Agriculture Reference
In-Depth Information
Among the lignolytic enzymes, laccase (EC 1.10.3.2) remained at low activity during the
first 6-8 months for
Quercus
and
Cistus
and
Myrtus
, respectively (Figure 8). Subsequently, it
increased rapidly in correspondence of the increase of fungal biomass and a strong correlation
was found between these parameters (P<0.001). Such activity was specific for each litter type
but no significant differences were found among incubation sites for
Quercus
litter or
between the microsites for
Cistus
litter. Therefore a qualitative change of the microbial
community occurred when the litters colonized by laccase producing fungi that take over
when the opportunist's microorganisms start to decrease.
Other enzymes like α- and β-amylase, degrading the starch, were controlled by the
substrate availability. They were high at the start of incubation and declined quickly as
decomposition progressed in all incubation sites (Figure 8). The starch, in fact, degrades
easily with respect to the other cellular components. The amylolytic microorganisms, r-
strategists, colonize quickly and easily their substrate, and quickly disappear in lack of it.
It is to emphasize that after 2 years of decomposition the cellulolytic and ligninolitic
activities were persistent because their substrate were not exhausted.
By comparison of the litters (Figure 8),
Quercus ilex
showed a higher activities than
Cistus
and
Myrtus
(Fioretto et al., 2000; Papa, 2000), in spite of its lower decomposition rate.
This discrepancy could derive by the fact that the activities are assayed in vitro in saturating
substrate where the effect of possible inhibitor compounds of the litter and/or produced by the
colonizing microorganisms disappears. Peroxidase activity, nevertheless, in
Cistus
was below
the detection limit of the assay for about a year of decay and a low activity was measured
after.
6.5
a
6
5.5
5
4.5
6.5
b
6
5.5
5
4.5
3
6
9
12
15
18
21
24
Jan
Oct
Jan
Apr
Jul
Oct
Apr
Jul
decomposition time (months)
Figure 9. Laccase (A) and peroxidase (B) isoforms during
Quercus ilex
leaf litter decomposition in the
holm-oak wood of WWF Oasis “Bosco di San Silvestro”. Data from Di Nardo et al., 2004.
