Holocene carbon dynamics and atmospheric radiative forcing of different types of peatlands in Finland

• Main Author: Mathijssen, Paul
• Other Authors: Yu, Zicheng, University of Helsinki, Faculty of Biological and Environmental Sciences, Department of Environmental Sciences, Environmental Change Research Unit, Helsingin yliopisto, bio- ja ympäristötieteellinen tiedekunta, ympäristötieteiden laitos, Helsingfors universitet, bio- och miljövetenskapliga fakulteten, miljövetenskapliga institutionen, Väliranta, Minna
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: Helsingin yliopisto 2016
• Subjects: Environmental change and policy; Subarctic
• Online Access: http://hdl.handle.net/10138/161250

Peatlands contain approximately a third of all soil carbon (C) globally and as they exchange carbon dioxide (CO2) and methane (CH4) copiously with the atmosphere, changes in peatland C budgets have a large impact on the global C balance and on the concentration of greenhouse gases in the atmosphere. How peatlands will react to future climate changes, however, is still relatively uncertain and as such there has been a growing interest in the reconstruction of past peatland C dynamics and linking these to past climate variations. In order to increase the understanding of peatland development and response patterns, I quantitatively reconstructed the Holocene (the last c. 11700 years) C dynamics of three different peatlands in Finland: a subarctic rich fen, a boreal poor peatland complex and a boreal managed pine bog. Several cores from each peatland were studied in order to reconstruct peatland succession, lateral expansion, peat and C accumulation rates, long term uptake of atmospheric CO2, CH4 fluxes and radiative forcing (RF). Peatland lateral expansion was most rapid during periods with relatively cool and moist climate conditions. The peatlands showed distinct successional pathways, which were sometimes triggered by fires. Successional stages were partly reflected in C accumulation patterns. In some cases, variations in C accumulation rates coincided with autogenic changes in peat type and vegetation, although accumulation rates were also related to the large-scale Holocene climate phases. The warm and dry conditions during the Holocene Thermal Maximum (between c. 9000 and 5000 years ago) reduced C accumulation rates in the subarctic fen and the boreal peatland complex. Reconstructed CH4 emissions suggest that CH4 emissions played a major role in the total C budget of the peatlands throughout the Holocene. The RF models based on long term CO2 uptake and CH4 emissions showed that the two boreal peatlands had a warming effect on the atmosphere for the first 4000-7000 years after the start of peat accumulation, ...