38 CIRCULAR 870, U. S. DEPARTMENT OF AGRICULTURE 



to close), half of the quadrats had practically no decaying vegetation on 

 the soil surface; one-fourth had a thin, spotty layer; and the remaining 

 fourth had a continuous layer about 34 to 3^2 mcn deep. The nearly 

 bare areas were found fairly generally over this pasture on most of the 

 better sites. Soil-surface conditions were better than in the closely 

 grazed pasture but still not satisfactory. 



In contrast, there was some old herbaceous litter flat on the soil surface 

 in all parts of the more lightly used pastures. For example, nearly half 

 of the 97 small quadrats examined in pasture 2 (grazed lightly) had a 

 continuous layer of decomposing herbaceous material between 34 and Y% 

 inch deep, and nearly one-fourth had a thin, spotty layer. The remain- 

 ing quadrats had almost no old litter, but these quadrats Avere of scattered 

 occurrence, falling almost entirely on poor, sandy soils, on recent rodent 

 workings, or on closely grazed swale bottoms or livestock trails. Such 

 small local areas of exposed soil can be found on any range, even though 

 it is in satisfactory condition. 



Observations within the other lightly or moderately grazed pastures 

 on the experimental range indicated that the soil-surface conditions were 

 similar to those in pasture 2 although more soil without any litter could 

 be found in parts of the moderately grazed pasture. The vigor of plant 

 growth and the general lack of exposed soil during the winter showed 

 that these pastures were in satisfactory condition under the present cover 

 of annual plants. 



The importance of unused vegetation and the layer of litter it produces 

 was shown by the yield of herbage in January 1943 from the 295 sample 

 quadrats (fig. 16). A rather continuous layer of the old litter, 34 to 3^ 

 inch deep, was designated as adequate. Where the layer of litter was 

 adequate, on quadrats that had been lightly grazed the preceding season, 

 the yield of new green herbage was nearly 300 pounds per acre, air-dry 

 weight, and on moderately grazed quadrats the yield was nearly 200 

 pounds. Such yields over a range area would provide sufficient green 

 forage to maintain cattle. With an adequate layer of litter, growth of 

 green forage was nearly sufficient even on the few quadrats that had been 

 closely grazed. 



Where the layer of old litter on the soil surface was thin and spotty, 

 designated as fair, growth of green forage was reduced on quadrats 

 that had been grazed moderately or closely during the preceding season. 

 On the few such quadrats that had been lightly grazed, forage growth was 

 satisfactory. 



Where there was virtually no layer of old litter, growth of new forage 

 was very greatly reduced, particularly on quadrats that had been grazed 

 moderately or closely during the preceding season. Even on the lightly 

 grazed quadrats, yields averaged less than 150 pounds per acre. 



These results show that moderate and light grazing promote winter 

 growth of herbage, but full winter production will be obtained only when 

 an adequate layer of litter has been built up by conservative use in pre- 

 ceding years. 



EFFECTS ON MATURE SPRING HERBAGE 



The effects of degree of grazing on plant vigor that were readily ob- 

 served during the winter were not so easily seen later in the season. 

 Differences in grazing during the current season partially obscured the 



