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 MD
2Biospheric Sciences Lab, NASA Goddard Space Flight Center, Greenbelt, MD
3U.S.D.A. Forest Service, Pacific Northwest Research Station, Corvallis, OR
4U.S.D.A. Forest Service, Rocky Mountain Research Station, Ogden, UT
5Earth and Environment Dept., Boston University, Boston MA
6NASA Ames Research Center, Moffett Field, CA
Disturbance, Age Structure, and Carbon
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)
Biologic
C Flux
Biomass
Atmospheric
source
Disturbance
Dominated
Regrowth
Dominated
Balanced
area histograms
Old
time
Forest Disturbance and NACP
• 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
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
% US Forest Cover Disturbed
NAFD National Disturbance Rates estimates
1985-2005 average = 2.77 Mha/yr (+/- 0.76)
= 1.1% US Forest Land
Masek et al, in review
% Forest Cover Disturbed
East versus West
East
West
US Quadrants
Western US
Central
Eastern US
Southeast
Coastal
Northeast
Forest Area Disturbed (Mha/yr)
Estimates of US Disturbance Rates
9
8
7
Harvest (Smith et al, 2009)
6
5
4
3
Fire (EPA, 2010)
Insects (USFS, 2010)
2
1
0
Western Insect
Mortality (200510)
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
0
%disturbed /yr
>2.0
LEDAPS Disturbance Map 1990-2000 (Masek et al., 2008)
• 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)
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)
Williams et al., in review
US forests could ~double
current stocks
NAFD Staff & Collaborators
University of Maryland (Goward, Huang)
Feng Zhou
Research Associate
Mary Ann Lindsey
GRA
Louis Keddell
GRA
Elaine Denning
GRA
USFS PNW/OSU (Cohen, Kennedy)
Stephen Stehman
Syracuse University
Zhiqiang Yang
Research Associate
Peder Nelson
GRA
USFS RMRS (Moisen)
Karen Schleeweis
Todd Schroeder
Chris Toney
NASA GSFC (Masek)
Chris Neigh
Khaldoun Rishwami
Collaborators
Liz LaPoint
USFS FIA
J. Collatz
NASA GSFC
Bev Law
OSU
J. Dwyer
USGS/EROS
Z. Zhu
USGS
H. Bastian
USGS