Environmental Change Research Unit - ECRU

Peatwater

PAST WATER TABLE FLUCTUATIONS AND RELATED CHANGES IN CARBON ACCUMULATION RATES IN MIRES - A QUANTITATIVE MULTI PROXY-BASED RECONSTRUCTION FROM DIFFERENT CLIMATE REGIMES

Funded by the Academy of Finland

Duration 1.1.2008-31.12.2010

To assess the role of northern mires as carbon sinks or sources in changing future climate, it is essential to understand how mires have responded to climate forcing before and how the changes in surface moisture were reflected in carbon accumulation rates. In general, pristine mires act as long-term sinks for atmospheric carbon. Resent mire studies measuring carbon gas exchange have however shown that mire ecosystems can swiftly turn to net sources of carbon during dry summer periods due to accelerated decomposition rates. Yet, the link between the long-term carbon accumulation rate and the historical variation in water table level is poorly known. Identification of past abrupt changes in hydrological conditions and site-by-site comparison of timing and duration of wet and dry shifts would show if the changes in moisture conditions have been simultaneous and thus could be interpreted to be climate-forced. Such information would give a background for scenarios of potential future dynamics in mire surface moisture and subsequent changes in carbon accumulation patterns.
In Europe earlier palaeohydrological mire research has largely concentrated on oceanic mid-latitude or semi-oceanic southern boreal bogs, while more continental and northern locations and different mire types have been almost completely neglected. Moreover, the earlier attempts to quantify past water table fluctuations have mostly produced wetness indices, instead of metric quantity. Finnish mire researchers have recently for the first time succeeded to quantify past water table fluctuations in a southern boreal bog sequence. Encouraged by this successful experiment the proposed project expands quantitative palaeohydrological multi-proxy-based mire research to sub-arctic and northern boreal continental mires in Russia and in Finland. The research methods will be plant macrofossil analysis (including macroscopic charcoals), testate amoebae analysis, carbon content analysis, radiocarbon dating and mathematical modelling. The main aims are 1) to produce several new temporally precise quantitative palaeohydrological reconstructions covering the last 3000 years from areas not studied earlier and 2) to provide quantitative high-resolution reconstructions of apparent carbon accumulation rates in relation to detected past water table variations over the studied time period.

Researchers

Docent Minna Väliranta, PI

Project partners

Docent E-S. Tuittila, Academy research fellow, Department of Forest Ecology, University of Helsinki, Finland
Prof. D. Charman, Department of Geography, University of Exeter, UK
Prof. A. Korhola, Department of Environmental Sciences, Environmental Change Research Unit, University of Helsinki, Finland
Prof. H. Seppä, Department of Geology, University of Helsinki, Finland
Prof. P. Kuhry, Department of Physical Geography and Quaternary Geology, University of Stockholm, Sweden

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