Carbon and Nutrient Budgets 465 



TABLE 12-3 Distribution of Carbon and Nutrient Pools in 

 Vascular Plants on 4 August, Time of Maximum 

 Aboveground Biomass in the Intensive Study 

 Site 



system (Chapter 11). The bulk of the nutrient pools of each trophic level 

 occur below ground. Except for potassium, 80% or more of all vascular 

 plant nutrient pools also are localized below ground (Table 12-3). Ani- 

 mal nutrient pools are concentrated below ground and are associated 

 with turnover of organic matter. Even during lemming population highs, 

 3 to 10 times more nutrients are present in soil invertebrates than in lem- 

 mings (Figure 12-2). 



AVERAGE ANNUAL FLUXES 



Carbon Budget 



During the growing season, the long period of daylight compensates 

 for low sun angle and consequent low light intensities, so that during 

 July the total daily input of photosynthetically active radiation is similar 

 in arctic and in temperate ecosystems (Billings and Mooney 1968). The 

 vegetation is seldom light-saturated and captures more than 1% of the 

 available energy in July (Chapter 4), an efficiency comparable to or 

 higher than that of most other natural communities (Ricklefs 1973). 

 Aboveground plant parts maintain a positive carbon balance 24 hours a 

 day during most of the growing season (Chapter 4), and 81 % of the pho- 

 tosynthate is converted to aboveground biomass or translocated below 

 ground. This aboveground net production efficiency is higher than that 

 of most temperate communities (Ricklefs 1973). Because of the minor 

 amount of dark respiration and the high photosynthetic and net produc- 

 tion efficiencies, relative production rates (g g"' day') for the coastal 



