1 - Ecologia Mediterranea

Gratani & Crescente Phenology and leafadaptative strategies ofMediterranean maquis plant
reactions of species to environmental stimuli create
the broad mosaic of resource utilization patterns,
which characterizes a multispecies plant community
(Kummerow et al., 1981). Phenology which describes
the functional rhythm of a plant community is not
simply the sum of the rhythms of individual species,
but is the result of inter-relationships among ail the
individuals of the community. It represents the lifehistory
strategies of a plant community and its
resource use.
At the end of the nineteenth century and during the
early part of the twentieth century, there was great
interest in determining the role of morphology in the
phenological adaptation of plants to specific
environments (Grime & Hunt, 1975; Carpenter &
Smith, 1981; Kikuzawa, 1989). These studies did not
have an experimental basis and their potential
functional significance has been investigated more
thoroughly only in recent times (Ehleringer & Werk,
1990).
The present paper deals with sorne phenological
pattern exhibited by Mediterranean maquis species
and their shoot and leaf growth dynarnics. The results
have been interpreted in terrns of adaptive strategies of
resouree use.
MATERIALS AND METHODS
The sample area, 1200 m 2 , is located within the
Presidential Estate of Castelporziano (S-SW of Rome,
Latium, ltaly). The experimental plot consists of
Mediterranean low maquis dominated by Quercus ilex
L., Pistacia lentiscus L., Phillyrea latifolia L., Smilax
aspera L., Arbutus unedo L., Cistus incanus L., Erica
arborea L., Erica multiflora L., Daphne gnidium L.,
Lonicera implexa Ait. and Rosmarinus officinalis L.
(Gratani & Marinucci, 1985; Gratani & Amadori,
1991). It is characterized by shrubs 0.5 - 1.5 m tall and
by 2.5 leaf area index (LAI) (Gratani, 1995).
Individuals were chosen randomly, and detailed
phenological observations were carried out at weekly
intervals from January 1992 to Deeember 1993. For
each species, 150 branches formed from the previous
year's growth were marked and labelled with nylontape
at about 1 mm from the end of the growing point.
The following phenological events were observed: (l)
presence of buds (when the length was less than
2mm); (2) vegetative activity (period of shoot
elongation, and unfolding of leaves until their final
size corresponding to mature leaves); (3) flowering
12
period (from bud flower opening until the end of
anthesis); (4) fruiting period (presence of fruits until
the seeds begin to fall); (5) leaf fall (six litter traps
consisting of 1 m 2 boxes with nylon mesh, were
randomly located in the study area, under shrubs).
Climatic data were provided by the Meteorological
Station located within the Estate. During the period
January 1992 - December 1993, soi! moisture was
monitored monthly by three soi! samples taken at 30
cm depth. Soi! dry weight was recorded after drying at
90° C until constant weight.
The seasonal course of shoot elongation and leaf
area development was monitored: each week fifty
leaves were collected for each species along the full
length of new shoots in order to coyer the whole range
of leaf size. Leaf surface area was measured by the
Image Analysis System (Delta-T Deviees, LID,
England). Leaf dry weight (drying at 90°C to a
constant weight) was determined. Relative growth rate
(RGR) was defined as the increase at any instant in
time of leaf dry weight and leaf surfaee area
(BIackman & Wilson 1951; Beadle et al., 1985).
Specifie leaf weight (SLW) was calculated as leaf dry
weight per unit of leaf surface area (Cappelletti,
1954). The cycle of phenological phenomena, such as
bud break, flowering, fruiting and leaf fall, is
traditionally linked with climate (Wells, 1971;
Larcher, 1995). It is possible to monitor seasonal
growth pattern and to assess the contribution of a
species to the community (Rorison, 1981).
RESULTS
The clirnate of the area was of the Mediterranean
type. The average total annual rainfall was 765 mm,
the mean minimum air temperature of the coldest
months (January and February) was 3.6 oC and the
mean maximum air temperature of the hottest month
(August) was 30 oC (data from 1981-1993) (Table 1).
Most of the total annual rainfall occured in autumn
and winter; during the summer drought soil moisture
was characteristically low (Figure 1).
Phenologieal periodicity of the Mediterranean
maquis species
Figure 2 summarizes the phenological periodicity
of the studied Mediterranean maquis species (mean of
the years 1992-1993).
ecologia mediterranea 23 (3/4) - 1997