Remote Sensing Projects at Jasper Ridge, California
Seasonal
Vegetation Patterns in a California Coastal Savanna Derived from Advanced
Visible/Infrared Imaging Spectrometer (AVIRIS) Data 
There is a need to better understand seasonal and
inter-annual variations in ecosystem characteristics and how these
properties interact with the climate system, in order to predict
long term environmental consequences of climate and land use changes
on ecosystem function and sustainability (USGCRP, 1996). We
have examined the relationship between vegetation structure patterns,
foliage distribution, and water availability for three dates in 1992
over a semiarid region in the central Coast Range of California. We
compare seasonal vegetation patterns when energy balance conditions
are markedly different to explore the use of AVIRIS data for monitoring
seasonal changes in surface and atmospheric properties.
Ustin, S.L., D.A. Roberts, and Q.J. Hart. (1997), Seasonal Vegetation Patterns in a California Coastal Savanna Derived from Advanced Visible/Infrared Imaging Spectrometer (AVIRIS) Data. In Remote Sensing Change Detection: Environmental Monitoring Applications and Methods, Elvidge, C.D., and Lunetta, R. (Eds.), Ann Arbor Press, MI, in press. |
This study examined the use of stepwise multiple linear regression to quantify leaf carbon, nitrogen, lignin, cellulose, dry weight and water compositions from leaf level reflectance (R). Two fresh leaf and one dry leaf datasets containing a broad range of native and cultivated plant species were examined using unconstrained stepwise multiple linear regression and constrained regression with wavelengths reported from other leaf level studies and wavelengths derived from chemical spectroscopy. Results suggest caution in the use of stepwise multiple linear regression on fresh leaf reflectance spectra. Band selection does not appear to be based upon the absorption characteristics of the chemical being examined.
Grossman, Y.L., S.L. Ustin, S. Jacquemoud, E.W. Sanderson, G. Schmuck, and J. Verdebout. (1996), Critique of Stepwise Multiple Linear Regression for the Extraction of Leaf Biochemistry Information from Leaf Reflectance Data. Remote Sensing of Environment, 56:182-193.
Relationships between
canopy chemistry and reflectance for plant species from Jasper Ridge,
California
Our study examined the statistical relationships
among a number of foliar biochemicals including carbon, cellulose,
lignin, nitrogen, and water on a leaf area (content) and dry
weight basis (concentration). Chemical determinations of total
carbon, nitrogen, lignin, cellulose, and water were made on a
subset of the data (26-38 samples depending on chemical). The
contents and concentrations of some of these biochemicals were
highly correlated with one another, but the degree of correlation
varied with the weight or area basis used. In general, more of
the variance was explained using an area basis than a weight
basis. Principal components analysis separated individual species
from one another. Stepwise multiple linear regression using the
first five principal component scores explained lower proportions
of the variance than did regression using log(1/R) and its derivatives.
Grossman, Y.L., E.W. Sanderson, and S.L. Ustin
(1994), Relationships between canopy chemistry and reflectance
for plant species from Jasper Ridge, California, in Proceedings
International Geoscience and Remote Sensing Symposium IGARSS
'94. August 8-12, 1994 California Institute of Technology.
Seasonal Changes Observed
in AVIRIS images of Jasper Ridge, California (1994)
We examined three 1992 Airborne Visible Infrared
Imaging Spectrometer (AVIRIS) images of Jasper Ridge Biological
Preserve (JRBP) for spectral changes associated with community
type and for phenological patterns over the growing season.
Images were analyzed with spectral mixture analysis using library
endmembers representing green foliage, non-photosynthetic vegetation,
and soils characteristic of the site. Vegetation endmember
fractions were used to define vegetation communities and compared
to the field-based vegetation map. After vegetation boundaries
were defined, we extracted the mean vegetation spectrum and standard
deviation of the spectrum for each vegetation type. Changes
in AVIRIS spectra over the season were compared among communities
and these spectra were compared to field-based reflectance and
biochemistry measurements of foliage that were representative
of each community over the same seasonal period.
Slide
Presentation
Ustin, S.L., L. Duan, Q.J. Hart. (1994), Seasonal
changes observed in AVIRIS images of Jasper Ridge, California.
in Proceedings International Geoscience and Remote Sensing Symposium
IGARSS '94. August 8-12, 1994 California Institute of Technology.
Functional Patterns in
an Annual Grassland during an AVIRIS Overflight
This study relates Airborne
Visible/Infrared Imaging Spectrometer (AVIRIS) imagery to ground
measurements of vegetation distribution, physiology, and productivity
at Stanford University's-Jasper Ridge Biological Preserve. Spectral
mixture analysis and the normalized difference vegetation index
(NDVI) calculated from AVIRIS data were used to evaluate spatial
patterns of vegetation type, productivity, and potential physiological
activity. Concurrent ground sampling revealed a high degree of
correlation between NDVI and estimates of canopy chemistry, structure,
productivity, and CO2 flux, supporting the use of
imaging spectrometry to estimate spatial and temporal trends
in vegetation physiology and productivity in this relatively
simple grassland ecosystem. Geostatistical analyses of both ground
and AVIRIS data supported the conclusion that the AVIRIS pixel
size was suitable for describing the influence of major landscape
features in this grassland and that spatial detail would he lost
at slightly larger pixel sizes typical of other imaging spectrometers.
Gamon, J.A., C.B. Field, D.A. Roberts, S.L.
Ustin, and V. Riccardo. (1993) Functional patterns in an
annual grassland during an AVIRIS overflight. Remote Sensing
of Environment 44:239-253
Jasper Ridge Vegetation
Five samplings of naturally occurring vegetation
were made at Jasper Ridge Biological Preserve, Stanford, CA during
1992-1993. Samplings were made on June 30, 1992, September
9, 1992, December 15, 1992, April 3, 1993 and May 27, 1993.
Using AVIRIS
Images to Measure Temporal Trends in Abundance of Photosynthetic and Nonphotosynthetic
Canopy Components
An AVIRIS image of Jasper Ridge was acquired
May 15,1991 (910515B, run 10, segment 2) under clear sky conditions.
Linear and nonlinear spectral mixture analysis was performed
and four spectral endmembers were identified. In 1991, plant
characteristics and surface reflectance measurements were made
at 20m intersections over a 6 ha. permanently staked grid referenced
to known coordinates. We examined spatial patterns for the photosynthetic
and nonphotosynthetic canopy fractions in the grasslands in relation
to field data and from aerial photography and their temporal
trends.
Ustin, S. L., M. O. Smith, D. A. Roberts,
J. A. Gamon, and C. B. Field. (1992). Using AVIRIS Images to
Measure Temporal Trends in Abundance of Photosynthetic and Nonphotosynthetic
Canopy Components. Summaries of the Third Annual JPL Airborne
Geoscience Workshop, Pasadena, CA, 92-14, 5-7.
Evaluation of
Spatial Productivity Patterns in an Annual Grassland During an AVIRIS
Overflight
In May, 1991, coincident with an AVIRIS overflight,
we completed a ground-based study covering 9 hectares of an annual
grassland. There were two goals to this ground study:
1) Obtain ecologically and physiologically
meaningful data for relating AVIRIS images to canopy structure,
biochemistry and physiology.
2) Evaluate the suitability of the 20-m AVIRIS
pixel size for depicting detailed spatial patterns of productivity.
Gamon, J. A., C. B. Field, and S. L. Ustin.
(1992). Evaluation of Spatial Productivity Patterns in an Annual
Grassland During an AVIRIS Overflight. Summaries of the Third
Annual JPL Airborne Earth Science Workshop: AVIRIS Workshop,
Pasadena, CA, 92, 17-19.
Mapping the
Spectral Variability in Photosynthetic and Non-Photosynthetic Vegetation,
Soils, and Shade Using AVIRIS
The primary objective of this research was to
map as many spectrally distinct types of green vegetation (GV),
non-photosynthetic vegetation (NPV), shade and soil (endmembers)
in an AVIRIS scene as is warranted by the spectral variability
of the data. Once determined, a secondary objective was to interpret
these endmembers and their abundances spatially and spectrally
in an ecological context.
Roberts, D. A., M. O. Smith, D. E. Sabol,
J. B. Adams, and S. Ustin. (1992). Mapping the Spectral Variability
in Photosynthetic and Non-Photosynthetic Vegetation, Soils, and
Shade Using AVIRIS. Summaries of the Third Annual JPL Airborne
Geoscience Workshop, Pasadena, CA, 92-14, 38-40.