100 



The Herbivore-Based Trophic System 359 



Adult 9, Litter of 7 

 July, Low Nutrients 

 100 



o 100 



Subadult 9, Litter of 8 



July, High Nutrients 

 T — 7-r 



a> 



o 



u 



» 

 a. 



+20 



40 



Doy of Run 



FIGURE 10-10. Simulated nutrient pools in repro- 

 ductive female lemmings with normal digestibility 

 of energy in diet (S), 20% higher digestibility ( + 20) 

 and 20% lower digestibility (-20). The assumptions 

 of the model are given in the text. The shaded area 

 represents lactation. (After Barkley 1976.) 



TABLE 10-5 Concentrations (Mean ± 1 SE) of Nutrients in Shoots of 

 Mature Graminoids from Four Temperate Grasslands 

 and from Coastal Tundra at Barrow 



Habitat 



No. of 

 species 



Nutrient (Vo dry wt) 



N 



Ca 



Reference 



1.07±0.22 0.53±0.11 0.19±0.07 Harner and Harper 



(1973) 

 1.43 ±0.34 0.28 ±0.08 0.14 ±0.05 Johnston and Bezeau 



(1962) 

 1.13±0.39 0.39±0.26 0.19±0.08 Gerloff et al. (1964) 



1.47 ±0.38 0.42 ±0.06 0.29 ±0.08 National Academy of 



Sciences (1969) 

 1.86±0.07 0.16±0.01 0.13±0.01 Chapin et al. (1975) 



