V. sitchensis, have been described in the Cascade 

 Mountains (Frankhn and Dyrness 1973). 



The other subalpine vegetation type was a heath, 

 dominated by red Phyllodoce empetriformis (mountain- 

 heather) (fig. IC). It also occurred imder an open can- 

 opy of A. lasiocarpa and P. engelmannii and in the 

 open. Ground cover was dense. Species diversity was 

 relatively low, given the dominance of Phyllodoce. For- 

 ests with similar ground cover vegetation have been 

 termed the Abies lasiocarpa/Phyllodoce empetriformis 

 association by Williams and Lillybridge (1983) and by 

 Agee and Kertis (1987). Phyllodoce heaths are among 

 the most widespread subalpine meadow communities 

 in the Pacific Northwest (Franklin and Dyrness 1973). 



The final type occurred above timberhne, at an eleva- 

 tion of about 2,000 m, below Slate Peak at the edge 

 of the Pasayten Wilderness. It was a sedge meadow, 

 predominantly Carex nigricans (black alpine sedge), 

 located in swales where snowmelt is unusually late 

 (fig. ID). The ground cover was a dense turf with rela- 

 tively low species diversity. This vegetation type is 

 widespread in the Pacific Northwest (Franklin and 

 Dyrness 1973). 



In sum, the Cascade vegetation types include one 

 type dominated by graminoids (Carex), one type domi- 

 nated by forbs (Valeriana), and two types dominated 

 by shrubs (Pachistima and Phyllodoce). Vegetation 

 types will be referred to by the genus of the most 



abundant ground cover species. One type is above 

 timberline; two partially forested types are in the sub- 

 alpine zone; the final type is in closed forest in the 

 montane zone. A list of the most abundant species 

 in each type can be found in the appendix. Nomen- 

 clature follows Hitchcock and Cronquist (1973). 



Bare Ground and Vegetation Cover 



Before trampling, three of the four Cascade Moun- 

 tain vegetation types were densely vegetated. Although 

 the forested Pachistima vegetation type had 17 per- 

 cent bare ground before trampling, no other type had 

 more than 2 percent bare ground. After trampling, 

 however, substantial amounts of bare ground were 

 exposed on all vegetation types (table 2). In the Valeri- 

 ana subalpine meadow, for example, mean bare groimd 

 was 19 percent after 25 passes, 51 percent after 75 

 passes, and 95 percent after 500 passes. After 500 

 passes the Valeriana meadow and the Phyllodoce heath 

 were almost entirely barren, the forested Pachistima 

 type was about one-half vegetated, and the Carex 

 alpine turf was about two-thirds vegetated. 



Measurements taken 1 year after trampUng indicate 

 how much the vegetation recovered. Bare ground di- 

 minished on two of the vegetation types (Carex and 

 Valeriana), increased on one type (Pachistima), and 

 remained relatively constant on the other (Phyllodoce). 



Table 2 — Percent bare ground before and after trampling and after 1 year of recovery for four vegetation types in Washington's 

 Cascade Mountains^ 



Number of passes 



25 75 200 500 700 



Pachistima myrsinites 

 (montane forest) 



Before trampling 



8(3)2 



18(5) 



15(4) 



24 (11) 



19(2) 





After trampling 



4(2) 



16(4) 



31 (12) 



44 (16) 



50 (18) 





After 1 year 



13(5) 



41 (4) 



38 (8) 



65 (8) 



79 (7) 





Carex nigricans 

 (alpine turf) 



Before trampling 



2(1) 





1 (+) 



1 (1) 



1 (1) 



2(1) 



After trampling 



10(2) 





16(3) 



23 (3) 



36 (6) 



51 (5) 



After 1 year 



5(2) 





5(2) 



10(2) 



8(2) 



10(3) 



Phyllodoce empetriformis 

 (subalpine heath) 



Before trampling 



+ w 



1 (1) 



+ W 



+ (+) 



+ (+) 





After trampling 



2(1) 



. 20 (8) 



17(7) 



48 (6) 



94 (5) 





After 1 year 



2(1) 



9(4) 



23 (10) 



54 (13) 



84 (5) 





Valeriana sitchensis 

 (subalpine forest-meadow) 



Before trampling 



+ (+) 



2(1) 



5(1) 



2(2) 



1 (1) 





After trampling 



+ W 



19(3) 



51 (6) 



79 (5) 



95 (2) 





After 1 year 



5(2) 



13(4) 



16(7) 



23 (2) 



15(7) 





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



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



5 



