What can we learn from year-round BVOC disjunct eddycovariance measurements? A case example from a temperate forest

Long term ecosystem-scale biogenic volatile organic compounds (BVOC) flux measurements by
disjunct eddy-covariance are needed to determine and characterize the BVOC
emissions/depositions from episodic events (budburst, stress) as well as the continuous
emission/deposition during vegetation growth and its seasonal evolution in interaction with
climate and environment. If the data coverage is sufficient, this technique has the potential to
provide a dataset covering the whole spectrum of meteorological and phenological conditions
encountered by the studied ecosystem ending in a statistically more robust dataset than what can
be provided by other BVOC measurement techniques. In addition, long term measurements allow
in Oxygenated VOCs (OVOCs) depositions to be estimated in a realistic manner with is not the
case with the enclosure technique.
Here we present a year-round campaign of disjunct eddy-covariance BVOC fluxes above a mixed
temperate forest performed in the frame of the IMPECVOC (Impact of Phenology and
Environmental Conditions on BVOC Emissions from Forest Ecosystems) project. We will
analyse the three main BVOC species (isoprene/monoterpenes and methanol) in order to illustrate
the interest of long-term flux measurements by investigating the main driving variables and the
underlying mechanisms of emission/deposition, how de novo carbon allocation to the
isoprene/monoterpenes skeleton structure is altered through the time. For methanol, we will show
the importance of deposition on a long-term basis and use an empirical model to discriminate the
physical and physiological components of the exchange.