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Soil organic carbon stock assessment for the different cropland land uses in Italy

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The aim of this work was to quantify the soil organic C (SOC) stock in the top 30 cm of mineral soil for the whole Italian territory, according to the different land use types of the Intergovernmental Panel on Climate Change (IPCC) cropland category (arable land, agroforestry, vineyards, olive groves, orchards and rice fields), as a basis for future land use scenarios and to address mitigation policy at country level. A database for SOC stock was created with the data from the national project denominated SIAS and partly from regional map reports. All data were referred to the year 2000 since they were derived from surveys conducted from 1995 to 2005. The data were stratified according to the Italian climatic regions, the landscape position and the IPCC cropland subcategories. Taking into account the uncertainty in the estimate, the mean SOC stock values of the different subcategories show significant differences (p<0.05) among climatic regions and landscapes, ranging from 41.9± 15.9 Mg C ha −1 in the vineyards to 63.3±27.9 Mg C ha −1 in the rice fields. Generally, a small decrease of the SOC stock from the temperate regions toward the Mediterranean ones is observed. Taking into account the mean value of each subcategory and the country area they occupied in 2000, the total C stored in the upper 30 cm of soil was estimated at 490.0±121.7 Tg C. The resulting estimate represents the 17% of the value reported by another study for the soil of the whole country down to 50 cm depth, suggesting the importance of preserving this large C pool. Considering the cropland category as a whole, the estimated mean SOC stock is 52.1±17.4 Mg C ha −1 , similar to that reported for other European countries, 50–60 Mg C ha −1 . In conclusion, the assessment of the mean SOC stock of the different cropland land uses, landscape position and climate regions could notably help when assessing the impact of different agricultural practices and future stock change evaluation.
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ORIGINAL PAPER
Soil organic carbon stock assessment for the different
cropland land uses in Italy
Tommaso Chiti &Lorenzo Gardin &Lucia Perugini &
Roberta Quaratino &Francesco Primo Vaccari &
Franco Miglietta &Riccardo Valentini
Received: 28 February 2011 / Revised: 21 June 2011 / Accepted: 23 June 2011
#Springer-Verlag 2011
Abstract The aim of this work was to quantify the soil
organic C (SOC) stock in the top 30 cm of mineral soil for
the whole Italian territory, according to the different land
use types of the Intergovernmental Panel on Climate
Change (IPCC) cropland category (arable land, agroforestry,
vineyards, olive groves, orchards and rice fields), as a basis for
future land use scenarios and to address mitigation policy at
country level. A database for SOC stock was created with the
data from the national project denominated SIAS and partly
from regional map reports. All data were referred to the year
2000 since they were derived from surveys conducted from
1995 to 2005. The data were stratified according to the Italian
climatic regions, the landscape position and the IPCC
cropland subcategories. Taking into account the uncertainty
in the estimate, the mean SOC stock values of the different
subcategories show significant differences (p<0.05) among
climatic regions and landscapes, ranging from 41.9±
15.9 Mg C ha
1
in the vineyards to 63.3±27.9 Mg C ha
1
in the rice fields. Generally, a small decrease of the SOC
stock from the temperate regions toward the Mediterranean
ones is observed. Taking into account the mean value of each
subcategory and the country area they occupied in 2000, the
total C stored in the upper 30 cm of soil was estimated at
490.0± 121.7 Tg C. The resulting estimate represents the
17% of the value reported by another study for the soil of the
whole country down to 50 cm depth, suggesting the
importance of preserving this large C pool. Considering the
cropland category as a whole, the estimated mean SOC stock
is 52.1± 17.4 Mg C ha
1
, similar to that reported for other
European countries, 5060 Mg C ha
1
. In conclusion, the
assessment of the mean SOC stock of the different cropland
land uses, landscape position and climate regions could
notably help when assessing the impact of different
agricultural practices and future stock change evaluation.
Keywords Croplands .Land use .Mitigation options .
Kyoto protocol .SOC stock
Introduction
Cropland soils are estimated to be the largest biospheric
source of carbon (C) loss to the atmosphere in Europe each
year (Janssens et al. 2003). The loss of soil organic C
(SOC) has detrimental effects on soil structure and soil
fertility, contributing to global warming by further increas-
ing the atmospheric concentration of carbon dioxide (CO
2
)
(Lal 1999; von Lützow and Kögel-Knabner 2009). The
possible decrease of the SOC stock from croplands
contrasts with the prevailing theory which assumes the
equilibrium between C inputs and outputs in the Ap
T. Chiti (*):L. Perugini :R. Quaratino :R. Valentini
Dipartimento di Scienze dellAmbiente Forestale e delle sue
Risorse (DISAFRI), Università della Tuscia,
Via San C. De Lellis s.n.c,
01100 Viterbo, Italy
e-mail: tommaso.chiti@unitus.it
L. Gardin
Studio Gardin,
via Guerrazzi 2R,
50132 Florence, Italy
F. P. Vaccari :F. Miglietta
Istituto di Biometeorologia (Ibimet) del Consiglio Nazionale delle
Ricerche (CNR),
via G. Caproni 8,
50145 Florence, Italy
F. Miglietta
FoxLab-Fondazione E. Mach,
Via E. Mach, 1 38010 S. Michele allAdige,
Trento, Italy
Biol Fertil Soils
DOI 10.1007/s00374-011-0599-4
horizon, i.e. the ploughed layer of agricultural soil
(Christensen 1989; Ellmer et al. 2000; Körschens et al.
1998). This theory is the result of long-term experiments
showing that the relative constancy of environmental and
agricultural conditions over decades led to relatively
constant levels of C in the Ap horizons. In contrast, other
studies carried out in Europe indicate a constant decrease of
the SOC stock with increasing cultivation time (Beyer et al.
1999; Gardi and Sconosciuto 2007; Lugato et al. 2007;
Morari et al. 2006; Sleutel et al. 2006,2003; Vleeshouwers
and Verhagen 2002), while others suggest a possible
increase mainly due to a high fertilizer application rate
(Nieder and Richter 2000; Van Meirvenne et al. 1996).
Hence, the characterization of the soil C stock and its
changes in agricultural soils allow the assessment of the
status of this pool in a land use type, which plays a relevant
role in the CO
2
emission and removals balance at country
level. Cropland is the major land use in Europe (Janssens et
al. 2005), and changes in the size of the cropland soil C
pool could significantly impact the European C budget
(Janssens et al. 2003). According to the Kyoto Protocol
(KP) of the United Nations Framework Convention on
Climate Change (UNFCCC 1998), C sequestration in
agricultural soils is accountable under Article 3.4, and thus,
management of cropland is among those activities that a
country signatory of the KP may elect for meeting its
emission reduction target. According to the accounting
rules established for the first commitment period of the KP,
20082012 (UNFCCC 2002), emissions and removals from
cropland management, together with grazing land manage-
ment and revegetation, should be compared with emissions
and removals from these activities during the base year
(1990), the so-called netnet accounting approach. Soil
organic C stock and dynamics in cropland soils are also
important for quantifying the C emissions/removals in-
volved in land use change processes, such as afforestation,
reforestation and deforestation activities, which are consid-
ered under Article 3.3 of the KP. The greenhouse gases
National Inventory Report, submitted by Italy to the
UNFCCC secretariat in 2010, indicates that cropland
removals share 14.1% of total CO
2
emissions and removals
of the land use, land use change and forestry sector
(LULUCF), identifying cropland remaining croplandas
akey category, i.e. a land use category that has a
significant influence on the country's greenhouse emis-
sion level as the absolute levelandtrendinemissionsand
removals (IPCC 2000;ISPRA2010). Although the
importance of the sector is well recognized, the informa-
tion published so far is scarce, fragmented, not homoge-
neous and limited to spotted studies at local scale. For this
reason, Italy has not yet elected cropland management
among the additional activities of Article 3.4 (Tedeschi
and Lumicisi 2006).
The aim of this work is to provide for Italy the most
updated information on the SOC stock for the different land
use types according to the IPCC cropland category (i.e.
arable land, agroforestry, vineyards, olive groves, orchards
and rice fields), in the different climatic zones and
landscapes of the country. The definition of a SOC stock
baseline is essential for future evaluations of the status of
this pool. Furthermore, the identification of a baseline for
the SOC stock in cropland ecosystems could contribute to
assess the starting or ending point of the stock change
occurring after land use changes from or to cropland, i.e.
changes in soil C stock due to afforestation/reforestation
activities on cropland, conversion of cropland into grass-
land or conversion of any land use into cropland. It is
important to mention that the study is restricted only to the
first 30 cm of the soil. This is the main depth of agricultural
activities, and land use changes should have an impact
mainly in this region, but in fact, a considerable amount of
SOC is also stored below 30 cm.
Materials and methods
Data sources and preparation
The pedological database used in this work derives from
different sources. The main source of information for the
SOC stock used in this study is the SIAS(Development
of Soil Indicators in Italy) national project, started in 2007
within the framework of the MEUSIS (Multi-Scale Soil
Information System) European project (http://eusoils.jrc.ec.
europa.eu/projects/Meusis/italy.html). The data stored in the
SIAS database refer to soil samples collected in different
regional surveys mainly from 1995 to 2005. In this study,
the whole dataset was considered representative of the year
2000. The database produced by the SIAS project reports
the elaborations and the metadata for two environmental
indicators, soil C stock and soil erosion, in agreement with
the IPCC standards (IPCC 2003). Following the European
Directive denominated Infrastructure for Spatial Informa-
tion for Europe (INSPIRE, COM 516/2004), the SIAS
data refer to the INSPIRE grid having cells of 1 by 1 km.
The value provided by the SIAS project for each cell is an
average value of the C stock of the upper 30 cm of mineral
soil, weighed on the real surface of the cell covered by soil.
The INSPIRE cell is characterized by an identification code
and coordinates of the centroid. In this way, it was possible
to get information in a unique reference system (interoper-
ability).
For the country areas not covered by the SIAS project,
an INSPIRE grid was created according to the guidelines
available at the European Soil Bureau website (http://
eusoils.jrc.ec.europa.eu). The analytical data used to calcu-
Biol Fertil Soils
late the soil C stock of the representative profiles for each
INSPIRE cell were obtained from map reports or regional
survey conducted across the year 2000. All these data can
be found also in the national soil database (Costantini et al.
2007). For areas where no updated C measurements were
available, the analytical data were directly elaborated from
the data of the database of the Ecopedological Map of Italy
(Rusco et al. 2003), which includes data from the AGRIT
project (19921994) of the Ministry of Agriculture.
Different methodologies have been used to spatialize the
SOC stock within each INSPIRE cell, ranging from the
most traditional ones, using soil mapping units and soil
typological units, to the geostatistical ones. Figure 1a shows
the distribution of the three different types of data sources
within the Italian territory. To increase the accuracy of the
SOC estimate, the INSPIRE cells with no sampling points
were excluded from the calculation.
The climatic subdivision of the Italian territory, according
to the different climate types, was done following the codes of
the type of climateavailable in the Georeferenced Soil
Database for Europe: Manual of Procedures Version 1.1. Eur
18092 EN(Finke et al. 1998). Accordingly, the Italian
territory was classified in seven areas with a different type of
climate: three temperate and four Mediterranean climate
types (Fig. 1b, Table 1).
The cropland subcategories taken into consideration
were: (a) arable lands, (b) agroforestry, (c) olive groves,
(d) vineyards, (e) orchards and (f) rice fields. To enable the
attribution of the soil organic C stock to the different
cropland subcategories, landscapes (i.e. mountains, hills,
flat valleys) and climatic regions, each INSPIRE cell was
overlaid to the CORINE Land Cover 2000 (Sinanet 2009),
the climatic database, the soil C stock database and the
ecopedological map, using the ESRI ARC/GIS software. To
increase homogeneity within the cells, dominant soil use
was considered as that representing more than 85% of the
cell area covered by soil.
Soil C stock calculation
As previously mentioned, SIAS database provided the SOC
stocks for each INSPIRE cell already as mean value. For
the Italian regions were no SIAS data were available, SOC
stocks were calculated according to the IPCC LULUCF
guidelines (2003):
SOC stock Mg ha1

¼Xhorizon ¼n
horizon ¼1SOC BD Depth 1frag
100

ð1Þ
where SOC is soil C content per unit area (megagrams of
C per hectare), [SOC] is the C concentration in soil
sample (kilograms of C per kilogram soil), BD is the soil
density of the fine earth (megagrams per cubic metre),
Depth is the thickness of the horizon within the considered
Fig. 1 On the left side (a), coverage distribution of the different data
sources used in this study. On the right side (b), climatic subdivision
of the Italian territory: 33 temperate sub-oceanic, 37 temperate sub-
continental to temperate continental partly mountainous, 38 warm
temperate sub-continental, 42 Mediterranean oceanic to Mediterranean
sub-oceanic partly mountainous, 43 Mediterranean sub-continental to
Mediterranean continental, 44 Mediterranean to sub-tropical, 45
Mediterranean mountainous
Biol Fertil Soils
section (centimetres) and frag is the percent of rock
fragments.
To be consistent with the SIAS data, only C concen-
trations determined through the WalkleyBlack method
(Walkley and Black 1934) and direct measurements of the
bulk density and stoniness were chosen for the calculation
of the SOC stock. For harmonizing the different data
sources (non-SIAS vs. SIAS data), the values were
converted to International Organization for Standardization
(ISO) standard (ISO 14235 1998) according to Eq. 2:
SOC iso14235 ¼0:0763 þ1:0288SOC W&B R2of 0:98

ð2Þ
where: SOCiso
14235
is the SOC in accordance with the ISO
standard, and SOC
W&B
is the SOC as determined by the
WalkleyBlack method.
Statistics
The KolgomorovSmirnov test was used to verify the
normality of the data, indicating that the hypothesis of
normality can be rejected at 5% level, but not at 1%
level. Outliers were excluded after the calculation of the
median value. Significant differences (p<0.05) for means
were tested by one-way analysis of variance and Tukey's
test.
Results
Arable land and agroforestry are the only subcategories
present in all the different climatic regions of Italy. The arable
land SOC stock shows significant differences (p< 0.05)
between soils of the different climate types. The higher
stocks are found in the strong depressions of the lowlands in
the temperate sub-oceanic region, 118.8±44.0 Mg C ha
1
,
and in the alluvial soils of the warm temperate continental
type of climate, 77.5±15.1 Mg C ha
1
. The lowest SOC
stock of this subcategory is observed in the Mediterranean
sub-continental region, 42.4±12.5 Mg C ha
1
(Table 2). A
SOC stock comparable to those of the arable lands is found
in soils of the agroforestry subcategory with values varying
from 40.1± 12.3 Mg C ha
1
in the Mediterranean sub-
tropical region to 70.1±23.3 Mg C ha
1
in the temperate
mountain one (Table 2). Significant differences are observed
among the climate types (p<0.05); in particular, the SOC
decreases from the temperate climate regions toward those
with a typically Mediterranean climate. Vineyards' SOC
stock varies from 39.0± 9.9 Mg C ha
1
on hills of the
Mediterranean sub-oceanic type of climate to 77.8±49.7 Mg
Cha
1
on the hills of the temperate sub-continental type of
climate (Table 3). Differences among climate types are
statistically significant (p<0.05). The olive groves subcate-
gory is distributed only in the most typically Mediterranean
type of climates. The minimum and maximum SOC stock
values are observed, respectively, in the lowland of the
Mediterranean sub-continental to continental type of climate,
42.1± 13.3 Mg C ha
1
, and in the Mediterranean sub-oceanic
to oceanic type of climate, 56.0± 35.0 Mg C ha
1
(Table 3),
with significant statistical differences (p<0.05). The
orchards' SOC stock varies significantly (p<0.05) from
38.2± 9.9 Mg C ha
1
in the Mediterranean to sub-tropical
region to 57.8±16.5 Mg C ha
1
in the Mediterranean sub-
oceanic to oceanic one (Table 3). Finally, the rice category
is only restricted to the lowlands and strong depressions of
the lowlands in the temperate sub-oceanic region, with
average values of 60.1± 11.6 and 234.4±80.4 Mg C ha
1
,
respectively (Table 3). The values are significantly
different (p<0.05).
Table 1 Features of the different climatic zones individuated in the Italian peninsula according to Finke et al. (1998)
Code Climate type Description
33 Temperatesub-oceanic Medium to (partly) high precipitation, moderately cold winter and moderately warm
summer, vegetation period 180 to more than 210 days
37 Temperatesub-continental to temperate
continental partly mountainous
Low to medium precipitation, cold to moderately cold winter and warm summer,
vegetation period 150 to more than 180 days
38 Warmtemperatesub-continental Medium to high precipitation, cold winter and moderately warm to warm summer,
vegetation period 180 to 210 days dependent on altitude
42 Mediterraneanoceanic to Mediterranean
sub-oceanic, partly mountainous
Medium to high precipitation in autumn, winter and springtime, regional only a short
dry period in summer
43 Mediterraneansubcontinetal to
Mediterraneancontinental
Medium to very low precipitation in springtime, autumn and winter, long dry period in
summer, partly arid, cold winter and hot summer
44 Mediterranean to sub-tropical Very low precipitation all over the year, temperate winter and warm summer, partly hot
and arid, partly with mountainous climate
45 Mediterraneanmountainous Medium to partly high precipitation, temperatures and vegetation period dependent on
altitude
Biol Fertil Soils
The aggregated values for each subcategory are signif-
icantly different at p<0.05 (Table 4). The rice field soils
show a higher mean C stock than the other subcategories,
63.3±27.9 Mg C ha
1
, followed by the arable land soils
(53.1±17.3 Mg C ha
1
), olive grove soils (51.5 ±19.8 Mg
Cha
1
), agroforestry soils (48.9 ±16.1 Mg C ha
1
) and
orchard soils (44.1±12.1 Mg C ha
1
). The vineyard soils
show the minimum value, with a mean SOC stock of 41.9 ±
15.9 (Table 4).
Discussion
Our results allow to define for Italy the mean SOC stock for
the different land uses of the cropland category in 2000,
according to the various climatic regions and landscapes.
This subdivision is functional to assess the impacts on the
SOC stock due to land use changes from and to agricultural
uses, providing the starting or ending point scenario. The
differences emphasized for the soils of a subcategory under
Table 2 Descriptive statistics of the complete dataset for the arable land (Al) and agroforestry (A) subcategories
Climate LU
a
Landscape Number
b
Mean
c
SD
d
SE
e
Max Min Median 1st quartile 3rd quartile
33 AL H 1,275 51.1d 12.5 0.4 95.4 9.3 48.7 42.4 59.9
33 AL V 21,690 58.1b 14.2 0.1 159.2 12.0 55.8 48.8 65.9
33 AL VD 689 118.8a 44.0 1.7 235.4 50.5 109.9 91.2 134.3
37 AL H 908 46.1d 17.7 0.6 89.1 15.2 49.4 36.5 70.0
37 AL AVB 512 49.5e 7.7 0.3 65.0 35.1 49.4 42.5 56.6
38 AL AVB 70 77.5a 15.1 1.8 120.4 29.0 77.6 49.1 112.1
42 AL H 5,333 46.1f 8.5 0.1 81.4 20.2 46.8 41.4 49.0
42 AL V 3,008 50.8c 8.1 0.1 70.9 31.2 51.1 44.6 56.4
43 AL H 3,285 42.4 12.5 0.2 103.9 23.0 41.2 32.7 46.4
43 AL M 1,046 52.6c 11.3 0.4 79.8 28.3 54.6 43.0 61.1
43 AL V 2,062 45.6f 11.4 0.2 83.4 15.0 47.6 39.2 52.1
44 AL H 2,715 45.8 11.7 0.2 83.1 29.1 43.1 39.5 48.6
44 AL V 3,608 44.8 11.7 0.2 89.4 24.6 42.3 37.1 50.7
45 AL H 2,326 50.0e 17.5 0.4 110.6 21.0 46.0 37.0 56.5
33 A H 1,239 46.6f 12.1 0.3 90.9 21.3 44.0 38.2 54.8
33 A V 1,999 53.9b 11.5 0.3 103.0 23.9 52.3 46.7 59.3
33 A H 615 57.1bc 16.9 0.7 127.2 36.0 50.7 42.8 66.9
37 A H 965 52.6c 18.7 0.6 116.2 15.2 50.3 42.8 61.1
37 A AVB 139 48.0de 11.2 0.9 97.1 29.5 46.3 39.6 55.4
38 A H 590 63.3a 14.7 0.6 119.8 28.6 60.3 50.7 74.2
38 A M 130 70.1a 23.3 2.0 132.0 35.9 64.1 51.5 83.5
42 A H 2,303 46.6f 16.6 0.3 118.2 22.1 46.1 35.4 53.6
42 A V 687 51.7d 14.5 0.6 104.1 23.8 52.3 42.4 61.2
43 A H 1,763 44.3e 19.0 0.4 120.2 10.3 39.8 32.7 51.4
43 A M 795 52.0d 12.2 0.4 91.5 21.6 54.5 43.1 59.8
43 A V 477 42.5fg 10.7 0.5 79.7 10.8 42.4 33.1 50.0
44 A V 709 40.1g 12.3 0.5 89.4 9.3 39.9 20.7 58.6
45 A H 1,391 44.5f 16.4 0.4 116.5 15.2 42.4 35.0 54.2
Climate types: temperate sub-oceanic (33), temperate sub-continental to temperate continental partly mountainous (37), warm temperate sub-
continental (38), Mediterranean oceanic to Mediterranean sub-oceanic partly mountainous (42), Mediterranean sub-continental to Mediterranean
continental (43), Mediterranean to sub-tropical (44), Mediterranean mountainous (45). Means in each row followed by the same letters are not
significantly different at p<0.05; means in each row not followed by a letter are significantly different from the mean of all the other groups at
p<0.05
Hhills, Vvalley, VD valley depression, AVB alluvial valley bottom, Mmountains
a
Land use: arable land (AL) and agroforestry (A)
b
Number of INSPIRE cells used in the calculation
c
Mean SOC stock expressed as megagrams per hectare
d
Standard deviation
e
Standard error
Biol Fertil Soils
the different types of climate can be possibly used for
future-oriented agricultural practices. The comparison of
the total mean values of the different cropland subcate-
gories shows significant differences in the SOC stock
(Table 4). Apart from the rice fields subcategory that
occupies a restricted surface area of the country, the arable
land and olive groves contain significantly higher mean C
stocks than the other subcategories. Similar stocks were
reported by Murillo (2001) for peninsular Spain: from
50.8± 33.7 to 57.6± 36.3 Mg C ha
1
for arable lands, 42.5 ±
28.9 Mg C ha
1
for vineyards and 39.9±28.3 Mg C ha
1
for
olive groves. Analogous stocks were also reported by Martin
et al. (2010) for France: 49.3±26.2 Mg C ha
1
for arable
land, 48.1±24.3 Mg C ha
1
for orchards and 39.4±26.5 Mg
Cha
1
for vineyards.
The amount of C stored in the different subcategories
can allow for a more precise calculation of the total C
stored in the agricultural soils of Italy. In this regard, the
National Statistical Bureau (ISTAT) reports annually the
surface area occupied by croplands, making a distinction
between the different cropland subcategories, but consider-
ing the agroforestry area included in that of the arable land.
Considering the year 2000 (ISTAT 2010), and applying to
each subcategory area the specific average SOC stock value
found in this study, the total amount of C stored in the upper
30 cm of the whole cropland category results to be 490.0±
121.7 Tg of C (Table 5). This amount represents about 17%
of the total SOC estimated by Fantappiè et al. (2010) for the
top 50 cm of soils of Italy, which reports about 2,900 Tg C,
thus indicating the importance to preserve this large SOC
Table 3 Descriptive statistics of the complete data set for the vineyards (V), olive groves (Og), orchards (O) and rice field (R) subcategories
Climate LU
a
Landscape Number
b
Mean
c
SD
d
SE
e
Max Min Median 1st quartile 3rd quartile
33 V H 390 39.6c 10.5 0.5 130.3 21.3 38.2 29.1 53.6
33 V V 78 50.8b 9.4 1.1 72.9 30.2 49.2 36.5 69.0
37 V H 92 77.8a 49.7 5.2 176.3 34.0 62.4 46.7 117.7
42 V H 264 39.0c 9.9 0.6 83.2 25.1 40.9 27.3 51.7
43 V H 20 43.5d 22.0 5.1 132.8 30.1 39.0 31.0 94.8
43 V M 203 39.2d 10.0 0.7 59.1 21.3 37.0 27.6 54.1
43 V V 50 40.5d 9.3 1.3 65.3 28.6 38.2 30.7 64.4
44 V H 420 40.0d 5.5 0.3 54.9 21.1 39.3 30.4 49.5
44 V V 566 39.8c 9.0 0.4 74.0 10.6 39.3 24.1 55.3
37 Og H 200 47.0b 10.2 0.7 99.7 16.2 49.0 31.5 63.1
42 Og H 674 56.0bc 35.0 1.4 123.4 16.9 46.1 26.4 98.7
43 Og H 883 52.8b 25.4 0.9 136.4 13.3 44.8 24.5 83.3
43 Og M 2,319 51.7a 9.3 0.2 83.6 24.7 54.0 35.8 65.3
43 Og V 126 42.1c 13.3 1.2 98.1 19.2 36.6 30.7 62.7
44 Og H 399 49.2b 16.0 0.8 119.0 21.1 45.4 29.5 76.8
44 Og V 211 42.6b 15.0 1.0 115.8 29.3 36.4 30.7 75.4
45 Og H 271 50.0 24.1 1.5 196.3 13.2 43.6 25.7 86.1
33 O V 112 52.2a 6.0 0.6 72.6 36.9 54.9 41.8 58.9
42 O V 67 57.8a 16.5 2.0 108.5 23.9 56.7 26.5 85.0
43 O V 192 41.6b 8.5 0.6 64.7 4.1 43.1 29.8 57.4
44 O V 226 38.2b 9.9 0.7 60.1 13.7 43.1 24.0 53.0
33 R V 1,779 60.1a 11.6 0.3 253.1 24.0 61.2 43.6 78.9
33 R VD 50 234.4b 80.4 11.5 332.6 67.9 261.5 88.5 309.7
Climate types: temperate sub-oceanic (33), temperate sub-continental to temperate continental partly mountainous (37), warm temperate sub-
continental (42), Mediterranean sub-continental to Mediterranean continental (43), Mediterranean to sub-tropical (44), Mediterranean
mountainous (45). Means in each row followed by the same letters are not significantly different at p< 0.05; means in each row not followed
by a letter are significantly different from the mean of all the other groups at p<0.05
Hhills, Vvalley, VD valley depression, Mmountains
a
Land use: Vvineyards, Og olive groves, Oorchards and Rrice fields
b
Number of INSPIRE cells used in the calculation
c
Mean SOC stock expressed as megagrams per hectare
d
Standard deviation
e
Standard error
Biol Fertil Soils
stock and avoid losses. The arable land, including also the
agroforestry, represents the land use subcategory storing
most of the SOC: ~70% of the total amount present in the
whole cropland category.
The mean value of the whole cropland category
estimated in this study, 52.1±17.4 Mg C ha
1
, is in the
range of those reported for other European countries. For
France, the SOC stock present in the agricultural soils (0
30 cm) has been estimated in 15 to 40 Mg C ha
1
in mid-
France and 4050 Mg C ha
1
in the richer and more
intensive cropping areas in the North and South-West
(Arrouays et al. 2001). In Belgium, Sleutel et al. (2006)
report an average SOC stock for cropland soils (030 cm)
of 5061 Mg C ha
1
, while Smith et al. (2001) suggest a
mean value of 53 Mg C ha
1
as an average value for all
European cropland soils. Also, a regional study conducted
in Italy agrees well with the estimate from this study
reporting values around 60 Mg C ha
1
, for fertile and
intensely cultivated areas of the Emilia Romagna region
(Ungaro et al. 2010).
Looking at the SOC dynamics for croplands at the
national level, recent studies indicate that the SOC pool is
near to the equilibrium with an average loss of about 0.2
0.5 Mg C ha
1
year
1
(Gardi and Sconosciuto 2007;
Janssens et al. 2005; Lugato et al. 2010; Morari et al.
2006). This loss of SOC is possibly attributable to the
intensification of agricultural practices in soils cultivated
for thousands of years (Gardi and Sconosciuto 2007;
Morari et al. 2006) and could be reduced by taking into
account some of the different mitigation options such as
reduced tillage, improved management or the use of animal
manure (Freibauer et al. 2004; Smith et al. 2000a,b;
Triberti et al. 2008).
However, to increase the size of the cropland SOC pool,
there is a need of a long-term national policy to promote
low-C-impact agricultural practices; otherwise, it is not
realistic to hypothesize that these changes will occur in a
short lapse of time.
In conclusion, given the few estimates available at
European level, repeated SOC inventories aimed to define
Table 4 Descriptive statistics of the complete data set aggregated for the cropland subcategories
Land use Number
a
Mean
b
SD
c
SE
d
Max Min Median 1° quartile 3° quartile
Arable land 48,617 53.1a 17.3 0.1 235 9.27 50.1 42.6 60.4
Agroforestry 13,663 48.9b 16.1 0.1 127.2 10.2 46.8 38.4 57.26
Vineyards 2,075 41.9c 15.9 0.4 318.3 10.6 39.4 34.1 46.7
Olive groves 5,075 51.5d 19.8 0.3 196.4 13.1 49.2 39.7 56.6
Orchards 593 44.1c 12.1 0.5 108.5 4.08 43.3 38.7 51.3
Rice fields 1,827 63.3e 27.9 0.6 267.1 23.9 61.9 51.9 67.3
Means in each row followed by the same letters are not significantly different at p< 0.05; means in each row not followed by a letter are
significantly different from the mean of all the other groups at p<0.05
a
Number of INSPIRE cells used in the calculation
b
Mean SOC stock expressed as megagrams per hectare
c
Standard deviation
d
Standard error
Table 5 Total SOC stock for the top 30 cm mineral soil of the whole IPCC cropland category in Italy
Land use Area in 2000
a
Mean SOC stock (030 cm) Total SOC stock (030 cm)
Mha MgCha
1
Tg C
Arable land 7.115±0.075 51.0
b
±16.7 362.9 ± 118.8
Vineyards 7.173± 0.008 41.9±15.9 30.1± 11.4
Olive groves 1.081± 0.011 51.5± 19.8 55.7±21.4
Orchards 6.309± 0.005 44.1 ±12.1 27.8±7.6
Rice fields 0.213± 0.001 63.3± 27.9 13.5± 6.0
490.0 121.7
Numbers on the right side are the uncertainties
a
The arable land subcategory includes also the agroforestry subcategory (M ha = million hectares)
b
Average of the mean stock from arable land and agroforestry subcategories
Biol Fertil Soils
the SOC content in cropland soils are important for future
stock change evaluation. Furthermore, assigning a precise
SOC stock to the different cropland subcategories is
fundamental for evaluating the impact of different agricul-
tural practices and addressing mitigation policy at country
level.
Acknowledgements This work benefited from the financial contri-
bution of the FISR Carboitaly project, funded by the Italian Ministry
for University and Research. A special acknowledgement is for the
SIAS project coordinators for making available all the SOC stock data
for different Italian regions and to Lugato E. for his precious
suggestions.
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Full text available from the European Soil Portal at the URL: http://eusoils.jrc.ec.europa.eu/esdb_archive/eusoils_docs/esb_rr/n05_ManualVer11EN4.pdf
Article
Using data from long-term experiments at the Loess-Chernozem site, Bad Lauchstadt und 12 other European sites, the carbon (C) and nitrogen (N) dynamics in soils, the determination of decomposable soil organic matter (SOM), the effect on yield of SOM as well as carbon and nitrogen balances are discussed. Both C and N in SOM have to be divided into an inert and a decomposable fraction. the inert C is strongly correlated with clay content, while most changes in both C and N occur in the readily decomposable fraction. In the experiments considered the latter ranges between 0.2 to 0.6% C and 0.02 to 0.06% N. The annual changes of the C-org content amount only to about 0.01% C-org corresponding to 500 kg/ha, even under extreme changes of the fertilizing system. Hot water extractable C(C-hwe) has proved to be an appropriate criterion for the calculation of the decomposable C and thus for the N release from soil. different methods to maintain a SOM balance are compared and first guideline values for an agronomically and ecologically justified SOM content of arable soils are recommended. In arable soils the exceeding of an upper C-org value influences neither crop yield nor the C and N balance in a positive way. In terms of ecology and environment, set-aside-programmes or fallows in a crop rotation affect the balances negatively. Atmospheric N deposition can amount to about 50 kg/ha.yr.
Article
Using data from long-term experiments at the Loess-Chernozem site, Bad Lauchstädt und 12 other European sites, the carbon (C) and nitrogen (N) dynamics in soils, the determination of decomposable soil organic matter (SOM), the effect on yield of SOM as well as carbon and nitrogen balances are discussed. Both C and N in SOM have to be divided into an inert and a decomposable fraction. The inert C is strongly correlated with clay content, while most changes in both C and N occur in the readily decomposable fraction. In the experiments considered the latter ranges between 0.2 to 0.6% C and 0.02 to 0.06% N. The annual changes of the Corg content amount only to about 0.01% Corg corresponding to 500 kg/ha, even under extreme changes of the fertilizing system.