The Great Plains Corridor rangeland project utilizes natural vegetation systems as phenological indicators of seasonal development and climatic effects upon regional growth conditions. A method has been developed for quantitative measurement of vegetation conditions over broad regions using ERTS-1 MSS data. Radiance values recorded in ERTS-1 spectral bands 5 and 7, corrected for sun angle, are used to compute a band ratio parameter which is shown to be correlated with aboveground green biomass on rangelands

Deering, D. W.

Haas, R. H.

Rouse, J. W., Jr.

Schell, J. A.

English

NASA Technical Reports Server

’aper A 20 
MONITORING VEGETATION SYSTEMS IN THE GREAT PLAINS WITH ERTS 
. W. Rouse, Jr., R. H. Haas, J. A. W e l l  and D. W. Deering, Remote Sensingcenter, Texas A&M 
hivemity, Colfegp Station, Texas 
ABSTRACT 
The Great Plains Corridor rangeland project being conducted 
at Texas A&M University utilizes natural vegetation systems 
as phenological indicators of seasonal development and climatic 
effects upon regional growth conditions. A method has been 
developed for quantitative measurement of vegetation con- 
ditions over broad regions using ERTS-1 MSS data. Radiance 
values recorded in ERTS-1 spectral bands 5 and 7,  corrected 
for sun angle, are used to compute a band ratio parameter 
which is shown to be correlated with aboveground green bio- 
mass on rangelands. 
INTRODUCTION 
The Great Plains of the central United States produces over forty per- 
cent of the nation’s beef and much of the country‘s grain. 
industry in this region is a $23 billion operation, which is extremely 
vulnerable to adverse seasonal or climatic conditions. 
of the beef and agricultural products industry in the Great Plains 
is contingent upon decisions made by the 400,000 farm and ranch owners 
in this region. These private operators need timely information on 
regional range forage conditions and crop production levels upon 
which to base their management decisions. This paper reports on an 
ERTS-1 study of rangelands in the Great Plains that has established 
the potential for using ERTS-type data to provide quantitative re- 
gional vegetative condition information required in support of these 
agricultural operations. 
The beef 
The stability 
The Great Plains Corridor rangeland project utilizes natural vegeta- 
tion systems as phenological indicators of seasonal development and 
climatic effects upon regional growth conditions. The basic task is 
that of monitoring the vernal advancement and retrogradation of vege- 
tation (green wave effect) throughout the uniform Mixed Prairie 
Grassland Association extending from south Texas into Canada. 
objective of the work is to determine the feasibility of using ERTS- 
type data to map regional vegetation conditions throughout the growing 
season for the Great Plains. 
The 
309 
https://ntrs.nasa.gov/search.jsp?R=19740022614 2020-03-23T04:28:21+00:00Z
The study employs a network of ten test sites in six states extending 
from south Texas into North Dakota. Ground observations recorded 
every eighteen days at each site include green biomass, moisture con- 
tent of vegetation, weather information, etc. ERTS-1 MSS data have 
been acquired for all sites for four full seasons. 
The ERTS-1 MSS data were computer processed for selected areas of 
each site. 
date for each site. The measurements were corrected for seasonal sun 
angle differences to permit temporal comparisons. 
recorded in ERTS-1 spectral bands 5 and 7 were used to compute a Band 
Ratio Parameter which is shown to be correlated with aboveground green 
biomass and vegetation moisture content. 
Spectral reflectance data were analyzed for each available 
Radiance values 
This research has established a method for obtaining a quantitative 
measurement of vegetation conditions over broad regions using ERTS-1 
MSS data. It is anticipated that this capability will be further 
developed to provide regional rangeland vegetation condition and grow- 
ing condition information needed in rangeland management and agri- 
business activities in the Great Plains. 
OBJECTIVES 
The objectives of the Great Plains Corridor Project were established 
to examine three basic hypotheses: 
Hypothesis 1: 
vegetation (green wave e f f e c t )  can be discriminated on a regional 
basis using repet i t ive  multispectral data. 
Hypothesis 2: 
information source f o r  regional agri-business use. 
The vernal advancement and retrogradation o f  
a;: 
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Natural vegetation parameters provide a net3 
t .... 1
Hypothesis 3: Temporal e f f ec t s  are important i n  discriminating 
broad landforms, so i l  associations, vegetation types, and other 
natural resource features. 
\ r', 
The specific objectives are: 
I .  \ 
r J  f 1. Establish a test site network for collection of ERTS-1 
correlated ground data in the Great Plains Corridor. 
Use ERTS-1 data for charting the "Green Wave Effect" in 
the Great Plains Corridor. 
2. 
3. Correlate changes in reflectance characteristics of vege- 
tation measured by ERTS-1 with environmental and growth 
conditions. 
310 
4. Evaluate the use of ERTS-1 data for measuring the kind, 
amount, and condition of rangeland vegetation. 
Evaluate the feasibility of an operational satellite 
system for monitoring the status of natural vegetation 
in the Great Plains Corridor. 
5. 
GREAT PLAINS CORRIDOR 
" " -~ 
tion. This test site netwo 
nine of which lie within t 
The headquarters study sit - - - - .  - - 
An effective rangeland test site network was established within the 
Great Plains Corridor region during the initial phases of the ERTS-1 
investiga 
(Fig= 1) 9 he Mixed Prairie grassland asso- 
ciat ion. e at College Station, Texas occurs 
within the closely allled but somewhat more humid True Prairie grass- 
land asso' 
rk consists of ten study sites 
'e at elevations of 314 a 
:orridor test site elevat 
North Dakota. Their ele 
With the ~ X E ~ V L U J I I  UI L I I ~  wdee;e Station and Weslaco study sites, 
which ar ind 225 ft., respectively, the Great 
Plains C Sons span only 1800 ft., from Texas 
through !vations range between 1100 and 2900 ft. 
Loamy s o u s  preaommace on mosc of the study areas within the Corridor. 
However, one southern site (Woodward) and one northern site (Sand Hills) 
are dominated by sandy soils. Two southern sites (Sonora and 
Throckmorton) and one northern site (Cottonwood) are dominated by 
clayey soils. 
Important community dominants within the Corridor include warm-season 
grasses (bluegrams, buffalograss, sideoats grams, and big and little 
bluestems) and cool-season grasses (western wheatgrass, needle-and- 
thread, and Texas wintergrass). Stipa and Bouteloua genera are con- 
sidered to be characteristic of the Mixed Prairie and are present 
throughout the association. 
Plains Corridor and of the included study sites, in terms of climate 
and soils as evidenced through vegetation expression, is demonstrated 
in Figure 2. 
Each of the ten sites is an established research area of a state 
agricultural experiment station or the USDA. 
by the experienced personnel normally associated with the several 
stations. 
passes include green biomass, standing biomass, moisture content of 
vegetation, and phenology of dominant species. 
and grass clippings are obtained during each sampling. 
mation is also recorded for all sites. 
The relative homogeneity of the Great 
All sites are monitored 
The ground observations recorded coincident with the ERTS-1 
Ground photography 
Weather inf or- 
3 11 
DATA PROCESSING 
The objectives of this study require the acquisition of ERTS-1 measure- 
ments showing temporal changes at each of ten locations throughout 
the Great Plains Corridor. 
from identical locations are multiple orbits has been handled in two 
stages. 
site is located, using a computer greymap, and the integrated 
radiance is computed for each of the MSS bands. 
in this paper were obtained from this type processing. 
stage involves "masking" the 7km x 7km sections to remove non- 
grassland areas. For many sites, this procedure removes only a 
small percentage of the scene, e.g. Throckmorton. 
The problem of obtaining radiance data 
In the first stage, a 7km x 7km area centered on the test 
The data presented 
The second 
The radiance measured in each MSS band is computed from the ERTS CCT 
counts and corrected for seasonal sun angle differences by dividing 
the CCT value by the sine of the inclination angle of the sun. The 
correction procedure has been tested using measurements of temporally 
independent targets. 
The data processing procedure has been formalized and implemented on 
a digital computer to generate the Site Processing Report shown in 
Figure 3 for each frame of usable data. 
SPECTRAL ANALYSIS 
The.processing of ERTS MSS data provides four parameters which can 
be analyzed relative to the ground observations. However, previous 
studies have shown that combinations of these four parameters can 
provide more useful parameters for specific comparisons. For the 
purposes of this project, the parameter obtained by taking the differ- 
ence between the radiance values in bands 5 and 7 has been found to 
be of particular significances. Although other combinations have 
been found which correlate with vegetation condition, this project 
has established that bands 5 and 7 do provide a single quantity 
indicative of the aboveground green biomass, and consequently the 
present analysis activity has been restricted to this parameter. 
The specific parameter employed is the Band Ratio Parameter (BRP) 
defined as the difference in the ERTS radiance value measured in 
bands 5 and 7, divided by their sum. The normalization procedure 
is used to eliminate seasonal sun angle differences and to mini- 
mize the effect of atmospheric attenuation. 
negative BRP values and the possibility that the variance of the 
ratio would be proportional to the mean values, a square-root 
transformation is also computed. This parameter, termed the 
To avoid working with 
3 12 
Transformed Vegetation Index (TVI), is equal to the square-root of 
the BRP plus an arbitrary constant. The constant selected was 0.5. 
A step-down regression analysis of twenty-nine data sets from the 
five southern test sites indicated that dry biomass, percent green 
estimate, moisture content, and their interactions accounted for 
60% of the variation in TVI values computed from the heterogeneous 
7km x 7km areas. 
near Throclanorton, Texas show that TVI is highly correlated to 
vegetation condition. At Throckmorton, the vegetation moisture con- 
tent and percent green estimate, along with their interaction, 
accounts €or 99% of the variation of TVI for eight sampling dates. 
The green biomass parameter alone accounts for 89% of the variation 
in TVI. 
interaction to the regression of green biomass with TVI increases the 
accountable variation to 93%. Figure 4 shows the relationship of TVI 
and green biomass measured for eight dates at the Throckmorton test 
site. 
However, data from the uniform grassland site 
Addition of the vegetation moisture content and green biomass 
Analysis of theb, u a L a  D U ~ ~ S D L  L u a L  a threshold exists such that the 
TVI is insensitive to biomass and/or vegetation moisture content below 
the threshold values. The implication is that sparsely vegetated 
areas are not amenable to TVI characterization. However, further 
analysis is neces 1 confirm this preliminary indication. isary to
-s appea 
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The TVI parameter 
vernal progressiorl aiiu ietrogradation of vegetation within the Great 
Plains Corridor and has good potential for measuring green biomass 
in increments to useful for regional agricultural applications. 
!r to be most adequate for monitoring the 
CONCLUSION 
This paper provides a brief summary of selected aspects of the Great 
Plains Corridor Project being conducted at Texas A&M University.. 
emphasis here is on the quantification of ERTS-1 MSS data to provide 
measurements of vegetation conditions on a regional basis. 
project includes other analysis activities using ERTS-1 data, including 
image analysis, using color composites and black and white images, and 
interactive computer analysis. 
confirmation that the basic hypotheses of the study are true. 
The 
The 
The net result of these activities is 
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3 16 
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Monitoring vegetation systems in the Great Plains with ERTS

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