Environmental Engineering Reference
In-Depth Information
Besides, most of Mediterranean WS show high size variability (Corona et al.
2012
and references within), so that the common techniques and algorithms used
for the forest tree species do not always fit well with maquis ones. Even ring anal-
ysis techniques often fail for these species because high environmental variability
makes interpretation of ring data difficult (Cherubini et al.
2003
). Because a stand-
ardised methodology is unavailable for these species, researchers have estimated
maquis biomass and the annual variation in the biomass using a variety of meth-
ods. As a result, the available data are seldom comparable (Corona et al.
2012
).
During the last four decades, plant ecologists have published hundreds of papers
and thousands of phytosociological relev￩s concerning the non-forest Italian plant
communities. This huge amount of data is mostly focused on floristic similarities
among coenoses, but many of the papers provide only basic information on the abi-
otic context (e.g., soil chemistry, bioclimate, slope, aspect, disturbance intensity and
frequency, etc.), and very few report the main structural patterns (vertical stratifica-
tion, cover of each vegetation layer, etc.). This makes dificult to compare the relev￩s
published in different works, even if they concern the same plant community. In this
chapter an attempt to interpret phytosociological data has been carried out in order to
provide a preliminary overview on the biomass values of Italian shrubland commu-
nities and/or their dominant/characteristic WS.
14.2 Basic Assumptions on Italian Shrubland Vegetation
Several thousands of phytosociological relev￩s concerning the Italian non-forest
woody communities published till June 2011 were considered (data not shown). In
order to facilitate modelling, we focused our attention on the similarities concern-
ing the following six parameters: (1) whole vascular flora (all taxa); (2) 'weighted'
vascular flora (all taxa also considering coverage values); (3) dominant WS; (4)
most frequent WS (i.e. whose frequence was
≥
50 %); (5) ecological (i.e., spe-
cies with similar edapho-climatic requirements); and (6) structural (i.e. cover rate,
stratification, etc.) patterns.
The nomenclature of vegetation units follows Biondi and Blasi (
2009
). All
those classes in which WS are dominant or frequent in only one or a few asso-
ciations, like the pioneer vegetation of screes and ravines (class
Thlaspietea rotun-
difolii
), the chasmophilous communities of undisturbed cliffs (class
Asplenietea
trichomanis
), the meso-xerophilous perennial grasslands (class
Festuco
-
Brometea
), the chamaephytic lithophilous communities prone to salt spray (class
Crithmo
-
Staticetea pro parte
), the rush-dominated prairies on salt-rich and humid
soils (class
Juncetea maritimi
) were excluded. The same decision was taken for
high maquis formations dominated by
Quercus ilex
,
Quercus suber
, and
Pinus
spp. because they should be ascribed to proper woodland communities (class
Quercetea ilicis
, order
Quercetalia ilici
s).
Many useful data on above- and belowground biomass (hereinafter Ab and Bb)
issued from investigations which have been carried out in other Mediterranean
