Strange ladies with a wheelbarrow!

We often get approached by people to undertake projects on our sites. These can range from surveys and updating knoweledge on certain species to filming scenes from a viking invasion (that actually got requested). This blog covers a very interesting project about something that I had no idea existed.

Strange ladies with a wheelbarrow!

Emma Karoune

If you have been down to Farlington Marshes over the last month, you might have seen me and my helpers (Siggy Osbourne, a final year undergraduate student, and Sarah Elliot, a postdoctoral researcher, both from Bournemouth University) walking around with a wheelbarrow, sitting on the ground examining the plants or even bagging up soil samples. 

You have probably been thinking, what are they up to?

Who I am and what I am doing?

I’m an archaeobotanist. This means I’m a scientist that specializes in examining plant remains from archaeological sites. I look at microscopic plant remains called phytoliths. These are silica shapes formed in living plant cells and they preserve in soils for thousands of years. I am developing a new method that can be used to find out about environmental changes in the past and what types of plants past humans exploited in Britain.

Before I can examine ancient remains, I have to understand how to recognise modern plants. So I am currently making a reference collection of southern coastal plant communities, in collaboration with Historic England, and I’m trying to work out what these look like when the phytoliths end up in the soil.  

This picture shows what phytoliths look like 

under a microscope when they are separated from soils.

What I’m doing at Farlington Marshes?

As well as being an important site for bird life, Farlington Marshes has some interesting plant communities including a saltmarsh, a grazing marsh, reed beds and grasslands. I have been taking samples of the different plant species found in each of the areas and I will use these plants to find out if they have unique phytoliths that can be used to identify the plants. I am also making herbarium samples that will be stored at Portsmouth Museum for other researchers to use.

The other method I am using is to sample using a quadrat. This is a 1m by 1m square that is used to take a standard size sample. In each quadrat, I have taken the plants found above-ground and samples of the topsoil below the plants. I will then look at the differences between the phytoliths found in the plants and the soil. This will help me to work out what is lost through wind and water movement and it also provides a reference to identify each plant community that can be used to identify past landscapes.

Taking soil samples from a quadrat in the lower salt marsh area at Farlington Marshes.

What happens to the plants and soils once they are taken from Farlington Marshes?

I start by taking photos of each type of plant, including using a microscope to look at certain parts that help with identification. As I am making a reference collection, I have to be sure that I am identifying the plants correctly so all my identifications are being checked by expert botanists from the Botanical Society of Britain and Ireland (BSBI). Most plants have unique flowering parts and grasses and sedges can be identified using the parts where the leaf meets the leaf stalk (called the ligule and auricles).

I have to dry the plants and soils to help preserve them. I do this by laying out the plants on newspaper and stacking them up with more newspaper and corrugated cardboard. It takes a few days to a week to dry the plants. They are then put into plastic sample bags and taken to the laboratory at Fort cumberland, Portsmouth – these are the scientific laboratories for Historic England.

To extract phytoliths from plants, each plant is burnt in a laboratory furnace at 500^oC for several hours until there is only a white ash. What is left is the phytoliths and they will be permanently mounted on to a microscope slide. Each slide will then be examined to work out if they have phytoliths that help to identify each specific plant. The slides will be part of a permanent reference collection kept at Fort Cumberland and will be accessible to other researchers. The reference collection will also be photographed for a free to access digital resource. 

Once I have worked out how to recognise the differences between each plant community, I can then start to use this new method on archaeological sites. This research has the potential to add to our knowledge of past plant use and long-term landscape changes in Britain. 

I would like to thank Chris Lycett for helping me access Farlington Marshes. This research is supported by small research grants from the Association Environmental Archaeology and the Botanical Society of Britain and Ireland.