RESEARCH EXTENSION NOTE
NO 2 – June 2008

The timing of peatland initiation in east-central
British Columbia: a first look

By
Paul Sanborn and Timothy Jull

The Natural Resources and Environmental Studies Institute
Research Extension Notes (REN) are peer-reviewed publications of
the research findings of NRES Institute members and of graduate
students in the NRES Graduate Program. NRESI Research
Extension Notes are intended to provide an outlet through which
Institute members can make their research findings available to a
non-technical audience.
Dr. Paul Sanborn is an Associate Professor with the Ecosystem
Science and Management program at UNBC. More information on
his research activities can be found at: http://web.unbc.ca/~sanborn/
Dr. Timothy Jull is a Professor of Geosciences at the University of
Arizona, Director of the NSF-Arizona AMS Facility, and Editor of
the journal Radiocarbon.
The correct citation for this publication is:
Sanborn, P., and T. Jull. 2008. The timing of peatland initiation in eastcentral British Columbia: a first look. Natural Resources and
Environmental Studies Institute Research Extension Note No. 2, University
of Northern British Columbia, Prince George, B.C., Canada.
This paper can be downloaded without charge from
http://www.unbc.ca/nres/research_extension_notes.html

Sanborn & Jull y Peatland Initiation

ii

The Natural Resources and Environmental Studies Institute (NRES
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iii

CONTENTS
Abstract ....................................................................................................... 2
Introduction................................................................................................. 3
Methods....................................................................................................... 4
Results and Discussion ............................................................................... 7
Conclusions................................................................................................. 9
References................................................................................................. 10
Further Readings or Resources ................................................................. 11
Acknowledgements................................................................................... 11

1

Research Extension Note No. 2

Abstract
A pilot study at the Aleza
Lake Research Forest (ALRF) in
east-central interior British Columbia
(BC) examined the timing of
peatland initiation using accelerator
radiocarbon dating of peat deposits.
At the ALRF, Sphagnum bogs
occupy numerous closed depressions
in an undulating plain underlain by
impervious, fine-textured glacial lake
sediments. Four adjacent Sphagnum
bogs differed greatly in depth, with
maximum peat thicknesses ranging
from 70 to >550 cm. The oldest peat
(9,177 ± 55 14C yr BP) occurred in a
deposit less than 2 m thick, while a
basal peat sample could not be
obtained from the

Sanborn & Jull y Peatland Initiation

deepest basin examined. Two bogs
with thinner deposits yielded
younger basal peat ages (<4000 14C
yr BP). More recent peatland
initiation in shallower depressions
may have been triggered by moister
regional climates after the midHolocene. Future studies of peatland
carbon stocks and peatland history in
central BC will need to consider this
potential climatic sensitivity and the
spatial variability in peat thickness.
Plant macrofossils and charcoal
preserved in peat deposits could
provide additional evidence for
Holocene paleoenvironments in this
region.

2

Introduction
Increasing concern over the
climatic implications of rising
atmospheric carbon dioxide
concentrations has stimulated major
efforts to estimate the magnitude and
rates of change of forest carbon (C)
stocks (Goodale et al., 2002). At the
national level, modelling projects
have greatly improved our
understanding of the carbon budget
of Canadian forests (Kurz and Apps,
1999.). But such efforts depend
critically on the quality of their
underlying empirical data, and
complete inventories of forest carbon
are scarce, particularly for
belowground components such as
soil organic C.

In east-central British
Columbia, a recent study at the
Aleza Lake Research Forest (ALRF;
Figure 1) has collected and
synthesized a large body of new data
on major forest C stocks, including
major components such as trees,
understory vegetation, dead wood,
and soils (Fredeen, 2006). This
study was intentionally restricted to
upland sites, as these were felt to be
most sensitive to land management
practices such as forest harvesting
and silviculture. But the ALRF
landscape (Figures 1, 2) contains
numerous small wetlands and bogs,
and although these occupy only 2%
of the ALRF area (D. Janzen,
personal communication), these

Figure 1* The Aleza Lake Research Forest (ALRF) lies at the eastern
edge of British Columbia’s central interior plateau in the wet and cool
subzone (SBSwk1) of the Sub-Boreal Spruce bioegeoclimatic zone.
Upland forests are dominated by interior spruce (Picea glauca x
engelmannii) and subalpine fir (Abies lasiocarpa). Mean annual
precipitation at the ALRF is 930 mm (1/3 as snow) and the mean annual
temperature is 3°C.
* Figure courtesy of D. Janzen, M.Sc. thesis.

3

Research Extension Note No. 2

features may be a significant C
reservoir. For example, an inventory
of soil carbon in Maine, USA, found
that organic soils covered less than
5% of the state, but contained more
than 1/3 of the total soil C (Davidson
and Lefebvre, 1993).
Peatlands, and the organic
deposits that comprise them, are also
important archives of past
environmental conditions (Charman,
2002). Peat accumulates when
inputs of organic matter exceed its
loss to decomposition. The changing
balance between these two
processes, as recorded in the
thickness, composition, and age of
peat deposits, can be a sensitive
recorder of both regional climates
and more local factors, such as
changes in drainage patterns. In
boreal and sub-boreal landscapes of
central and northern BC, with a
climate that is much drier than that
of the coastal region, peat
accumulation is restricted to
topographic depressions where high
water tables and anaerobic
conditions suppress decomposition.
At the beginning of the
Holocene (postglacial time), peat
accumulation began in suitable
locations exposed by the retreating
ice sheets. The timing of peatland
initiation in a given basin can be
estimated by radiocarbon dating of
the deepest peat. Using a database of
1680 such dates, a North American
overview of this process was
recently compiled by Gorham et al.
(2007). Although peatland initiation
appears to have peaked 7000-8000
years ago, it continues to the present
day. Variations in the frequency of
peatland initiations during
postglacial history may reflect
climatic fluctuations. For example,
Sanborn & Jull y Peatland Initiation

periods of drier climates would lead
to fewer peatland initiations and/or
reduced accumulation rates for
existing peat deposits. Conversely,
wetter climates would tend to favour
peatland initiation and expansion.
For central and east-central
BC, very little radiocarbon dating of
peat deposits has been done. We
lack even basic information on the
thickness of peat deposits in this
region of the province. Such
information will enable estimation of
the magnitude of peatland C
reserves, and contribute to an
understanding of the sensitivity of
these deposits to environmental
changes. This Note reports the
results of a pilot study that attempts
to remedy this knowledge gap by
obtaining radiocarbon dates for
peatland initiation at the ALRF,
complementing the more extensive C
inventory for upland forests. By
concentrating on a small but
representative area of the ALRF, our
goal was to examine the local
variability in peat thickness and
basal peat ages.

Methods
We examined four
adjacent bogs occupying
closed basins in the
undulating plain that
comprises the southern
portion of the ALRF (Figure
2). The underlying clay-rich
sediments, deposited in a
meltwater lake that
temporarily occupied the
Prince George area during
deglaciation, are very
impervious. The resulting
strong contrasts in soil
moisture regime across very
small elevation differences

4

Figure 2. Peat sampling locations in the southern portion of the Aleza
Lake Research Forest. Note the numerous closed depressions occupied by
bogs with little or no tree cover.

Figure 3. View of bog vegetation (Site 1 in Figure 2) at the Aleza Lake
Research Forest.

(<10 m) create striking
contrasts in vegetation,
ranging from productive
upland forests to bogs with
only scattered, stunted trees.
The bogs are dominated by
Sphagnum moss, with

5

abundant low shrubs such as
Labrador tea (Ledum
groenlandicum) and scattered
black spruce (Picea mariana)
and lodgepole pine (Pinus
contorta) (Figure 3).
Research Extension Note No. 2

Using a peat auger
(Figure 4), we probed
systematically across the
bogs to identify the thickest
deposits, and recovered
complete peat cores in 50 cm
increments down to the
underlying glacial lake
sediments. Cores were stored
in longitudinally split PVC
pipe and kept frozen until
sampled. The deepest
recognizable peat material
was collected from each core,

and submitted for accelerator
radiocarbon dating at the
NSF-Arizona AMS Facility
(University of Arizona,
Tucson, Arizona, USA).
Sample types were identified
as either Sphagnum or basal
peat based on visual
recognition in the field.
Further work would be
needed to confirm the
botanical origin of the
deepest portions of the cores.

Figure 4. Extracted core showing transition between basal peat (R) and
glacial lake sediments (L). The bluish-gray colour of the sediments
indicates anaerobic (oxygen-poor) conditions.
Dates are reported in
radiocarbon years before
present (14C yr BP), which by
convention is fixed as AD
1950, and also as calibrated
ages expressed in calendar
years before present. Age in
radiocarbon years is
calculated from the
abundance of 14C in the
sample and the known decay
Sanborn & Jull y Peatland Initiation

rate of this isotope (half-life
of 5730 ± 40 years).
Radiocarbon dates can be
expressed in actual calendar
years, but to do this requires
a calibration process that
allows for the fluctuating
content of 14C in the
atmosphere. At different
times, organic materials will
have different initial

6

abundances of this isotope.
Calibration is done with
computer programs that
incorporate these fluctuations
as measured for organic
materials that have been
dated by independent
methods (e.g., ancient treerings). Because of these
fluctuations, calibrated ages
are not exact single numbers
but contain built-in

uncertainties, and are
expressed as an age range
with a certain level of
probability. The calibrated
ages (Table 1) were
calculated with the CALIB
program (Stuiver and Reimer,
1993; Reimer et al., 2004)
and are stated as age ranges
estimated at the 1 s (68%)
and 2 s (95%) levels of
probability.

Table 1. Radiocarbon dates and peat sampling locations, Aleza Lake
Research Forest.
*

14

Lab No.

Material

C age
BP

Calibrated age
(calendar years
BP): 1 σ and 2 σ
ranges

1-1-165

AA78463

basal peat

9,117 ± 55

10,220 – 10,374
10,193 – 10,478

54º 3’ 43.7” N, 122º
2’ 56.2” W

1-1-100

AA78464

sphagnum

8,929 ± 49

9,934 – 10,186
9,905 – 10,212

(same as above)

1-3-125

AA78465

basal peat

7,747 ± 51

8,458 – 8,585
8,419 – 8,602

54º 3’ 44.0” N, 122º
2’ 57.0” W

2-1-70

AA78466

basal peat

2,408 ± 39

2,352 – 2,486
2,345 – 2,698

54º 3’ 44.8” N, 122º
3’ 16.2” W

3-4-550

AA78467

sphagnum

8,001 ± 52

8,777 – 8,997
8,650 – 9,012

54º 3’ 50.0” N, 122º
3’ 17.0” W

4-1-70

AA78468

basal peat

3,990 ± 42

4,419 – 4,518
4,298 – 4,570

54º 3’ 50.1” N, 122º
3’ 25.7” W

Sample

Latitude,
Longitude

*

Sample codes indicate: bog site number (see Figure 2) – core number – depth in core (cm)

Results and
Discussion
One unexpected
finding of our field work was
the remarkable range in peat
thicknesses between the four

7

bogs that we cored (Table 1).
There were no obvious
topographic or vegetation
indicators that differed
between the two shallowest
bogs (sites 2 and 4:
maximum depths of 70 cm)
and the deepest (site 3: >550
Research Extension Note No. 2

cm deep). Presumably the
deeper depressions originated
as kettles created by
stranding of ice blocks when
the glacial meltwater lake
drained. Because our coring
equipment could not reach
the underlying lake sediments
at site 3, the initiation of peat
accumulation in this basin
must predate 8,000 14C years
BP.
Site 1 contained
thinner peat deposits (< 165
cm), and the oldest dates in
this project (Table 1). Note
that peat accumulation in
core 1 at this site was initially
rapid, with little difference in
age between the 165 and 100
cm depths, followed by a
much lower accumulation
rate for the balance of the
Holocene. Additional dating
higher up in this core might
reveal further temporal
variations in peat
accumulation rates.
Approximately 10 m away
(core 3), the peat was thinner
(125 cm) and the basal date
was approximately 1200 14C
years younger, suggesting
that peat accumulation
initially began in the deepest
point of the basin, then
spread outward. In the two
shallowest peat deposits (70
cm thick at sites 2 and 4),
basal dates were considerably
younger: 2,408 ± 39 and
3,990 ± 42 14C years BP.
This small sample
must be interpreted
cautiously, but these data do
suggest patterns and
Sanborn & Jull y Peatland Initiation

hypotheses that would be
worth examining in a larger
study. First, it makes sense
that older basal ages were
obtained for thicker deposits
occurring in deeper basins –
these would be more likely
than shallower basins to have
been wet enough to favour
peat accumulation throughout
postglacial time. Second,
initiation of the shallower and
younger deposits may be a
response to more recent
climatic change. The current
climate at the ALRF, with
over 900 mm of annual
precipitation, reflects its
location on a steep
precipitation gradient
between the drier interior
plateau to the west and the
inland rainforests on the
windward side of the Cariboo
and Rocky Mountains to the
east. Small shifts in this
gradient toward moister
climates might tip the balance
toward peat-accumulating
conditions in shallow
depressions underlain by
impervious sediments.
Postglacial climate and
vegetation changes in this
region of BC remain poorly
documented, but a provincial
synthesis of
paleoenvironmental evidence
suggests that climates
became cooler and perhaps
moister in the 4,500-3,000
14
C years BP period (Hebda,
1995), with subsequent
glacial advances in the Rocky
Mountains in the late
Holocene (Osborn et al.
2001). If rates of peat

8

accumulation in this region
have fluctuated considerably
in response to postglacial
climatic changes, then a more
complete inventory of this C
reservoir must consider not
only its current size but its
climate sensitivity.
These preliminary
observations represent only a
small part of the wealth of
paleoenvironmental
information preserved in
these peat deposits. Future
investigations could include
detailed reconstructions of
past vegetation changes
through identification of
plant macrofossils, an
approach that has been
applied in adjacent regions
(Bauer et al., 2003). We also
observed numerous thin (<2
mm) charcoal bands in these
cores, and such features can
enable reconstruction of local
fire history (Ohlson et al.,
2006).

9

Conclusions
Based on a small pilot study
involving four bogs at the
Aleza Lake Research Forest,
both peat thicknesses and the
timing of peatland initiation
show considerable local
variation. Peat accumulation
began later in the Holocene
in shallow depressions, and
initiation of these younger
deposits may be climaticrelated. If this is borne out
by a larger study in this
region, then the potential
response of peatlands to
future climatic changes will
need to be considered in any
evaluation of the fate of this
C reservoir. Studies of plant
macrofossils and charcoal
preserved in peat deposits can
contribute to our
understanding of the
postglacial environmental
history of this poorly-studied
region of the province.

Research Extension Note No. 2

References
Bauer, I.E, Gignac, L.D., Vitt, D.H. 2003. Development of a peatland
complex in boreal western Canada: lateral site expansion and local
variability in vegetation succession and long-term peat accumulation.
Canadian Journal of Botany 81: 833–847.
Charman, D. 2002. Peatlands and Environmental Change. John Wiley,
New York. 312 p.
Davidson, E.A., P.A. Lefebvre. 1993. Estimating regional carbon stocks
and spatially covarying edaphic factors using soil maps at three scales.
Biogeochemistry 22: 107-131.
Fredeen, A.L. 2006. How is forest management influencing carbon
storage in sub-boreal forests? Research Extension Note No. 1.
Natural Resources and Environmental Studies Institute, UNBC. 11 p.
Goodale, C.L. et al. 2002. Forest carbon sinks in the northern hemisphere.
Ecological Applications 12: 891-899.
Gorham, E. et al. 2007. Temporal and spatial aspects of peatland initiation
following deglaciation in North America. Quaternary Science
Reviews 26: 300-301.
Hebda, R.J. 1995. British Columbia vegetation and climate history with
focus on 6 ka BP. Géographie physique et Quaternaire 49: 55-79
Kurz, W.A., Apps, M.J. 1999. A 70-year retrospective analysis of carbon
fluxes in the Canadian forest sector. Ecological Applications 9: 526547.
Ohlson, M., Korbøl, A. Økland, R.H. 2006. The macroscopic charcoal
record in forested boreal peatlands in southeast Norway. The
Holocene 16:731-741.
Osborn, G.D., Robinson, B.J., Luckman, B.H. 2001. Holocene and latest
Pleistocene fluctuations of Stutfield Glacier, Canadian Rockies.
Canadian Journal of Earth Sciences 38: 1141-1155.
Reimer, P.J. et al. 2004. IntCal04 terrestrial radiocarbon age calibration,
0–26 cal kyr BP. Radiocarbon 46: 1029-1058.
Stuiver, M., Reimer, P.J. 1993. Extended 14C data base and revised
CALIB 3.0 14C age calibration program. Radiocarbon 35: 215-230

Sanborn & Jull y Peatland Initiation

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Further Readings or Resources
National Wetlands Working Group / B.G. Warner, C.D.A. Rubec (eds.).
1997. The Canadian wetlands classification system. 2nd ed. Wetlands
Research Centre, University of Waterloo, Waterloo, Ontario. 68 p.
Available from: http://www.portofentry.com/Wetlands.pdf [Accessed:
Feb. 24, 2008]
Natural Resources Canada. 2007. Canada’s Wetlands.
http://wetlands.cfl.scf.rncan.gc.ca/accueil-home-eng.asp [Accessed:
Feb. 24, 2008]

Acknowledgements
We thank the Aleza Lake Research Forest for supporting this pilot study
from its seed grant program and assisting with Figure 2, Marten
Geertsema (BC Ministry of Forests and Range) for loaning sampling
equipment, and Art Dyke, Alain Plouffe, and Ruth Errington (Natural
Resources Canada) for sharing data and helpful advice on sampling
methods. UNBC undergraduate research assistant Sarah Campbell
provided enthusiastic field assistance. The Arizona AMS Facility is
supported by the National Science Foundation.

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Research Extension Note No. 2