one type dominated by shrubs (Vaccinium), one type 

 dominated by short forbs (Trifolium), and one type 

 dominated by erect forbs {Geranium). One type is above 

 timberhne; one type is an open subalpine meadow; one 

 type is a subalpine spruce-fir forest; and one type is 

 a montane aspen forest. A Ust of the most abundant 

 species can be found in the appendix. Nomenclature 

 follows Weber (1976), with the few exceptions of Geum 

 (which Weber calls Acomastylis), Polygonum (which 

 Weber calls Bistorta), and Poa pratensis (which Weber 

 calls P. agassizensis). 



Bare Ground and Vegetation Cover 



Before trampling, the Kobresia (turf) and the Gera- 

 nium (montane forest) vegetation types were very 

 densely vegetated; bare ground was only 2 to 3 per- 

 cent. The Trifolium (subalpine meadow) type had 

 more bare ground (mean of 11 percent), and the Vac- 

 cinium (subalpine forest) type had the most (mean of 

 18 percent). Tramphng exposed substantial amounts 

 of bare ground on all vegetation types (table 8). In 

 the Geranium type, for example, mean bare ground 

 was 11 percent after 25 passes, 26 percent after 75 

 passes, and 86 percent after 200 passes. After 500 

 passes, the Geranium lanes were 90 percent bare 

 ground. The 500-pass lanes were nearly as barren 

 in the Vaccinium and Trifolium types (83 and 79 



percent bare ground, respectively), but substantially 

 less barren in the Kobresia type (61 percent bare 

 ground). 



After 1 year, vegetation cover was again approach- 

 ing the original levels in the Geranium type but had 

 not recovered in the other types. In Trifolium, gopher 

 activity on control lanes caused bare ground to in- 

 crease fi'om 8 to 29 percent during the year following 

 trampling. It is impossible to estimate what might 

 have happened if the gophers had not been present. 

 In the Vaccinium type, and to a lesser degree in the 

 Kobresia type, bare ground exceeded the original lev- 

 els 1 year after trampling, even on the most lightly 

 trampled lanes. 



Relative vegetation cover after trampling differed 

 significantly both with the amount of trampling and 

 the vegetation type (table 9). The interaction between 

 these two effects was not significant. After the year 

 of recovery, differences in relative vegetation cover 

 for the trampling levels and vegetation types were 

 still highly significant. In this case, the interaction 

 between trampling levels and vegetation types was 

 significant and substantial. The effect of trampling 

 on the Vaccinium type was much more pronounced, 

 1 year after trampling, than for any of the other veg- 

 etation types. 



Of the four vegetation types, the forb-dominated 

 aspen forest (Geranium) lost the most vegetation 



Table 8 — Percent bare ground before and after trampling and after 1 year of recovery for four vegetation types in Colorado's 

 Rocky Mountains^ 



Number of passes 



25 75 200 500 700 



Trifolium parryi 



(subalpine meadow) 



Before trampling 



8 (3)2 



7(3) 



10(5) 



14(3) 



16(5) 





After trampling 



21 (3) 



22 (5) 



29 (8) 



59 (4) 



79 (5) 





After 1 year 



29 (12) 



28 (3) 



28 (8) 



33 (5) 



39 (5) 





Kobresia myosuroides 

 (alpine turf) 



Before trampling 



2(1) 





1 (+) 



2(1) 



3(1) 



2(1) 



After trampling 



4(1) . 





14(6) 



41 (9) 



61 (10) 



84 (4) 



After 1 year 



6(2) 





10(3) 



16(6) 



35 (5) 



54 (3) 



Vaccinium scoparium 

 (subalpine forest) 



Before trampling 



19(5) 



17(3) 



23 (4) 



13(6) 



16(6) 





After trampling 



20 (6) 



26 (3) 



43 (3) 



56 (1) 



83 (4) 





After 1 year 



23 (5) 



28 (6) 



56 (1) 



73 (3) 



90 (4) 





Geranium rictiardsonii 

 (montane forest) 



Before trampling 



5(1) 



2(1) 



3(1) 



3(1) 



4(1) 





After trampling 



6(2) 



11 (2) 



26 (4) 



86 (2) 



90 (+) 





After 1 year 



2(2) 



2(1) 



3(2) 



5(2) 



5(2) 





^Percent bare ground is the mean proportion of each quadrat that Is not vegetated. 

 ^Standard errors are in parentheses. A + indicates standard error less than 0.5 percent. 



17 



