Figure 3 — One year after a severe stand-killing fire in tfie aspen there is 

 almost a complete coverage of globemallow and pinegrass on this Man- 

 ning Basin site. 



The calcium concentration of plants was generally lower 

 on burned areas than it was on nonbumed areas. Lay 

 (1957) reported similar findings. Lower calcium contents 

 produce lower calcium/phosphorus ratios on these burned 

 areas. The possibility of interference with phosphorus 

 metabolism in the animal is reduced with low calcium/ 

 phosphorus ratios. Burning, at least in the first postburn 

 year, improved calcium/phosphorus ratios by lowering 

 them. Even then, with the exception of grass, all of our 

 plant samples had much higher ratios than optimal for 

 ruminants. Ratios of 1:2 to 2:1 are excellent, 2:1 to 3:1 are 

 good, 3:1 to 5:1 are fair, and those larger than 5:1 are poor 

 (Urness 1973). However, plants poor in phosphorus may 

 be good sources of protein, energy, or other nutrients. 



Pinegrass in the first postburn year was similar on both 

 burned and unburned areas (tables 3 and 4). (Different 

 August 22 values in tables 3 and 4 are due to different 

 subsamples and runs on aspen and pinegrass; the data 

 are correct.) By the next year, pinegrass on burned areas 

 was significantly lower in digestibility and crude protein 

 than on unburned areas (table 5). 



Vegetative reproduction of perennial species usually 

 occurs rapidly and vigorously afler burning (Hadley 1970; 

 Old 1969; Vogl 1965; Wright 1969). Shoots of herbaceous 

 species produced after fire often are stiffer and more erect 



than on unburned sites (O'Connor and Powell 1963). In- 

 creased numbers of grass and forb flowers are stimulated 

 by burning (Curtis and Partch 1950; Ehrenreich and 

 Ackman 1963; Lemon 1949, 1968; Lloyd 1972), including 

 pinegrass (Crane and others 1983; Weaver 1974). On our 

 sites, pinegrass on the severely burned areas not only 

 produced more biomass, but uniformly flowered and pro- 

 duced a seed crop as well (fig. 3).This flowering and seed 

 production of pinegrass likely caused the decrease in its 

 quality on the burned areas (Chapin and Van Cleve 1978; 

 Van Soest 1982). 



Flowering in forbs increased, too; but it is not usually 

 associated with large changes in nutritive value, despite 

 leaf loss through senescence (Van Soest 1982). Thus, the 

 forbs had higher forage quality at the end of the season 

 than did the grasses, even though their phenology was 

 similar. 



Our study showed that burning causes changes in the 

 digestibility and nutrient content of selected species grow- 

 ing in common on burned and unburned sites. However, 

 relatively much larger changes in forage species composi- 

 tion and structure occurred on these sites after fire (figs. 2 

 and 3). These, no doubt, were more important to rumi- 

 nants than our documented changes in nutrient contents 

 or digestibility (Canon and others 1987). 



6 



