vast majority of studies in which tramplers walked 

 along each treatment lane, using a natural gait, for a 

 predetermined number of passes. 



4. Sampling procedures.— Most treatment lanes are 

 sampled and the size of the sampling unit varies. Be- 

 cause trampling stress is most highly concentrated in 

 the center of each lane, narrow sampling units in the 

 center of the lane will experience more overall trampling 

 stress than a wider unit that includes some of the less- 

 trampled edge of the lane. 



5. Timing of trampling.— Some studies spread the 

 trampling over a season, while others apply all of the 



trampling at once. Some have examined the importance 

 of the period of time over which trampling occurs by 

 comparing the effects of the same number of passes ap- 

 plied either all at once or spread over the season. Such a 

 comparison is difficult to interpret because (1) the effect 

 of one-time trampling varies with the time of year the 

 trampling is applied, and (2) in many cases the period of 

 time between trampling application and measurement 

 has varied, so more recovery is possible in some cases 

 than in others. 



6. Basis of comparison.— Several studies have not 

 measured the pretrampling condition of treatment lanes. 



100 



LU 

 > 



o 

 o 



5P 



of 



HI 

 > 



o 



- (a) POTR/HELA 

 FOREST 



50 'i- 



100 



50 i- 



mm 



(b) POTR/SYAL 

 FOREST 







100 

 50 



400 



800 



(c) PIEN/ARLA 

 FOREST 



100r 



50 ij- 



-1 



400 



(d) PICO/THVE 

 FOREST 



800 



400 



1 00 p (e) ABLA/LUHI 

 FOREST 



50 hr 



800 



400 



1 00 r (f) PIAL/V ASC 

 FOREST 



50 



800 



J 



400 800 



O lOOir (g) EMNI SAND DUNE HEATH 



50 - 



-L . J 1_ 



400 



800 1000 



J 



400 



800 



100 f- (h) POPR/FEID 



GRASSLAND 



50 



1200 1600 

 100 



2000 



2400 2560 



cc 

 ai 

 > 

 O 



O 100 - 

 50 



_l_ 



J 



400 



(j) VAME 

 FOREST 

 SHRUBLAND 



800 1000 



400 



800 



lOOp (I) VASI 



FORB MEADOW 



50 



50 

 



100 

 50 



O 



100 

 50 



(i) FESC 



GRASSLAND 



400 



800 



(k) XETE 



SUBALPINE 

 MEADOW 



^ 1 J 



400 800 



(m) LUPE 



SUBALPINE MAT 

 COMMUNITY 



400 



800 



400 



800 



NUMBER OF PASSES 



Figure 1. — The relationship between vegetation cover (see text for definitions of 

 relative and estimated relative cover) and amount of trampling (number of passes) 

 for previously studied vegetation types. An asterisk by the source indicates that 

 relative cover was estimated (refer to text for definitions). 



2 



