Shrubs in the CLM-DGVM

Sam LevisLMWG meeting

March 2006

(Sturm et al. BioScience 2005)

Motivation

• Shrub density increasing in tundra

• Shrub albedo < grass albedo (leaf & stem)

• Diff. morphology (eg height) affects albedo of snow-covered sfcs

CLM has shrubs!(when vegetation is prescribed)

• Broadleaf Deciduous (Boreal & Temperate)

• Broadleaf Evergreen (Temperate)

% BDS Boreal

% Broadleaf Deciduous Shrubs (Boreal)

courtesy of Peter Lawrence

SATELLITE DATA

Activating Shrubs in the DGVM

1. Bioclimatic limits:

IBIS-DGVM uses GDD0>100

But when DGVM is definedCLM can only put C3 grass in tundra…

Tundra 68ºN 149ºW

PFT COVER

Activating Shrubs in the DGVM

1. Bioclimatic limits:IBIS-DGVM uses GDD0>100shrubs behave too much like trees

2. C allocation to leaves, stems, roots3. Light competition with trees4. Drought & fire tolerance

Do we need higher PFT resolution?

Kaplan et al. (2003) Tundra PFTs

Cold Shrub evergreen

Cold Graminoid or Forbsummergr.

Cushion Forb evergreen

Epstein et al. 2000

Longer list…

Extras

Tundra 68ºN 149ºW

% C3 Grass Arctic

% C3 Grass (Arctic)

courtesy of Peter Lawrence

SATELLITE DATA

% BET Boreal

% Broadleaf Evergreen Trees (Boreal)

courtesy of Peter Lawrence

SATELLITE DATA