Introduction and Site Description 37 



Soil 



The Barrow soils (Brown and Veum 1974) have mostly formed on flat 

 to gently sloping landscapes during conditions of low temperature and 

 high moisture. These soils are relatively high in organic matter, of which 

 some has accumulated in place and some has been mixed to various depths 

 by frost churning. Additional organic matter results from the burial of 

 pond or lake sediments in the thaw-lake cycle. 



The Barrow soils have a strong thermal gradient during summer when 

 the surface may reach 25°C while at the same time the horizons at 20 or 30 

 cm are below 2''C. This surface warming dries out the surface layers but 

 the lack of drainage keeps the soil moisture contents at depths below 4 cm 

 at greater than 85% of water-holding capacity. Consequently, vascular 

 plants rarely lack moisture. On the other hand, the abundant moisture 

 combined with low pore volume in mineral layers causes the deeper 

 horizons to become anaerobic early in the summer. 



Chemically, most of the soils are highly organic, strongly acid, and 

 not very fertile (Bunnell et al. 1975). Apparently, the base nutrients are 

 usually sufficient for plant needs; N and P, although stored in large 

 quantities, are released only slowly from the organic matter. 



Primary Producers 



Plant production in the Barrow tundra has been extensively studied 

 for many years; the data and results are reviewed in Bunnell et al. (1975), 

 Tieszen (1978a), and Brown et. al. (in press). 



In summer, the coastal tundra vegetation resembles a yellow-brown 

 grassland, relieved only by strips of greener vegetation in troughs between 

 polygons or at the edges of ponds. The yellow-brown color results from the 

 large accumulation of dead plant parts of grasses and sedges. All plants 

 are short ( 1 to 1 5 cm high) and many have broad, flat stems. 



Compared with most ecosystems, the Barrow tundra is indeed 

 uniform. Although there are 100 species of vascular plants (plus 96 

 bryophyte and 57 lichen species), the low relief of the coastal region 

 produces only small environmental differences between lowlands and 

 uplands. The result is that all species of the extensive marshes also occur 

 on the uplands and most of the species of the driest upland sites are also 

 found whenever hummocks appear in the wetter areas (Bunnell et al. 

 1975). Webber (1978) has divided this continuum of vegetation at the IBP 

 site into eight plant assemblages. Five of these cover 9 1 % of the area. They 

 are: mesic Salix rotundifolia heath in dry, low-center polygons (7%); mesic 

 Carex aquatilis/Poa arctica meadow on dry, flat, polygonized areas 



