Intensification effects on the energy, water and carbon balance of managed forests

Denis Loustau, Sébastien Lafont, Jean-Pierre Lagouarde, Christophe Moisy, Delphine Picart, Alexandre Bosc (1)Virginie Moreaux (1,2)Fabienne Benest (3)

(1)Inra, ISPA, Villenave d’Ornon, France (2)Global Change Research Group, San Diego State University, San Diego, Ca. 92182, USA, (3)Institut Géographique National, Bordeaux 33000, France

EGU Annual Assembly 2014.

Climatic Impacts of Forest intensification(Lee et al., Nature 2011; Bright et al., GCB 2014; Luyssaert et al. Nature Climate Change, 2014 )

1.GHG budget (CO2, CH4, N2O)1. Net Atmospheric Exchange 2. Fossil fuel consumption (management)3. Carbon stocks in situ: biomass, soil 4. Carbon stocks ex situ: harvested products, residues5. Fossil fuel substitution : bioenergy, building, etc..

2.Water balance1. Evapotranspiration2. Runoff, groundwater recharge

3.Energy balance1. Surface radiative budget (a, Ts)2. Convective exchanges (ra, rs, LE, H)

Intensification of temperate Pine Forests

Tillage NPK Stocking Thinnings Parts harvested

Age at clearcut

Pine Extensive (P60) 0 0 1600 4 Stem 60

Pine Standard (P45) X + 1600 6 Stem45

Pine Intensive (P30) XXX +++ 1600 1Stem

CrownStump

30

Forest model

Climate scenario

2015 2045 2075

Approach: Comparison of homogenous forest landscapes converted from low (P60) to high (30) management intensity

1. Biogeochemical effect (carbon)

RF, GHG

2. Biophysical effect (albedo)RF, albedo

3. Overall effect at 30 years (GWP)𝐺𝑊𝑃= න ሺ𝑅𝐹𝐺𝐻𝐺 + 𝑅𝐹𝑎ሻ 𝑑𝑡𝑡2𝑡1

1985

P30

P45

P60

1. Biogeochemical effects, RF GHG (CO2)

In situ Carbon cycle modelled across x 90 ecoregions (GO+ INRA model)

Ex situ emissions & fossil C displacement• Bioenergy: emissions same year, displace 0.7 fossil CO2• Timber: emissions delayed 60 yrs, displace 2.5 fossil CO2

Asymptotic decline of airborne fraction of CO2

Overall radiative forcing according to Myhre et al. 98, Moreaux et al. 2008

Soil

Atmosphere

Fossil C

HarvestVegetation

Net CO2 balance

Trees

Soil

Understorey

Water cycle

Energy balance

Carbon cycle

Plant developmentMicro

climate

Climate forcing

Management forcing

RF GHG (CO2) : Forest model GO+ (INRA)

Groundwater

Soil (root depth)

40cm

80cm

120 cm

- increases 2-3 fold the biomass production- more efficient in fertile site / favourable climates:intensification efficiency reduced in 2075 by drought

Managt

1985 2015 2045 2075

Results - Intensification impact on yield (90 ecoregions boxplots)

Soil (root depth)

40cm

80cm

120 cm

Intensification may enhance soil carbon storage (litterfall ↗)In 2075, soil carbon is reduced at 70% of 2015 level.

Managt

1975 2015 2045 2075

Results- intensification impact on soil carbon stock

Soil (root depth)

40cm

80cm

120 cm

Effect is stronger in fertile sites and humid climate

1975 2015 2045 2075

Biomass carbon stock depleted by 30 % in intensified landscapes

Managt

Results- intensification impact on standing biomass

-1.00000E-04

-5.00000E-05

0.00000E+00

5.00000E-05

RF GHG (CO2) : Results synthesis in terms of radiative forcing

RF (W.m-2) P60 P30

1971 1980 1990 2000

RFNEERFHP

Net RFCO2

Cooling

Warming

• In situ sequestration effect (NEE) is offset by mineralisation of harvested products (HP);

• The resulting net CO2 effect is due to storage in soil, biomass and products;

1 30

1 30

1 30

1 30

1 30

1 30

1 30 1 30

RF (W.m-2) P45 P30

1970 - 1999

2000 - 2029

2030 - 2059

2060 - 2099

P60 P30

Vertical axis range is 5 to - 10 E-5 W.m-2

• Cooling impact from P60 to P30

• Intensification effectsdecreases in the future

• Opposite trends evidenced for the P45 P30 conversion

RF GHG (CO2) : Results synthesis in terms of radiative forcing

Pine Forest, Bordeaux, SW France. 5km:

RFalbedo Calibration from GEOLAND and MODIS products

Reference Site:

continuous cover including multiple ages

ManagedSite:

~even distribution of age classes [0 to 30]

Comparison of monthly albedo time series at landscape level

SW FranceCOPERNICUS ALBEDO product (AL-BH-BB) from VGT sensor. 1km / 10-day

0.05

0.1

0.15

0 3 6 9 12

N - New ZealandModis product MCD43A1 Collection 5 shortwave actual albedo0.5 km / 8-day

0.05

0.1

0.15

0 3 6 9 12

Intensive Reference unmanaged

SW France N New-zealand

RF albedo : Results - Interannual mean of monthly values in albedo

Albedo

RF (W.m-2)

3. Overall impacts of forest intensification

P45 P30

1970 - 1999

2000 - 2029

2030 - 2059

2060 - 2099

P60 P30

1 30 1 30

1 30 1 30

1 30 1 30

1 30 1 30

Vertical axis range is - 10 E-5 W.m-2

1 30

CO2

Bioenergy

Timber

CO2

Albedo

GWP30 (W.m-2)

3. Overall impacts of forest conversion on GWP30

P60 P30

-2.00E-03-1.00E-030.00E+00

1985

2015

2045

2085

CO2 Albedo

Main points to take home.

•Intensification effects interact with climate and soil

•Albedo of intensively managed forests is 0.01 to 0.03 larger (not implying colder surface, Moreaux et al. 2011, Luyssaert et al. 2014)

•Changes in radiative forcing albedo and GHG have similar magnitudes– results are quite sensitive to fossil fuel displacement ratio;

– Biogeochemical (CO2) impact > albedo’s under fertile conditions (climate & soil)

•Complete regional case studies are needed

–Integration of fossil fuel cost of intensification

–LCA of HP: biofuels, timber, biochar, biodiesel, electricity, heat..

–Radiative forcing adapted to local conditions e.g. using a 1D-column model

INRA ISPA SUPPORT •Alexandre Bosc•Sébastien Lafont•Denis Loustau•Christophe Moisy•Virginie Moreaux*•Delphine Picart•Jean-Pierre Lagouarde

IGN •Fabienne Benest

* (present address San Diego University)

 

FORÊVER