DRAFT
Paleoenvironmental Reconstruction and Landscape Interactions in Lake Clark
and other Southwest Alaska Lake Systems,
Southwest Alaska Inventory and Monitoring Network
Module I
Paleoecology and Vegetation History
Lake Clark and Katmai Regions
Patricia A. Heiser
UA Geography Program
University of Alaska Fairbanks
Fairbanks, AK 99775
September 2007
National Park Service
Southwest Alaska Network
Inventory and Monitoring Program
Project / Task Agreement No.: J9W88030009
CESU Cooperative Agreement No.CA9088A0008
DRAFT
Paleoecology and Vegetation History Lake Clark and Katmai Regions
Patricia Heiser, UAF Geography Program and Nancy Bigelow, Alaska Quaternary Center
Introduction
The Southwest Area Network (SWAN) park units of Southwest Alaska encompass an
extensive range of geographic physiographic, climatic, and ecologic provinces and gradients.
Ecosystem types show strong variation across the landscape including relatively dry interior
boreal forest, alpine herb tundra, shrub tundra lowlands, and cool coastal forests. Some park
units such as Lake Clark are located in
transition zones between these major
ecosystem types (Spencer 2001). As
glaciers retreated and climate
ameliorated during the Holocene,
significant changes have occurred in
the dominant vegetation assemblages
in the area. Likewise, Little Ice Age
moraines are prominent in many
valleys and suggest there might also be
detectable records of shorter-term
Holocene climatic events. The study
of pollen assemblages recorded in lake
sediments is one of the most widely
used indicators of past environmental
changes. Recent studies have shown
that late Quaternary vegetation of
Alaska and the Bering Strait region
http://www.nature.nps.gov/im/units/swan
has been “marked by great spatial and
Figure 1. Location of SWAN parks and study areas.
temporal variability” (Brubaker 2001),
and defining patterns of vegetation change through time and at different spatial scales has
become critical in determining causal factors and driving forces for landscape change (Bartlein et
al 1998). Few studies of vegetation change have been conducted in southwest Alaska. Two
pollen records obtained from Idavain and Snipe Lakes in Katmai and Lake Clark National Parks
respectively, record distinctive changes in dominant vegetation type over the last ~12,000 years.
These cores were compared with records obtained on a transect running from Interior Alaska to
Bristol Bay (Brubaker et al 2001). While the information in these cores is valuable to
understanding regional landscape dynamics surrounding SWAN systems, it is important to
compliment these results with more local, and perhaps higher resolution, and better dated records
from transition areas like Lake Clark, and from areas with unusual vegetation patterns such as
near Nonvianuk Lake in Katmai National Park (Fig X). Additionally, vegetation studies around
lakes from which historic records of salmon abundance are being obtained may be valuable to
the interpretation of those records. Salmon history is reconstructed using nitrogen isotopes, and
appearance of nitrogen fixing plant species (e.g. alders) may potentially influence the N record
used as a proxy for salmon abundance. Vegetation change is also an important component in
efforts to understand timing of colonization, succession, and nutrient cycling in riparian habitats
and lake systems. This study will complete the picture of landscape change and freshwater
ecosystem development in the Southwest Network parks.
DRAFT
Study Areas
Two lakes were
selected for this
paleoecological study
across SWAN units.
Informally named
“Tommy Lake” in
Lake Clark National
Park and Preserve
and “Pikelet” Lake
near Nonvianuk Lake
in Katmai NP&P
were cored in the
summer of 2005. The
study lakes were
chosen for their
geomorphic position
and surrounding plant
communities .
Tommy Lake
LACL
Pikelet Lake
KATM
TOMMY LAKE
Tommy Lake
Figure 2. Satellite image showing location of Tommy Lake in Lake Clark National
is located along the
Park (LACL) and Pikelet Lake in Katmai National Park (KATM).
southwest shore of
Lake Clark approximately 500 meters inland and 40 meters above the current shoreline elevation
of Lake Clark. “Tommy Lake” is actually a small pond ~ 2500 m2 with a maximum depth of 2.5
meters. It is one of a series of ponds formed in a covering of thin glacial till over bedrock.
Outcrops of bedrock and large erratics influence the elevation and position of Tommy and
surrounding lake and ponds.
The vegetation in the Lake Clark region is
highly varied due to topographic variation and
strong climatic gradients (wetter to east, drier to
the west). The western side of the park is
dominated by a series of linear lakes dammed by
terminal moraines that mark the extent of glacial
ice from Alaska Range valleys to the east. Low
ridges and subdued mountains between these
lakes are host shrub/alpine tundra and occasional
scattered spruce in the valley floors. The northern
part of the park, by the Stony River, is boreal in
character, with black spruce, muskeg, aspen and
Figure 3. Vegetation classification around Lake Clark.
birch, and subject to wildfire (NPS Ecological
Profile). Further south, and around Lake Clark itself, topographic relief is high (250-3500 ft)
with steep valley walls and deep glacially carved valleys. Lake Clark occupies a very deep fault
controlled glacial valley. Vegetation is a mosaic of spruce and mixed spruce/birch or cottonwood
forests, paper birch, low shrubs dominated by dwarf birch, dwarf shrub tundra with ericaceous
DRAFT
shrubs, scattered wetlands, and alpine tundra. Dense alder zones cover alluvial and scree slopes
between the mixed hardwood spruce forests around the lake, and the higher alpine zones (NPS
Ecological Profile). In general Lake Clark valley is located at an ecological intersection between
interior boreal forest, upland shrub tundra, mixed spruce/birch forest of glaciated valleys, and
humid coastal forests along Cook Inlet on the east side of the Alaska Range. Of interest. is the
timing of the arrival of spruce trees, and the likely ‘source’ for spruce expansion into the Lake
Clark valley after deglaciation. Also of interest is the timing and nature of the arrival of alder,
which shows dramatic increases in abundance ~7,000 cal yr BP in Snipe Lake and in other
pollen records in SW Alaska.
Tommy Lake
Figure 4. Vegetation classification and satellite image of landscape around Lake Clark and Tommy Lake.
The vegetation at the shoreline and adjacent to the pond is a mixture of sedges (Carex sp.
and Eriophorum sp.), horsetail (Equisetum sp.) and shrubs such as Myrica gale [sweetgale],
shrub birch (both Betula glandulosa and B. nana), willows (Salix sp.) and ericads (Vaccinium
vitis-idaea [lowbush cranberry], Vaccinium sp. [blueberry], Empetrum hermaphroditum.
[crowberry], Ledum decumbens [narrow leaf Labrador tea], and Andromeda polifolia [bog
rosemary]). Interestingly, no Alnus (alder) was encountered near Tommy Lake, although the
mountainside above the lake and the slopes descending to Lake Clark have abundant alder.
Spruce are present a short distance (<20 m) from the shoreline, mainly Picea mariana (black
spruce). White spruce (P. glauca) was not seen at the lake, but probably grows on well-drained
sites above the lake. The emergent vegetation within the pond includes buckbean (Menyanthes
trifoliata), pondweed (Potamogeton sp.), and possibly water milfoil (Myrophyllum sp.).
Hippuris (mare’s tail) was probably also present, but not emergent.
Methods:
Approximately 5.5 meters of sediment were retrieved from Tommy Lake in overlapping
cores. The lake was cored in the deepest basin in approximately 2.5 meters of water.
Overlapping drives were aligned using numerous and distinct volcanic ashes and ash sequences
present through the cores. Cores were split, described, and sampled for tephra analysis,
radiocarbon dating, and pollen analysis. For the pollen study, volumetric samples were collected
from the core and processed using slightly modified techniques outlined in Faegri and Iversen,
1989. This includes additional washes in hot KOH to remove lignins and in some cases, a
DRAFT
slightly longer soak in a boiling water bath during acetolysis. Prior to analysis, a known quantity
of exotic spores (Lycopodium) were added to the samples. Lycopodium exotics were counted in
tandem with the pollen, so that the pollen concentration can be assessed. Pollen grains were
identified based on comparison with the reference collection at UAF’s paleocology laboratory or
with various published atlases and keys, such as Faegri and Iversen, 1989; McAndrews et al.,
1973; Moore et al., 1991. Pollen frequencies were calculated on a variety of pollen sums. Trees,
herbs and forb frequencies are based on a sum of those taxa (= Pollen sum); spore frequencies
(Pteridophytes) are based on the pollen sum plus the spore sum; aquatic frequencies are based on
the pollen sum plus the aquatic sum, and the Pediastrum frequency is based on the pollen sum
plus the Pediastrum sum. This method of calculation prevents the non-terrestrial and non-seed
producing plants from overwhelming the terrestrial pollen signal.
Tommy Lake / Lake Clark Pollen History
Four major pollen zones are preserved in the Tommy 05 core (Figure 5).
Herb zone (547-530 cm). The basal two samples represent the final stages of the herb zone,
when graminoids (grasses and sedges) and forbs dominate the landscape. The transition to the
birch zone occurred about 14,500 cal yr Bp (12,000 14C BP), when Betula (birch) pollen
frequencies abruptly increase from about 20% to nearly 70%.
Birch zone (530- 410 cm). The birch zone encompasses more than 1 m of sediment, spanning
from about 14,500to 10,000 cal yr BP (12,000 to 7000 14C BP). While birch pollen dominates,
willow, ericads, graminoids and some forbs are also present. The concentration (# pollen
grains/cc of sediment) of herbaceous pollen does not markedly decrease with the birch rise,
indicating that these taxa (grasses, sedges, Artemisia, and other forbs) continued to be a
significant part of the vegetation. The vegetation was probably a birch shrub tundra, with
occasional herbs, willows, and ericads, especially at the end of the zone. When it was possible to
identify the ericads to the species level, Empetrum (crowberry) and Ledum (Labrador tea) were
also probably present. Monolete spore (ferns) frequencies present an interesting picture. Ferns
are sensitive to warmth and moisture; an increase in spore frequencies may indicate climatic
amelioration. Two fern peaks are present in the birch zone, separated by a period of low spore
frequencies. This may correlate with the “fern gap as noted by Peteet and Mann, 1997 in their
work from Kodiak Island. However, the current chronology for Tommy places the onset of fern
dip at about 13,500 cal yr BP, about 700 years before the Kodiak record. Fern spores and
Pediastrum nets (an alga) are abundant towards the end of this zone, Pediastrum may be an
indicator of overall lake productivity. Both taxa may be responding to increasing early Holocene
warmth, but the Pediastrum peak is slightly earlier than the fern peak, indicating other factors
may also be important.
Alder zone (410-170 cm). The alder zone includes more than 2 m of sediment, from about
10,000 to 3800 cal yr BP (7000 to 3400 14C BP). Alder frequencies increase rapidly from less
than 5% to over 70% over the space of 10 cm. The frequencies are highest at the onset of the
period (ca. 80%), decreasing to about 50% by the period’s end. Alder is a prolific pollen
producer and the pollen frequency over-represents the actual plant abundance on the landscape.
20% frequency probably indicates local presence of the plant (Anderson et al., 1991). Low
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DRAFT
frequencies of Populus pollen (probably cottonwood) are present at the onset of the zone,
indicating scattered trees may have grown as gallery stands along stream margins. Ericaceous,
graminoid, and forb pollen, while present, are less abundant than the preceding zone. Sweet gale
(Myrica gale) appears in the pollen record at about 240 cm (ca 5200 cal yr BP). Myrica is not
common in boreal pollen records from Alaska; its presence here suggests the plant has grown
around the lake (as it does today) since the mid-Holocene. The vegetation during the alder zone
was a mixed alder and birch shrub tundra (including Myrica at the lake) with minor amounts of
cottonwood, willow and other shrubs.
Spruce zone (170-0 cm). This zone encompasses 3800 cal yr BP. to the present. Spruce (Picea)
pollen is present at low frequencies prior to this zone; the taxon may have been present in the
region at this time, but probably was not growing near Tommy Lake until roughly 3000 cal yr
BP. Like alder, spruce is an abundant pollen producer. As a rule of thumb, 5% to 10% spruce
frequency indicates it was growing locally.( Anderson et al., 1991; Hu et al., 1993). After about
3000 cal yr BP the vegetation was probably not markedly different from today’s vegetation.
Towards the end of the zone, ericads, Sphagnum, and monolete spores increase, probably
indicating increasing soil moisture.
Snipe
Lake
Tommy
Lake
Spruce expansion. The late arrival of spruce to the Lake Clark
area (at ca. 3500 cal yr BP) is consistent with its ultimate
migration from the north, where spruce was present by at Snipe
Lake (about 40 km to the north) by about 5800 cal yr BP
(Brubaker et al., 2001). Trees may have crossed the low passes
separating the two lakes. Some of the passes are about 300 m
in elevation and today spruce are present in scattered localities
which increase in density towards the approaches to the Lake
Clark basin. In any case, the current chronology suggests the
migration from Snipe Lake took more than 2000 cal yr.
.
PIKELET LAKE
Pikelet Lake (58o58’36.43”N, 155o39’33.19”W) is a small pond located at the south
end of Pike Lake, approximately 6 km southwest from the outlet of Nonvianuk Lake, in Katmai
National Park and Preserve. The basin is separated from the larger lake by a 2-4 meter gravel
ridge. The surface of Pikelet is slightly higher than Pike (<20cm) and a 2m wide wet spot, with
very little water exchange evident, may join the lakes at higher water levels.
Pike Lake, Pikelet and surrounding small lakes are kettles formed in glacial till of a recessional
moraine deposited by a glacier flowing NW out of the Coville valley. The lakes are located just
behind the crest of the terminal moraine that appears contemporaneous with the moraine
bounding Nonvianuk Lake. These moraines are assigned to the Iliamna Stade of the Late
Wisconsin glaciation (~18 k yr ago) (Reihle and Detteman 1993).
DRAFT
The topography surrounding Pikelet Lake is more subdued than the relief around Lake
Clark and Tommy Lake.
Nonvianuk
Glacial valleys carved by
Lake
ice flowing from the east
and southeast are
moraine crests
occupied by Kulik and
moraine dammed
Nonvianuk Lake just to
the northeast of the study
site. The morianal
topography in which
Pikelet
Pikelet Lake has formed
was deposited by ice
flowing from the south
thorough valleys now
occupied by Grosvenor
and Colville lakes. While
peaks between the glacial
valleys reach to 3500
feet, the lowlands in front
Figureand
6. Pikelet
Lake
location
and
terminal
fromatCoville
and Nonvianuk.
subdued
relief.
Pike
Lake
is at moraines
an elevation
584 feet,
of the lakes, are of lower elevation
with the moraine crest at about 600 feet. The low moraines and outwash plains slope to near sea
level along the Alagnak and Kvichak Rivers, which empty into Bristol Bay about 75 kilometers
to the west.
Vegetation around Nonvianuk and Kukaklek lakes is dominantly shrub tundra on the
low-relief hills. Thin bands of alder are present on steeper slopes at the head of Nonvianuk and
Kulik lakes and the Coleville valley to the south, alder is otherwise scattered on the landscape.
An interesting and somewhat anomalous ‘tongue’ of spruce and mixed forest extends from the
south, up the Coleville into the Nonvianuk / Alagnak drainage. The pattern of boreal / mixed
a.
b.
Kukaklek
Nonvianuk
Idavain
Coville
Figure 7. Pikelet Lake study area including nearby lakes and vegetation cover.
forest corresponds very closely to the moraine crest, with the mixed forest zone occupying the
moraine crest. The location for this study was chosen because of the unusual pattern of spruce in
the area. To the south and around Naknek Lake, treeline reaches to elevations of 900-1000 feet.
DRAFT
To the north and west, spruce is much more scattered, and does not reach above 600 feet around
Illiamna and Kukaklek Lakes. Field studies of tree rings at Nonvianuk Lake revealed that most
of the trees were approximately 90 years old , and may have germinated shortly after the 1912
Katmai eruption. This site was specifically chosen for its potential in evaluating some of the
factors influencing spruce treeline, distribution on the landscape, and colonization events.
Previous studies (Tae, 1997) have suggested that volcanic eruptions or other geologic
disturbance events may induce changes in plant communities or colonization.
The emergent vegetation at Pikelet includes water lily (Nuphar polysepalum) and
mare’s tails (Equisetum sp.). Sedges (Carex sp.) and mare’s tails (Equisetum sp.) dominate the
shoreline vegetation, though marsh cinquefoil (Potentilla palustris) and Rubus sp. are also quite
common. Ridges and slopes descending to the lake have vegetation typical of somewhat betterdrained settings, including abundant willow shrubs (Salix sp.), shrub birch (Betula glandulosa)
and heath vegetation. Alder (Alnus incana) is present in patches. White spruce trees (Picea
glauca) are widely scattered, separated by birch, alder, and willow shrubs on the western shore
and mare’s tails and coltsfoot (Petasites sp.) on the eastern shore. No black spruce (Picea
mariana) or birch trees (Betula neoalaskana) were noted in the vicinity of Pikelet.
Pikelet Lake Pollen History
A 2.8 m long piston core was retrieved from Pikelet lake in the summer of 2005. Core
drives were offset in to ensure overlapping drives. Both core holes ended in sandy pebble gravel
at approximately 560 cm. Pollen analyses for Pikelet follow the same methods as outlined for the
Tommy Lake core above.
Pikelet Lake does not exhibit pollen zones as distinct as those present in Tommy Lake
to the north. The alder rise, so abrupt at Tommy Lake, is more gradual in Pikelet and is not
accompanied by a significant drop in birch. We define zones for Pikelet Lake nonetheless, to
help aid discussion and interpretation of the core (Figure 8).
Birch Zone (276-235 cm). The basal date for Pikelet Lake, and the beginning of this pollen zone
is 11006+40 cal yr BP (~10,000 14C yr BP) and it runs to 9400 cal yrBP (8400 14C BP). Pollen
from the bottom of the core shows relatively abundant amounts (70%) of Betula (birch) pollen,
with ~20% graminoids. Ericads, willows, and Artemisa are also present. These relative
percentages are similar to the Birch Zone identified in the Tommy core and is is likely
correlative. The lack of an earlier Herb zone, as seen in Tommy, may be a result of a later date of
lake formation (11,000 at Pikelet vs 15,000 cal yr BP at Tommy). Whether this indicates a later
glacial advance/retreat in the Katmai area vs. Lake Clark, or simply a late forming lake in a
terminal moraine will be discussed in a following paper on glacial histories of the region.
Populus-Willow Peak (240 cm). At 240 cm (ca. 9800 cal yr BP), there is a small peak in Salix
(willow) and Populus (cottonwood or aspen). This is the local expression of the widespread
Populus zone that is well-developed to the east (c.f. Wein and Farewell lakes), but is less
important in southwest Alaska (Brubaker et al., 2001). At Pikelet, this brief shift probably
reflects expansion of cottonwood and willow along streams and perhaps lake shores. As in other
regions, this expansion may reflect the Holocene Thermal Maximum, which in Alaska is dated
between about 12,000 and 9000 cal yr BP (Kaufman et al., 2004).
Alder-Birch Zone (235-10 cm). Alder and birch pollen dominate the record after about 9400 cal
yr BP. At this time, the relative amounts of Betula (birch) and Alnus (alder) increase as amounts
of Salix (willow), Poaceae (grasses), Cyperaceae (sedges), Artemesia, and Apiaceae (umbels)
1912 Katmai Ash
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1912 Katmai Ash
Core Depth (cm)
Age
Calendar years BP
Core Depth (cm)
4196 +90
Calibrated yr BP
2808 +40
Calibrated yr BP
Pikelet Lake
Herbs and Forbs
0
1000
2000
DRAFT
decrease. The reduction of alder pollen between about 9300 and 8000 cal yr BP is unusual and
difficult to explain, unless alder was in fact less common on the landscape. After 8000 cal yr
BP, the pollen frequencies of all the taxa fluctuate slightly, but without any clear pattern.
Alder-Spruce zone (10-0cm). The top 10 cm (ca. 100 yrs ago to the present) of the Pikelet
pollen diagram records small but significant changes (increases in spruce and alder) in the pollen
record. Spruce was probably present in the region much earlier, by about 2500 cal yr BP (as
indicated by persistent, but low frequencies [<5%] of spruce pollen). However, spruce was
probably not growing locally (and only as widely scattered trees as they are today) until possibly
as early as about 500 years ago (when pollen percentages first cross the 5% threshold [Hu et al.,
1993]). An increase in spruce pollen to 10% indicates the forest spread, or increased in density
after the 1912 Katmai eruption. This expansion may have been due to ash-induced release of the
existing spruce, as has been suggested for Kodiak Island at the same time (Tae, 1997). However,
climatic factors such as post Little Ice age amelioration can not be excluded. The spruce pollen,
where identifications are possible, is nearly all from white spruce (P. glauca). This is unusual, as
black spruce pollen (P. mariana) is present (sometimes abundant) in all Alaska boreal pollen
cores where the identifications have been made. The dominance of white spruce pollen at
Pikelet is consistent with the local
vegetation, which is all white spruce.
Alder pollen frequencies also
increase after the 1912 Katmai eruption,
suggesting alders grew more abundantly
then than for much of the Holocene. A
post 1912 Katmai alder rise is also
seen at Little Takli island, off the
Figure 9. Pikelet core top showing Katmai ash and pollen changes.
south coast of the Alaska Peninsula
(Bigelow, 2004). The Katmai ash is low in nitrogen (Shipley, 1919), which may have favored
nitrogen fixers such as alder or other legumes. However, like the spruce above, climatic factors
cannot be excluded
Discussion
Climate vs. ash fall effects on the vegetation
The presence of the 7 cm-thick 1912 Katmai ash in the Pikelet pollen core provides an excellent
opportunity to asses climate vs. tephra affects on the vegetation. Prior to the 1912 eruption, the
Little Ice Age (LIA) was the dominant factor affecting the climate in the region. The LIA is a
widespread period of cooling which in Alaska dates generally from about AD 1700 to about AD
1900. Ice advances in coastal areas (Wiles, Kaufman), narrow tree rings (Darrigo Jacoby) and
possibly intensification of the Aleutian low (Darrigo) all suggest climate deterioration, probably
cooler summers. The amount of cooling was probably small (ca. 0.5° C), but would have been
significant in areas where cool summers already limited tree growth. At Pikelet, the brief
reduction (as measured in only one sample) of spruce pollen just prior to the Katmai ashfall may
reflect spruce retraction due to LIA cooling. The question remains however whether the spruce
and alder increases after the eruption are due to the ashfall itself or to post LIA climate
amelioration and glacial retreat.
DRAFT
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Ecological Profile: Lake Clark National Park and Preserve