Environmental Engineering Reference
In-Depth Information
Fig. 11.6
Average
(Taverage), maximum
(Tmax) and minimum (Tmin)
air temperature values,
and rainfall amount in the
Serdiana site
Fig. 11.7
Energy balance
components in the Serdiana
site
the accuracy of measured data. A discrepancy between 20 and 30 % from the clo-
sure is commonly observed in surface energy budget measurements (Wilson et al.
2002
), and the closure observed in this research was in line with those reported in
the literature (Fig.
11.7
). More available energy (
R
n
-
G
) was partitioned to latent heat
flux (
LE
) than sensible heat flux (
H
) in June and July (
LE
>
H
), presumably because
there was adequate water available from irrigation. From late August to the end of
the year, energy was approximately equally partitioned between
H
and
LE
.
Carbon exchanges between the ecosystem and the atmosphere were partitioned
in NEE, GPP, and ecosystem respiration (Reco). Daily values revealed that NEE
was directly affected by high temperature and rainfall (Fig.
11.8
a). In particular, a
NEE value close to zero was observed in Day Of Year (DOY) 205 when maximum
air temperature was about 42 °C. Also, picks in NEE positive values in DOY 253
and 267 were probably due to the soil microbes respiration, which was stimulated
by the first rainfall after the summer. Monthly values revealed two periods with
different ecophysiological behaviour: the vineyard acted as a C
sink
from June to
September (NEE negative values), and C
source
in winter (NEE positive values)
(Fig.
11.8
b). During the growing period (June-September), the vineyard was able
to accumulate about 170 g C, even if the amount varied between months related
to weather conditions. From June to the end of the year, the vineyard was a net C
sink
, with cumulated NEE value of 89 g C m
−
2
y
−
1
.
