Carbon and Nutrient Budgets 481 



The movement of carbon and nutrients from terrestrial to aquatic 

 systems plays a relatively minor role in the annual budgets of these sys- 

 tems. Nonetheless, awareness of the slow alternation of the terrestrial 

 and aquatic landforms across any point in the landscape is essential to an 

 understanding of the overall functioning of coastal tundra, because this 

 alternation prevents long-term nutrient accumulation in soil organic mat- 

 ter. The impact of industrial activities on the whole biosphere and on the 

 tundra itself, either directly or indirectly, is likely to speed up these cycles 

 and processes. From the present work, we have gained considerable 

 knowledge about the coastal tundra ecosystem. Needed now are quanti- 

 tative data on rates of ecosystem change through time. Upon these, we 

 can construct models of what this tundra ecosystem may be like in the fu- 

 ture. The initiation of such long-term ecological research is required so 

 that utilization of this coastal ecosystem can proceed in the most rational 

 and scientific manner possible. 



SUMMARY AND CONCLUSIONS 



This study of energy flow and nutrient cycling examined the causal 

 relationships linking low solar irradiance with the unique features of the 

 wet coastal tundra at Barrow (Figure 12-5). Although the low light inten- 

 sity limits photosynthetic rate directly, low annual solar irradiance exerts 

 its influence most strongly by limiting the length of the season for most 



Short active 

 season 



Permafrost 



Poor soil 

 aeration 



Low solar 

 irradiance 



Low 

 temperature 



J^ilT 



Organic matter 

 accumulation 



Low pH 



Slow 

 deconn position 



I 



Slow 

 N-fixation 



Low nutrient 

 availability 



Negligible 

 chemical 

 weathering 



Low 

 precipitation 



Low atmospheric 

 nutrient input 



Low 

 productivity 



FIGURE 12-5. Causal relationships between low solar irradi- 

 ance and low primary productivity of arctic coastal tundra. 

 Thickness of arrows indicates magnitude of effect. 



