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MISCELLANEOUS PUBLICATION 1271, U.S. DEPARTMENT OF AGRICULTURE 



ships of the ecosystem (48)- Such predictions as 

 "This is going to be a good clover," "filaree," or 

 "grass year" are commonly made in recognition 

 of the dynamic nature of the annual range plant 

 community which may have a significantly dif- 

 ferent species composition each year. Talbot and 

 others (50) reported such variations (table 1). 



The date of opening rains is an important 

 factor in determining the species composition. 

 Bromus mollis L. and Erodium botrys (Cav.) 

 Bertol. are likely to be abundant with early ef- 

 fective rains, while the initiation of rains later 

 in the season appears to favor a greater range 

 of species, including the annual legumes. A 

 drought period often follows the first rain. Under 

 such conditions, species which are more drought 

 resistant in the seedling stage are likely to be the 

 most abundant. Subsequent studies by many 

 workers (11, 12, 21) on the California annual 

 range type confirm that yearly variations in spe- 

 cies composition are caused by weather patterns 

 that follow the early period of germination. 



Species composition changes are also subject to 

 annual fluctuations in the upper Great Basin and 

 Columbia Basin regions. In these regions, com- 

 position does not change as much as the density 

 of the stand does in response to favorable or un- 

 favorable weather conditions. Klemmedson and 

 Smith (26) reported that, at Arrow Rock, Idaho, 

 one year's cheatgrass production was 361 pounds 

 per acre, and in the following year, it was 3,461 

 pounds per acre — a tenfold increase, primarily 

 in response to favorable precipitation. 



Table 1. — Year to year fuctuations between plant 

 groups. (From data published by Talbot and 

 Biswell (50)) 



Percentage by years 



Plant group 



1935 1936 1937 1938 1939 



Annual broadleaved 



Plants 74.8 53.2 43.5 61.7 52.6 



Annual grasses 20.6 45.4 55.5 34.1 47.1 



Annual grasslike plants 2.9 .5 .5 3.6 'T 



Total 



98.3 99.2 99.5 99.4 99.7 



T= trace. 



Is the annual range of sufficient importance to 

 maintain it as a type without considering conver- 

 sion to perennial grass ? Many of the early studies 

 dealt with intensity of grazing, to determine the 

 effect on stand density and whether management 

 could favor the return of perennial grasses. Tal- 

 bot and Biswell (50) stated that, at the San 

 Joaquin Experimental Range in the central val- 

 ley of California, the sparse perennial grasses 

 showed no increase in response to management 

 during a 5-year stud}' period. Even in completely 

 protected places the stand of annual grasses and 

 forbs continued to predominate. A report of later 

 work (3) indicated an average of 4,400 pounds 

 per acre harvested forage in swales as compared 

 with 1,850 pounds of air dry forage on open roll- 

 ing slopes in good years. During a 12-year study 

 period, the estimated average production of air 

 dry herbage per acre was 1,660 pounds, with the 

 extremes fluctuating from 1.200 pounds to almost 

 2,400 pounds per acre. During this time the aver- 

 age precipitation was about 20 inches. 



Bentley and Talbot (3) concluded that restor- 

 ing the original cover did not appear possible, nor 

 was it necessarily a logical objective. Instead, 

 they recommended range management that would 

 produce a forage cover composed of the better 

 species of introduced and native annuals and 

 perennials. Also range management should be 

 aimed at effective use of the annual plant forage 

 in its most productive condition with adjustments 

 to increase the valuable perennial plants where 

 they are important in the stands. They hoped that 

 it was possible to produce a forage crop superior 

 to the original cover. These statements have 

 proved to be true, especially in view of more re- 

 cent work in which improved management prac- 

 tices, particularly fertilization, have produced 

 forage yields as high as 4,400 pounds with the ad- 

 dition of super-phosphate and introduced annual 

 legumes (62) in the foothills of the Sacramento 

 Valley. Nitrogen fertilizers at rates of N up to 80 

 pounds have increased total yield more than 

 threefold (15, 21). A combination of 100 pounds 

 of nitrogen and 88 pounds of phosphorus in the 

 Sacramento Valley have produced yields of over 

 4,000 pounds per acre (39). 



Annual cheatgrass range in the northern Great 

 Basin and parts of the Columbia Basin are ex- 

 tremely important to the livestock industries in 



