Environmental Engineering Reference
In-Depth Information
occupy discontinuous areas, their biomass is very significant at national level.
Nevertheless, the few available data concerning some of the most common mantle-
dominating species can be used to assess community biomass through modeling.
14.4 Discussion and Research Perspectives
All Italian shrubland plant communities may be consolidated within few 'land-
scape macrocategories' through multivariate statistics, a task that is still in
progress. Thus, we shall avow that at present it is still hard to obtain inequivo-
cal proxies to predict the productivity of all Italian shrubland ecosystems.
Nonentheless, available information arising from field investigations already car-
ried out abroad allows to estimate the range of variation of the biomass values of
some phytosociological classes such as
Sarcocornietea fruticosae
.
In particular, even though little attention has been paid to the vegetation com-
munities with medium values of biomass and with widespread distribution
(Table
14.1
), these ones deserve emphasis as they face desertification threats.
This is the case of the salt-tolerant communities of
Pegano
-
Salsoletea
,
Crithmo
-
Staticetea
, and
Sarcocornietea fruticosae
along the coasts of Italy and its major
islands.
Also summer-deciduous maquis communities referred to the alliance
Periplocion angustifoliae
are worth to be studied adequately, because they colo-
nize the harshest areas of Italy (i.e. the coasts and southern Sicily and some of its
satellite islets) and are prone to severe stress factors.
Another knowledge gap which should be filled concerns the shrubby commu-
nities colonizing the top of Mediterranean mountains; during recent decades, the
role of these low (and slow) growing communities in carbon storage has increased
along with the surfaces they occupy due to a strong reduction in traditional mow-
ing and grazing practices, which has enhanced succession on a large scale.
If we take into account their distribution and their average biomass values,
the deciduous shrubberies ascribed to
Prunetalia spinosae
and the 'true maquis'
referred to
Quercetalia calliprini
play a prominent role among Italian non-forest
woody vegetation.
At the moment it is still difficult to disentangle the effect of vegetation struc-
ture, dominat WS size and local bioclimate: for example, when calculated through
dominant WS or by using the entire communities, their biomass values show sub-
stantial variation (Table
14.1
). This is even true when the values concern the same
study area but are derived from different papers; for instance, the values for the
maquis biomass of Castelporziano range from 6,100 to 9,000 g/m
2
in Gratani et al.
(
1980
) and from 600 to 3,000 g/m
2
in Gratani and Crescente (
2000
).
Thus, in order to avoid underestimating the biomass variability (cfr.
Erica arbo-
rea
in Table
14.2
) of maquis and mantle communities with high structural (aver-
age height, dominant growth form, etc.) and floristic (species and WS richness)
complexity, field measurements on the biomass of these communities should be
