At the end of November 2015 I participated to a 10-days field-work in Tasmania with the research group led by Dr. Michael Fletcher from the department of Geography of the University of Melbourne. The aim of this field-work was to collect sediment cores from Western Tasmania lakes in order to study how vegetation has changed after the LGM (Last Maximum Glacial). In particular, they are interested in understanding the role played by bush-fires in vegetation dynamics and its long-term impacts by studying the past vegetation history revealed in the pollen records, with a greater interest on the contrast between fire-prone and fire-sensitive plant taxa. Tasmania is an optimal place to study this relationship as fire-sensitive (like conifer temperate forests) and pyrophytic (like eucalyptus woodlands) vegetation types coexist together in a patchy vegetation mosaic. The increase in biomass burning during the recent millennia is linked to the effects of the ENSO (El Niño Southern Oscillation) and the European colonization. Two PhD students are involved in this project. Kristen Beck is using diatoms and pollen proxies to understand the relationships between climate, vegetation and aquatic environments of Paddys Lake and Lake Vera cores. Michela Mariani is instead interested in quantifying the regional vegetation changes occurred in Western Tasmania by studying several pollen records, charcoal and trace elements from cores collected in this area.
During this field work we sampled in three lakes: Dove Lake, Lake Vera and a small lake without name close to Cradle Mountain.
Sampling lake cores is quite challenging and physically demanding. These kind of field-works are usually very hard because it is required to spend a lot of time on the platform in the middle of a lake under every meteorological condition. In Tasmania the climate is very humid therefore we were constantly working under the rain and wind (the last is a prohibited word because you get very superstitious upon a platform!). Sometime the sun came out but not for too long as the weather conditions were constantly changing very quickly.
Setting up and dismantling the platform is a very tough and long work because the gear is very heavy and there are lots of pieces to assemble. Our group was mostly formed by women but we smashed it! Tough women for tough works!
The platform consists of two big inflatable pontoons with wooden boards on top and a hole in the middle fitting the tripod coupled to the coring device. The coring devices is formed by a metallic cable and 30-kg-hammer that has to be attached at the top of the pipe used to collect the sediment from the bottom of the lake.
The coring process starts with a survey around the lake on a small rubber-boat to find the deepest point. After that, we had to bring the platform to the selected site and get ready to start coring. First of all, the pipe has to be sunk and touch the bottom of the lake. Then, we repeatedly hit with the hammer the top of the pipe which progressively sank through the lake sediment. In that way, the sediment is collected by being sucked inside the pipe. When the pipe touches the bed-rock of the lake basin you cannot go any further deep therefore we knew that we could start to pull out the pipe filled up with the sediment…. and it made us very happy!.
This experience was amazing as it allowed me to discover the beautiful wilderness of Tasmania and getting familiar with some techniques used in a different paleoclimatic field from mine. I have also learn a bit about Tasmanian flora and how to recognise some plants. I have also really liked spending 5 days in a hut in a very remote place without electricity and drinking rain water. To get to the hut we had to hike for 17 km and therefore the platform with all the gear had to be transported by the helicopter.
I hope to have the chance to participate to another similar field work again.
For more information about Dr. Michael Fletcher research you can visit his blog: https://michaelsresearch.wordpress.com/