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Investigating Tundra and Taiga
Biomes with Remote Sensing
Jessica Robin
SSAI/NASA/GSFC
Photo courtesy of M. K. Raynolds
Outline of presentation
• Climate change and arctic vegetation
• Remote sensing research
• Field research by Martha Reynolds (UAF)
• Research with GLOBE data
Photo – M. K. Raynolds
Arctic Temperatures (1966-1995)
Image courtesy of National Snow & Ice Center
2001 temperatures compared to 1950
to 1981 “normal” temperatures
Image courtesy of Goddard Institute of Space Science
Northern Greening (1981-1999)
Image courtesy of Liming Zhou, Boston University
Arctic Climate Impact Assessment
Report put out in 2004 by the Arctic
Council and the International Arctic
Science Committee (IASC)
International panel
The summary report, graphics and
detailed scientific report can be found
on the web at:
http://www.acia.uaf.edu/
Photo – D. A. Walker
Key Findings of the ACIA regarding
vegetation
Arctic vegetation zones are very likely to shift
causing wide-ranging impacts.
• Treeline is expected to move northward and to higher
elevations, with forest replacing a significant fraction of
existing tundra, and tundra vegetation moving into polar
deserts.
• More productive vegetation is likely to increase carbon
uptake, although reduced reflectivity of the land is likely to
outweigh this, causing further warming.
• Disturbances such as insect outbreaks and forest fires are
very likely to increase in frequency, severity and duration,
facilitating invasion by non-native species.
• Where suitable soils are present, agriculture will have the
potential to expand northward due to a longer and warmer
growing season.
Remote Sensing Research
Recent studies have
shown increases in
satellite-sensed indices
(NDVI) of circumpolar
tundra vegetation.
NDVI of boreal forests
shows decreasing trends.
1991
1992
1993
1994
1995
1996
1997
1998
1999
Time-integrated NDVI
Jia and Epstein
Strong Positive
Positive
Near Zero
Negative
Strong Negative
Low
High
Goetz et al. 2005 summary of
1981-2003 trends in AVHRR
NDVI
The spring season has started earlier
and max NDVI has increased
• NDVI trends for the forested
and tundra regions, broken
down by six-year intervals.
• The forested areas show a
recent decline in the maximum
NDVI.
• Tundra regions have shown a
continued increase in NDVI
and a marked 10-day shift
toward earlier onset of
greening.
• There is no corresponding shift
in the cessation of the
10% increase in NDVI
10-day spring shift in growing season length
Goetz et al. 2005. PNAS,102: 13521-13525
Changes in arctic shrubs
(Sturm et al. 2001)
Yukon Flats National Wildlife Refuge, Riordan et al. 2006 JGR
Shrinking lakes due to warmer temperatures leading to changes
in permafrost and more evaporation affects vegetation.
• Satellite data show changes
• Greenhouse warming experiments show changes
Community changes in ITEX experiment after 6 years
Control
Open-top chamber
• but very few studies have been able to document
changes occurring to undisturbed tundra
Field Research
Current research by Martha K. Raynolds
University of Alaska Fairbanks
• Trying to measure existing tundra
vegetation conditions in enough detail and
in enough places that future changes due
to climate change can be measured.
Greenland
Arctic tundra bioclimate subzones
a – mosses, liverworts and lichens, b – forbs, c – prostrate dwarfshrubs, d – non-tussock graminoids, e -hemiprostrate dwarf shrubs,
f – erect dwarf shrubs, g – low shrubs, h – tussock graminoids
Plant physiognomy occurring in different Tundra Bioclimate Subzones
• A – mosses, liverworts and lichens with some grasses and forbs
• B – rushes and prostrate dwarf shrubs with mosses, liverworts and lichens
• C – hemiprostrate and prostrate dwarf shrubs with bryophytes and lichens
• D – sedges, erect and prostrated dwarf shrubs with bryophytes and lichens
• E – tussock sedges, low and erect dwarf shrubs with bryophytes and lichens
Landscapes
of the Tundra
Bioclimate Zone
Subzone A
N
A = coldest
E = warmest
Subzone B
No shrubs
Hummocks
Subzone C
Mounds
Subzone D
S
Erect dwarf Tussocks
shrubs
Subzone E
Research with GLOBE Data
Monitoring vegetation phenology with
GLOBE Data
• Satellite data from the past two decades shows
a corresponding increase in growing season in
northern latitudes
(Myneni, R.B., Keeling, C.D., Tucker, C.J., Asrar, G., and Nemani, R.R., 1997, Increased plant growth in the
northern high latitudes from 1981 to 1991, Nature, 386:698-702.)
• However, minimal on-ground observations of
plant phenology exist to validate such satellite
findings
OBJECTIVES
1. Analyze the efficacy of phenology
monitoring using GLOBE and satellite
derived vegetation indices from AVHRR
and MODIS data
2. Compare AVHRR and MODIS data
GLOBE SCHOOLS
10 Schools
Elementary-High School
Public, Charter, Private, Home
Anchorage area (3)
Fairbanks area (7)
Lat: 61.17° – 64.85° N
Lon: 147.52°-149.41° W
FIELD
MEASUREMENTS
Birch
• Students made observations & measurements (2001-2004)
– budburst, green-up, leaf growth & green down
– research focused on budburst and green-up
• Trees/Shrubs: Betula, Populus, Salix
(Viereck, Leslie, A. and Little, Elbert L. Jr. 1972. Alaska Trees and Shrubs. Agriculture Handbook No. 410. Forest Service, USDA, Washington D.C)
Willow
GLOBE Students, Alaska
Photo courtesy of Cheryl Pratt and Elena Sparrow, U of Alaska Fairbanks
Poplar
SATELLITE DATA
AVHRR
• Advanced Very High Resolution Radiometer
• On board NOAA’s POES (Polar Orbiting
Environmental Satellites) since 1979
•Research includes NDVI data for Fairbanks
and Anchorage regions from 2001 - 2004
SATELLITE DATA
MODIS
• Moderate Resolution Imaging Spectroradiometer
• On board Terra – Earth Observing System (EOS)
• Terra satellite launched in 1999
• This research includes NDVI data for Fairbanks and
Anchorage regions from 2001 - 2004
Comparison of satellite data
Conclusions
• Different processing and spectral
characteristics restrict continuity between
AVHRR and MODIS NDVI datasets
• NDVI has limitations in boreal regions due
to snow, large extent of conifers, and
clouds