498 
older pollen and spores consist of high per- 
centages of Erkales (55 per cent) , Gramineae 
(22), and Lycopodium (17), with some Cypera- 
ceae (2.9). Thus, the lower sample represents 
the Empetrum heath of higher altitudes (Hul- 
ten, 1937^; Bank, 1952). The younger pollen 
and spores show high percentages of Grami- 
neae (56), Cyperaceae (23) , and Ranunculaceae 
(9.0), with some Ericaks (3.7), Dryopteris (3T), 
and Umbelliferae (2.2). This sample indicates 
a vegetation very similar to the Calamagrostis 
meadow which exists today at the place of 
the profile. 
The results of this preliminary pollen study 
are, of course, inconclusive. What they do 
indicate is that pollen analysis of at least some 
strata in Aleutian ash profiles is possible. 
Certain changes in vegetation are indicated, 
i.e., from an earlier Lycopodium-Empetrum 
heath to a Calamagrostis-UmhtlYiitmt meadow, 
and these changes can be interpreted as due 
to climatic fluctuation from dry, continental- 
arctic to moist, oceanic-subarctic. However, 
great dependence upon pollen shifts at iso- 
lated sites as an indication of widespread cli- 
matic changes is extremely hazardous for two 
main reasons: (1) it seems likely that heavy 
ash falls not only destroyed existing vegeta- 
tion but also produced such radical changes 
in the local habitat that the succeeding vege- 
tation may have been of totally different char- 
acter for edaphic reasons; and (2) the normal 
instability of Aleutian biota, to which I have 
already called attention, operates to produce 
major changes in natural biotic groupings for 
reasons much less basic than climatic inter- 
ference. 
Raup (1950) has discussed this latter gen- 
eral problem of physiographic ecology in 
arctic and subarctic regions. He says (p. 8): 
' 'Approaches to equilibrium or relative sta- 
bility such as we find in the temperate regions 
and are wont to call climax, are almost im- 
possible to define in the Arctic and much of 
the Subarctic. At best they are ephemeral in 
time and space.” And again (p. 10), . . it 
becomes apparent that one of the prime re- 
PACIFIC SCIENCE, Vol. VII, October, 1953 
quisites for development of dominance and 
succession-long continued stability in the 
substratum— is absent or very poorly repre- 
sented over vast areas in the Arctic and Sub- 
arctic.” 
An example of a constantly unstable sub- 
stratum in the Aleutians is found in the alpine 
regions where the unceasing wind, more than 
any other ecological factor, restricts plant 
growth, molds vegetational structure so to 
speak, and, when aided by subsurface water, 
often radically changes the vegetational char- 
acter of large areas in a comparatively short 
period of time. Thus in high, exposed places 
one frequently comes upon bare patches of 
gravel or ashy soil having a slight ridge along 
the lower margin. These areas are wet and are 
usually on slopes. Underground seepage has 
saturated the soil, which lies thinly over bed- 
rock, with the result that large soil patches 
have flowed downhill carrying vegetation with 
them. Surface water further erodes these areas, 
and wind removes all loose plant fragments. 
The bare patches may be reinvaded by plants, 
but irregular shallow depressions in the sur- 
face of the vegetational mat identify the spot 
as a former slough area. Frequently these are 
continually eroded by the high winds, and 
scalloped gravel pits are formed. The gravel- 
blasting effect of the wind prohibits all but 
the hardiest plants from gaining a foothold. 
At first only gnarled, almost leafless, dwarfed 
(6 inches tall) willows may grow. In time 
these eroded patches are probably covered by 
willows and lichens, which in turn offer some 
protection from the wind to less hardy plants, 
among them Campanula lasiocarpa, Primula 
cuneifolia, Antennaria dioica, and Polygonum 
viviparum. 
Probably the best examples of vegetational 
instability are found in the wet habitats. Often 
these develop in the middle of an otherwise 
dry Aleutian meadow or heath area. In such 
places subsurface water may begin to seep 
from the hillside and form bog-like drainage 
slopes on which a number of bog plants, 
especially Sphagnum, begin to grow. Soon 
