16 J. Brown et al. 



is slightly higher than the pond-covered areas to the east and west, sug- 

 gesting that it is older. It is unlikely that more than one major lake has 

 occupied the area of the terrestrial research sites, but the adjacent 

 aquatic research site has gone through at least three lake cycles. 



The activities of man have led to significant changes in the Biome re- 

 search area since the mid-1940s. The tracks of off-road vehicles have 

 produced thermal disturbance and subsequent formation of small ponds 

 at ice wedge intersections, shifts in vegetation composition and, in some 

 cases, severe erosion. More dramatic is the alteration in drainage caused 

 by the lowering of Middle Salt Lagoon to sea level and the complete 

 draining of Footprint and Dry Lakes in 1950. These actions created a 

 new erosional base level in the basin (Figure 1-5). Prior to this lowering, 

 the water level in Middle Salt Lagoon stood at approximately 2.5 m ele- 

 vation. Since then there has been massive and rapid headward erosion as 

 Footprint Creek readjusts to the new base level conditions (Lewellen 

 1972). After the water level was lowered, the floor of the previously 

 flooded valley was exposed and Footprint Creek entrenched further to 

 form the present marginal terrace. The gravel road on the east side of the 

 Biome research area has caused some ponding and mehing of ice wedges. 



TERRAIN SUBDIVISIONS AND FORMATION 



Ahhough tundra might appear to be a featureless plain, it actually 

 possesses a considerable variety of landforms, both on meso- and micro- 

 scales, and is an extremely dynamic landscape (Britton 1957). The Biome 

 research area and areas immediately adjacent to it consist of several ma- 

 jor terrain units, each composed of characteristic landforms and associ- 

 ated microtopographic units (Figure 1-7). Adjacent to Footprint Creek 

 are alluvial terraces, floodplains, and steep- and gently sloping stream 

 banks. Immediately to the south are the weakly developed polygons that 

 compose much of site 2 (Figure 1-4). Site 4, farther to the south, consists 

 of a highly polygonized landscape containing both high-centered and 

 well-developed low-centered polygons (Figure 1-8). 



Polygons give rise to several microtopographic units — rims of low- 

 centered polygons, tops of high-centered polygons, basins (centers) of 

 low-centered polygons, and polygon troughs — and to a diverse range of 

 soil types, vegetation, and habitats. These recur over short distances, 

 commonly on the order of several meters (see Figures 1-8 and 1-9). Since 

 the troughs are interconnected they serve as pathways for the movement 

 of water, nutrients and plant litter, especially during snowmek. In winter 

 they are extensively used by lemmings under the deeper snow and low 

 density depth hoar (Chapter 2). The basins of low-centered polygons are 

 relatively poorly drained and many are areas of continuing organic 



