Modelling the impact of atmospheric

nitrogen deposition on French forests

in the context of climate change.

N Gaudio1, S Belyazid2 , C Obeidy, JC Gégout3, D Alard4, E Corcket4, T Gauquelin5,

B Nihlgård6, JP Party7, A Mansat1, H Sverdrup6, A Probst1

1 Toulouse University; UPS, INP; CNRS; EcoLab (Functional Ecology and Environment laboratory) - France 2 Belyazid Consulting & Communication AB - Sweden 3 UMR AgroParisTech, ENGREF, INRA - France 4 UMR BioGeco INRA Bordeaux - France 5 IMEP, Provence University - France 6 Lund University - Sweden 7 Sol-Conseil - France

Nitrogen deposition:

Impacts.

• Influence on:

Soil processes (acidification, eutrophication…),

Trees (nutrition, phenology…),

Ground vegetation (species richness, species composition…).

• Examples in literature: with increasing N deposition…

Stevens et al. 2004, Science

…loss of species richness

Gilliam 2006, J. Ecol.

…shift in species abundance

Nitrogen deposition:

European environmental policy.

Convention on Long-Range Transboundary Air Pollution (CLRTAP, 1979)

GOAL = reduce and prevent atmospheric pollution

Working Group on Effects GOAL = understand the impact of the main air pollutants on human health and environment

International Cooperative Programmes ICP (Forests, Water, Modelling and Mapping, etc)

GOAL = quantify the sensitivity of ecosystems to nitrogen

map and model these critical loads

National Focal Centre NFC (CNRS, Toulouse in France) GOAL = modelling and mapping at the French scale

Critical loads of nitrogen CL(N) =

“A quantitative estimate of an exposure to one or more

pollutants below which significant harmful effects on

specified sensitive elements of the environment do not

occur”. (Nilsson & Grennfelt, 1988).

→ Assessment of the sensitivity on the ecosystems to N. Probst & Leguédois, 2008

Forest ecosystems

Nitrogen deposition:

Assessment of nitrogen critical loads in forests.

Empirical modelling

Using field experiments and experts knowledge

No prediction and spatialization

Biogeochemical modelling

Using nitrogen cycling balance

No real consideration of ecosystem functioning

CL(N)bioch < CL(N)emp

NEW APPROACH: mixed biogeochemical and ecological model

Nitrogen deposition:

Modelling – the tool.

Belyazid 2006, Thesis, Lund University

Wallman et al. 2005, For. Ecol. Manage.

VEG

ForSAFE

Validated in Sweden and Switzerland

Nitrogen deposition:

Modelling – the tool.

ForSAFE Biogeochemical model

INPUTS Climate

Soil

Forest management

Nitrogen deposition Belyazid 2006, Thesis, Lund University

Wallman et al. 2005, For. Ecol. Manage.

VEG Ecological model

VEG

ForSAFE

OUTPUTS

INPUTS Vegetation database

(French flora, Ecoplant, Ellenberg)

OUTPUTS = cover,

species composition

ForSAFE-VEG model

Gégout et al. 2005, J. Veg. Sci.

Ellenberg et al. 1992

Validated in Sweden and Switzerland

Nitrogen deposition:

Modelling – the validation in France.

RENECOFOR

102 forest sites

27 sites with measurements:

deposition, soil characteristics,

climate, vegetation surveys, forest

stand characteristics.

Q. robur (9)

Q. pertraea (19)

Q. robur/pertraea (2)

F. sylvatica (20)

Pseudotsuga sp. (6)

Picea abies (11)

Larix decidua (1)

Pinus laricio (2)

Pinus pinaster (7)

Pinus sylvestris (14)

Abies alba (11)

From www.onf.fr/renecofor/sommaire/sites

Cl

0

50

100

150

200

250

300

350

400

450

500

1993 1995 1997 1999 2001 2003 2005 2007 2009

Year

Cl- (

µE

q.l

-1)

Modelled

MeasuredBasic Cations

0

100

200

300

400

500

1993 1995 1997 1999 2001 2003 2005 2007 2009

Year

Basic

cati

on

s (

µE

q.l

-1)

Modelled

Measured

Calibration and validation in progress,

particularly for nitrogen cycle…

pH

4

4,5

5

5,5

6

6,5

7

7,5

1993 1995 1997 1999 2001 2003 2005 2007 2009

Year

pH

Modelled

Measured

Nitrogen deposition: Modelling – climate and deposition scenarios.

Nitrogen deposition scenarios SRES climate scenarios

A2

B1

Current T°

Simulations from CNRM and IPSL models (Braconnot et al. 2009) Simulations from EMEP + ForSAFE

ForSAFE-VEG Coupled biogeochemical and ecological model

0

30

60

90

120

150

180

1800 1850 1900 1950 2000 2050 2100

Year

NO

x d

ep

osit

ion

(m

Eq

.m-2

.yr-1

) MFR

CLE

MFR Maximum Feasible Reduction

CLE Current Legislation in Europe

Dynamic model

0

30

60

90

120

150

180

1800 1850 1900 1950 2000 2050 2100

Year

NO

x d

ep

osit

ion

(m

Eq

.m-2

.yr-1

) MFR

CLE

MFR Maximum Feasible Reduction

CLE Current Legislation in Europe

No control

Background

Nitrogen deposition: Modelling – climate and deposition scenarios.

Nitrogen deposition scenarios SRES climate scenarios

A2

B1

Current T°

Simulations from CNRM and IPSL models (Braconnot et al. 2009) Simulations from EMEP + ForSAFE

ForSAFE-VEG Coupled biogeochemical and ecological model

0

30

60

90

120

150

180

1800 1850 1900 1950 2000 2050 2100

Year

NO

x d

ep

osit

ion

(m

Eq

.m-2

.yr-1

) MFR

CLE

MFR Maximum Feasible Reduction

CLE Current Legislation in Europe

Dynamic model

Predictions: Exceedance of critical loads

Biodiversity response to scenarios

Forest stand productivity

Nitrogen deposition: Modelling – climate and deposition scenarios.

Preliminary results...

• Nitrogen decrease ↔ decrease of grasses cover

Simulation: results on one forest site…the grasses response over 2010-2100.

0

30

60

90

120

150

180

1800 1850 1900 1950 2000 2050 2100

Year

NO

x d

ep

osit

ion

(m

Eq

.m-2

.yr-1

) MFR

CLEMFR

CLE

A2

B1

B1

CLE

MFR

Preliminary results...

• Nitrogen decrease ↔ decrease of grasses cover

Simulation: results on one forest site…the grasses response over 2010-2100.

• From 2050, distinction of two groups MFR + CLE-A2

MFR + CLE-B1

= Response more pronounced

Influence of climate change stronger than influence of nitrogen deposition

B1

A2

0

30

60

90

120

150

180

1800 1850 1900 1950 2000 2050 2100

Year

NO

x d

ep

osit

ion

(m

Eq

.m-2

.yr-1

) MFR

CLEMFR

CLE

A2

B1

To conclude

• A coupled biogeochemical – ecological model

• Integration of nitrogen deposition into forest processes,

combined with climate change

BUT model is in progress

calibration of nitrogen cycle

make functional groups within vegetation database

work on vegetation indicators of critical load exceedance

prediction of vegetation response

THANK YOU !