Table 3. — Comparisons of mean relative cover for tfiree pairs of treatments withi different 

 trampling frequencies but approximately ttie same number of total passes^ 



Compared treatments 



Habitat type 



1-100 16-5 



3-25 16-5 



1 -300 3-100 



Abies lasiocarpa/ 



Clintonia uniflora 



Abies lasiocarpa/ 



Clintonia uniflora- 



Vaccinium caespitosum pfiase 



Abies lasiocarpa/ 



Vaccinium caespitosum 



Abies lasiocarpa/ 

 Xerophyllum tenax 



Pseudotsuga menziesii/ 

 Symphoricarpos albus 

 Festuca scabrella- 

 F. idahoensis 

 All fiabitat types 



39 



99 

 67 



Mean relative cover (percent) 



37 



53 < 82 



78 63 



77 > 60 



38 < 73 



100 

 71 



35 



79 

 53 



100 

 71 



37 



82 

 63 



96 > 60 

 50 < 73 



100 

 71 



99 

 44 



10 



23 19 



59 > 16 



38 < 71 



10 < 50 



99 

 49 



'The 1-100 treatment, for example, indicates ttiat 100 passes were administered once during the 

 season. < and > symbols between pairs indicate that the more concentrated treatment was more or 

 less damaging, respectively: no symbol Indicates no significant difference (t-test; « = 0.05). 



between treatment lanes— differences that existed prior 

 to treatment— proved to be a major source of uncontroll- 

 able variation throughout this experiment. 



This study could not prove that frequency of tram- 

 pling had no effect on amount of impact. However, one 

 can conclude that frequency of trampling has no consis- 

 tent effect and is less important than total number of 

 passes, habitat type, and local differences in species 

 composition. 



Effect of Trampling Intensity 



A one-way analysis of variance was used to examine 

 the effect of number of passes on relative cover for each 

 vegetation type (fig. 10). Significant differences between 

 treatments were identified using Duncan's multiple 

 range test {a = 0.05) (Steel and Torrie 1960). In each 

 habitat type, cover generally decreased as trampling 

 increased. For some habitat types, however, the rate of 

 decrease was much more rapid than for others. In addi- 

 tion, the general decrease was erratic on some types, 

 namely ABLA/VACA (fig. 10c), ABLA/XETE (fig. lOd), 

 and PSME/SYAL (fig. lOe). These types have patchy 

 representation of particularly resistant species. Lanes in 



which resistant species were particularly abundant fre- 

 quently lost less cover than other lanes despite receiving 

 higher levels of trampling. 



The relationship between trampling intensity and rela- 

 tive cover is distinctly curvilinear for all five forested 

 habitat types; most of the cover loss occurred after a 

 small number of passes. Increases in trampling beyond 

 200 to 300 passes caused little additional loss of cover. 

 The data for these types fit closely to a regression line 

 with the form 



Y = a + b log X, 

 where Y is transformed (inverse sine) relative vegetation 

 cover and X is number of passes. This corroborates the 

 findings, reviewed earlier, of most other studies. 



Of the forested types, cover loss was least rapid in the 

 ABLA/XETE type. In this type more than 75 passes 

 were required to cause a statisticedly significant reduc- 

 tion in cover (fig. lOd). Beyond this level cover loss was 

 rapid; over 50 percent of the original cover was lost after 

 400 passes. Further losses of cover were minimal; 37 per- 

 cent cover survived 1,600 passes. In fact, increasing 

 tramphng beyond 300 passes caused no statistically sig- 

 nificant increases in cover loss. 



13 



