Probabilistic indicator species-based climate reconstructions using Sphagnum macrofossils
2025
Larsson, Elina
Organic material can be preserved in peat for millennia, providing a fossil record that may give us insight into how the climate has developed during the Holocene. Indicator species-based climate reconstruction methods utilize modern occurrence data to define the climate preferences of individual proxy species. Macrofossils are often used in indicator-species based climate reconstructions, but despite Sphagnum macrofossils often being the principal component of peat they have been given little attention as proxy species. Here I show that a Sphagnum-based climate reconstruction could reconstruct annual degree days, although at a course resolution. Climate was reconstructed for fossil peat sequences from three separate sites with different sample sizes (81, 18 and 12). The expected decrease in annual degree days since the Holocene thermal maximum could be seen only in the reconstruction with the largest sample size. The results show the importance of a high temporal resolution of fossil samples in climate reconstructions. Although a high-resolution climate reconstruction could not be made based on Sphagnum as the only indicator, it should serve as a worthy inclusion to be used together with other proxies. In addition, the results show that Sphagnum species are responsive to climate change. This calls for future studies to investigate how the distribution of Sphagnum can be expected to change in the future.
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