LPJ-GUESS

• Vegetation state representation

• Plant functional types

• Processes

• Application examples

• Trends and outlook in large-scale ecosystem

modelling

a large-scale ecosystem model

NGEN02 Ecosystem Modelling 2017

LPJ-GUESS population mode – typical representation of vegetation

in a DGVM of intermediate complexity*

Modelled area (grid cell)c. 100-2500 km2

Average individual

for PFT population

PFT 1 PFT 2 PFT 3 uncolonised

fractional cover (FPC) PFT

Average individual for PFT population

tree grass

crown area

height

fine roots

leaves

LAI

sapwood

heartwood

0-50 cm

50-100 cm

leaves / LAI

fine

roots

stem

diameter

*Sitch et al. 2003 Global Change Biology 9: 161-185

Average individual for PFT or species cohort

in patch

Modelled area (stand)c. 10 ha - 2500 km2

replicate patches in various

stages of development

Patch

0.1 ha

tree grass

crown area

height

fine roots

leaves

LAI

sapwood

heartwood

0-50 cm50-100 cm

leaves / LAI

fine

roots

stem

diameter

crown area

height

fine roots

leaves

LAI

sapwood

heartwood

sapwood

heartwood

0-50 cm50-100 cm

leaves / LAI

fine

roots

stem

diameter

Cohort mode – detailed representation distinguished

individual trees and patches with different disturbance histories*

*Smith et al. 2001 Global Ecology and Biogeography 10: 621

Parameter

max establishment

rate (ha1 yr1)

max longevity (yr)

survival in shade

optimal temp for

photosynthesis (°C)

bioclimatic

distribution

allocation to stem

growth

leaf:sapwood area

ratio (m2 cm2)

leaf phenology

crown spreading

boreal

10-25

evergreen

0.3

150

0.05

high

900

1250

temperate

15-25

summergreen

0.4

250

0.05

high

900

1250

boreal-temperate

10-25

summergreen

0.4

250

0.1

low

300

2500

no limits

10-30

summergreen-

raingreen

-

-

-

low

-

-

Trait differences influence functioning and interactions

among plant functional types / species

• Colonisation of unvegetated areas (primary succession)

• Inter- and intraspecific competition for light, space and soil resources

• Landscape as aggregate of stands / patches with differential history of disturbance, colonisation and succession

• Disturbances leading to complete or partial destruction of individual stands

• differential establishment, growth and mortality of species with alternative trade-offs between productivity and survivorship under stress

Elements of structural and compositional dynamics of vegetation

simulated by LPJ-GUESSb

iom

ass (

kg

C m

2)

year

Hickler et al. 2004.

Ecology 85: 519-530

Coupled plant carbon and water balance

)(),,APAR(

),,(min max

maxVfR

TcfJ

TcVfJA leaf

iE

iC

n

leafNkV max

),( cai gcfc

soil water supply

PAR

APAR =

PAR · [1 exp( k · LAI )]

AET

Ci

AET

Ci

stomatal conductance, gc

gc

AET Monteith 1995D

S

CO2

• physiological representation at leaf-level (modified Farquhar-model)

• light extinction in vegetation canopy (Beer’s law)

• humid boundary-layer increases stomatal conductance (Monteith 1995)

(Beer’s law)

Autotrophic (plant) respiration

RA = Rm + Rg

Temperature response of maintenance respiration Rm

Living tissue maintenance respiration

Growth respiration Rg = 1/3 of NPP

NPP = GPP Rm Rg

46

1

56

1309exp)(

TTg

)(N:C

TgC

rRm

Rg = 0.25 (GPP Rm)

Net primary production

T

Rm

T

Rm

Tree allometry and carbon allocation

Leaf-sapwood area ratio (Shinozaki et al. 1964)

Leaf-root mass ratio (functional balance)

Height-stem diameter relationship (forestry literature)

Diameter-population density relationship

(Reineke 1933)

rootlrleaf CkC

3/2

2 DkH

SAkLA lasa

D

H

D

CA

average individual

structureaccrued C

(annual NPP)

allometric constraints

’old’

structure

new

structure

3/51

−5/3

1

DkCA

NCA

DN

×

age

proportion of

cohort surviving

to age

max sapling

establishment

rate

juvenile

phase

adult

phase

recruitment-

juvenile growth

rate relationship

maximum

non-stressed

longevity

Cohort mode population dynamics

resource-stress

mortality

constant parameter

dynamic process

Cover crop

Irrigation

Yearly cutting

Succession of abandoned farmland

PASTURE CROPLAND

NATURAL MGD. FOREST

Crop rotations

N limitationLand cover/land use

change (gross vs. net)

Continuous forestry

Daily grazing

Detailed forest management

Managed land version accounts for land use*

*Lindeskog et al. 2013. Earth System Dynamics 4: 385-407

Olin et al. 2015. Biogeosciences 12: 2489-2515

*Olin et al. 2015. Earth System

Dynamics 6: 745-768

Agricultural crop yields*

Sample applications of LPJ-GUESS

• Quantify and attribute uncertainty

GCM-derived uncertainty in future terrestrial ecosystem C balance

• Predict complex system dynamics

→ C-N interactions under future climate and CO2

• Account for biosphere-atmosphere feedback

evapotranspiration and albedo feedback in RCM-simulated future

climate

• Assess land use and management impacts

productivity and damage risk in Swedish forestry

N export to the Baltic Sea

GCP residual land flux 0.8 PgC

LPJ-GUESS

other DGVMs

Interannual variation in net ecosystem C balance

Sitch et al. 2015

Biogeosciences 12: 653-679

uptake

release

drought-induced anomaly 2005

Re

sid

ua

l la

nd

C s

ink (

Pg

C y

r1)

Global terrestrial ecosystem C balance

under a ”business-as-usual” future climate scenario

from different climate models (GCMs)

Terr

estr

ial ecosyste

m C

pool (G

tC)

sink

source

neutral

Ahlström et al. 2012

Environmental Research Letters 7

LPJ-GUESS

RCP8.5

radiative

forcing

AR5 GCM

increased sink /reduced source

reduced sink /increased source

Robust patterns for some global regions

kgC m2 yr1

0.150

0.150

0

∆ Net ecosystem C balance

(2071-2100)(1961-1990)

latitude

earlier leaf-out→ photosynthesis

milder autumn→ respiration

increased productivityin parts of tropics

Some robust seasonal and regional trends

month

increased sink /reduced source

reduced sink /increased source

J F M A M J J A S O N D

increased sink /reduced source

reduced sink /increased source

Ahlström et al. 2012

Environmental Research Letters 7

total

uncertaintytotal

uncertainty

Terr

estr

ial ecosyste

m C

pool (G

tC)

sink

source

neutraluncertainty

due to

factor A

(e.g. NPP)

uncertainty

due to

factor B

(e.g. biomass

turnover)

remaining

uncertainty

LPJ-GUESS

RCP8.5

radiative

forcing

AR5 GCM

Contributions of individual model factors

to simulation spread

Factor Contribution to

uncertainty (%)

NPP 57

biomass turnover biome shifts 6

stand dynamics 2

wildfires 11

non-fire disturbance 3

environmental sensitivity of

soil respiration

21

Total 100

Anders Ahlström

unpublished data

Contributions of individual model factors

to simulation spread

latent heat

(evapo-

transpiration)sensible

heat

incoming

shortwave radiation

incoming

shortwave radiation

Vegetation cover and leafiness affect

partitioning of return heat flux from surface

– more latent heat reduces near-surface warming

sensible

heatlatent heat

(evapotranspiration)

15

10

5

2.5

–2.5

–5

–10

–15

15

10

5

2.5

–2.5

–5

–10

–15

Feedback contribution

LEdynLEstat

Temperature change JJA °C

(2071-2100)(1961-1990) Tdyn

Latent heat flux change LEdyn

Feedback contribution TdynTstat

2000 21002020 2040 2060 2080

0

5

4

3

2

1

2000 21002020 2040 2060 2080

0

8

6

4

2

Leaf area index

LPJ-GUESS

RCA3

A1B

emissions

ECHAM5

Changed latent heat flux enhances summer warming in

southern Europe, dampens warming i central Europe*

*Wramneby et al. 2010. J. Geophys. Res. 115

Arctic vegetation feedbacks*

LPJ-GUESS

RCA4

RCP

forcing

EC-EARTH

Additional temperature change due to vegetation feedback

(2071-2100)(1961-1990)

*Zhang et al. 2014

Biogeosciences 11: 5503-5519.

• Seasonality shift – longer growing season, earlier temperature peak

• Evaporative cooling evens out growing season temperature profile

• Ecological implications?

Additional temperature change due to biogeophysical feedback

-0.4

-0.2

0

0.2

0.4

0.6

0.8

1

2000 2020 2040 2060 2080 2100

RCP26RCP45RCP85

(a)

Te

mp

era

ture

( C

)

-3

-2

-1

0

1

2

3

J F M A M J J A S O N D

(b)

Tem

pera

ture

( C

)

∆T (

°C)

albedo feedback

evapotranspirationfeedback

(2071-2100)(1961-1990)

*Zhang et al. 2014

Biogeosciences 11: 5503-5519.

Arctic vegetation feedbacks

latitu

de ( N

)la

titu

de ( N

)

Damage risk (m3 ha1)

Production (m3 ha1 yr1)

1961-1990 2071-2100

1961-1990 2071-2100

Effects of management choices

on forest productivity and damage risk*

*Jönsson et al. 2015

Mitigation & Adaptation

Strategies for Global Change

20: 201-220

Management:

continuous cover forestry

+5-10% broadleaved trees

successively shortened rotation length

current forest management

Climate:

A1B scenario

Trends in large-scale ecosystem modelling

• Nutrient (N, P) cycles, long-term response to elevated CO2

• Trace gases – methane, N2O, biogenic volatile organic compounds

(BVOCs)

• Crops, forest management, land use change

• Coupled component in global and regional Earth system models

(ESMs)