Figure 4 is an aerial oblique photograph taken in late August of a portion oi the site 2 plots. 

 At that time a majority of the plots had been enclosed to prevent subsequent grazing by lemmings. 

 The large rectangular enclosure will be used for lemming grazing studies in 1971. 



The artificial manipulations are those which exceed the range of conditions to which the tundra 

 is ordinarily subjected. In several cases these simulated the real and anticipated effects of man's 

 activities on the tundra. These are located primarily on site 1 and include: 



Heated soil. The proposed buried oil pipeline will provide a year-round heat source within 

 the soil. In order to evaluate the effect of warm soils on natural vegetation, a double loop of 1.25 cm 

 copper tubing through which hot fluids circulate was buried at the 10-cm depth in the tundralsoil. 

 Warming of the soU. began in early July. In late August, one half of the buried loop covering a 

 3 X 6-m area was shut off for the winter. The experimental design and sampling will be discussed 

 in greater detail in a later section. 



Heated air. Temperature and wind or a combination of both have often been considered limiting 

 factors in arctic plant growth. In order to test the hypothesis under field conditions, a 5 x 5-m by 

 1-m-high Fiberglas greenhouse was installed over an experimental plot. This greenhouse not only 

 permitted elevated air temperatures, but served as a wind shield. 



Physical disturbance. The effects of tracked vehicles on tundra vegetation are dramatic and 

 long lasting. In order to ascertain short term influences of physical damage, two plots were roto- 

 tilled while the surface was still frozen. On one plot, two complete passes at right angles covered 

 the plot. This treatment constituted the intense disturbance. Single passes at right angles on the 

 other plot constituted the light disturjjance. 



r 



M 



Figure 5. Site 1. 

 10 



