ES d 
  
  
    
GEOBOTANICAL TECHNIQUES FOR DISCRIMINATING SERPENTINE ROCK TYPES 
IN WESTERN UNITED STATES 
by 
D. Mouat 
NASA Ames Research Center 
Moffett Field, California, U.S.A. 
and 
C. Elvidge and R. Lyon 
Stanford University 
Stanford, California, U.S.A. 
ABSTRACT 
Serpentine-derived soils have a significant affect on species comp- 
osition, vegetation density, and vegetational spectral response as a result of 
several factors including low calcium/magnesium ratios and high concentrations 
of chromium, cobalt, and nickel. 
Remote sensing techniques involving airborne scanner imagery and 
several statistical and image processing techniques were used in three diverse 
test sites in western United States to discriminate vegetation parameters 
associated with serpentine rock types. 
Vegetation parameters which were found to be most useful for 
discriminating the serpentine rock types included species composition changes 
and density. In general, more xeric vegetation types occur within the areas 
of serpentine. In regions of mixed woodland and forest, serpentine soils 
tend to be characterized by coniferous tree species while in semiarid terrain, 
serpentine soils are characterized more by shrubby than by grassy species. 
These broad vegetation differences and more specific vegetation types were 
readily discriminated by the remote sensing analysis. Useful techniques 
involved relatively simple visual image analysis, contrast stretching of 
individual bands, stepwise discriminant analysis, and principal components 
analysis. 
INTRODUCTION 
Vegetation on serpentine soils is commonly sparser and of different 
composition than the vegetation occurring on neighboring non-serpentine soils. 
This phenomenon has been reported from various locations around the world, in- 
cluding New Zealand, Poland, the Soviet Union, and the United States 
(Whittaker, 1954; Brooks, 1972). The identification of serpentine and the 
host ultramafic rock pes is of considerable interest as they Commoniy 
contain economic deposits of metals such as Cr, Ni, and Co. 
There are several distinctive properties of serpentine soils that 
are adverse to the growth and development of many plant species. Serpentine 
soils are usually low in Ca and high in Mg. Both of these elements are 
4155