

Figure 4. Site 2. 



Clip and uncleared. In many cases vegetation cut by winter activity of lemmings is not washed 

 away, but falls to the ground to enter the litter compartment of the system. The lemmings thus 

 convert material from above-ground "standing dead," where it is subject to very slow decomposi- 

 tion, to litter, where it is subject to much more rapid decomposition by below-ground saprovores 

 and decomposers. Thus, in addition to the physical effects of grazing on the plants, the lemmings 

 cause the sudden input of organic matter into the saprovore food chain. These effects were 

 mimicked on two plots, one sampled intensively and one reserved for nondestructive and future 

 sampling. 



Mulch. Plant material cut by lemmings and transported by meltwater frequently accumulates 

 in low areas where drainage is retarded. Such areas experience a large increment of litter and, 

 in addition, a great increase in the insulative layer over the tundra surface. The latter may be 

 expected to influence near-surface temperature, and especially soil temperature and depth of thaw. 

 Two plots were treated with natural plant litter (including that removed from the clip and clear 

 plots). One plot received 107.3 g/m^, an amount equal to that removed from one clip and clear 

 plot, and approximately equal to the amount of plant material produced in one season. The other 

 plot received a much heavier application of 240.9 g/m^ The intense application produced a layer 

 of litter which covered the lower portion of the vegetative canopy. 



Fertilizer. The treatments were employed to determine the effects of increased nutrient 

 availability without the additional physical effects of cutting the vegetation and alteration of the 

 insulative layer. This was accomplished by the addition of commercial nitrogen-phosphaus-po- 

 tassium (N, P, K) fertilizers at a rate equal to 400 lb/acre (45 g/m*). One plot received a 20-10- 

 10 mixture, and the second plot received an 8-32-16 mixture. 



9 



