LEAF LITTER DECOMPOSITION DYNAMICS IN MEDITERRANEAN AREA - Soil Ecology Research Developments - page 48

microsites (under Cistus or Myrtus shrubs). Nevertheless, the effect of different rhizosphere
microbial populations could not be excluded and the contrasting data of mass loss dynamic
and microbial activity could depend on complex interaction among litter quality, microbial
communities colonizing litters as well as rizhosphere communities.
The decomposition rate of Fagus sylvatica litter showed similar results. It was higher in
the beech stand than in a beech-fir stand of Monte Taburno during the first 15 months of
exposition (Figure 7). Its higher decay rate could be related to different microclimatic
condition as well as to interaction among beech, fir and decomposers (Virzo De Santo et al.,
1985). Similar differences were also found by Herlitzius (1983) for beech leaf litter exposed
in beech and Picea abies woods.

70

beech-fir
beech

60

50

40

30

20

10

0

0 100 200 300 400 500 600 700 800 900

decomposition time (days)

Figure 7. Accumulated mass loss versus decomposition time of Fagus sylvatica litter incubated in a
beech stand and a fir-beech stand on Monte Taburno (Campania Apennines, South Italy). Data from
Virzo De Santo et al., 1985.

M ICROBIAL A CTIVITY D URING D ECOMPOSITION

Water availability is the main factor affecting microorganism activities in the
Mediterranean area as suggested by the strong correlation between soil and litter water
content and microbial respiration (Papa et al., 2002; Fioretto et al., 1998; 2000; 2001). So,
even if microbial respiration generally increases with temperature, it was at the lowest level in
hot and dry summer and at highest level in spring and autumn for the needle litter of the three
pine types in P. laricio wood either as well as for Q. ilex litter in the three relative stands and
for M. communis and C.incanus litters in the low maquis (Fioretto et al., 1998; 2000; 2001 b).
Similar seasonal trend was also evidenced by litter enzyme activities (Figure 8). The
extractable activities of cellulase (EC 3.2.1.4) and xylanase (E.C 3.2.1.8), degrading cellulose
and hemicellulose, respectively, as well as of peroxidase (EC 1.11.1.7), lignolytic enzymes,
showed seasonal variations in Cistus , Myrtus and Quercus litters during the decay process
(Figure 8) (Fioretto et al 2000, 2001 b; Papa, 2000). This pattern was independent from site or
microsite of incubations; therefore, as said before, no significant differences of activity were
found in the Cistus litter incubated under Cistus and under Myrtus shrubs (Fioretto et al.,
2000) as well as among the Q. ilex litter incubated in the three woods (Papa, 2000).