Instead, they rely on a control lane as an estimate of 

 pretrampling conditions. Most plant communities are so 

 heterogeneous that this introduces significant loss of 

 precision. The preferred design, used in many studies, 

 utilizes control and treatment lanes and includes pre- 

 and posttreatment measurements on each. 



The implications of these variations in study design 

 need to constantly be kept in mind. Nevertheless, many 

 studies are directly comparable and with others some 

 generalization is possible. Questions that can be partially 

 answered at this time are: (1) What is the nature of the 

 relationship between amount of trampling and vegeta- 

 tion and soil disturbance? (2) Which plant community 

 types and growth forms are more resistant to damage 



than others? (3) How does the timing and frequency of 

 trampling affect amount of disturbance? 



Relation Between Amount of Trampling 

 and Amount of Vegetation Loss 



All studies show that increased trampling leads to a 

 general increase in cover loss; however, for each plant 

 community the curve that describes this relationship 

 varies in shape. Figure 1 presents curves relating surviv- 

 ing cover to number of passes for the 22 plant communi- 

 ties where this relationship can be described. In some of 

 these, the dependent variable is "relative cover," defined 

 as the percentage of original cover remaining after tramp- 

 ling, adjusted for any changes that occurred on control 



UJ 



> 

 O 



o 



100 



50 - 



OC " 

 liJ 



> 100 



o 

 o 



50 



100 



50 



100 



50 



100 



50 - 



(n) ANOC/TRLA 

 SUBALPJNE 

 MEADOW 



400 



(p) PHGL 



SUBALPINE 

 HEATH 



800 



400 



800 



(r) CANI 



SUBALPINE 

 MEADOW 



J. 



400 



800 



(t) DROC 



ALPINE CUSHION 

 COMMUNITY 



400 



800 



(v) LULE/CAPH 



ALPINE STONE-STRIPE 

 COMMUNITY 



100 



50 



100 



50 



100 



50 



100 



50 



(o) TRLA 



SUBALPINE 

 MEADOW 



400 



(a) CAME 



SUBALPINE 

 HEATH 



800 



J 



400 



800 



(s) ANLA/CANI 



ALPINE SNOWBANK 

 COMMUNITY 



A. 



400 



800 



1200 



(u) ASAL/PHDI 



ALPINE CUSHION 

 COMMUNITY 



400 



800 



1200 



O 400 800 1200 



NUMBER OF PASSES 



Key to Species Abbreviations: 



SOURCES : 



♦ NAGY4 SCOTTER, 1974 (a,b,c.d.e.i,k,o,t) 

 WEAVER 8 DALE. 1978 (f,h) 

 HYLGAARD & LIDDLE, 1981 (fl) 



♦ LANDALS & SCOTTER. 1974 (i.l.m.q.r) 



♦ LANDALS & SCOTTER. 1973 (n.p) 



♦ BELL & BLISS, 1973 (s.y) 

 SINGER. 1971 (u) 



ABLA = Abies lasiocarpa 

 ANOC = Anemone occidentalis 

 ANLA = Antennaria lanata 

 ARLA = Arnica latitolia 

 ASAL = Aster alpigenus 

 CANI = Carex nigricans 

 CAPH = Carex phaeocephala 

 CAME = Cassiope merlensiana 

 DROC = Dryas octopetala 

 EMNI = Empetrum nigrum 



Figure 7. — (con.) 



FEID = Festuca idahoensis 

 FESC = Festuca scabrella 

 HELA = Heracleum lanatum 

 LUPE = Luetkea pectinata 

 LULE = Lupinus lepidus 

 LUHI = Luzula hitchcocl(ii 

 PHDI = Phlox diffusa 

 PHGL = Phyllodoce glanduliflora 

 PIEN = Picea engelmannii 

 PIAL = Pinus albicaulis 



PICO = Pinus contorta 

 POPR = Poa pratensis 

 POTR = Populus tremuloides 

 SYAL = Symphoricarpos albus 

 THVE = Thalictrum venulosum 

 TRLA = Trollius laxus 

 VAME = Vaccinium membranaceum 

 VASC = Vaccinium scoparium 

 VASI = Valeriana sitchensis 

 XETE = Xeroptiyllum tenax 



3 



