Agriculture Reference
In-Depth Information
Table 1. Some climatic and edaphic characteristics of the studied sites (Continued)
Golia
Forest
Castel
Volturno
Reserve
Taburno-
Camposauro
WWF
Oasis
S.Silvestro
Tirone Alto
Vesuvio
Reserve
(Terzigno)
Soil pH
5.5
8* 8.5**
7.8***
6.2
7.0
6.0
Soil organic matter
content (%)
8.7
2.2* 4.1**
13.6***
19
13.5
6.1
Nitrogen content (%)
0.22
0.19* 0.21**
n.d.***
0.9° 0.65°°
0.5
0.3
C/N ratio
21.5
6.9* 11.4**
n.d.***
16° 14°°
26
24
* under
C. incanus
shrubs; ** under
M. communis
shrubs; *** under
P. angustifolia
shrubs; ° Beech
stand, °° Beech-fir stand
n.d. no determined
Data from: Virzo De Santo et al., 1993; Fioretto et al., 2001; De Marco et al., 2004; Papa et al., 2002
The litters showed different litter mass loss rates (Figure 2). The leaf litter of
M.
communis
and
C. incanus
showed the highest accumulated mass loss at about 2 years of
decomposition. For these two litters the degradation went on and after 3 years (data not
shown) the masses lost were about 90% and 70%, respectively (Fioretto et al., 2005 a). Lower
mass loss rates were observed in the litters of
F. sylvatica
,
A. alba
,
Q. ilex
and finally by
P.
laricio
and
P. pinea
. The two latter litters lost only about 20% of the initial mass after two
years.
P. angustifolia
litter showed a different pattern of mass loss. In fact, during the first
100 days of exposure it lost about 25 % of the initial mass, but subsequently further losses
were not recorded, suggesting that it quickly reached limit values of decomposition.
The differences in decomposition rates among the species really emerge by comparing
the decay constants (Table 2). For all species, apart from
P. angustifolia
, the decay constant
values suggested that the decomposition could be divided in two intervals: the first year of
decay and the remaining period of about 400-480 days.
M. communis
had the highest decay
constant in both periods.
C. incanus
, that among the species showed a middle constant value
in the first year around 59% of that of
M. communis
, increased its decomposition rate in the
second year retaining about the same difference with
M. communis
.
F. sylvatica
and
A. alba
,
that had the highest decay constants in the first year, even if lower than that of
M. communis
,
reduced such rate to 1/3 and 1/4, respectively, in the remaining period.
Q. ilex
and
P. pinea
litter showed the same constant values in the first year and in the second year, even if they
were reduced to 50%. Finally,
P. laricio
had the lowest decay constant among the tested
species in the first year but not after.
The mass loss of all the litters at the end of the first year of decomposition showed a
positive correlation, even if not statistically significant, with the Lang aridity index (annual
precipitation/annual mean temperature). One of the main limiting factors in Mediterranean
environments is the summer aridity, therefore an increase of precipitations or a decrease of
temperature promotes the decomposition rate. By comparing the measured mass loss with
those of the other litter types in the Mediterranean area (Table 3), it emerges that, because the
