US Forest Disturbance Trends observed with Landsat Time Series

Samuel N. Goward1 (PI), Jeffrey Masek2, Warren Cohen3, Gretchen Moisen4, Chengquan Huang1, 

Robert Kennedy5, Karen Schleeweis1, Rama Nemani6

1Department of Geography, University of Maryland, College Park MD2Biospheric Sciences Lab, NASA Goddard Space Flight Center, Greenbelt, MD 3U.S.D.A. Forest Service, Pacific Northwest Research Station, Corvallis, OR4U.S.D.A. Forest Service, Rocky Mountain Research Station, Ogden, UT5Earth and Environment Dept., Boston University, Boston MA6NASA Ames Research Center, Moffett Field, CA

Biomass

BiologicC Flux

Atmosphericsource

Disturbance, Age Structure, and Carbon

Old

Disturbance Dominated

Regrowth Dominated ar

ea h

isto

gram

s

Balanced

time

Understanding the history of land use, management, and disturbance is critical because disturbance and recovery are major determinants of the net terrestrial carbon flux.” - 2007 SOCCR (SAP 2.2)

• 56 NACP project descriptions include “Disturbance”

• NACP Disturbance Synthesis 2010-2011 (Kasischke)

• JGR-B Special Section “Impacts of Disturbance on the North American Carbon Cycle”

• Many new products, analyses

Forest Disturbance and NACP

North American Forest Dynamics (NAFD):  Landsat-based sample of US forest disturbance

•50 sample scenes across US;  probability-based sample for area estimates (East, West strata)•Annual time series of Landsat data for each sample (1985-2005)•Disturbance events mapped using Vegetation Change Tracker (VCT approach) (Huang et al, 2010)

Vegetation Change Tracker (VCT): Huang et al (2010)

Example: Fire & Harvest, Sierra Nevada CA

NAFD National Disturbance Rates estimates%

US

For

est

Cov

er D

istu

rbed

1985-2005 average = 2.77 Mha/yr (+/- 0.76) = 1.1% US Forest Land

Masek et al, in review

East versus West%

For

est

Cov

er D

istu

rbed

West

East

US QuadrantsWestern US Eastern US

Central

Coastal

Southeast

Northeast

Masek e

t al (2

008)

Hans

en et

 al (2

010)

NAFD (

raw)

NAFD (

adjus

t)

FIA Ag

e

Inven

tories

Medde

ns (2

012)

0

1

2

3

4

5

6

7

8

9

Insects (USFS, 2010)

Fire (EPA, 2010)

Harvest (Smith et al, 2009)

Western Insect Mortality (2005-10)F

ore

st A

rea

Dis

turb

ed

(Mha

/yr)

Estimates of US Disturbance Rates

US Forest Carbon Fluxes from Recent Disturbance (Williams et al., 2012 GBC; in review RSE)

• CASA calibrated to match FIA biomass-age curves for each forest type & region

• Landscape age distribution from FIA and NAFD time since disturbance

• Landscape-scale estimates of NPP, NEP, biomass based on age, type, region

Higher NAFD Disturbance = Lower NEP Estimate

Williams et al., in review

NAFD Phase III

• Annual Time Series (1972 -2012) • Wall-to-wall  (440 * 40+ = > 17,000 annual maps) via NEX 

computing environment (Nemani – NASA ARC)• Systematic Validation (Cohen – USFS PNW)• Disturbance Causes (Moisen USFS RMS)• Regrowth Dynamics  (Masek – NASA GSFC)

0 %disturbed /yr

LEDAPS Disturbance Map 1990-2000 (Masek et al., 2008)

>2.0

Geography of Disturbance Causes(No Insects yet)

Schleeweis , 2012

Conclusions

• US Forest Disturbance Rates estimated at 1.1%/yr from 1985-2005 via NAFD Landsat analysis… but RS methods tend to miss considerable

partial disturbance (thinning, insect mortality, storm damage)

• Overall disturbance rates varied by ~x2 during mapping epoch

• Western variability driven by fire, insects;  Eastern variability driven by management (GDP?)

Forest Carbon Dynamics

“The relative importance of these broad factors in accounting for the current [forest carbon] sink is unknown… Understanding the history of land use, management, and disturbance is critical because disturbance and recovery are major determinants of the net terrestrial carbon flux.” - 2007 SOCCR (SAP 2.2)

Attribution of Disturbance Variability

Masek et al, in review

US Forest Biomass and C Storage Potential (PgC)

US forests could ~double current stocks

Williams et al., in review

NAFD Staff & CollaboratorsUniversity of Maryland (Goward, Huang)

Feng ZhouResearch Associate

Mary Ann LindseyGRA

Louis KeddellGRA

Elaine DenningGRA

CollaboratorsLiz LaPointUSFS FIA

J. Collatz NASA GSFC

Bev Law OSU

J. Dwyer USGS/EROS

Z.  Zhu USGS

H. BastianUSGS

USFS PNW/OSU (Cohen, Kennedy)Stephen StehmanSyracuse University

Zhiqiang YangResearch Associate

Peder NelsonGRA

USFS RMRS (Moisen)Karen Schleeweis Todd Schroeder Chris Toney

NASA GSFC (Masek)Chris Neigh Khaldoun Rishwami