Agriculture Reference
In-Depth Information
In addition, in
C. incanus
and
M. communis
litter the decay constants of lignin in the first
year was higher than that of organic matter suggesting that lignin was more quick degraded
than other litter components (Table 2 and Table 5).
Table 5. Residual lignin amount, as per cent of the initial (T
0
) after about 1 year (T
1
), 2
years (T
2
) and 3 years (T
3
) of decomposition in the eight litters. The lignin decay
constant (
K
per year) for the first year (
K
1
), for the second (
K
2
)
and third year (K
3
) were
also reported
Residual amount
(% of the initial)
Lignin decay rate
K
y
-1
T
1
T
2
T
3
K
1
K
2
K
3
Fagus sylvatica
66
41
31
0.41
0.47
0.39
Abies alba
68
63
53
0.38
0.08
0.21
Myrtus communis
44
37
22
0.80
0.14
0.59
Cistus incanus
68
39
31
0.38
0.82
0.31
Quercus ilex
100
~100
~100
0
0
0
Phillirea angustifolia
90
-
-
0.10
-
-
Pinus laricio
~100
~100
87
0
0
0.07
Pinus pinea
-
-
-
-
-
-
In this view,
F. sylvatica
and also
C. incanus
showed a lignin decay constant higher than
that of organic matter in the second year. The other litters showed lower values.
To degrade lignin, Mn, among other nutrients, seems to be essential. High level of Mn
can enhance the production of Mn peroxidase, a lignin degrading enzyme having Mn as
cofactor (Perez and Jeffrey, 1992; Archibald and Roy, 1992).
Among the studied species
P. laricio
had the highest initial Mn concentration and
P.
angustifolia
the lowest (Table 4). For the other litters the values ranged from 40 to 70 μg g
-1
.
The lignin decay constants of our litters appeared positively related to initial Mn
concentration (K
1
-Mn for P< 0.05; K
2
-Mn for P<0.01). However, in the advanced decay
phase, when lignin degraded very slowly, Mn appeared no a stimulating factor but rather an
inhibitor because a negative relationship was found between lignin decay constant during the
third year and Mn initial content (P<0.05). The lignin decay constants were also negatively
related to initial N content (K
1
-N for P<0.001; K
2
-N n.s.; K
3
-N for P<0.01). On the contrary,
lignin decomposition rate was not correlated to climatic conditions.
Q
UALITY
E
FFECT ON
D
ECOMPOSITION
R
ATE
Quality effect on decomposition rate was tested incubating different litter types in a same
stand.
In this view, the dead needles of
P. laricio
and
P. pinea
, collected in their woods in the
Fossiata Forest and Tirone Alto-Vesuvio Reserve, respectively, as well as of
P. sylvestris
collected in Jädraås (Sweeden) were simultaneously incubated in the
P. laricio
and in the
P.
pinea
woods.
Pine litters differed in their chemical composition. The highest content of N, S, Mg and
Ca, among the macronutrients, were found in the
P. pinea
litter (Table 4) while the lowest
ones in the
P. sylvestris
litter (4.9 mg g
-1
; 0.66 mg g
-1
; 0.30 mg g
-1
; 3.44 mg g
-1
, respectively).
