicable across many biomes between large-scale isoprene emission and a series of potential predictor variables, including both observed and model-estimated variables related to gross primary production (GPP) and canopy temperature. We used remotely sensed atmospheric concentrations of formaldehyde, an intermediate oxidation product of isoprene, as a proxy for isoprene emission in 22 regions selected to span high to low latitudes, to sample major biomes, and to minimize interference from pyrogenic sources of volatile organic compounds that could interfere with the isoprene signal. Formaldehyde concentrations showed the highest average seasonal correlations with remotely sensed (r = 0.85) and model-estimated (r = 0.80) canopy temperatures. Both variables predicted formaldehyde concentrations better than air temperature (r= 0.56) and a "reference" isoprene model that combines GPP and an exponential function of temperature (r = 0.49), and far better than either remotely sensed green vegetation cover, fPAR (r = 0.25) or model-estimated GPP (r = 0.14). Gross primary production in tropical regions was anti-correlated with formaldehyde concentration (r = −0.30), which peaks during the dry season. Our results were most reliable in the tropics, where formaldehyde observational errors were the least. The tropics are of particular interest because they are the greatest source of isoprene emission as well as the region where previous modelling attempts have been least successful. We conjecture that positive correlations of isoprene emission with GPP and air temperature (as found in temperate forests) may arise simply because both covary with canopy temperature, peaking during the relatively short growing season. The lack of a general correlation between GPP and formaldehyde concentration in the seasonal cycle is consistent with experimental evidence that isoprene emission rates are largely decoupled from photosynthetic rates, and with the likely adaptive significance of isoprene emission in protecting leaves against heat damage and oxidative stress.
Issue Date: 1-Jul-2014
Date of Acceptance: 16-May-2014
URI: http://hdl.handle.net/10044/1/69646
DOI: https://dx.doi.org/10.5194/bg-11-3437-2014
ISSN: 1726-4170
Publisher: Copernicus Publications
Start Page: 3437
End Page: 3451
Journal / Book Title: Biogeosciences
Volume: 11
Issue: 13
Copyright Statement: © 2014 Author(s). This work is distributed under the Creative Commons Attribution 3.0 License (https://creativecommons.org/licenses/by/3.0/).
Keywords: Science & Technology
Life Sciences & Biomedicine
Physical Sciences
Ecology
Geosciences, Multidisciplinary
Environmental Sciences & Ecology
Geology
TERRESTRIAL ECOSYSTEMS
MONOTERPENE EMISSION
MODEL
FORMALDEHYDE
CLIMATE
THERMOTOLERANCE
PHOTOSYNTHESIS
VARIABILITY
VEGETATION
MEMBRANES
04 Earth Sciences
05 Environmental Sciences
06 Biological Sciences
Meteorology & Atmospheric Sciences
Publication Status: Published
Open Access location: https://www.biogeosciences.net/11/3437/2014/bg-11-3437-2014.pdf
Online Publication Date: 2014-07-01
Appears in Collections:Department of Life Sciences
Grantham Institute for Climate Change