The role of soil respiration in the carbon balance of a semiarid ecosystem in the South East of Spain

João Raimundo1, Ana Rey1, Cecilio Oyonarte2

1 Estación Experimental de Zonas Áridas, 2 Universidad de Almería

IntroductionThe importance of Soil Respiration (SR) in the whole ecosystem functioning has been widely recognised. Semiarid ecosystems are poorly studied and thus not well understood. Other factors that so far have not been taken into account may play an important role in determining SR in semiarid ecosystems characterised by high temporal and spatial variability as well as high temperatures and low water availability.

IntroductionThe importance of Soil Respiration (SR) in the whole ecosystem functioning has been widely recognised. Semiarid ecosystems are poorly studied and thus not well understood. Other factors that so far have not been taken into account may play an important role in determining SR in semiarid ecosystems characterised by high temporal and spatial variability as well as high temperatures and low water availability.

3000Annual sun hours

Calcaric leptosolSoil type

Mediterranean steppe alpha grass (Stippa tenacissima L.)

Vegetation

200 mmAnnual mean precipitation

72%Annual relative humidity

18 ºCMean annual temperature

205 m asl (BB), 50 m asl (AM)

Altitude

N 36º56’26.0’’; W 2º01’58.8’’

Latitude

Dry Subtropical desert(semiarid)

Climate

Cabo de Gata Natural Park, Almería

Location

Study Field SitesBalsa Blanca – BBAmoladeras - AM

3000Annual sun hours

Calcaric leptosolSoil type

Mediterranean steppe alpha grass (Stippa tenacissima L.)

Vegetation

200 mmAnnual mean precipitation

72%Annual relative humidity

18 ºCMean annual temperature

205 m asl (BB), 50 m asl (AM)

Altitude

N 36º56’26.0’’; W 2º01’58.8’’

Latitude

Dry Subtropical desert(semiarid)

Climate

Cabo de Gata Natural Park, Almería

Location

Study Field SitesBalsa Blanca – BBAmoladeras - AM

(AM) (BB)

MethodologySR is being measured with a portable CO2 EGM-4 Gas Analyser and RS SRC-1 Chamber (PP-System, UK) in two field study sites (Balsa Blanca – Pristine and Amoladeras – Land Degradation).Soil temperature and soil moisture are measured at the same points.Six plots of 10 x 10 m were set up (n=6) and in each plot three replicates of soil collars were placed in three different soil covers: E (Under plant) C (Biologic crust) S (Bare soil)

Plot 66.2

10 m

5 m

5 m10 m

Plot 1

Plot 5

Plot 4

4.1

4.2

4.3

5.1

5.2

5.3

6.1

1.1

6.3

1.2

1.3

Plot 22.2

2.3

2.1

Plot 3

3.1

3.3

3.2

5 m

CENTER OF THE PLOT

REPLICATES

BIOLOGIC CRUST (C)

BARE SOIL (S)

UNDER PLANT (E)

Plot 66.2

10 m

5 m

5 m10 m

Plot 1

Plot 5

Plot 4

4.1

4.2

4.3

5.1

5.2

5.3

6.1

1.1

6.3

1.2

1.3

Plot 22.2

2.3

2.1

Plot 3

3.1

3.3

3.2

5 m

CENTER OF THE PLOT

REPLICATES

BIOLOGIC CRUST (C)

BARE SOIL (S)

UNDER PLANT (E)

Under Plant

Biologic Crust

Bare Soil

Replicate

Replicated in both BB and AM sites

www.climatescience.gov

Experimental design

Workshop, 5-9 September 2008, Technical University of Crete, Chania, Crete 3rd

Temporal and Spatial Variability

SR measured on Plot 2 from BB during 14 h

SR measured in BB and AM every week (every fortnight in Summer):-Diurnal Variation; Seasonal Variation; Interannual Variability.-SR variability between soil covers (E,C and S)

DIURNAL VARIABILITYBalsa Blanca

0.000.200.400.600.801.001.201.401.601.80

7 8 9 10 11 12 13 14 15 16 17 18 19 20 21

Time of the Day (h)

SR

Rat

e

(µm

ol m

-2 s

-1)

Under Plant Biologic Crust Bare Soil

30/05/2008

TEMPORAL VARIABILITY Amoladeras

00.5

11.5

22.5

33.5

4

Soil R

espir

atio

n R

ate

(µm

ol m-2

s-1)

Spring Summer

Balsa Blanca

00.5

11.5

22.5

33.5

4

113 119 129 133 141 155 165 178 190 205 214 229

Julian Day

Soil R

espir

atio

n R

ate

(µm

ol m-2

s-1)

Under Plant Biologic Crust Bare Soil

Spring Summer

Land Degradation

0.712

1.081

0.760

1.211

0.710

1.110

0.00

0.20

0.40

0.60

0.80

1.00

1.20

1.40

Mea

n So

il R

espi

ration

(µm

ol m-2

s-1)

Under Plant Bilogic Crust Bare Soil

LAND DEGRADATION

Land Degradation (AM) Pristine (BB)

SR measured in two field sites every week (every fortnight in Summer):- Amoladeras (Land degradation)- Balsa Blanca (Pristine)

SR measurements after every rainfall events.

05

1015202530354045

Julian Day

Pre

cip

itation

(m

m)

RAIN EFFECTBalsa Blanca

0

0.5

1

1.5

2

2.5

3

3.5

SR

Rate

(µm

ol m

-2 s-1

)

Under Plant Biologic Crust Bare Soil

Rainfall Effect

Yan Li. 2008. Have Desert Researchers Discovered A Hidden Loop in the Carbon Cycle?. Science 320: 1409-1410.

Inorganic Carbon

.Understanding of which factors control SR in semiarid ecosystems that have not been considered so far..Quantification of the relative importance of rainfall events on the whole carbon balance..Prediction of SR at ecosystem level by formulating a model that takes into account the temporal, spatial variability. .Impact of land degradation on SR in semiarid regions..Quantification of the dynamics of inorganic C and its contribution to SR.

Expected results