Palynological Study of Pollen in Massawepie Mire:  St. Lawrence County, NY
Nathan W. Vogan, Department of Geology
Dr Stephen D. Robinson, Department of Geology
Dr. William Rivers, Department of Biology
St. Lawrence University, Canton, NY 13617
Introduction
Palynology is the study of organic-walled microfossils which include pollen, spores, dinoflagellates, acritarchs, tasmantids, and chitinozoa (MacDonald, 1990).  Pollen can be treated as an aeolian (wind blown) sediment that will accumulate on any undisturbed surface (Bradley, 1985).  If it is not used in the fertilization of another plant, the cellulose and exine in pollen will very rapidly breakdown.  In order to be preserved in the stratigraphic record, pollen has to fall in areas with accumulating organic and/or inorganic sediments.  This is still not enough to preserve the pollen grains.  In order to prevent decomposition of the grain, it must be rapidly buried under large quantities of sediments or deposited in high pH and/or anoxic environments.  Therefore pollen is most commonly studied in peat deposits from bogs and marshes and sediments taken from relatively shallow lakes.
The Massawepie Mire is an 900 acre, ombrotrophic mire in southern St. Lawrence County in the Adirondacks (Figure 1).  An ombrotrophic mire is a specific type of bog/marsh that receives almost all of its moisture from the atmosphere (dew and precipitation).  The high levels of organic matter in the bog help create highly acidic and anoxic conditions that prevent the organic decay of the pollen grains.  The mire also continues to grow in situ in a series of hummocks and swales, resulting in layers that increase in age with increasing depth below the surface.  This in situ growth allows for peat accumulations to accumulate at high rates over long periods of time.  Therefore, the Massawepie Mire is a perfect site for pollen preservation.  Peat can also be reliably dated using radiometric decay (carbon-14).
Theory of Pollen Analysis
Pollen analysis is based upon the fundamental principles that pollen grains are:  a) extremely resistant to decay and possess morphological characteristics which are specific to a particular genus or species of plant; b) produced in vast quantities and are widely distributed from their sources; and c) reflect the natural vegetation around the preservation site (Bradley, 1985). 
Grain Morphologies
Pollen is preserved in sediments and in peat because of its chemically resistant outer layer, the exine.  The exine is made of soropollenin, (C90H142O36)n, a complex polymer that is resistant to all but the most extreme oxidizing and reducing agents (Bradley, 1985).  The grains range in size from 10 to 150 um.  Each grain is morphologically distinct from other genera and species of plants based upon its distinct shape, size, sculpting (surface ornamentation), and the number of apertures (openings or thin parts in the exine) (Figure 2a,b,c) (Bradley, 1985).
Pollen Rain
The vast majority of pollen grains are dispersed by the wind.  However, much of the pollen grains travel no more that 500 m beyond their source (Bradley, 1985).  Therefore, pollen deposition is not restricted to local conditions, but  is rather an approximation of the regional vegetation.  This limiting factor means that unless the sample is taken very near to the pollen source, individual plants should not be distinguishable from the regional pollen rain.  The amount of pollen a plant produces is largely dependent upon species type, the mechanism for dispersal, and the proximity of other plants for fertilization.  Wind driven dispersal mechanisms for anemophilous plants force the production of billions of pollen grains during a single spring with the more arboreal species (higher winds); thereby producing the highest numbers of grains overall (MacDonald, 1990).  The cleistogamous (flowering) and entomophilous (insect pollinated) plants produce much lower amount of pollen, only a few thousand grains (MacDonald, 1990).
Applications of Pollen Analysis
Paleoclimate Reconstruction
Pollen analysis is an important tool in interpreting regional vegetation both at the present and the distant past.  The abundance of pollen grains can be plotted on graphs to show the total relative percentages of plants within the area of pollen accumulation and the rates of accumulation during each sublayer in the peat core.  These graphs help show the dominant vegetation in the area and how they have varied and developed through time.  The intent with these pollen graphs is to associate previous plant communities with modern analogs in order to interpret the past climate regimes of a particular region.  There is increasing evidence that modern vegetation communities do not have a long history and are simply “temporary aggregations of species developed under certain historical and climatic factor (Birks, 1981).”  Therefore, variations within a region in pollen content can used as rough indicators of wetter/drier or hotter/cooler paleoclimatic conditions based upon proper correlation with modern analogs.  This is most often evident with indicator species that are often not very abundant and are limited by certain climatic conditions (Bradley, 1985).
Plant Succession
Another important use of pollen analysis is the study of plant succession.  Plant succession refers to the steady introduction of different species of plants one after another until a climax state has been reached.  Plant succession is driven by the varying migration rates of particular taxa into cleared land from often distant refuges (Bradley, 1985).  Primary plant succession is associated with the development of soil on glacial recently glaciated terrain, such as northern New York 12,000 years ago (Livingstone, 1968; Brubaker, 1975; Delcourt and Delcourt, 1991).  The pioneer species of lichens, mosses, and grasses in open ground communities last for only a few decades.  There is then a steady progression of plant species to there is ultimately the establishment of a climax state (e.g. maples).  Secondary succession is associated with repeated natural disturbances, usually fire.  Pollen is an important indicator of the vegetation prior to, during, and after the fire.  The response time is different for different genera of plants.  The early responders include pine, larch, spruce, willow, and elm; followed by oak and ash; and ultimately followed by beech balsam fir, hop-hornbeam, and maples (Delcourt and Delcourt, 1991).
Anthropogenic Influences
Humans have a dramatic impact on their environment, especially as they practice agriculture.  Once agricultural land has been cleared the flora of the region has been changed.  Previously unknown or limited species become dominant weeds, and therefore become a dominant part of the pollen rain (Faegri and Iverson, 1975).  There is also some crop pollen associated with the increase of these weed pollens.  However, most crops are self-pollinating and produce very little in the way of pollen (Faegri and Iverson, 1975).  Therefore, evidence of crop pollen in a peat core is an almost sure indicator of cultivation in the region.
References
Birks, H.J.B.  1981.  The use of pollen analysis in the reconstruction of past climates:  a review.  In Climate and history, T.M.L. Wigley, M.J. Ingram, and G. Farmer (eds.), 111-38.  Cambridge:  Cambridge University Press. Bradley, R.S.  1985.  Quaternary Paleoclimatology:  Methods of Paleoclimatic Reconstruction. Winchester:  Allen & Unwin Inc., 472 pages. Brubaker, L.B.  1975.  Postglacial forest patterns associated with till and outwash in north central Upper Michigan.  Quaternary Research.  5, 499-528. Delcourt, H.R., and P.A. Delcourt.  1991.  Quaternary Ecology:  A paleoecological perspective.  New York:  Chapman & Hall,  242 pages.
Faegri, K., and J. Iverson.  1975.  Textbook of Pollen Analysis.  Munksgaard:  Scandinavian University Books,  295 pages.
Jackson, S.T., and D.R. Whitehead.  1991.  Holocene Vegetation Patterns in the Adirondack Mountains.  Ecology no 72(2), 641-653.
Livingstone, D.A.  1968.  Some interstadial and postglacial pollen diagrams from eastern Canada.  Ecol. Monogr.  38, 87-125.
MacDonald, G.M.  1990.  Palynology.  In Methods in Quaternary Ecology, B.G. Warner (ed.), 37-52.  Newfoundland:  Geological Association of Canada.
Moore, P.D., and J.A. Webb.  1978.  An illustrated guide to pollen analysis.  London:  Hodder and Stoughton.
Ogden, E.C., and D.M. Lewis.  1960.  Airborne Pollen and Fungus Spores of New York State.  New York State Museum and Science Service, Bulletin no. 378. Overpeck, J.T.  1985.  A Pollen Study of a Late Quaternary peat bog, south-central Adirondack Mountains, New York.  Geological Society of America Bulletin, v. 96, 145-154.
Field work and Processing
In early July we retrieved a 2.9 m peat core from Massawepie Mire using a Russian peat corer (Figure 3a,b).  I then sampled this core at 10 cm. intervals for both pollen analysis and loss on ignition (LOI).  LOI is where the peat is burned at very high temperatures to eliminate all the organic material and leaves behind only the mineral sediment.  This step is important to determine if there have been any major allogenic (outside) factors influencing the development of this peatland.  The samples of peat were subjected to a rigorous series of chemical reactions adapted from Faegri and Iverson (1975).  After all of the chemical processing is complete, I am left with a residue of concentrated pollen.  Once the pollen residue has been obtained, three hundred grains of arboreal pollen were counted for each sample.
Figure 1.  Aerial image of Massawepie Lake and Massawepie Mire (highlighted), National Aerial Photography Program, April 1998.  http://www.apa.state.ny.us/Research/stlawr2/stlawrence2welcome.html
Figure 3. a) Taking a sample of peat at Massawepie Mire; b) actual appearance of a 50 cm. section of the core.
A.
B.
Preliminary Observations and Interpretations
The samples that I have counted so far agree with trends for this region already established by Overpeck (1985) and Jackson and Whitehead (1991).  This entire region was glaciated up until about 10,000 years ago.  Therefore, there should be a steady progression from pioneering species (spruce, alder, etc.) to the climax stage vegetation (maples, beech, etc.) that is common in the Adirondack region today.  There should also be a progression from cold climate vegetation to more temperate ones as the glaciers continued to retreat.  The percentage of the genus within the total arboreal pollen count in each sample (Table 1) agrees with these trends.  Near the base of the core (M230-M280)  there is evidence of a spruce (Picea) dominated forest similar to the modern northern boreal forest in Canada and Alaska.  There is a gradual decline in spruce and increase in pine (Pinus) and birch (Betula) as we go higher in the core (M160-M30).  The progression is completed with the influx of more hardwood genera by M90-120.  This shows the establishment of the modern mixed-hardwood forest of the Adirondacks today.
One surprising piece of data is the sudden influx of massive amounts of pollen from eastern hemlock (Tsuga) at M160.  This is very interesting because the base of this core has only been dated to 5600 BP.  There was a widespread decline in Tsuga during the middle Holocene (approx. 4800 BP).  So by this point there should be little Tsuga pollen entering the peatland.  This may be an example of when the pollen rain is being overpowered by an immediate local source of pollen.  Further sampling on either side is needed to determine if this spike is very localized or may be the part of a larger Tsuga spike.
Conclusions
This research is still a work in progress.  Many more hours are needed to be spent in the lab to finish a complete pollen analysis of peat core.  Once this analysis is complete I can fully recognize the trends in forest development of this region for the last 6000 years or so.  However, the results that I have obtained so far have provided a sound basis on to which to proceed with my research.  The pollen analysis is indicating a progression from a more northern boreal forest to a mixed hardwood-conifer  forest.  Once a full analysis is available, I can decide on certain parts of the core to radiocarbon date to accurately trace out the forest history of this region.
Acknowledgements
I would like to thank my advisors Dr. Stephen Robinson and Dr. Wil Rivers for all their hard work, direction, and dedication in helping me struggle with pollen.  I would also like to thank the university and the Baker family for their support for this project. 
0
0
0
0
0.7
0
0
0
0
0
Populus
0
0
0
0
0.3
0
0
0
0
0
Tilia
0
0
0
0
5.6
6
12.8
12.8
13.8
1.4
Ostrya/Carpinus
0
3.2
0
0
0
0
0.8
0.8
0
4.2
Corylus
3.9
0
2
0.6
0.7
0.6
0
0
5.2
2.8
Larix
0
2.6
0
0.5
0
0
1.5
1.5
1.7
0
Alnus
0
1.3
0
0
0.3
0
0
0
0
0
Salix
0
5.2
7
7.7
16.6
31.7
28.6
28.6
24.1
23.9
Betula
0
0
0
0
0
0
0
0
1.7
0
Ulmus
0
0
0
0
0
0
0
0
0
0
Quercus
0
0
0
0
1
0
3
3
0
7
Carya
0
0
0
0
1
0
0
0
0
0
Fraxinus
3.8
2.6
1
5.6
3
3
3
3
3.4
1.6
Acer Undiff
0
3.9
0.5
4.2
4
9
6
6
1.7
4.2
Fagus
0
0.6
1.5
5.6
40.7
1.2
3.8
3.8
5.2
2.8
Tsuga
15.4
18.9
5.5
16.4
3.7
15
18
18
15.5
14.1
Pinus Undiff
23.1
8.4
31.6
17.4
13.7
30.5
13.5
13.5
19
22.5
Haploxylon Pinus
0
0
0
0
0.7
0
0
0
0
1.4
Diploxylon Pinus
53.8
52.7
49.9
42
7.3
3
9
9
7
14.1
Picea
0
0.6
1
0
0.7
0
0
0
1.7
0
Abies
M280
M250
M230
M200
M160
M120
M90
M50
M30
M0
Genus
Table 1.  Percentage of genera in total arboreal pollen count in Massawepie peat core.  Note the yellow highlighted trends for forest development from a northern boreal forest to a more temperate mixed hardwood-conifer forest, and the red spike of Tsuga in M160.
Figure 2  Pictures of pollen taken at 400X magnification  a)  Triangular grain is Betula (Birch); b) Large oval, blotchy grain is Tsuga (Eastern Hemlock) and Mickey Mouse shaped grain is Pinus (Pine); c) circular grain with “parentheses” is Fagus (Beech)
A
B
C
Younger
Older