Greenhouse-gas budget of soils under changing climate and land use (BurnOut) • COST 639 • 2006-2010
43
Evaluation of soil respiration variability among
different land uses
C. GARDI1 and C. MENTA2
1Department
2Department
of Environmental Science, University of Parma, Italy
of Evolutive and functional Biology, University of Parma, Italy
Introduction
The need to solve problems related to climate
change has determined an increasing interest in
processes causing emission of greenhouse gases.
Soil respiration is one of the main sources of CO2
to the atmosphere, accounting for over 25% of
global emissions (Bouwmann and Germon, 1998).
The correct evaluation of soil respiration allowed
to differentiate ecosystem acting as source or as
sink of carbon. Despite the importance of this
process, knowledge about the factors controlling it
and its variability across ecosystems is still quite
limited (Raich and Schlesinger, 1992; Rustad et al.,
2001). Soil CO2 efflux is difficult to estimate due to
the high spatial variability that characterises it
(Fang et al.,1998; Stoyan et al., 2000; Xu and Qi,
2001). The objective of this preliminary study was
to characterize the small-scale variability of soil
respiration in five different land uses in the
Northern Italian Apennine.
Apennine experiment
Materials and methods
The study area is located in the Northern Italian
Apennine (44°22’ N, 11°32’ W; 840 m a.s.l), and
the measurements were performed in five different
land uses (Tab. 1). The climate sub-humid, with a
mean annual rainfall and temperature of 1035 mm
and 11,5° C, respectively.
Soil CO2 efflux was measured in situ using an
infrared gas analyzer system (model EGM4, PP
Systems, Hitchin, UK) equipped with a flow-
through closed chamber. Measurements were
carried out in July 2006, between 12.00 and 14.00
of solar time, when the soil temperature is relatively stable. During the measurements, the
chamber, which had an area of 78 cm2 and a
volume of 1170 cm3, was inserted 2 cm into the
soil. Measurements at each sampling point took
120 s, a sampling interval long enough to get reliable estimates of CO2 efflux with the equipment
used (PP Systems, 1993). We measured soil
temperature during soil respiration measurements
with protected platinum thermoresistors (PT100)
buried at 5 cm depths.
Results and discussion
The five land uses were selected in order to represent a vegetation succession occurring on the
Apennine after the abandonment of agricultural
land. We found significant differences in soil
temperature (P<0.01) and soil respiration rate
(P<0.05) among land uses. Soil respiration
increase according to the vegetation succession,
from the agricultural land to dense shrubland; the
only exception is represented by the woodland,
were the differences in soil texture, and more in
general, in soil profile affected both, soil moisture
and soil organic carbon content. Soil respiration
was related to the organic carbon content, but
probably also to the intensity of root respiration; in
fact in the dense shrubland ecosystems, were the
distribution and the size of plants is more irregular,
we found the highest variability in soil respiration.
Although soil temperature was lower in the
shrub and tree plant communities (due to the
shading effect of vegetation), we found the highest
respiration rate in the shrubland.
44
Greenhouse-gas budget of soils under changing climate and land use (BurnOut) • COST 639 • 2006-2010
Table 1.
Soil respiration rate, temperature and organic carbon content of the five investigated land uses
Land use
n
Respiration (g CO2 m-2 h-1)
Soil temperature
Organic
carbon
(0-10 cm)
Mean
Std. deviation
Mean
Std. deviation
(mg g-1)
Arable land
6
0.40
0.14
19.22
0.60
23.7
Permanent grassland
6
0.40
0.14
19.18
0.61
45.3
Shrubland
6
0.46
0.14
14.87
0.27
62.1
Dense shrubland
6
0.68
0.22
15.10
0.30
74.4
Wood
6
0.33
0.13
15.45
0.30
56.7
Table 2.
Soil respiration rate, temperature and organic carbon content of the five investigated land uses
Respiration
(g CO2 m-2 h-1)
Soil temperature
(°C)
Soil water content
(g g-1)
Land use
n
Mean
Std. deviation
Mean
Std. deviation
Mean
Std. deviation
Forested area
30
0.88
0.29
17.73
0.21
0.31
0.03
Alfalfa field
30
1.24
0.18
19.85
0.18
n.d.
n.d.
Alluvial plain experiment
Materials and methods
The study areas are located in the Po Valley alluvial
plain (44°48’ N, 10°18’ W; 65 m a.s.l), SW of Parma.
The climate sub-humid, with a mean annual rainfall
and temperature of 775 mm and 14,4°C, respectively. The measurements were performed in two
different land uses: an arable land cultivated with
alfalfa, and a small forested area.
Soil CO2 efflux was measured with the same
procedures described for the Apennine experiment. For each site 30 measures were performed,
on the base of a regular grid of 5 x 10 m, in order to
evaluate the small scale spatial variability of soil
respiration process. Measurements were carried
out in September 2006, between 12.00 and 14.00 of
solar time.
Soil temperature was also measured at 5 cm
depth and for each point of measure it was taken a
soil sample, in order to determine the water and
the organic carbon content.
Results and discussion
The experimental data on soil respiration showed
the presence of large small-scale variability,
confirming data obtained from other researchers in
a variety of land uses and ecosystems (Maestre and
Cortina, 2003; Robertson et al., 1997; Stoyan et al.,
2000; Buchmann,2000; Rayment and Jarvis, 2000;
Xu and Qi, 2001). The spatial structure of soil
respiration is characterized by an almost pure
nugget effect; this behaviour can be explained by a
very weak spatial correlation, indicating a possible
heavy influence of the instrumental errors, and/or
by the existence of a spatial variability at a smaller
scale than the minimum distance of measures.
However a possible influence of the errors in the
measurement techniques is showed by the analysis
of two parameters correlated with soil respiration
rate, such as soil temperature and water content,
that showed a spatial correlation much stronger.
The expected higher spatial variability of the
forested area, in terms of soil respiration rate, soil
temperature and soil water content, was confirmed
by the experimental data (Tab. 2); however also the
alfalfa field, that should represent a very homogeneous soil environment, showed a rather high
spatial variability, with a weak spatial correlation.
In figure 1 it is showed the spatial variability of
soil temperature, soil water content and soil respiration rate within the forested area.
We found a positive relationship between soil
respiration rate and soil temperature (Fig. 2), while
the relationship with soil water content was very
weak.
Greenhouse-gas budget of soils under changing climate and land use (BurnOut) • COST 639 • 2006-2010
45
Parma Campus forested area
45
45
45
40
40
40
35
35
35
30
30
30
25
25
25
20
20
20
15
15
15
10
10
10
5
5
5
0
0
0
5
10
15
Soil temperature (°C)
20
0
0
5
10
15
Soil water content (% weight)
20
0
5
10
15
20
Soil respiration rate (g CO2 m-2 h-1)
Figure 1.
Contour maps showing the spatial variability of soil temperature, water content and respiration rate within
the forested area of the alluvial plain experiment.
2,00
Soil respiration (g CO2 m-2 h-1)
1,80
Forested area
vitch, J., GCTE-NEWS, 2001. A meta-analysis of the response of soil respiration, net nitrogen mineralisation
and above-ground plant growth to experimental ecosystem warming. Oecologia 126, 543-562.
y = 0,7559x - 12,526
R2 = 0,2974
1,60
Stoyan, H., De-Polli, H., Bohm, S., Robertson, G.P., Paul, E.A.,
2000. Spatial heterogeneity of soil respiration and related
properties at the plant scale. Plant Soil 222, 203-214.
1,40
1,20
Xu, M., Qi, Y., 2001. Soil-surface CO2 efflux and its spatial and
temporal variations in a young ponderosa pine plantation
in northern California. Gobal Change Biol. 7, 667-677.
1,00
0,80
0,60
Maestre F. T., Cortina J., 2003. Small-scale spatial variation in
soil CO2 efflux in a Mediterranean semiarid steppe. Appl.
Soil Ecol., 23:199-209.
0,40
0,20
0,00
17,2
17,4
17,6
17,8
18
18,2
Soil temperature (° C)
Figure 2.
Regression between soil temperature and soil respiration rate within the alluvial plain forested area.
References
Bouwmann, A.F., Germon, J.C., 1998. Introduction. Biol. Fertil. Soil 27, 219.
Fang, C., Moncrief, J.B., Gholz, H.L., Clark, K.L., 1998. Soil CO2
efflux and its spatial variation in a Florida slash pine plantation. Plant Soil 205, 135-146.
Raich, J.W., Schlesinger, W.H., 1992. The global carbon dioxide
flux in soil respiration and its relationship to vegetation
and climate. Tellus 44B, 81-99.
Rustad, L.E., Campbell, J.L., Marion, G.M., Norby, R.J.,
Mitchell, M.J., Hartley, A.E., Cornelissen, J.H.C., Gure-
Robertson, G.P., Klingensmith, K.M., Klug, M.J., Paul, E.A.,
Crum, J.R., Ellis, B.G., 1997. Soil resources, microbial activity, and primary production across an agricultural
ecosystem. Ecol. Appl. 7, 158-170.
Buchmann, N., 2000. Biotic and abiotic factors controlling soil
respiration rates in Picea abies stands. Soil Biol. Biochem.
32, 1625-1635.
Rayment, M.B., Jarvis, P.G., 2000. Temporal and spatial variation of soil CO2 efflux in a Canadian boreal forest. Soil
Biol. Biochem. 32, 35-45.
Authors:
C. Gardi
Department of Environmental Science
University of Parma
Viale delle Scienze, 33a
43100 Parma, Italy
E-mail: [email protected]
C. Menta
Department of Evolutive and functional Biology,
University of Parma
Via Farini 90, 43100 Parma, Italy