Primary Producers 

 Primary terrestrial production and photosynthesis 



Larry Tieszen* 

 Sharon Tieszen 

 Ken Olson 

 John Ahrendt 

 Doug Johnson 

 Dave Harrison 



Augustana College 

 Augustana College 

 Augustana College 

 Augustana College 

 Augustana College 

 Augustana College 



Dale Greiner 

 Bob Vaughn 

 Frank Bogardus 

 Martyn Caldwell 

 John Dennis* 



University of Michigan 

 University of Alaska 

 University of Alaska 

 Utah State University 

 University of Calgary 



The central role of producers in determining the amount of available energy for the entire system 

 necessitated that a thorough study of primary production and its interrelationships with environ- 

 mental factors, energy flow through the various compartments, and nutrient cycling be undertaken 

 at Barrow, Thus, the subprojects which concentrated on aspects of primary production generally 

 focused on three integrated objectives. 



The principal objective was a determination of the efficiency of energy incorporation and its 

 dependence upon both the physical factors of the above-ground environment and individual species 

 responses. These studies included a detailed examination of micrometeorological factors (especial- 

 ly temperature and light intensity) both above and through the canopy, a thorough analysis of 

 community composition and canopy structure, and a rather complete characterization of photosyn- 

 thetic responses and limiting factors in most of the predominant plants. 



The second objective concerned more directly the flow of nutrients and energy. These studies 

 involved primary production related to nutrient availability, nutrient uptake and retention, and 

 nutrient release. In a similar manner, the distribution of matter and energy from the primary pro- 

 ducer compartment via herbivory, accumulation and loss of litter, decomposition, and saprovore 

 activity were studied. 



The third objective was to attempt to determine the causal factors associated with the range 

 of production values found in the various community types at Barrow and to compare production 

 values and canopy structures from the coastal plain of Alaska and the latitudinal transect and 

 between the intensive sites of the Arctic and the Alpine at Colorado. 



Plant production was estimated by clipping 0.1-m^ quadrats at the base of the moss layer, 

 separating all higher plants by species, and subsampling for dry weight, caloric determinations, 

 nutrients, chlorophyll, lipids, and carbohydrates. Net above-ground production attained a maximal 

 value of about 100 g dry wt/m^ shortly after 1 August, which is approximately 6 weeks after snow- 

 melt. Thus, most of the above-ground production occurs in a six-week period or less (Fig. 14). 

 In this early part of the growing season production appears to be linear with time and is associated 

 with an apparent increase in caloric content from a mean of around 4300 cal/g at the beginning of 

 the season to a maximum of 4500 cal/g at the peak. This trend is present in each of the species, 

 and preliminary data indicate that it is correlated with a similar increase in lipid content. 



Comparison of primary production with sample years dating back to 1960 at the Gasline site 

 of Schultzt (Fig. 2, site 12), shows that 1970 was an exceptionally good year for growth. Both 

 Eriophorum angustifolium and Dupontia (ischeri production exceeded that of previous peak years. 

 The unusually large production was apparently the result of low lemming numbers coincident with 

 a favorably long growing season. 



Subsurface standing crops of vascular plants were measured at peak season in early August 

 on two plots. Total standing crop of all living material present in the top 20 cm of soil ranged 

 from 1075 to 1600 g/m^ Subsurface -to- shoot ratios ranged from 11:1 to 14:1. In the organic mat. 



♦ Principal authors 



t Observations provided by Schultz's subproject 



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