TY - JOUR

T1 - The effects of glacial atmospheric CO2 concentrations and climate on isoprene emissions by vascular plants

AU - Possell, Malcolm

AU - Hewitt, C. N.

AU - Beerling, D J

PY - 2005/1

Y1 - 2005/1

N2 - Isoprene (C5H8) emissions by terrestrial vegetation vary with temperature and light intensity, and play an important role in biosphere-chemistry-climate interactions. Such interactions were probably substantially modified by Pleistocene climate and CO2 cycles. Central to understanding the nature of these modifications is assessment and analysis of how emissions changed under glacial environmental conditions. Currently, even the net direction of change is difficult to predict because a CO2-depleted atmosphere may have stimulated emissions compensating for the negative impacts of a cooler climate. Here, we address this issue and attempt to determine the direction of change from an experimental standpoint by investigating the interaction between isoprene emissions and plant growth of two known isoprene-emitting herbaceous species (Mucuna pruriens and Arundo donax) grown at glacial (180 ppm) to present (366 ppm) CO2 levels. We found a significant enhancement of isoprene emissions per unit leaf area in M. pruriens under subambient CO2 concentrations relative to ambient controls but not for A. donax. In contrast, canopy emissions remained unaltered for both plant species because enhanced leaf emissions were offset by reductions in biomass and leaf area. Separate growth experiments with M. pruriens revealed that lowering day/night temperatures by 5degreesC decreased canopy isoprene emissions irrespective of the CO2 level. Incorporation of these results into a simple canopy emissions model highlights their potential to attenuate reductions in the total isoprene flux from forests under glacial conditions predicted by standard models.

AB - Isoprene (C5H8) emissions by terrestrial vegetation vary with temperature and light intensity, and play an important role in biosphere-chemistry-climate interactions. Such interactions were probably substantially modified by Pleistocene climate and CO2 cycles. Central to understanding the nature of these modifications is assessment and analysis of how emissions changed under glacial environmental conditions. Currently, even the net direction of change is difficult to predict because a CO2-depleted atmosphere may have stimulated emissions compensating for the negative impacts of a cooler climate. Here, we address this issue and attempt to determine the direction of change from an experimental standpoint by investigating the interaction between isoprene emissions and plant growth of two known isoprene-emitting herbaceous species (Mucuna pruriens and Arundo donax) grown at glacial (180 ppm) to present (366 ppm) CO2 levels. We found a significant enhancement of isoprene emissions per unit leaf area in M. pruriens under subambient CO2 concentrations relative to ambient controls but not for A. donax. In contrast, canopy emissions remained unaltered for both plant species because enhanced leaf emissions were offset by reductions in biomass and leaf area. Separate growth experiments with M. pruriens revealed that lowering day/night temperatures by 5degreesC decreased canopy isoprene emissions irrespective of the CO2 level. Incorporation of these results into a simple canopy emissions model highlights their potential to attenuate reductions in the total isoprene flux from forests under glacial conditions predicted by standard models.

KW - Arundo donax

KW - canopy-scale emissions

KW - glacial climates

KW - isoprene

KW - modelling

KW - Mucuna pruriens

KW - photosynthesis

KW - subambient CO2 concentrations

KW - ELEVATED CO2

KW - MONOTERPENE EMISSION

KW - CARBON-DIOXIDE

KW - QUERCUS-PUBESCENS

KW - ORGANIC-COMPOUNDS

KW - STOMATAL DENSITY

KW - GAS-EXCHANGE

KW - ASPEN LEAVES

KW - CH4 INCREASE

KW - PHOTON FLUX

U2 - 10.1111/j.1365-2486.2004.00889.x

DO - 10.1111/j.1365-2486.2004.00889.x

M3 - Journal article

VL - 11

SP - 60

EP - 69

JO - Global Change Biology

JF - Global Change Biology

SN - 1354-1013

IS - 1

ER -