163 
Fig. 7. Diagrammatic representation of Prudhoe Bay vegetation types in rela- 
tion to moisture gradient and elevation. Numbers in brackets are vegetation 
types in accordance with the Webber /Walker scheme (this volume): 
Webber/Walker Vegetation Continuum 
Type 1 Type2 Type3 Type4 TypeS Type6 ~ Type? 
Normal moisture ———EE 
gradient increasing wetness 
Sand dunes Type 15 Type 16 Type 17 
Streams Type 13 Type 12 
Pingos Type 10 
Snowbanks Type 9 
Frost boils Type 8 
The numbering of the sand dune communities is tentative and will probably change following more extensive 
mapping in the dunes. The following is a brief description of the current types: 
Type 15 — Pioneering communities consisting mainly of E/ymus arenarius, Artemisia spp and Salix ovalifolia. 
Type 16 — Drier communities on stabilized dune sand which has developed polygonal patterning. This type is 
similar to Type 2 and 3 but with much more Sa//x ovalifolia and Artemisia spp. 
Type 17 — The wetter communities in the dunes which are similar to Type 4 but with abundance of Salix 
ovalifolia. 
Sand Dunes 
Vegetation Key: Webber/Walker Scheme for Prudhoe ae 
Bay (Key to the most common vegeta- ovalifolia 
tion types of Prudhoe Bay) Elevation ti7y_ol tet 
1. Lichens abundant Poe | 
Lichens rare 3: Standing Carex Eriophorum | Dryas Solin 
2. Many fruticose and crust lichens INAFE 1 Water | aquotilis | angustifolium| integrifolia | rotundifolia | Rive 
Mostly only fruticose lichens TYPE 2 VEG) Pe ai pee) Sa See 
3. Dryas and/or Salix spp. abundant nNAre 3 | | Duportia \ Bro 
Dryas and/or Salix spp. rare 4. Perea as paar 
4. Mosses rare TYPE 6 ey Creek 
Mosses abundant 5. | ee 
5. Drepanocladus species dominant TYPE 4 3 a = Increasing Wetness + 
Scorpidium scorpioides dominant iN RES [ ] Vegetation type- Webber/ Walker Scheme 
were distinguished using Sdrensen’s index of 
similarity: 
oe 2.c.100 
S atb 
where a is the number of plant species in a stand 
of vegetation with a constancy 250; 6 is the 
equivalent value for the compared stand; c is the 
number of shared species. The mean index of 
similarity between stands within types was 64.7 
(SD = 9.1) and between vegetation types 24.7 
(SD = 17.6). The vegetation types correspond to 
the criteria of associations, but a formal classifi- 
cation was not attempted due to lack of data on 
the cryptogams. Vegetation types were named 
after the dominant species in each type. 
Vegetation distribution in the study area was 
surveyed in four ground transects covering the 
land area between lakes. Lakes and sand dunes 
were recognized from aerial photographs and 
maps, and their distribution assessed in five map 
transects. The results of the ground transects are 
shown in Table 8, and the combined ground and 
aerial transects, in which free-water cover was 
deleted, is shown in column 8 of Table 8. Also 
shown in Table 8 are the same vegetation types 
with their appropriate designation, according to 
Webber’s vegetation map for Prudhoe Bay (this 
volume). 
Caribou grazing patterns and dispersion 
(a) Caribou preference for vegetation types. 
Groups of caribou were observed for 10 min 
