Environmental Engineering Reference
In-Depth Information
(1992-2006) and 3,113 ha of poplar plantations (2002-2006) have been estab-
lished in the Region.
The average density per hectare in mixed broadleaf plantations was equal to
1,690 29 stumps ha
−
1
. The species composition was quite varied although
there was a prevalence of common ash (
Fraxinus excelsior
L.), cherry (
Prunus
avium
L.), maple (
Acer campestre
L.) and oak (
Quercus robur
L.). Aboveground
carbon stock (stems and branches) in the selected plantations ranged from 1.5 to
37.3 Mg C ha
−
1
at 3 and 23 years, respectively.
Modeled aboveground carbon stock grew asymptotically with stand age, and a
good correlation between modeled and measured values was found (Fig.
13.2
a).
On average, mean aboveground carbon stock was 25.3 Mg C ha
−
1
(Table
13.1
).
According to the model, maximum aboveground NPP is reached at 9-10 years
(3.4 Mg C ha
−
1
y
−
1
) and then it gradually decreases to 0.4 Mg C ha
−
1
y
−
1
at
23 years. Aboveground productivity is therefore rather high even though maxi-
mum NPP is reached quite early probably because of the high stand density and
the absence of thinnings. Magnani et al. (
2005
) reported an aboveground NPP of
1.8 Mg C ha
−
1
y
−
1
for a 12 year old plantation. The same authors showed that
maximum NEE was reached at 9-10 years. In our plantation, at the same age
aboveground NPP was 2.7 Mg C ha
−
1
y
−
1
. Considering all the realized plantations
(1992-2006), mean annual aboveground NPP is 2.4 Mg C ha
−
1
y
−
1
, a value lower
than 4.3 Mg C ha
−
1
y
−
1
estimated by Anderle et al. (
2002
).
The average density per hectare in poplar plantations was around 204 stems
ha
−
1
. Aboveground carbon stock ranged between 2.7 and 56.1 Mg C ha
−
1
in 3
and 9 year old stands, respectively. A good agreement between measured values
and values reported by the yield table for Veneto (Famiglietti
1968
) was found
(Fig.
13.2
b). Aboveground NPP, derived from the yield table, was between 0.9 and
12.0 Mg C ha
−
1
y
−
1
, underlying the very high productivity of this species.
A good correlation between soil carbon and aboveground carbon stocks was
found in both chronosequences (Table
13.2
). Soil carbon stock ranged between
49.8 and 56.9 Mg C ha
−
1
at 0 and 30 years in mixed broadleaf plantations and
Table 13.1
Average carbon stock and average annual stock change in different pools (above-
ground, roots and soil) for mixed broadleaf and poplar plantations in Friuli Venezia Giulia
Aboveground
Roots
Soil
−
1
)
Mixed broadleaf
25.3
6.6
54.3
Carbon stock (Mg C ha
40.3
10.5
77.0
Poplar
Carbon flux (Mg C ha
−
1
y
−
1
)
Mixed broadleaf
2.4
0.6
0.4
9.4
2.4
1.1
Poplar
Table 13.2
Regression coefficients between soil carbon stock and aboveground carbon stock in
both the chronosequences (Y
=
a X
+
b)
a
R
2
b
n
p
-value
0.18
49.73
0.96
4
0.02
Mixed broadleaf
Poplar
1.12
68.58
0.76
5
0.06