Paleohistory of a Giant Sequoia Grove: The Record from
Log Meadow, Sequoia National Park1
R. Scott Anderson2
Abstract: The giant sequoia (Sequoiadendron giganteum) of California's
Sierra Nevada, the world's largest living organism, includes some of the
oldest trees known. Its modern distribution is among the most unusual of
any major North American conifer, occurring as a local dominant in some
75 disjunct groves within the Sierra montane forest. Recent analysis of
pollen and plant macrofossils from Log Meadow in the Giant Forest grove
of Sequoia National Park has contributed to our understanding of the
development of modern giant sequoia groves. Giant sequoia trees were
rare around Log Meadow during the early and into the middle Holocene,
increasing in abundance only after ca. 4,500 years ago. The rarity may
have been due to the more arid climate predominating during the early
Holocene. A return to a cooler or wetter climatic regime or both during
the middle to late Holocene allowed the expansion of the tree, and the
establishment of the modern grove.
The causes and mechanisms which force vegetation
change within forest communities have been a dominant theme
in ecological research. Plant communities have been
continuously stressed by environmental variables such as
geologic events, natural disturbances, climatic perturbations
and human activities. Each of these variables operates on
different timescales. For instance, extremely long-term
changes in vegetation communities, occurring over millions
of years, may be caused by movements of the Earth's crust,
such as the rise of the Sierra Nevada itself. In addition,
natural disturbances (i.e., fire and insects) and human activities
measured over relatively short timescales of years to decades,
contribute to vegetation disturbance as well. Thus, any or
all of these variables may cause changes in structure or
composition of plant communities.
Climatic perturbations, on the order of hundreds to
thousands of years, have also been linked to vegetation
changes; and in fact, evidence suggests that climatic change
is the driving force behind major vegetation change (Imbrie
and Imbrie 1979). Periods of interglaciation, e.g., warm
periods of about 10,000 years, have alternated with glacial
periods, which average about ten times longer. Assuming
that species respond individualistically to varying climatic
parameters, over geologic time then, it is clear that vegetation
associations are temporary aggregates of species (Davis 1989).
This paper addresses the development of the Sierran
mixed-conifer forest, which has occurred during the Holocene
(last 10,000 years) interglacial period, but concentrates on
1
An abbreviated version of this paper was presented at the Symposium
on Giant Sequoias: Their Place in the Ecosystem and Society, June 23-25,
1992, Visalia, California.
2
Assistant Professor, Environmental Sciences and Quaternary Studies
Programs, Northern Arizona University Flagstaff, AZ 86011
USDA Forest Service Gen. Tech. Rep.PSW-151. 1994.
the history of giant sequoia (Sequoiadendron giganteum)
from a site located within the sequoia/mixed-conifer forest.
The giant sequoia of California has been the subject of
curiosity since its initial discovery and exploitation in the
late 1850's (Hartesveldt and others 1975; Johnston 1983).
Its modern distribution is among the most unusual of any
major North American conifer. Although it rarely is found in
monospecific stands, it occurs as a local dominant in
approximately 75 disjunct groves within the mixed-conifer
forest of the Sierra Nevada, California (Rundel 1969). Major
associated tree species today include California white fir
[Abies concolor (Gord. & Glend.) Lindl.], sugar pine (Pinus
lambertiana Dougl.), and incense-cedar [Calocedrus decurrens
(Torr.) Florin] (see table 1 for scientific and common names of
species mentioned in this paper). California red fir (Abies
magnifica A. Murr.) is important at higher elevations, while
ponderosa pine (Pinus ponderosa Dougl. ex P. & C. Lawson)
and California black oak (Quercus kelloggii Newb.) are
common at lower elevations. Minor associated trees include
Jeffrey pine (Pinus jeffreyi Grev. & Balf. in A. Murr.),
Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco], Pacific
yew (Taxus brevifolia Nutt.), Pacific dogwood (Cornus
nuttallii And.), and white alder (Alnus rhombifolia Nutt.),
along with species of buckthorn (Ceanothus L.), among
others (Weatherspoon 1990).
Most individuals of the species occur within the southern
portion of the range, and the groves become smaller
and more disjunct to the north (Hartesveldt and others 1975)
(fig. 1). Hypotheses for this disjunction include the effects of
Pleistocene cooling (Muir 1876; Axelrod 1959) and middle
Holocene warming (Axelrod 1986). Implicit in the latter is
the suggestion that a wider distribution occurred at the end
of the last glaciation. Although widespread reports of "red
wood" are found in well logs from Pleistocene Lake Tulare
at the western foot of the Sierra Nevada (Schmidt 1972), few
data exist on the late Wisconsin distribution of the species
(Cole 1983).
Log Meadow, in the Giant Forest of Sequoia National
Park (fig. 1), was chosen as a study site for investigating the
development of the sequoia/mixed-conifer forest type. The
meadow occurs at an elevation of 2,048 m, and measures ca.
750 m long by ca. 125 meters wide. Sediments include
accumulations of alluvial, colluvial and peaty deposits.
Bedrock within the area consists of Cretaceous granodiorite
(Sisson and others 1983). Local topography is a classic
example of "stepped topography," where subaerial weathering
of the granodiorite has caused formation of a local baselevel,
in this case impeding streamflow and resulting in wet meadow
formation (Wahrhaftig 1965).
49
Table 1-Scientific names of species mentioned in the text and figures, with common name
equivalents.
Scientific Name
50
Common Name
Abies concolor (Gord. & Glend.) Lendl.
California white fir
Abies magnifica A. Murr.
California red fir
Aesculus californica (Spach) Nutt.
California buckeye
Alnus Hill
Alder
Alnus rhombifolia Nutt.
White alder
Ambrosia L.
Ragweed
Arceuthobium Bieb.
Dwarf mistletoe
Arctostaphvlos Adans.
Manzanita
Artemisia L.
Sagebrush / wormwood
Calocedrus decurrens (Tory.) Florin
Incense-cedar
Ceanothus L.
Buckthorn
Chenopodiaceae
Goosefoot family
Chrysolepis sempervirens (Kell.) Hjelmquist
Bush chinquapin
Compositae
Sunflower family
Cornus nuttallii Aud.
Pacific dogwood
Corylus cornuta Marsh. var. californica (A. DC.) Sharp
California hazel
Cruciferae
Mustard family
Cyperaceae
Sedge family
Galium L.
Bedstraw
Gramineae
Grass family
Liliaceae
Lily family
Mimulus L.
Monkeyflower
Oxypolis occidentalis Coult. & Rose.
Cow-bane
Pinus jeffrevi Grev. & Balf. in A. Murr.
Jeffrey pine
Pinus lambertiana Dougl.
Sugar pine
Pinus murrayana Grev. & Balf. in A. Murr.
Lodgepole pine
Pinus ponderosa Dougl. ex P. & C. Lawson
Ponderosa pine
Polvgonum L.
Knotweed
Polypodiaceae
Ferns
Pseudotsuga menziesii (Mirb.) Franco
Douglas-fir
Quercus L.
Oak
Quercus kelloggii Newb.
California black oak
Ranunculus L.
Buttercup
Rumex L.
Sorrel
Salix L.
Willow
Sequoiadendron giganteum (Lindl.) Buchh
Giant sequoia Taxodiaceae-Cupressaceae-Taxaceae
T-C-T
Taxus brevifolia Nutt.
Pacific yew
Thalictrum L.
Meadow-rue
Tsuga mertensiana (Bong.) Carr.
Mountain hemlock USDA Forest Service Gen. Tech. Rep.PSW-151. 1994
Figure 1-Location of study sites mentioned in the text, along with the modern
distribution of giant sequoia groves (irregular blackened spots).
Methods
In July 1987 a Livingstone corer was used to collect
a sediment core (Wright 1967). Sediments were retrieved
in 1-meter increments for a total of 10.4 meters. In the
laboratory, small sediment samples were extracted from the
larger core for pollen and plant macrofossil analysis. For
pollen analysis, 1-cc sediment subsamples were processed
using a modified Faegri and Iversen (1989) technique. Some
samples needed a sodium pyrophosphate treatment, including
USDA Forest Service Gen. Tech. Rep.PSW-151. 1994.
seven um sieving to remove clays (Cwynar and others 1979).
Resulting pollen assemblages were mounted in silicone oil.
Pollen was identified and counted at 400X using a Reichert
microscope, referring to the modern pollen reference
collection as necessary at the Laboratory of Paleoecology,
Northern Arizona University. Plant macrofossils were
concentrated by gentle water washing of the delicate plant
fragments through 20 and 80 mesh soil seives. Plant materials
51
were identified by comparison with modern reference
materials, or, in the case of pine needle fragments, through
careful sectioning (Anderson 1990a).
Results
Sediment Stratigraphy and Radiocarbon Dates
From the top of the core down to about 2.25 meters were
bands of medium to coarse peat alternating with medium
grained colluvial/alluvial sediments. Below this, the organic
content was reduced. The section from approximately 2.25
to 6.00 meters consisted of alternating bands of organic
silts with medium to coarse grained colluvial and alluvial
sediments. Below 6.00 meters the amount of sand increased,
although the alternation with bands of organic silts continued. The sediments below 8.50 meters were predominantly
medium to coarse sands.
A total of four radiocarbon dates were obtained from the
core, providing chronologic control (table 2). The bottom
date suggests that organic sedimentation began sometime
after about 10,500 years ago. A constant rate of sedimentation
is assumed between dates.
Pollen and Macrofossil Stratigraphies
The Log Meadow record can be divided into three
distinct periods (not described here as formal pollen zones),
based on changes in the pollen and macrofossil stratigraphies.
These include sediments deposited between (a) approximately
10,500 and 9,000 yr BP (years before present), (b) 9,000
to about 4,500 yr BP; and (c) sediments deposited after
4,500 yr BP.
10,500-9,000 yr BP. In sediments deposited prior
to 9,000 years ago, a diverse group of species of pine
dominates the fossil assemblages. These species include
sugar, ponderosa, and lodgepole (Pinus murrayana Grev. &
Balf. in A. Murr.) pines (fig. 2). Fir pollen and macrofossils
(white fir) are also abundant. Other commonly occurring
pollen include bush chinquapin [Chrysolepis sempervirens
(Kell.) Hjelmquist], hazel [Corylus cornuta Marsh. var.
californica ( A . DC.) Sharp], sagebrush (Artemisia L.), and
ferns (Polypodiaceae). The frequency of giant sequoia pollen
is extremely low, and macrofossils are absent, indicating the
absence of the plant locally and in the immediate vicinity
(Anderson 1990b).
Table 2 - Radiocarbon Dates from Log Meadow.
Laboratory Number
Depth (cm)
C14 Date (yr BP)
Beta-25934
240 - 248
2,690+80
Beta-25935
355 - 392
4 ,190+90
Beta-25936
707 - 715
9,010+ 120
Beta-22449
945 - 955
10,210+180
52
9,000-4,500 yr BP. This period encompasses most of
the early Holocene and into the middle Holocene, ending
about 4,500 years ago. During this time the major pollen
types are once again pine (primarily sugar and ponderosa
pines) and fir, this time with oak. A parasite primarily
on pines, dwarf mistletoe (Arceuthobium Bieb.), occurs in
maximum amounts. Because the pollen of mistletoe is not
widely distributed, the proximity of pines to the site is
indicated (Anderson and Davis 1988). Shrubby species which
are common before this period are considerably diminished.
Giant sequoia pollen remains very sparse, although the
first macrofossils of the species are found shortly after the
opening of the period. Increases in sedges (Cyperaceae), and
somewhat later, cow-bane (Oxypolis occidentalis Coult. &
Rose.), indicate the inception of a moist meadow at the site.
4,500 yr BP-Present. The greatest changes in the entire
record occur subsequent to 4500 years ago. Giant sequoia
pollen percentages increase from near absence,
culminating in maximum percentages in the most recent
centuries. Declines in oak, dwarf mistletoe and pine occur,
while buckthorn and fir pollen increase slightly. Macrofossil
remains indicate a mixed-conifer assemblage, dominated by
sugar and ponderosa pine, and white fir.
Discussion and Conclusions
Pollen dispersal studies from modern stands of giant
sequoia suggest that pollen is not widely dispersed from the
source trees (Anderson 1990b). For small, isolated stands,
giant sequoia pollen constitutes generally less than five
percent of the total pollen assemblage at the grove boundary.
For larger, less isolated stands, giant sequoia pollen is
dispersed somewhat greater distances (five percent pollen at
450 meters). In other words, deposition of giant sequoia
pollen is largely a local occurrence. Because modern pollen
data are used to interpret fossil pollen in sediment cores,
amounts of giant sequoia pollen as low as five percent
within the core are interpreted as rarity or general absence
locally of the plant itself.
The data from Log Meadow can be used to infer the
establishment and development of one giant sequoia grove
within the species' modern range. At least for this location,
these data suggest that groves of middle elevations today
have developed relatively recently, and that the tree was
extremely rare during the first half of the Holocene. The
macrofossil record (fig. 2) indicates that a few individual
trees must have been present near the coring site at Log
Meadow at times prior to 4,500 years ago. Based upon the
modern pollen studies, however, the local giant sequoia
population of the early and middle Holocene (when pollen
percentages averaged less than two percent) must have been
quite small compared to that after 4,500 yr BP.
Vegetation change at Log Meadow is summarized in
figure 3. Dominant trees at the site prior to 9,000 years ago
were lodgepole, sugar and ponderosa pines, which grew in a
relatively dry meadow. A sugar and ponderosa pine/mixed-
USDA Forest Service Gen. Tech. Rep.PSW-151. 1994
Figure 2-Summary diagram of important pollen and macrofossil types found in the core from Log Meadow, Sequoia National Park.
USDA Forest Service Gen. Tech. Rep.PSW-151. 1994.
53
Years
Before
Present
Log Meadow
0
2,000
Sequoia/
Mixed Conifer;
Sedge Meadow
4,000
6,000
Sugar,
Ponderosa Pine/
Mixed Conifer
(minor Sequoia?)
8,000
10,000
Lodgepole, Sugar,
Ponderosa Pine
Dry Meadow
Figure 3-Summary of vegetation change at Log Meadow
since the initial formation of the meadow about 10,500 years
ago.
conifer forest, with very minor amounts of giant sequoia,
grew there from roughly 9,000 to 4,500 years ago. Wetter
meadow conditions prevailed during this time than during
the previous period. The modern sequoia/mixed-conifer
forest developed only over the last 4,500 years.
Additional biologic and geomorphic evidence provide
support for the influence of climate in the expansion of giant
sequoia during the late Holocene. For locations within the
subalpine and upper montane, early Holocene forests were
structurally different from those of today. From approximately
10,000 to 6,000 years ago, an open pine forest dominated
most locations, with montane chaparral shrubs [buckthorn,
bush chinquapin, manzanita (Arctostaphylos Adans.)] growing more commonly in forest openings. Several tree species
characteristic of the modern subalpine forests [mountain
hemlock (Tsuga mertensiana (Bong.) Carr.) and red fir]
were rare or restricted to more mesic habitats (Anderson
1990a; Anderson and Smith 1991; Davis et al. 1985; Smith
and Anderson 1992). In addition, trees grew in areas that
54
presently support wet meadows, lake levels in the Sierra
Nevada were lower and flushing of small hollows by intense
rain storms declined (Wood 1975; Anderson 1990a; Reneau
and others 1986). Upper treeline was higher in the neighboring
White Mountains (LaMarche 1973). These data suggest
warmer temperatures and lower soil moisture conditions than
the present, and thus, significantly drier conditions prevailed.
Recent paleoclimatic models provide possible explanation
for these observations (COHMAP 1988; Kutzbach and Geutter
1986). During the late Wisconsin to Holocene transition
the seasonal distribution of summer insolation differed from
today. Seasonality was greater with seven percent more solar
radiation in the summer and seven percent less in winter.
Given the scale of the models, intensified summer drought is
projected for the Sierra Nevada, with cooler winters. Since the
most important single factor in mortality of seedlings and
maintenance of adult individuals of the species is proximity
to abundant subsurface moisture, a lengthening of the summer
drought during the early Holocene may have precluded
largescale establishment of giant sequoia through-out its
modern elevational range (Harvey 1980). Only in particularly
mesic locations did the species find refuge.
Preliminary data suggest that the tree disappeared from
the fossil record below 1,300 meters elevation by 14,200
years ago (Cole 1983). Though present in its modern range
at a few localities during the early Holocene, giant sequoia
was apparently quite rare during that period, much more so
than today. At Log Meadow, the species has not been as
abundant at any time during the last 10,000 years as it is
today, and aged individuals within the grove may be direct
descendents-third or fourth generation-of initial pioneers.
Thus, this study suggests that the unusual distribution of
giant sequoia in California can be attributed largely to
changing climatic conditions during the Holocene.
Additional research will investigate the importance of other
factors, such as fire, on the biogeography of the species.
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