100 200 300 400 500 100 200 300 400 500 



Number of Passes 



Figure 30 — Relative vegetation heigiit after trampling and after 1 year of re- 

 covery in four vegetation types in North Carolina's Great Smoky Mountains. 

 Vertical bars represent 1 standard error above and below the mean. 



in Dryopteris. After 200 passes, relative height was 

 1 percent in Dryopteris and 5 percent in the three 

 other types. During the year after trampling, height 

 recovered greatly in all four types. Compared with 

 the other study areas, these vegetation types had very 

 similar responses. They all experienced dramatic re- 

 ductions in height and substantial recovery. 



In all four vegetation types height was lost more 

 quickly than cover. This difference was most pro- 

 nounced in Carex. One year after trampling, however, 

 height tended to be closer to original conditions than 

 cover. Again, this difference was most pronounced in 

 Carex. For example, after recovery on the 500-pass 

 lanes, relative cover in Carex was 45 percent and 

 relative height was 81 percent. 



Species Richness and Composition 



Species richness declined on all four vegetation types 

 as trampling intensity increased (fig. 31). The response 

 was most rapid on the Carex and Amphicarpa types, 

 which had significant reductions on the 75-pass lanes. 

 The other types first had significant reductions on the 

 200-pass lanes. In all four types, species richness was 

 only 25 to 35 percent of original levels on the 500-pass 



lanes. One year after trampling, species richness ap- 

 proached or exceeded original levels on virtually all 

 lanes and types. The only exception was the 500-pass 

 lane in Amphicarpa, where richness 1 year after tram- 

 pling was 80 percent of the original. 



Shifts in species composition occurred in all four 

 vegetation types following trampling; however, the 

 rate and magnitude of change varied (fig. 32). The 

 Carex type was least affected. Only the 200- and 

 500-pass lanes were significantly different fi-om the 

 controls. Even on these lanes, the similarity of floris- 

 tic composition values were about 70 percent. Both 

 Amphicarpa and Drypoteris experienced significant 

 changes in composition after just 25 passes. Change 

 was greatest in Dryopteris where similarity values on 

 the 200- and 500-pass lanes were just 5 to 10 percent. 

 In Potentilla, changes were signficant only on lanes 

 trampled at least 75 times. However, after 500 passes, 

 similarity values were only about 30 percent — a more 

 substantial change than on 500-pass lanes in Amphi- 

 carpa. In all four vegetation types, changes declined 

 over the year of recovery. One year after trampling, 

 the only lanes where species composition was signifi- 

 cantly different fi'om controls were the 500-pass lanes 

 in Amphicarpa and Dryopteris. 



41 



