42 CIRCULAR 870, U. S. DEPARTMENT OF AGRICULTURE 



This study and widespread observations show that when grazing use 

 is too light on California foothill range, tall-growing annual grasses crowd 

 out filaree, clover, and other valuable low-growing plants. This change 

 to a less desirable mixture is most rapid — and most complete — on fertile 

 soils and with fairly high rainfall. On the experimental range virtual 

 nonuse was required to bring about this undesirable increase in tall 

 grasses ; the change has been observed under light use on more productive 

 soils. The conclusion is that even though complete protection from 

 grazing for 1 or 2 years may be justified to restore a litter cover on a de- 

 pleted range, continued very light grazing will not maintain a satisfactory 

 forage plant mixture on annual-plant ranges. 



As to herbage composition, then, a satisfactory mixture of annual 

 plants was maintained under degrees of grazing ranging from a little 

 closer than moderate to light. Under close grazing there was some in- 

 crease in weedy species. Moderate grazing has maintained a satisfactory 

 forage mixture and yield under all conditions that have been observed on 

 foothill range. 



Recognizing Satisfactory Range Utilization 



The lack of pronounced changes in the composition of the herbaceous 

 cover during the grazing-intensity studies emphasized that relying on 

 the percentage of any annual-plant species as an indicator of grazing use 

 has definite limitations on these granitic soils. Also, the plant mixture 

 under each degree of grazing changed in species composition from year 

 to year, as is typical on foothill ranges. The only conspicuous change in 

 the mixture to indicate the effects of close grazing was the appearance 

 of smooth cats-ear in pasture 3. This species has also been observed 

 growing on other relatively bare soils, including soils derived from sedi- 

 mentary and igneous rocks, under a wide range of precipitation. Under 

 these variable conditions, however, the lack of old litter on the soil surface 

 was ample indication of close grazing without reference to composition 

 of the plant mixture. 



In fact, without reference to the condition of the soil, appraisal of 

 annual-plant forage production on the range is both difficult and apt to 

 be misleading. The level of herbage production cannot be judged merely 

 by the general appearance of the plant cover in the spring. Yields, for 

 example, were different between range pastures having about the same 

 percentage of each dominant species in the cover. Similarly, differences 

 in yields at plant maturity cannot be evaluated readily by general 

 observations because the vegetation is grazed at different intensities 

 during its growing season. The only exception to this principle that 

 could be seen in the experiment was the noticeably reduced vigor of the 

 forage plants in the swales of the most closely grazed pasture. 



The studies at the San Joaquin Experimental Range have provided 

 two useful guides to satisfactory utilization of annual-plant range. The 

 first is a simple means for judging adequacy of old litter on the soil 

 surface. The second is a practical method for rating the degree to which 

 herbage of the current year has been utilized. 



JUDGING ADEQUACY OF OLD LITTER 



Full production of forage depends upon an adequate layer of old de- 

 composing litter lying flat on the soil surface. The extent and thickness 



