Environmental Engineering Reference
In-Depth Information
agriculture since a few years); (3) PG
=
grasslands dominated by perennial grasses;
(4) GS
=
garrigues and low shrublands; (5) MA
=
maquis; (6) FO
=
natural forests.
In every bioclimate the most representative succession pathways were chosen, for
each site, except for supra-mediterranean belt, where the successional stages 3 (PG)
and 5 (MA) are missing.
In addition to the soil samples taken in different successional stages, also sam-
ples in nearby artificially afforested sites (AF) were analyzed. All sampled affor-
ested sites were Pine plantations, wherein the dominant Pine species depended
on the bioclimatic belt (
Pinus halepensis
Mill. and
Pinus pinea
L. in the thermo-
and meso-mediterranean belt,
Pinus nigra
J.F. Arnold in the supra-mediterranean
bioclimate).
Soil was sampled according to the protocol of the Italian National Inventory of
Forests and Forest Carbon pools (Gasparini et al.
2008
). After litter removal, min-
eral soil samples were collected at depths of 0-10 and 10-30 cm, using a 340 and
a 680-cm
3
cylinder, respectively. For every site and succession stage/afforestation,
three replicates of both soil depths were taken, respectively.
The soil samples were gently broken, passed through a 2-mm sieve, air dried,
treated with HCl 2:1 to remove carbonates and then analysed for C content using
a CHN-Elemental Analyzer. SOC content was first expressed as a percentage
(g of C per 100 g of dry soil 100) and then converted to tons per hectare based
on bulk density (BD) and soil depth. Bulk density was measured based on the
volume of the collected sample and the weight of dry soil in the sample (Blake
and Hartge
1986
). Mass correction of SOC stock estimates based on BD is crucial
for estimating the effects of land-use change because land-use change is always
accompanied by changes in BD. All data were adjusted to 30 cm depth.
12.2.2 Data from Literature
Existing literature including SOC analyses in Sicilian sites was screened for data
taken in successional stages or in land use classes, which could be compared, as
similar to stages of secondary succession. Moreover, SOC data of afforested areas
(
Pinus
spp.,
Eucalyptus
spp.) in proximity to the successional areas were included
in the analyses (Ballatore and Fierotti
1970
; Raimondi et al.
1983
; Panno et al.
1986
; Ferro et al.
2008
; Agnese et al.
2011
; Novara et al.
2012
; La Mantia et al.
2013
).
12.2.3 Data Analysis
For data analyses, average SOC stock values were computed from sites and repli-
cated for each succession stage and for afforested sites within the three bioclimatic
groups.
