1 - Ecologia Mediterranea

Bergmeier
Fine-scale species composition
The total number of spring-reproducing taxa was
only slightly higher in the grazed microplots - 91 as
against 86 (table 4). The mean number of taxa per
microplot, however, was significantiy higher in the
non-grazed plots (15.3 as against 19.5; t-Test with p <
0.001). The same was true for the total and mean
numbers of reproduction units.
Post-tire Grazed Non-grazed
management (n = 50) (n = 50)
Total number of taxa 91 86
Mean number of taxa
per microp1ot 15.3 19.5
Total number of
reproduction units 5397 6493
Mean number of repr.
units per microplot 107.9 129.9
Table 4. Diversity characteristics of the microplots
The quantitative analysis of the microplots reveals
that certain taxa were promoted by non-grazing, others
were not (figure 2). Particularly Asteraceae such as
Picris altissima, Crepis commutata and Urospermum
picroides were supported by non-grazing; as were
certain legumes (Lotus peregrinus, Lotus edulis) and
grasses (Avena barbata, Bromus intermedius, Hyparrhenia
hirta). Similar results were detected concerning
the reproduction units (table 5). On the other hand, a
small number of taxa was affected by non-grazing.
Valantia hispida and Galium murale displayed lower
constancy as weIl as fewer individuals. Crepis cretica
was also much less abundant in the non-grazed plots
but so far maintained its high constancy. It should be
emphasized that no taxon promoted by non-grazing is
lacking completely on the grazed ground, and so far,
the reverse is also true.
DISCUSSION AND CONCLUSIONS
Pre-tire vs post-tire
In the present case study, fire had only little effects
on the overall diversity of phrygana. AIready in the
first post-fire spring the composition of herbaceous
6
Combined effects offire and grazing on phrygana
taxa was almost identical to that of the pre-fire vegetation.
This is in accordance with Bôhling (1994), but
apparently not with Arianoutsou-Faraggitaki & Margaris
(1981: 187; 1982) who found the ground "carpeted
with annual and perennial herbaceous species
rarely seen in the undisturbed sites". However, noth­
ing in detail is said in the latter study about pre-fire
species composition and vegetation structure, so one
might assume a rather dense and species-poor scrub
which supports a floristic post-fire flush (Arianoutsou
& Margaris, 1981; Papavassiliou & Arianoutsou,
1993). In the present study, only Lavatera bryoniifolia,
and to a minor degree Asphodelus ramosus and
Sarcopoterium spinosum, were stimulated after fire.
The coverage of the herbaceous vegetation on the
grazed ground was but slightly higher than before the
fire. The dwarf shrub layer was destroyed completely
and, after two years, the process of regeneration had
only just started. While the unburned phrygana shrubs
provide effective protection against soil erosion (Dieckmann
et al., 1985), the post-fire phrygana is highly
susceptible to erosion as long as the shrub layer did
not regenerate.
The pre-fire dwarf shrub layer was rather homogeneous
with dominant Calicotome vil/osa and Coridothymus
capitatus, and with sparse Sarcopoterium
spinosum. The high proportion of seedlings of the
latter species in the grazed post-fire vegetation (table
3) suggested that the post-fire shrub layer, once reestablished,
might be richer in Sarcopoterium than the
pre-fire vegetation, at least temporarily. This is corroborated
by numerous observations of Sarcopoterium
dominating initial regeneration stages of phrygana
(Raus, 1979; Arianoutsou-Faraggitaki & Margaris,
1982; Arianoutsou-Faraggitaki, 1984; Bohling, 1994;
Bergmeier, 1995). Sarcopoterium spinosum is known
to be fire-promoted (Roy & Arianoutsou-Faraggitaki,
1985), and there is evidence for its representation in
seed banks of Mediterranean dwarf scrub ecosystems
(Litav & Orshan, 1971). Moreover, S. spinosum often
regenerates by both seeding and resprouting, the latter
strategy according to Papanastis (1977) chiefly in
more humid regions.
This flexible response may prove favourable under
variable ecological conditions.
ecologia mediterranea 23 (3/4) - 1997