introduction - Ecologia Mediterranea

Shoot elongation
PHENOLOGY AND GROWTH OF QUERCUS ILEX IN DIFFERENT ENVIRONMENTAL CONDITIONS IN SICILY u
Although the entire apical activity can last up to 12
weeks (fig. 2), the true elongation phase is usually shorter
than eight weeks (fig. 3). Mean annual shoot elongation
is rather moderate in all sites. It never exceeds
10 cm yr -1 , except at Mt Pellegrino (table 2). In that site,
a precocious sprouting and a higher elongation rate was
observed (fig. 3). In addition, the south-eastern facing
branches showed much higher values and a second
conspicuous flush in both 1998 and 1999.
Diameter growth
The cambial activity is almost synchronous to sprouting.
Growth is more intensive until the end of spring;
although strongly reduced, it goes on through the summer
and definitively stops in late autumn. As the elongation,
it is higher at Mt Pellegrino; furthermore, only in
that site, cambial activity seems almost uninterrupted in
both the years of observation (fig. 4).
ecologia mediterranea, tome 29, fascicule 1, 2003, p. 15-25
Figure 2.
Phenological phases
of Quercus ilex
in the investigated sites.
Leaf expansion and leaf longevity
At Mt Pellegrino leaf area at the end of leaf expansion
is larger than in all the other sites (7.8 cm 2 vs. 4.9-
6.3 cm 2); whereas it is become smaller at the end of the
second year of observation (4.3 cm 2 vs. 5-5.5 cm 2) (table
2). The general trend of leaf area variation through time
is similar in all sites (fig. 5). A rapid increase of the enlargement
rate can be observed in the first 5-7 weeks from
sprouting. A second expansion phase was observed in
September, at Mt Pellegrino, and in January at Piano
Zucchi. Leaf area gradually drops after the end of May
of the second year, whereas only at Mt Carcaci leaf growth
seems definitively ended at June of the first year. In 1year-old
leaves, leaf area remarkably decreases since June.
As regard to turnover, leaf shedding is particularly intensive
during spring sprouting (fig. 2). The mean leaf longevity
is usually between two and three years; about 50 %
of leaves sheds since the second year, whereas the turnover
is completed during the third year (fig. 6).
19