Environmental Engineering Reference
In-Depth Information
It must be pointed out, though, that our study analysed the abandonment of
permanent woody crops and ploughed annual crops, but not the abandonment of
pastures. Since in Sicily pastures are the main agricultural land use in the areas
characterized by a supra-mediterranean bioclimate, research on carbon dynamics
in ex-pastures should be carried out to integrate the data here presented.
Furthermore, the results of this study confirmed that the agricultural abandoned
areas where secondary succession is going on are the more valuable C sinks. In
Sicily, according to the extrapolation of our data, between 1990 and 2006, a total
of 6,835,431 Mg of C have been incorporated in soils after agricultural abandon-
ment of annual and permanent crops along with secondary succession processes
(Table
12.1
). It is very important, though, to highlight that C incorporation in soil
through secondary succession can only be achieved if these vegetation dynamics
are not interrupted by disturbances. On the other hand, in Sicily and throughout the
whole Mediterranean region, wildfires frequently disturb agricultural abandoned
areas, thus biasing forest communities' set up. So, the areas where secondary suc-
cession processes are going on should be protected from disturbances in order to
obtain a further increase of C sink capacity of agriculturally abandoned soils.
Regarding afforestation, this review of SOC data showed that for C sequestra-
tion in the soil, artificial afforestation is not convenient in comparison to natu-
ral afforestation by spontaneous secondary succession processes. So, in order to
increase C storage in abandoned agricultural lands, management choices should
aim at the protection of these spontaneous processes, and could also actively
enhance spontaneous woody encroachment by bird-mediated seed addition or
selective seedling planting techniques. In contrast, in strongly degraded areas or
in abandoned agricultural lands where severe disturbance factors such as frequent
wildfires and overgrazing occur, afforestation could be a management choice,
because under intense and frequent disturbance factors secondary succession
Table 12.1
Gain in soil C (Mg) in areas subject to agricultural abandonment (change from culti-
vated to abandoned soils) and progressive secondary succession (change from a younger succes-
sion stage to an older one) in the three considered bioclimatic belts of Sicily from 1990 to 2006
Change between 1990 and 2006
Thermo
Meso
Supra
694,075
672,848
1,213
From CU to HE/GR
966,958
1,496,419
15,585
From CU to GS/MA
From CU to FO
438,479
732,179
4,013
2,099,513
2,901,446
20,811
Total agricultural abandonment
From HE/GR to GS/MA
73,032
773,696
61,351
From HE/GR to FO
73,980
382,926
19,548
176,068
250,510
2,549
From GS/MA to FO
Total progressive succession
323,081
1,407,132
83,448
Total abandonment
+
succession
2,422,594
4,308,578
104,260
CU
cultivated areas,
HE
herb-dominated plant communities,
PG
perennial grasslands,
GS
gar-
rigues and low shrublands,
MA
maquis,
NF
natural forests,
AF
artificial afforestations;
Thermo
thermo-mediterranean,
Meso
meso-mediterranean,
Supra
supra-mediterranean bioclimate
