Rannoch Moor in the Little Ice Age
University of Glasgow &
the University of Montana, USA
Biography
Megan Denis is a second year PhD student from the University of Montana, USA. Her PhD project, entitled ‘It Takes Two to Tango: Cooperation in the Archaeological Record’, examines the changing use of different mechanisms of cooperation in Housepit 54 of British Columbia through the spatial patterns of artifacts and distribution of wealth across the housepit’s fifteen floors. Her research interests include the wider field of archaeology, but more specifically, paleoethnobotany/archaeobotany, evolutionary archaeology, and First Nations pre-contact household archaeology.
Introduction
During her EARTH Scholarship exchange, Megan studied at the University of Glasgow, where she participated in ongoing wetlands research to explore Rannoch Moor’s environmental history. The aim was to understand how the wider landscape has been transformed by human activity and climate change. This research consisted of the study of pollen grains and other microfossils from wetlands to understand the history of a past landscape and how humans may have impacted it. She also learned how to identify and analyze parenchymatous tissue from hearth contexts in an archaeological site from British Columbia, Canada. These two pieces of research can be used in concert in future research opportunities to analyze the effects previous humans have had on the landscape, which may help illuminate the direction humans must take to ensure the health of the environment and the planet’s future.
Research
Over the course of her time with the Earth Scholarship, this scholar has learned two methods of archaeobotanical analysis that she had no prior laboratory experience with – only a scholarly enthusiasm for. Through this program, she received training on how to identify parenchymatous tissue from an archaeological context, pollen from a peat bog, as well as the wider field of general plant anatomy and behavior. The plant anatomy section focused on how cell walls are structured in different plants and organs, as well as how the structure of these cells changes if manipulated in any way – such as after repetitive burnings or processed for consumption by mashing. The plant behavior focused on how different types of plants spread their pollen, and how pollen travels in general.
The researcher first began by learning how to identify parenchyma from an archaeological record. This material was sampled from one housepit over a large time span from the Bridge River Village in British Columbia, Canada. This is a First Nations site where the descendent community lives down the hill from where their ancestors lived in the village, who collaborate with the researcher’s home university in the research of this site. The samples analyzed for parenchyma were from differently shaped hearth pits in different regions of the floor from different time periods, with the hope that it would be possible to identify what plant materials these past peoples were eating, and if these materials changed over time or space. Comparing the results would have exciting social implications and could provide a fascinating picture of what the relationships of the people who lived within the house were like in the past.
To accomplish this task, the researcher first learned how different plants organize themselves and their cell walls, and then how to identify this difference. She learned about the systems of transferring energy, water, and nutrients among different plant parts, how these systems appear in different plants, and what different root systems indicate for which type of plant. Wood parenchyma appears very organized into thin, relatively even lines, regardless of what plane it is broken on. It is possible to determine the type of wood from the organization and thickness of the cells, but as this project’s goal was food plant oriented, the specifics of wood identification were left for later exploration. Instead, the researcher focused on attempting to identify vascular bundles, secretory tissues, and different manners in which parenchyma breaks. A Leica M80 microscope was used to sort the samples, separating the wood parenchyma and the more interesting, likely food related, parenchyma (see Figure 1 for an example). At this juncture, the scholar learned about the sheen that might form on parenchyma if it is a particularly starchy plant, such as a tuber, as well as the complete disorganization that mashing a plant has on the structures of the parenchyma. She learned what an epidermal layer looks like after charring and the fusing of the parenchyma that occurs after several instances of heating.
A picture of some parenchyma under the Leica M80 microscope, possibly from a tap root.
After successfully learning how to identify parenchyma under a microscope, the researcher then used a Scanning Electron Microscope (SEM). First, she learned how to use this machinery, and the process of preparing samples for examination. Then, she explored the samples using the SEM, learning how to identify interesting structures such as vascular bundles and secretory cavities in much closer detail than with the Leica M80 microscope. The broken edges of the parenchyma samples appeared to have more interesting features, which indicates the possibility of identifying them. However, there is a general lack of comparative collections for parenchymatous material, especially in this specific research area. The researcher ended this portion of her scholarship with the plan to create a comparative collection in collaboration with the local First Nations band, which is in the planning phase to accomplish her next field season next summer.
The second portion of the Earth Scholarship was spent learning the process of palynological analysis. This project’s aim was to unearth and study the pollen record from Rannoch Moor, hoping to discover the pollen from the Little Ice Age, and more specifically, within the last 500 years. Little is currently known about the pollen record from this period, as cutting the peat to use as a fuel source was a popular and inexpensive way for people to warm themselves for much of the area’s history. There is an intact record starting from about 1,000 years ago and further back in time, but at this point, there were several different tree species throughout the landscape. As can be seen from the landscape today, something drastic changed within the last 1,000 years, as there are few trees to be seen on Rannoch Moor today, also representing significantly fewer species. This change could be due to general climate change or directly due to human presence and use of the peatland. This is an important research question for the current climate crisis, as how landscapes reacted to different pressures in the past, especially human caused ones, can help inform the present climate changes and help to inform environmental policy on a regional or even global scale.
This process began first with the removal of the pollen core from the peat at Rannoch Moor. The area that was most likely to result in the deepest sequence was identified by taking several smaller cores to first explore the layout of the bog. Once this was accomplished, the core was removed using a Russian corer, resulting in a sequence of 103 centimeters. The stratigraphy of the core was assessed and described, requiring the researcher to explore the physical components of the peat and examine how the peat content has changed over time. At the top of the sequence, the core still had whole plant parts and very little humified sediments, but this changes further down in the sequence due to the passage of time, allowing for more humification to occur, thereby allowing the plants to degrade into a peatier consistency. About midway through the sequence, there was evidence of tree parts still held within the peat, indicating the presence of more trees on the landscape at that point in time.
After the physical characteristics of the core were observed and recorded, roughly 1 cubic centimeter worth of material was removed every four centimeters, resulting in a total of 27 samples. From here, the samples were taken to the University of Aberdeen, where the researcher learned how to extract pollen from the peat samples. This was accomplished through a series of chemical additions to the samples to remove extraneous material from the peat, such as organic material, lignin, cellulose, clays, and other soils. Each of these steps were followed by several water washes and centrifuging, until only the pollen remained. The pollen grains were then suspended in a silicone fluid, then returned to the University of Glasgow, where each sample was mounted onto slides for counting.
At this juncture, the researcher learned how to describe pollen and how to identify pollen to the genus and species level, in some instances. This was accomplished with the help of several books, online resources, and modern reference collections under the microscope. Once comfortable with the general pollen shapes, the researcher began systematically counting pollen grains on each slide using a Leica DM2000 microscope, with the goal of at least 300 grains counted (see Figure 2 for an example of the pollen grains under the microscope). This venture was successful, for the most part – the top two levels only had 10 and 47 grains, respectively. These samples were also the two with the most modern plant material and were primarily composed of organic material, which was removed during the process of pollen extraction, so the lack of pollen grains on these slides are not surprising.
Some pollen under the high-powered Leica DM2000 microscope. There is Pinus pollen in the top right corner.
The researcher took her raw counts for each of the species per sample and calculated the abundances of each species per sample. These data were then put into a pollen diagram generator to create a pollen diagram for this sequence from Rannoch Moor. Upon the initial investigations, it does not appear that this sequence is from the last 1,000 years based on previous palynological explorations of Rannoch Moor, but further research must be funded and completed to know a more specific time range.
The researcher also performed a loss-on-ignition test on each of the 27 samples, to explore how much organic material was in each sample. This process involved cutting another sample next to each of the original samples, then weighing the samples. These samples were then dried out and weighed again to calculate the water weight. Then, the samples were burned in a muffle furnace at 500 degrees Celsius for four hours, then weighed again to calculate the weight of the organic material. Knowing the amount of organic materials within the samples can help calculate the rate of accumulation and sediment formation, which may be used to estimate a broad time range and may be useful information in light of the current climate crisis.