VOLATILE
ORGANIC COMPUOUNDS IN A VOLATILE WORLD
An
exploration of forest eco-physiological model responses to
the inclusion of biogenic VOC emission processes, and a model
comparison.
TREVOR
KEENAN, SANTI SABATE, and CARLOS A. GRACIA
CREAF, Autonomous University of Barcelona, Barcelona, Spain.
Email: t.keenan - at - creaf.uab.es
Phone: +34 93 581 2915
Department of Ecology, University of Barcelona.
Abstract:
Plants
emit a broad spectrum of biological volatile organic compounds
that play multiple roles in plant protection. These emissions
are important in atmospheric chemistry, constituting a major
source of non-methane atmospheric hydrocarbons, but also use
a potentially large amount of assimilated carbon. The predicted
extent, and affect, of this loss of assimilated carbon is
investigated here, having been reported to range from 0.1%
to 50% in previous Mediterranean field studies. Various emission
models were applied to predict the emission of Isoprene and
Monoterpene. The models compared range from purely empirical
based algorithms, to process based models linked to leaf photosynthetic
characteristics. These models were coupled to the Gotilwa+
terrestrial biogeochemical ecosystem model to scale leaf emissions
to the stand level.
Gotilwa+
is a process based model which works both at the individual
tree scale and the stand level, and simulates carbon and water
uptake and fluxes through forests in different environments
(from North boreal Europe to Mediterranean), for different
single tree species stands (coniferous or broad-leaved, evergreen
or deciduous), in changing environmental conditions, either
due to climate or to management regimes.
Simulation
results run over forested areas in Europe on a 10’x10’
pixel resolution show that biogenic volatile organic compound
emissions, though often an overlooked element of forest growth
models, play a significant role in the processing of carbon
produced by photosynthesis in certain species. GPP can be
significantly affected, and the affects on NPP are even more
profound due to feedbacks in the ecosystem. High emissions
in stressed periods such as drought can also alter the mortality
rate in forest stands. This is of particular importance in
making accurate predictions on forest ecosystem responses
to climate change scenarios, and should be incorporated into
any such modelling attempt.
Keywords:
Volatile Organic Compounds, Emissions, Ecosystem Models
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