Figure 4. — Mountain big 

 sagebrush (Artemisia 

 tridenta a ssp. vaseyana) 

 growing in a luxuriant 

 stand of smooth brome 

 (Bromus inermis) in 

 Ephraim canyon^ Utah. 



Artemisias contain a variety of natural chemical products, most notably terpenoids 

 and phenolics. Many individual compounds have been isolated and identified, particularly 

 in recent years. Terpenoids include the monoterpenes of the essential oils that produce 

 the characteristic odors of sagebrushes and wormwoods (Guenther 1952; Halligan 1975; 

 Buttkus and others 1977; Scholl and others 1977). Sesquiterpene lactones are another 

 class of terpenoids common in the Artemisias (Kelsey and others 1973; Geissman and Irwin 

 1974; Rodriguez and others 1976). Two principal classes of phenolic compounds are pre- 

 sent, the coumarins (Shafizadeh and Melnikoff 1970; Brown and others 1975) and the 

 flavonoids (Rodriguez and others 1972; Segal and others 1973; Brown and others 1975). 



In addition to terpenoids and phenolics, a third class of chemicals--the alkane 

 hydrocarbons--was studied by Bachelor and others (1972) . The rich array of natural 

 chemical products in Artemisia has proven to be useful in delimiting taxonomic boundaries 

 (Hanks and others 1973; Kelsey and others 1973; and Geissman and Irwin 1974). Although 

 the physiological importance of many of the natural chemical products is unknown, some 

 have been implicated in the allelopathic properties of Artemisia. Many Artemisias have 

 allelopathic qualities; under certain conditions they may chemically inhibit growth of 

 seedlings and established plants of competitive species, and even growth of their own 

 seedlings. These allelopathic qualities might contribute to the dominant position of 

 sagebrushes and wormwoods in many communities. A. odlifomica, A. absinthium^ A. herba- 

 aVba, A. vulgaris, A. tridentata, and A. oana have been shown to have allelopathic prop- 

 erties (Schlatterer and Tisdale 1969; Halligan 1975; Friedman and others 1977; Hoffman 

 and Hazelett 1977; Weaver and Klarich 1977). Nevertheless, in many instances Artemisias 

 are part of communities rich in species (fig. 4). So, the significance of allelopathy 

 in Artemisia communities remains in doubt. 



The natural chemical products might account for the differential palatability among 

 Artemisia taxa (Hanks and others 1973; Sheehy and Winward 1976; Scholl and others 1978). 



Artemisia arbuscula Nutt. (low sagebrush^) 



Low sagebrush is a low, spreading, irregularly branched shrub up to 5 dm high (fig. 

 5a). The slender erect twigs are densely canescent, but may become nearly glabrous and 

 thus darker green in late summer. The plant layers infrequently. 



Also called little sagebrush, scabland sagebrush, dark sagebrush. 



6 



