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Northeastern Naturalist Vol. 24, No. 1
2017 NORTHEASTERN NATURALIST 24(1):25–36
Late-Glacial Vegetational History of the Edmund Niles
Huyck Bog, Rensselaerville, New York
Abstract - Pollen analysis of a 10-m core from the Niles Huyck Bog in Rensselaerville,
NY, yields a history of late-glacial and postglacial vegetational change from the beginning
of sediment deposition into the bog basin following ice withdrawal to the present. A radiocarbon-
dated sequence is provided as time control for the upper 6 m. Late-glacial pollen
assemblages seen near the base of the core consist of Abies spp. (fir) and Picea spp. (spruce)
as the principal tree genera and grasses and sedges as the main herbaceous components, and
resemble pollen assemblages elsewhere in New York and New England. These assemblages
were replaced by ones consisting primarily of Pinus spp. (pine), which became dominant
ca. 9000 years before present (YBP). By 8000 YBP, pine gave way to Tsuga canadensis
(Eastern Hemlock), Quercus spp. (oak), and Fagus grandifolia (American Beech), denoting
a more mesic climate. Thereafter, the replacement of oak by beech is a notable trend that
continues throughout the pollen profile and is interrupted only by the hemlock decline at
4723 YBP. The pollen spectra then begin to reflect vegetation of a more local character, and
ca. 3000 YBP the beginning of the closure of the catchment basin is marked with the sustained
increase of Sphagnum spp. (sphagnum) spores. An Ambrosia spp. (ragweed) pollen
signal marks European settlement near the top of the core. A pollen signature near the base
of the core (Zone H-2) suggests a Younger Dryas (YD; 12,900–11,300 YBP) cooling event
for this region, making the sediments below probably equivalent to the Allerød Interstadial
for the Niles Huyck Bog. The date for this event is ca. 13,000–14,500 YBP. An estimated
date of 14,344 YBP is based on the time needed to accumulate the last 60 cm of sediment
and adding it to the end of the YD. This date is in close agreement with the dates recorded
for both the nearby Meadowdale Bog and the Great Bear Swamp and supports the hypothesis
of a “bottom to top” mode of deglaciation in this region.
The history of vegetational change following deglaciation in the northeastern
United States is written in the pollen record recovered from bog and lake sediments
and has been broadly outlined (Gadreau and Webb 1985). Nevertheless, gaps
still remain, especially for the Catskill Mountains region of New York where late-
Quaternary vegetational dynamics are largely unknown, except for some documented
pollen-stratigraphic investigations of late-Quaternary sediments in the western
Catskills (Ibe 1985, Ibe and Pardi 1985). More palynologic studies of pollen-bearing
sediments within and adjacent to the Catskills region might shed light on some details
of the mode of deglaciation in this important area. Did vegetation in the late-glacial
take hold and spread out in the valleys first or did the rise in vegetation begin first in
*Biology Department, State University of New Paltz, 1 Hawk Drive New Paltz, NY 12561;
Manuscript Editor: Roland de Gouvenain
2017 Vol. 24, No. 1
the upper reaches of the mountains? In other words, did ice leave the valley systems
first, or did deglaciation begin first from the summits? Rich (1934) contended that at
least some of the higher Catskill summits stood out as nunataks during the last full
glacial period, and that evidence of glaciation (e.g., erratics, glacial striae) above
1189 m on Slide Mountain, for example, is entirely lacking. It is uncertain whether the
higher Catskill summits provided a focal point for the spread of late-glacial vegetation
or whether the early forests spread north through major deglaciated corridors,
perhaps the Wallkill and Hudson Valley systems. One approach to determine whether
the mode of deglaciation was “top to bottom” or “bottom to top” is to provide radiocarbon
dates marking the beginning of sedimentation in lake and bog sediments.
Unfortunately, sufficient organic material for radiocarbon dating is not available in
most basal sediments, but Peteet et al (2012) has shown that many lakes and bogs contain
macrofossils for accelerator mass spectrometry (AMS) dating in basal clays that
have less than 10% organic matter. They suggest that many sites need to be revisited
with a view to examining the macrofossil data for AMS dates. This paper focuses on
the Niles Huyck Bog sediments in close proximity to Meadowdale Bog, elevation
105 m and ~5 km to the northwest, and in Great Bear Swamp, elevation 370 m and ~3
km to the east (Dineen 1986). A comparison of basal sediment dates from these sites
should provide an almost contiguous series of data points on which to make some tentative
conclusions related to the mode of deglaciation in this region.
The Niles Huyck Bog, elevation of ~560 m, is located on the Rensselaerville,
NY, USGS topographic quadrangle, 7.5-minute series (42°54'76"N, 74°18'10"W)
and lies just outside the boundaries of the Niles Huyck Preserve (Fig. 1). The bog itself
is covered completely by sphagnum moss and supports the usual variety of bog
vegetation, including Drosera rotundifolia L. (Sundew) and Sarracenia purpurea
L. (Pitcher Plant). Some dense stands of common Ilex verticillata (L.) A. Gray
(Winterberry) and Acer rubrum L. (Red Maple), and invading Betula spp. (birch)
are common associates. The periphery of the bog is dominated by members of the
Osmundaceae and by polypodiaceous ferns. The surrounding area consists of rolling
hills which have been cut over several times in the past for the establishment of
farms, but the native Pinus strobus L. (White Pine), Tsuga canadensis (L.) Carrière
(Eastern Hemlock), and hardwood forests are making a comeback in several areas,
such as the Partridge Run Game Management Area. Bedrock is principally Helderberg
limestone overlain with Catskill deltaic sediments (Broughton et al. 1966).
I used a Livingstone sampler to raise a 10-m sediment core from the deepest part
of the Niles Huyck bog, as ascertained by repeated test borings. Samples for pollen
analysis were taken at 10 cm intervals along the length of the core, placed in plastic
containers, and frozen pending processing. Radiocarbon age determinations were
performed by Beta Analytic, Inc., Coral Gables, FL, on samples collected at 1.0-m
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intervals from the top of the core to a depth of 6.0 m. These determinations provide
time horizons that intersect vegetational events through time and form the basis for
the calculation of sediment accumulation (Fig. 2) expressed as years per centimeter
(yr/cm) and were derived by dividing a core section (in cm) by the number of years
spanning its deposition. The latter was calculated by taking the difference in years
between radiocarbon dates that bracket the section, and then dividing the remainder
by the section length. It should be pointed out that sediment accumulation varies
with changes in lithology, compaction, and hydrology, and hence the results are
I thawed and processed sediment samples following standard acetolysis procedures
(Faegri and Iversen 1975). This process included hydroflouric acid (HF)
treatment when appreciable sand was present, followed by acetolysis, safranin
staining, and mounting in glycerin. Large amounts of clay were first treated with
7% sodium pyrophosphate prior to acetolysis (Bates et al. 1978). Pollen was concentrated
on microscreens before being mounted on slides (Cwynar et al. 1979). I
tallied at least 300 pollen grains from each slide to form the basis for the relativefrequency
histogram. Relative spore frequency is based on the pollen sum plus
the number of spores tallied in the course of counting the pollen. I identified both
pollen and spores by comparison with a modern reference slide collection and with
taxonomic keys provided by McAndrews et al. (1973). I conducted pollen counting
Figure 1. Portion of the USGS Rennselaerville Quadrangle indicating the location of the
coring site (“drill site”) at the Niles Huyck Bog.
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routinely at a magnification of 400x (n.a. = 0.6) using an A.O. Spencer binocular
microscope. Critical identification of problem types was made under oil immersion
at 1000x (n.a. = 1.25).
I constructed a relative frequency (%) histogram of the pollen taxa for the Niles
Huyck Bog (Fig. 3). Pollen frequencies of each taxon were plotted against depth
and arranged into 3 major groups: Arboreal pollen from trees and shrubs (AP);
non-arboreal pollen from terrestrial and aquatic herbs (NAP); and spores from
sphagnum and vascular cryptogams. The value of each taxon is expressed as a percentage
of the sum of the AP + NAP pollen counts, including spore types. Values
of 2% or less are shown as a tic mark. Percentage amounts for each taxon appear
on the “x” axis. Lithological column and depth coordinates appear on the left of the
diagram, as do the radiocarbon dates. Pollen zones appear on the right. Corrected
radiocarbon dates became available after the diagram was finished and appear as
cal. kyr BP in Table 1.
Dates plotted against depth (Fig. 2) show considerable variation in sediment
accumulation along the top 6.0 m of the core. Accumulation is slowest in clay
Figure 2. Plot of corrected radiocarbon age determinations and sediment depth for the Niles
Huyck Bog. The sediment deposition is expressed in yr/cm.
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Figure 3. Radiocarbon-dated pollen histogram for the Niles Huyck Bog, Rensselaerville, NY.
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(22.4 yr/cm) between 5.0–6.0 m and fastest in peat (5.2 yr/cm) between 2.0 and
3.0 m. The beginning of sediment deposition is unknown but can be roughly estimated
by examination of the pollen signatures associated with well-dated events
and inserting these dates into the lithological column for comparison with work
done in nearby sites.
Pollen frequency diagram
The relative pollen frequency diagram for Niles Huyck Bog (Fig. 3) is divided
into 8 horizontal zones depicting pollen assemblages believed to represent major
vegetational shifts in the dominant vegetation.
Zone H-1 marks the change in lithology from clay to sand that occurs around
9.4 m. There is a heterogeneous mixture of pollen from fir, spruce, pine, birch, oak,
and hemlock as well as herbaceous pollen from the sedges and grasses, which is
compatible with a warming trend seen in the Allerød Interstadial.
Zone H-2 witnesses a distinct increase in herbs, mainly sedges and grasses, and
a marked drop in oak pollen in the profile. The Alnus (alder) pulse, while small, is
distinct and, together with the decline in birch and pine, seems almost certainly a
Younger Dryas (YD) pollen signature.
Zone H-3. Herbaceous pollen from grasses and sedges drop precipitously. Fir
reaches a maximum while spruce declines to 0% at the upper boundary of this zone.
Pine begins to increase here (to ~25%), with concomitant declines in birch, hemlock,
Zone H-4. A pine maximum is registered near the base of this zone but declines
soon after while giving rise to a distinct oak maximum. Near the upper half of zone
H-4 there is a pronounced rise of hemlock and Fagus grandifolia Ehrh. (American
Beech) pollen that is accompanied by a decline in oak pollen and that signals more
Zone H-5. This zone embraces maximum hemlock pollen (~40%) throughout the
lower half of the zone that abruptly declines to its lowest values throughout the core
and marks the hemlock decline seen throughout the Northeast. Oak values retreat
from their maxima seen in Zone H-4 along with a sharp reduction in pine pollen.
Beech pollen shows a steady increase reaching a maximum of nearly 20% near the
top of Zone H-5.
Zone H-6. Pine and hemlock slowly recover from their previous lows but never
attain their former high values, while beech drifts somewhat lower to the top of
Table 1. Uncorrected radiocarbon dates appear as 14C YBP; corrected dates appear as cal. kyr BP. The
depth in meters for each date appears in the column on the left.
Depth (m) 14C YBP cal. kyr BP
1 1450 ± 70 1364 ± 155
2 2840 ± 50 2953 ± 165
3 3240 ± 80 3471 ± 157
4 4170 ± 120 4688 ± 317
5 5650 ± 110 6450 ± 203
6 7830 ± 190 8693 ± 419
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the zone. Red Maple attains a presence not seen throughout the entire core, while
other deciduous trees such as ash, elm, and other maple spp. are well represented.
Herbaceous and aquatic pollen attain values in this zone that are their highest in the
Zone H-7. Slight increases in birch, pine, and hemlock pollen are evident in
this zone, and deciduous pollen from maple, ash, elm, hickory, and basswood take
on a more local character before giving way to the land-clearing practices of early
European settlement. A very high peak of ~60% Sphagnum spp. (sphagnum) spores
at 2.7 m marks the closing of open water in the bog.
Zone H-8. A high Ambrosia spp.(ragweed) peak at the top of the core together
with the disappearance of hemlock, beech, maple, ash, elm, hickory, and other
hardwood species marks the beginning of European settlement and intense farming
activities in this area.
Deglaciation in the Rensselaerville area and surrounding region probably occurred
as a patchy quiltwork of downwasting, stagnant ice (Dineen 1986). The
clay/sand lithology at the base of the core is consistent with this scenario of glacial
wastage, and was probably deposited by low-velocity meltwater derived from
residual stagnant ice. Bottom sediments of the Niles Huyck Bog were organically
poor, and the age for this depositional episode cannot be established with certainty,
although the YD pollen signature seen in Zone H-2 places an age boundary between
12,900 and 11,300 YPB. If this is reliable, then lower sediments seen in Zone H-1
would be the equivalent to the Allerød warming event occurring around 13,000-
14,500 YBP but may even be older if the sediments also include part of the Older
Dryas Interstadial. Projecting the accumulation values for clay seen in Figure 2
(22.4 yr/cm) from the lower boundary of the presumed YD to the base of the core
(9.4–10.0 m) yields a value of roughly 1344 years to accumulate 60 cm of clay.
Adding this figure to the beginning of the presumed Allerød warming event yields
an estimated date of 14,344 YBP for the beginning of sediment deposition into
the Niles Huyck bog. Basal sediments from nearby Meadowdale bog near Voorheesville,
NY (42°39'36"N, 73°59'07"W), yield a radiocarbon date of ca. 16,650
YBP. An extrapolated date for basal sediments from Great Bear Swamp, 5 miles
west of the Alcore Reservoir (42°28'45"N, 74°03'15"W) places the beginning of
sediment deposition ca. 15,060 YBP (Dineen 1986). These dates are not in close
agreement with the estimated date of 14,344 YBP for Niles Huyck Bog but are
considerably older than a previously estimated age of 13,800 YBP for deglaciation
in this region (Connally and Sirkin 1973). The extrapolated date of 13,380 YBP for
basal sediments at Balsam Lake in the western Catskills (Ibe 1985), the 12,870 ±
370 YBP dated bottom sediments in the higher reaches of the White Mountains of
New Hampshire at Lost Pond at 650 m elevation, and the 13,000 ± 400 YBP dated
sediments at Little Lost Pond at 800 m elevation (Davis, et al. 1980), tentatively
places younger dates for bottom sediments at higher elevations and older dates for
corresponding basal sediments at low-relief positions. However, these dates were
2017 Vol. 24, No. 1
provided at a time when AMS dating procedures did not exist, and these sites need
to be revisited with new dating methods. Nevertheless, the data suggest that glacial
wastage occurred first in the lower regions of the Northeast and that ice in the higher
montane areas disappeared sometime later. The apparent trend in glacial meltdown
from “bottom to top” (see Connally 1982) has important implications with respect
to early centers of plant dispersion following ice withdrawal, and does not support
the theory that the higher reaches of the Catskills and elsewhere may have
served as active refugia from which late-glacial forests began. Most late-glacial
and postglacial plant-migration patterns have been amply described (see Delcourt
et al. 1983, Webb 1980), but whether early plant colonization and migration were
supplemented, or even dominated, by existing montane refugia flora is unknown.
An inventory of basal sediment dates for remaining high altitudes and low-relief
positions within the Catskill region would be extremely helpful in resolving some
aspects of the dynamics of glacial meltdown and plant immigration patterns for this
important area. Identification and AMS dating of macrofossils collected in bottom
sediments would be a very useful proxy in this regard (Peteet et al. 2012).
The pollen stratigraphy for Niles Huyck Bog shows a postglacial pollen sequence
that is similar in many respects to pollen spectra reported for most of the Northeast
(Gadreau and Webb 1985). The incorporation of a well defined spruce–fir–grass–
sedge assemblage within the bottom 2-m sediment section of the core is evidence
for a park-tundra vegetation already present at the site when sediment deposition
first began, and typifies a recently deglaciated landscape capable of supporting
arboreal species with pronounced lateral root development (recently deglaciated
landscapes would have thin soils capable of supporting trees that spread roots
laterally rather than vertically). Pollen evidence for tundra landscape (e.g., Dryas)
preceding park-tundra is not recorded in the pollen stratigraphy and may have been
obscured by a time lag between warming and ice wastage. The disappearance of
residual ice long after conditions optimal for tundra vegetation had changed from
cold to warm may account for the lack of a distinct T (tundra) zone. The appearance
of abundant pine, oak, and birch at this level in the core is probably due to longdistance
wind transport from more southerly areas where these genera were already
established (Sirkin 1967). The high percentage of mixed coniferous–deciduous
pollen seen at the base of the core is unusual because of the lack of chronological
or successional sequences among these genera, and analogs for this spectrum are
lacking in present-day forests. One explanation for this anomaly is that very little
canopy existed during the early depositional period for this basin. High percentages
of grass and sedge pollen found at the base of the core are typical of an open
canopy where the filtration effect on long-distance wind-transported pollen would
be minimal. The appearance of oak and pine pollen in Zone H-4 signals a shift in
climate from cold and wet to warmer and drier conditions.
Rapid replacement of fir and spruce pollen by a rise in pine pollen ca. 9000
YBP in the Middle Atlantic and New England States (Gadreau and Webb 1985, Ibe
1985) persisted for nearly 2000 years until the vegetation became dominated by a
mixed hardwood forest. Application of the sediment accumulation rate of 22.4 yr/
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cm between 5 to 6 m yields a date of ca. 9500 YBP for the pine maximum at the
Niles Huyck Bog. This extrapolated date concurs with the B (pine) zone at Great
Bear Swamp and Meadowdale Bog, and indicates that sediment accumulation for
the interval of time between 8693 ± 419 cal. kyr BP (Fig. 2) and the pine maximum
were probably accurate. Thereafter, hemlock and beech pollen became prominent,
signaling more mesic conditions. The hemlock “crash” is evident at around 4723
YBP and is in agreement with other clusters of dates in the Northeast marking
this event (Gadreau and Webb 1985) but occurred somewhat later (4180 Y BP) at
Sutherland Pond in the Hudson Highlands Maenza-Gmelch (1997). Decimation of
hemlock appears to have occurred in a remarkably short period of time, spanning
an interval of about 900 years, from 4100 YBP at Rogers Lake, CT (Davis 1967), to
almost 5000 YBP in New Hampshire (Davis et al. 1980). The ubiquitous and sudden
decline of hemlock pollen in most pollen diagrams throughout the northeastern
United States and Canada has stimulated several theories to explain this event.
Miller (1973) postulated drought as a causative agent in hemlock mortality because
hemlock’s shallow root system is vulnerable to prolonged periods of dryness. He
cited as evidence the severe damage to hemlock during the 1930s drought described
by Secrest et al. (1941) who showed extensive damage to hemlock in the 93,078-
ha (230,000-acre) Menominee Indian Reservation in Wisconsin between 1931 and
1933. Elsewhere, hemlock tree mortality reached 75% as a result of drought in an
area near New Haven, CT (Stickel 1933). In a comparative study of the effects of severe
drought on different tree species in central Pennsylvania, McIntyre and Schnur
(1936) showed that hemlock mortality was much higher than that of either oak or
Acer saccharum Marshal (Sugar Maple). Davis (1981) contends that the hemlock
“crash” may be attributable to the spread of disease rather than to climatic change.
Davis reasoned that the abruptness of the decline followed by the coordinated increases
in other mesic species (e.g., beech), argued for a biological explanation,
perhaps disease or insect attacks which were selective for hemlock. Indirectly
supporting Davis’s theory of insect attack is work done by Booth et al. (2012) who
showed beech vulnerability to drought in Michigan during the Medieval Climate
Anomaly (MCA) that took place between 1050 and 600 BP. Pollen diagrams of
the northeastern United States do not show a decline in beech during the hemlock
crash, and if the hemlock decline was due to drought, then this should be reflected
in a coeval decline in beech. Shuman et al. (2004) suggest that climatic changes
toward drier conditions weakened hemlock and made it more susceptible to phytophagous
attacks. Further south in the “sky lakes” of the Shawangunk Mountains
of southeastern New York, a date of 4770 14C yr BP has been assigned to the sudden
hemlock collapse at Lake Minnewaska (Menking et al. 2012). The hemlock crash
is a conundrum that is in need of a conclusively substantiated explanation.
Arboreal pollen spectra in more recently deposited sections of the core that
exhibit the hemlock decline show very little change in most of the major taxa
represented. Pollen input from hemlock increases through the top 4.0 m of the
core but never attains its pre-decline dominance. This pattern may be the result
of competition with beech, another mesophytic species prominent in the spectra
2017 Vol. 24, No. 1
at this time. Maple pollen never reaches values of more than 12–14% between
1–2 m, but this result can be misleading. Some recent studies of modern pollen
rain–vegetation relationships in both the Catskill and Adirondack Mountains of
New York (Ibe 1984, Ibe and Sperling 1986) and in New Jersey (Ibe et al. 1990)
demonstrate that maple is grossly underrepresented in the pollen rain. Maple can
play a subdominant role in the forest while contributing no more than 10% of the
total pollen rain recovered locally. An increase in herbaceous and aquatic pollen
followed by a large maximum from sphagnum spores just prior to the increase
in maple pollen represents a shift from regional to local pollen rain and indicates
a significant drop in the water depth favorable to the growth of aquatic vegetation.
These changes no doubt contributed to a local environment favorable to the
development of maple as an important component of the local forest composition
in this area and accounts for the increase in maple pollen at this time. It is instructive
to notice a maximum from pollen of Red Maple at the very top of the diagram
(Fig. 3). This occurrence is a clear signal that the sphagnum bog from which the
core was taken was now almost completely filled in enough to support certain
trees, particularly Red Maple, which is typically found growing in the sphagnum
mat, along with other species, notably larch. The uppermost 1 m of sediment
features a dominant birch-pollen peak coeval with a noticeable increase from
ragweed pollen from regional sources. These events are consistent with European
settlement and agricultural clearing practices; birch is a pioneer genus whose
abundant pollen reflects a recent invasion into abandoned farmland.
In summary, the pollen record of the Niles Huyck Bog depicts a history of
late-glacial and postglacial vegetational change similar in many respects to corresponding
changes depicted in pollen diagrams for most low-relief positions in the
northeastern United States. Sediment deposition into the Niles Huyck Bog probably
began around 14,500 YBP. The clay/sand lithology at the base of the core suggests
low-velocity deposition of sediments derived from ice stagnation and down wastage
as a probable mode of deglaciation in this region.
A well-defined spruce–fir–grass–sedge pollen assemblage between 8.0 and
10.0 m typifies cold, wet conditions indicative of park-tundra. Gradual warming
encouraged the spread of pine and oak which became the dominant genera ca. 9500
YBP and remained so for more than 1000 years before giving way to hemlock and
beech, signaling more mesic conditions ca. 9000 YBP. The hemlock “crash” seen
in most pollen diagrams for the northeastern United States is in agreement with the
time of the sharp hemlock decline seen in the pollen diagram for Niles Huyck Bog.
Subsequently, bog-supported aquatics and herbaceous pollen provide a more local
character to the pollen spectra, and oak, birch, maple, and other hardwoods are testimony
to the stable mesic nature of the climate of this region. By ca. 2800 YBP, the
pollen catchment surface of the bog appears almost completely closed off. Thereafter
local pollen impacted onto the surface of the sphagnum mat was recorded as the
sphagnum sank lower into the bog waters. The upper surface of the pollen record
reflects land clearing by the appearance of ragweed, grasses, and sedges, and the
disappearance or reduction of many arboreal species, such as oak, hemlock, Ulmus
spp. (elm), ash, and pine.
Northeastern Naturalist Vol. 24, No. 1
This research was funded in part by the Edmund Niles Huyck Preserve Scientific Advisory
Committee. The author thanks Dr. David Lemmon and 2 anonymous reviewers for their
critical reading of the manuscript and their valuable feedback.
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