had 39 days with minimum temperatures at or below freezing during July and August versus 10 days 

 at Prudhoe, indicates the potential difference in growing seasons between the two locations. 



Primary production and vegetation 



On 29 July a ground tour of the Prudhoe Bay area was conducted and plant species were col- 

 lected and identified at numerous stops. These species are listed in Appendix B. This should 

 not be considered a complete list of the plants of the Prudhoe Bay area, since many species were 

 undoubtedly not found, and in some groups, notably the genera Carex, Salix, aiid Draba, field identi- 

 fications could not be made. The flora of Prudhoe Bay appears to be more diverse than that of the 

 Barrow area. This is probably the result of greater habitat variability at Prudhoe since individual 

 community diversity does not appear dramatically larger. The sand dunes adjacent to the . 

 Sagavanirktok River are one example of the greater habitat varialiility. They support many species 

 not found on the adjacent tundra at Prudhoe Bay or at Barrow. In addition, the Prudhoe tundra 

 supports many species not found at Barrow, while most of the common Barrow species were also 

 found at Prudhoe. 



Four representative sites were selected for careful analysis of the vegetation. The first three 

 sites were located at three points along a continuous moisture gradient and represent a large pro- 

 portion of the tundra at Prudhoe (Fig. 34, Location B). The fourth site represents a large expanse 

 of a relatively homogeneous community consisting, however, of a diverse species composition 

 (Fig. 34, Location A). These are listed below: 



Location B: Site 1 - Near the top of a well-drained slope, in an area dominated by tussock 



(Eriophorum vaginatum var. spissum and Eriophorum angustifolium) tundra. 



Location B: Site 2 - Near the bottom of the same slope, ground broken by small hummocks. 



Location B: Site 3 - A low-centered polygon basis adjacent to a large lake and immediately 

 below site 2. Dominated by Carex aquatilis. 



Location A: Site 4 - A flat, drained lake basin. 



At each of these sites an inclined point frame, identical to frames described for the Barrow 

 sites, was used to determine the composition and canopy structure of the vegetation. The results 

 are given in Table XXXIL As discussed earlier in the Barrow sectiai of the report, the leaf area 

 index may be considered as the ratio of area of leaf surface to the area of ground surface. Thus, a 

 leaf area index of 0.8 means that 80% of the land area is covered by leaves. The leaf area index 

 for live leaves for the comparable period at the intensive site at Barrow is greater than that for 

 Prudhoe. 



The vegetation at Prudhoe is taller than that at Barrow, but is less dense, especially in the 

 lowest 5 cm of the canopy. Thus, the vegetation at Prudhoe consists of fewer, more robust shoots, 

 while that of Barrow consists of more numerous, smaller shoots. This is not due to a difference in 

 species composition at both sites Eriophorum angustifolium, Carex aquatilis, and Duporjtia fischeri 

 are the three most abundant species (Table XXXIll). These make up 83% of the point-frame contacts 

 at Barrow. The major difference in composition is the greater abundance of Dupontia fischeri at 

 Barrow. At both locations, grasses and other species with a grass-like growth form (sedges, rushes) 

 predominate in the vegetation. 



The rooted vegetation was clipped at the base of the moss layer from an area 0.1 m\ immediately 

 under the location selected for point-frame analysis. The clipped vegetation was returned to the 

 laboratory where the green material (produced in the present growing season) was separated from the 

 standing dead material (produced in prior growing seasons). The materiid in each of these categories 

 was dried and weighed. In addition, subsamples of the green material were ajialyzed spectrophoto- 

 metrically for chlorophyll content. 



90 



