Agriculture Reference
In-Depth Information
Cistus incanus
is a summer deciduous species while
Myrtus communis
, an evergreen
species. This two type of shrubs create different microclimatic conditions on the top soil
because of their different habits. For example, soil temperature at 5 cm dept before midday,
similar in winter, were higher over 2-4°C under
Cistus
than under
Myrtus
shrubs in summer.
Moreover, even if there was no significant change in water availability at the sampling time
(about 3 h after dawn) also in summer, however, some dew, was formed by the high nocturnal
humidity, and it moistened the litter under the bare
Cistus
but not under
Myrtus
at sunrise.
These microclimatic conditions affected decomposition: both litters incubated under
Myrtus
showed reduced decomposition rate during the dry summer of the first year of decomposition
when the litter bags were more exposed to air because less covered by new litter. The mass
loss rate of
Cistus
litter incubated under
Cistus
, instead, did not change (data not shown) in
the same period (Fioretto et al. 2000). Probably under
Cistus
the daily drying and rewetting
cycles in summer can favour mechanical fragmentation and decomposition, as reported for
sweet chestnut and oak leaf litters (Anderson, 1973; Witkamp and Olson, 1963).
In addition, the distribution of soil enzyme activities suggested a different microbial
community in the soil under the two shrub types. The activities, in particular of xylanase,
cellulase and invertase, were almost twice in the soil under
Cistus
during the wet periods,
clearly indicating a different functionality of the community (Fioretto et al., 2005 b; Papa et
al., 2007).
The litters of
Cistus
, incubated under
Cistus
and
Myrtus
shrubs, as well as of
Myrtus
,
incubated under
Myrtus
plants, showed similar decomposition rate during the first 8 months
of incubation (Figure 6) (the average decay constant (k) ranged between 0.29±0.03 y
-1
and
0.33±0.03 y
-1
) (Fioretto et al. 2000). Subsequently, it increased only for litters incubated
under
Myrtus
shrubs in line with the increase of the fungal biomass (Figure 5).
90
M.communis C.incanus
Cistus under .Myrtus
80
70
60
50
40
30
20
10
0
0
100
200
300
400
500
600
700
800
900
decomposition time (days)
Figure 6. Accumulated mass loss versus decomposition time of Cistus incanus litter incubated on top
soil under Cistus shrubs and Myrtus shrubs in a Mediterranean maquis. As comparison, also
accumulated mass loss of Myrtus litter under Myrtus shrubs is reported. Data from Fioretto et al., 2000.
The enzyme activities (discussed below), on the contrary, differenced only between the
two litter types (always higher in
Myrtus
than in
Cistus
) independently from incubation
