480 



F. S. Chapin III et al. 



^ 



Aquattc 



' Lake 



/ Drainage 



/ 



Succession 



Phosphorus 



FIGURE 12-4. Comparison of nutrient pools in terres- 

 trial and aquatic systems on tundra during the course 

 of thaw lake cycles. The relative sizes of the circles on 

 the left indicate differences between terrestrial and 

 aquatic habitats in pool sizes of organic carbon or 

 available N or P. Solid arrows represent annual net 

 transfers by fixation (F), respiration (R), erosion (E) 

 and transport by runoff at thaw (T). Dashed arrows 

 indicate conversion of habitat from aquatic to terres- 

 trial or vice versa. 



