Plant species influence on soil C after afforestation of Mediterranean degraded soils

María T. Domínguez, Carlos García-Vargas, José M. Murillo, Engracia Madejón and Teodoro Marañón Instituto de Recursos Naturales y Agrobiología de Sevilla (IRNAS-CSIC) Reina Mercedes Av, 10. E-41012, Seville (Spain)

• The loss of soil organic C is one of the main environmental problems in the Mediterranean basin, where 75 % of the soils have low or very low organic matter content (< 2 %).

• Afforestation of degraded lands is one of the key strategies to achieve an increase of C sequestration in ecosystems.

• Plant species differ in their mechanisms of C-fixation, C allocation into roots and interactions with soil microorganisms, all these factors influencing the dynamics of soil C following the afforestation of degraded soils.

Background

• How do different woody plant species affect soil C dynamics in degraded and afforested Mediterranean soils?

Key Question

Acknowledgements: The RECARE project is funded by the European Commission FP7 Programme, ENV.2013.6.2-4 ‘Sustainable land care in Europe’. EU grant agreement: 603498.

RECARE website: www.recare-project.eu; RECARE Information Hub: www.recare-hub.eu; Twitter@RECARE_EU; vimeo.com/channels/RECARE; facebook.com/groups/RECARE/

Studied Area and Plant Species

The Guadiamar Green Corridor (SW Spain) is a large-scale soil

remediation project, where different native plant species were

afforested after a mine spill in 1998 that contaminated soils with

trace-elements (1)

C pools and CO2 fluxes underneath the cover of 4 woody plant

species were analyzed 15 years after land remediation and

compared with soils without woody cover (2), in 3 sites with

different degree of soil contamination.

Main Results

Differences in total soil organic C among species were more pronounce in the more acidic site (5). Concentrations of phenols and sugars in the dissolved organic C (DOC), which might indicate its biodegradability, were similar among species.

Microbial biomass and activity (e.g. phenol-oxidase activity) was highly influenced

by soil pH (3), and plant species had a significant influence on soil pH in the more acidic site (4). Soils

under Retama shrubs were more acidified.

Soil CO2 fluxes were more influenced by the plant

species than total soil C content (6). Soils under

Retama shrubs showed the lowest fluxes. This might be

related to the low decomposability of its litter.

Soil Respiration

Nutrient

availability Microbial biomass

and activity

DOC/ DON

Retama shrub

(Retama sphaerocarpa

(L). Boiss) Mastic tree

(Pistacia lentiscus L.)

Wild olive tree

(Olea europaea subs. europaea L.)

Total soil C

Litter layer

White poplar (Populus alba L.)

(2)

(1)

• 15 years after the establishment of the plantations the influence of the planted species is still limited, being more pronounced in the more acidic and nutrient-poor soils.

• Changes in soil C stocks after the afforestation of degraded Mediterranean soils are hardly detectable at decadal time-scales; more dynamic variables (microbial biomass, CO2 fluxes) must be monitored to determine which plant species should be promoted to enhance C sequestration capacity in the long-term.

Conclusions

Soil pH

3 4 5 6 7 8

Mic

robia

l B

iom

ass

(mg C

kg s

oil

-1)

0

500

1000

1500

2000

2500

p <0.0001

r2 = 0.18

Soil pH

3 4 5 6 7 8

Phe

no

l-o

xid

ase

activity

(m

ol g

-1h

-1)

-2

0

2

4

6

8

p <0.0001

r2 = 0.32

Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr

So

il re

spir

atio

n (

CO

2 m

-2 h

-1)

0.0

0.2

0.4

0.6

0.8

1.0

1.2O. europaea

P. alba

P. lentiscus

R. sphaerocarpa

Herbaceous cover

(3)

(4)

(5) (6)

Herbaceous cover

Contact details: María T. Domínguez (IRNAS-CSIC)

maitedn@irnase.csic.es