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MISCELLANEOUS PUBLICATION 1271, U.S. DEPARTMENT OF AGRICULTURE 



mingling of species; Plant composition is influ- 

 enced by both macro and micro climates as well 

 as by differences in texture and chemistry of soils. 

 Past grazing, clearing of the land for agricul- 

 ture, and fire are also factors affecting composi- 

 tion. 



Big sagebrush and its subspecies occur im- 

 portantly over as much as one-half of the area 

 of the northern desert shrub (4,22). Major shrubs 

 may grow intermixed or in alternes with each 

 other or with salt desert shrubs. The alkalinity of 

 the soil determines whether sagebrush or shrubby 

 chenopods, such as black greasewood (Sarcobatus 

 vermiculatus [Hook.] Torr.) or Gardner saltbush 

 (Atriplex gardixeri [Moq.] D. Dietr.), are dom- 

 inant. This variation in species denotes the dis- 

 tinction between northern desert and salt desert 

 shrublands. 



The juniper-piny on and mountain brush types 

 intermingle importantly and extensively with 

 each other, as well as with the northern desert 

 type and, to some extent, with the salt desert 

 shrub type. Freezing is frequent in all of these 

 types through much of the dormant growth period 

 in winter, but the severity varies greatly between 

 localities. On their southern limits, all four types 

 are transitional with the southern desert shrub 

 and to some extent with the chaparral. 



Chaparral is probably the most distinct of the 

 six types, but its shrubs do occur widely in the 

 other types. Nearly half of the chaparral type 

 occurs in California. Other tracts exist in Ari- 

 zona, New Mexico, Nevada, and southern Utah. 

 The woody plants of this type are mostly broad- 

 leaf evergreens which are highly prone to burn- 

 ing and which sprout vigorously when the above- 

 ground parts are removed. As catastrophic floods 

 often follow burning, an important research proj- 

 ect by the Pacific Southwest Forest and Range 

 Experiment Station of the Forest Service, U.S. 

 D.A., is aimed at finding fire retardant plants 

 which can be established as live firebreaks (36). 



All of these types are tremendously important 

 for production of livestock and game animals. 

 The northern desert shrub, salt desert shrub, and 

 juniper-piny on are especially important for win- 

 ter and spring-fall grazing for sheep and cattle. 

 This is true not only for the browse these types 

 provide but often more importantly for the 

 grasses which . are associated with them (28) . 



In the southern desert shrub and elsewhere 

 where there is a prevalence of summer precipita- 

 tion, warm season growing grasses, such as the 

 galleta grasses (Hilaria spp.) and grama grasses 

 (Bouteloua spp.). predominate (27. 30). The 

 wheatgrasses (Agropyron spp.), wildryes (Ely- 

 mus spp.), and bluegrasses (Ppa spp.) prevail 

 where most of the accumulated moisture for plant 

 growth results from winter precipitation. Indian 

 ricegrass (Oryzopis hymenoides [Roem. and 

 Schult.]), bottlebrush squirreltail (Sitanion hy- 

 strix [Nutt.] J. G. Smith var.), and needlegrasses 

 (Stipa spp.) are common in both summer and 

 spring growing areas. 



Sagebrush and rubber rabbitbrush (Chryso- 

 thamnus nauseosus [Pall.] Britton) ; Utah jun- 

 iper (Juniperus osteosperma [Torr.] Little) ; 

 two-leaf piny on (Pin/us edulis Engelm.) and 

 single-leaf pinyon (P. monophylla Torr. and 

 Frem.) ; as well as velvet mesquite (Prosopis fu- 

 ll folia [Swartz] DC.) ; creosote bush (Larrea di- 

 varlcata Cav.) ; and tar bush (Flourensia cernua 

 DC.) have increased their prevalence and ex- 

 panded their areas of occupancy on what were 

 once primarily grasslands (8, 29, 30, 39, 41, 44)- 

 Some have considered that the increase of sage- 

 brush and other shrubs, at a time when there 

 was severe depletion of herbs, actually favored 

 an increase of deer (32, 47). 



Range Improvement 

 Treatment Methods 



A good deal of what is being done to restore 

 the range is experimental or in pilot programs. 

 Restoration is essentially confined to experiment- 

 al plantings where annual precipitation is not in 

 excess of 250 mm. (7, 42, 43)- 



Improvement of all types involves techniques 

 that reduce the undesirable competing plants 

 which have gained control. After competition is 

 reduced, desired species are planted. If the de- 

 sirable native species released from competition 

 are abundant enough, such planting may not be 

 necessary. 



Mechanical and chemical means and burning 

 are all being used to reduce competition. Over 

 most range areas, mechanical techniques are 

 more widely accepted and used than spraying 

 with selective herbicides. One of the favorite and 



