Valeriana ty^e regained much of its original height. 

 One year after trampling, relative height was 90 per- 

 cent on the 25-pass lane and 53 percent on the 500-pass 

 lane. In the Phyllodoce type, relative height was lower 

 1 year after trampling than it had been immediately 

 afterward. This may reflect some dieback of shrub 

 stems and branches. 



When comparing the rate of height reduction to the 

 rate of cover loss with increased trampling intensity, 

 only the Phyllodoce type showed a substantial differ- 

 ence. Phyllodoce was much more resistant to height 

 reduction than to cover loss. In the Carex type, height 

 was reduced somewhat at low levels of trampling (75 

 to 200 passes) that had little effect on relative cover. 



Species Richness and Composition 



Species richness declined on all four vegetation types 

 as trampUng intensity increased. The decline was most 

 rapid on the Valeriana type, where the mean nimiber 

 of species on the 25-pass lane declined from 18 before 

 trampling to 14 after trampUng; on the 500-pass lane, 

 the mean number of species declined from 20 before 



trampling to five after trampling (fig. 4). In the Pachi- 

 stima and Phyllodoce types species richness did not 

 decline significantly before 200 passes; species rich- 

 ness did not decline significantly before 500 passes 

 in the Carex type. Five hundred passes reduced spe- 

 cies richness about 40 percent in the Carex type, 50 

 percent in the Pachistima type, and 75 percent in the 

 Phyllodoce and Valeriana types. However, afl^r 1 year 

 species richness approached or exceeded the original 

 levels for all trampling intensities and all vegetation 

 types. This suggests that short-term trampling does 

 not cause a long-term loss of species in these vegeta- 

 tion types. 



Species composition shifts with trampling if certain 

 species are more likely to survive and recover from 

 trampling than others. Floristic similarity values pro- 

 vide an indication of shifts in species composition by 

 depicting the similarity between the original composi- 

 tion and the composition immediately after trampling 

 and after 1 year of recovery. A floristic similarity value 

 of 100 percent would mean that the relative abimdance 

 of species was identical before and after trampling. 

 Even on controls, species abundance is expected to 



0) 



c 



(0 



CO 



o 

 o 



0> 

 Si 



E 



(A) 

 20- 



15- 



10- 



5- 



Z 15- 



10- 



5- 



Pachistima myrsinites 



□ Before trampling 

 ■ After trampling 

 H After 1 year 



(B) Carex nigricans 

 20-1 



15- 



10- 



5- 

















25 



75 



200 



500 



75 200 



Valeriana sitciiensis 



500 



(C) Pliyllodoce empetriformis 

 20 T 



Number of Passes 



Figure 4 — Species richness before and after trampling and after 1 year of recovery 

 in four vegetation types in Washington's Cascade Mountains. Vertical bars repre- 

 sent 1 standard error above the mean. 



700 



9 



