Environmental Engineering Reference
In-Depth Information
isoprenoid emission model is complex due to the different emission mechanisms
followed by monoterpenes in Mediterranean plant species. While some decidu-
ous and evergreen trees, such as
Quercus ilex
L. (Ciccioli et al.
1997
) and
Fagus
silvatica
L. (Dindorf et al.
2006
; Moukhtar et al.
2005
), emit monoterpenes with
the same temperature and light dependent mechanism followed by isoprene in
isoprene-emitting plants (Guenther et al.
1995
), other evergreen conifers, such
as
Pinus cembra
L., emit monoterpenes according to a temperature-dependent
mechanism (Steinbrecher et al.
2009
). Finally, in some conifers, such as
Pinus
pinea
L. (Staudt et al.
2000
) and
Abies alba
Mill. (Steinbrecher et al.
2009
) both
mechanisms appear to be active. Complexity is increased by the fact that the
basal emission of isoprenoids (i.e. the emission measured at 1,000 µE m
−
2
s
−
1
of Photosynthetically Active Radiation-PAR-and 30 °C) is not constant through
the year, but follows a distinct seasonal trend also in evergreen species (Ciccioli
et al.
2003
; Staudt et al.
2000
; Steinbrecher et al.
2009
). To meet both the res-
olution and reactivity requirements, a GIS-based model was developed in the
CarboItaly Project so to predict BVOC emission from the Italian forest eco-
systems. The possibility to generate emission maps for isoprene and individual
monoterpenes at high spatial (1 km
2
) and temporal resolutions (<12 h) was con-
sidered to be a fundamental tool to assess the amount of NEP lost in the form of
reduced carbon, and to predict the impact of BVOC emission on the production
of secondary pollutants in Italy. The performances of the model were verified by
comparing the predictions with BVOC fluxes measured in previous years but also
with BVOC fluxes measured in a CarboItaly site using the gradient method with
tethered balloon.
3.2 Model Description and Its Main Properties
Vegetation maps of Italy with a spatial resolution (grid cell size) of 1 km
2
were
produced for the year 2006, by combining the information of the Corine IV
Land Cover 2000 (CLC) system with those of the National Forest Inventory
(INFC
2005
), that was validated through field observations carried out at a very
detailed scale (administrative regions). By using this approach, it was possible to
define vegetation classes according to their potential for isoprene and individual
monoterpene emission. For each vegetation species, a database of isoprene and
individual monoterpene emissions was generated by taking into account the dif-
ferent processes leading to their emission. In particular, the relative contribu-
tion to the basal emission coming from both the temperature dependent pool (T)
and the light and temperature dependent pool (T
+
L) were assessed for each
monoterpene. For the most representative vegetation species present in Italy,
such as
Fagus sylvatica, Quercus cerris
L.
, Castanea sativa
Mill.
, Quercus ilex
L.
, Quercus suber
L. and few others, emission values were also verified through
