As part of my MSc Biological Sciences (University of Amsterdam) research project entitled “Assessing the effect of human induced fire regime changes on vegetation in the Drakensberg mountains” (for further details click to see previous post). I’ve travelled to Africa, where I’ll be staying a month. During this mini blogpost series I’ll take you with me on my travels!
During the first poster session, I presented my poster which went into detail on how we are developing a proxy to reconstruct past fire using micro-Fourier Transformed Infrared Spectroscopy (µFTIR). These reconstructed fire temperatures can then be compared with phytolith or pollen data to assess the effects of different fire temperatures on local vegetation over time. The presentation and poster were well received!
After my poster presentation there were two more congress days which were filled with interesting talks and beautiful posters.
Hello Ecology of the Past readers, my name is Jelle Kraak and I’m currently doing a research project for my MSc Biological Sciences (University of Amsterdam) supervised by William Gosling (University of Amsterdam), Jemma Finch (University of KwaZulu-Natal), and Trevor Hill (University of KwaZulu-Natal). The project is entitled: “Assessing the effect of human induced fire regime changes on vegetation in the Drakensberg mountains”. During the project I will visit South Africa to work at the University of KwaZulu-Natal and visit field site thanks to partial funding from the Amsterdam University Funds.
Research project outline
As many of you know, humans have been interacting with the environment for millennia in various ways. One of the ways in which humans interact with the environment is through the ignition of fires. By doing so, humans may change fire regimes (fire frequency, severity and/or intensity), which in turn can cause changes in vegetation composition and structure. By using a combination of phytolith (local vegetation) and charcoal (fire) data from two sediment cores obtained from wetland environments in the Drakensberg mountains, we aim to assess the effect of fire regime changes on vegetation over the last 6000 years.
The phytoliths (biogenic silica microfossils) allow for the reconstruction of the past vegetation. Charcoal fragments characterize all aspects of past fire regimes: (i) frequency (time series analysis of charcoal data), (ii) severity (abundance of charcoal in samples reflecting biomass consumed), and (iii) intensity (spectral properties of individual charcoal fragments reflecting combustion temperature).
The most interesting part of this project (in my humble opinion) is that this study is the first to use micro-Fourier Transformed Infrared Spectroscopy (µFTIR) to reconstruct fire temperatures from field samples ánd combine these accurately reconstructed temperatures with local vegetation data! It is important to accurately estimate fire temperatures, as the temperature of a fire dictates the type of plant materials which are consumed in a fire (the higher the temperature, the greater the proportion of woody material burning up). Similar studies have been conducted previously, however, these studies compared fire severity i.e. total burnt biomass with vegetation data. Although this works decently, total burnt biomass is not an accurate representation of fire intensity or temperature, as at very high temperatures biomass turns to ash, which cannot be detected in sediment cores. Through parameterizing both the vegetation changes and the fire regime we will provide a comprehensive picture of how changing human fire use practices modified the vegetation. We anticipate that: (i) a decrease in fire intensity resulted in woody encroachment of the surrounding vegetation, which was concomitant with the arrival of agropastoralists c. 600 years ago, and (ii) a shift in the proportion of C3 and C4 grass species in reaction to temperature changes in the Drakensberg mountains.
de Weger, L.A., Verbeek, C., Markey, E., O’Connor, D.J. & Gosling, W.D. (2024) Greater difference between airborne and flower pollen chemistry, than between pollen collected across a pollution gradient in the Netherlands. Science of The Total Environment 172963. DOI: 10.1016/j.scitotenv.2024.172963
Gosling, W.D. & McMichael, C.N.H. (2023) The use of micro infrared spectroscopy in reconstructing past ecological and environmental change. Reference Module in Earth Systems and Environmental Sciences (ed. by R. Bradshaw) Elsevier. DOI: 10.1016/B978-0-323-99931-1.00087-8
Jardine, P.E., Hoorn, C., Beer, M.A.M., Barbolini, N., Woutersen, A., Bogota-Angel, G., Gosling, W.D., Fraser, W.T., Lomax, B.H., Huang, H., Sciumbata, M., He, H. & Dupont-Nivet, G. (2021) Sporopollenin chemistry and its durability in the geological record: an integration of extant and fossil chemical data across the seed plants. Palaeontology https://doi.org/10.1111/pala.12523
Woutersen, A., Jardine, P.E., Bogota-Angel, R.G., Zhang, H., Silvestro, D., Antonelli, A., Gogna, E., Erkens, R.H.J., Gosling, W.D., Dupont-Nivet, G. & Hoorn, C. (2018) A novel approach to study the morphology and chemistry of pollen in a phylogenetic context, applied to the halophytic taxon Nitraria L.(Nitrariaceae). PeerJ 6, e5055. DOI: 10.7717/peerj.5055
Jardine, P.E., Abernethy, F.A.J., Lomax, B.H., Gosling, W.D. & Fraser, W.T. Shedding light on sporopollenin chemistry, with reference to UV reconstructions. Review of Palaeobotany and Palynology 238: 1-6. DOI: 10.1016/j.revpalbo.2016.11.014
An international team of scientists have reconstructed the longest ever record of past sunshine using pollen trapped in lake sediments collected in Ghana, Africa. The study published today in Scientific Reports enables us to understand past changes in solar input to the global system over the past 140,000 years. Previously we have had to rely upon computer models to mathematically determine past solar inputs to the Earth. “This work really is a first; being able to peer back in time to understand how the Sun has driven our global system over many of thousands of years is a very exciting prospect” said joint-lead author Dr. Phillip Jardine of The Open University.
The Sun is a key component of our natural environment, driving a multitude of processes at Earth’s surface, from photosynthesis generating energy within plants, through to global-scale circulation patterns in our oceans and atmosphere. Understanding more about how the Sun has behaved in the past, and the influence this had on Earth’s environment, will help scientists predict future climate change.
Dr. Jardine used a technique pioneered by one of his co-authors, Dr. Wesley Fraser of Oxford Brookes University, to determine past changes in solar input, specifically changes in ultraviolet (UV) radiation. Plants protect themselves from the harmful nature of ultraviolet radiation by incorporating a number of specific chemical compounds into their tissues that absorb and dissipate the energy of UV radiation. Pollen grains of flowering plants are also provided protection by these UV-absorbing chemicals, thus act as a long-term recorder of ultraviolet radiation from the Sun.
Pollen grains are readily trapped in lake sediments, where they can be preserved for millions of years. By extracting material from Lake Bosumtwi, Ghana, the pollen that was released by flowering plants thousands of years ago can be separated from the lake sediment and chemically analysed for UV-absorbing chemical compounds. It is this chemical signature within the ancient pollen grains that provides us with information about past levels of solar ultraviolet radiation.
“What we present here is a new opportunity to explore how the Earth has changed” said Dr. William Gosling (University of Amsterdam). “I am particularly excited about this because it will means that we can gain a better understanding of why vegetation changed in the past, and consequently this will allow us to anticipate better what the likely impacts of projected future climate change will be.”
Ecology of the past 