Environmental Engineering Reference
In-Depth Information
The SOC pools were assessed using RothC (v. 26.3) model developed to
estimate the turnover of carbon in soil at monthly temporal step (Coleman
and Jenkinson
1996
). RothC includes four soil C compartments (DPM—
Decomposable Plant Material, RPM—Resistant Plant Material, BIO—Microbial
Biomass, and HUM—Humified Organic Matter). It requires input data at monthly
scale, related to climate (rainfall, evapotranspiration, air temperature), soil (clay
content, cover), and plant residues (litterfall). With respect to the litterfall, the
model is designed to run in two modes: 'forward', which permits to calculate
changes in soil organic matter using available litterfall input, and 'inverse' mode,
which calculates the litterfall rates from the values of SOC.
The Soil Map (for clay content) and the Land Use (LU) Map of Sardinia were
processed using a GIS, and almost 380,000 polygons (homogeneous for soil char-
acteristics and Land Use class) were detected. In each polygon covered by crops,
the actual SOC (related to the top 0.24 m of mineral soil) was estimated using
RothC coupled with the actual climate data (available at 250 m resolution). We
used literature and our unpublished data for the input data related to plant residues.
The scheme of the methodology used is reported in Fig.
8.4
. The model results
were compared with soil analysis values made in different Land Use typologies,
and the litterfall input for each LU class was adjusted to find the best fit ('inverse'
run of the model). After a validation using others independent measured SOC
points, a new run of RothC was performed to obtain a SOC database of Sardinia
croplands for the actual climate and under climate change conditions (A1B sce-
nario, source: CMCC, Euro-Mediterranean Centre for Climate Change).
Fig. 8.4
Scheme of the methodology
