180 F. S. Chapin III et al. 



Ungrazed 



CVI 



C 



o 



c 

 o 



'E 



E 



3 



D 



o 



D 



2.0- 



1,0- 



Grazed 



CM 



600 



en 



I/) 



^ 400 



E 

 o 



CD 200 



I 



MM 



5 15 5 3 24 

 June July Aug 



^ Prior Years' Roots 



^ Current Year's Roots 



5 12 19 26 3 

 June 



H Rhizome 

 m Stem Base 



10 17 24 31 

 July 



n stioot 



7 14 

 Aug 



FIGURE 5-19. Standing crops of plant nitrogen, calcium and biomass in 

 moist meadow tundra with and without maximum lemming grazing, cal- 

 culated assuming: 1) the total plant nutrient and biomass contents were 

 altered through the season only by grazing (i.e. that no nutrient gain or 

 loss occurred through uptake, senescence, or leaching, and that mainten- 

 ance and growth respiration equaled photosynthesis); 2) translocation to 

 aboveground parts after grazing occurred at the maximum rate observed 

 during the 1970 growing season; 3) grazing occurred weekly and totally 

 removed the aboveground compartment; 4) roots did not normally serve 

 a storage function (nutrients and carbohydrates contained in roots were 

 translocated upward only after all other reserves were exhausted); and 5) 

 no new roots were produced when plants were intensively grazed. (After 

 Chapin 1975.) 



I 



