Peatland dynamics in response to past and potential future climate change : A regional modelling approach

• Main Author: Chaudhary, Nitin
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: Lund University, Faculty of Science, Department of Physical Geography and Ecosystem Science 2017
• Subjects: Earth and Related Environmental Sciences; Physical Geography; PEATLANDS; PERMAFROST; Carbon accumulation; Microtopography; LPJ-GUESS; Earth system models; Arctic; Bleue; Canada; Stordalen; Climate change; Northern Sweden; permafrost
• Online Access: https://lup.lub.lu.se/record/adfb11ee-7719-4337-9d03-4ccd03fbbef5; https://portal.research.lu.se/files/23561369/kappa.pdf

The majority of the northern peatlands developed during the Holocene as a result of a positive mass balance between net primary productivity (NPP) and heterotrophic decomposition rates. Over that time they have sequestered a huge amount of carbon in terrestrial ecosystems. A significant proportion of these areas also coincides with areas underlain with permafrost and shows a diverse range of peat accumulation patterns. Thus, for predicting and understanding the long-term evolution of peatland carbon stocks across the pan-Arctic, mechanistic representations of both peatland and permafrost dynamics are needed in the modelling framework. In this thesis, a novel implementation of dynamic multi-layer peatland and permafrost dynamics in the individual- and patch- based dynamic vegetation and ecosystem model (LPJ-GUESS) is described. The major emphasis of this work goes into enhancing the current understanding of the processes involved in the long-term peat accumulation and its internal dynamics, including how these systems are influenced by small-scale heterogeneity, vegetation dynamics and interactions with underlying permafrost. A simple two-dimensional microtopographical (2-DMT) model was also developed to address the established hypotheses concerning stability, behaviour and transformation of these microstructures and the effects of this small-scale heterogeneity on the coupled dynamics of vegetation, hydrology and peat accumulation. LPJ-GUESS was calibrated and validated using data from a mire in Stordalen, northern Sweden, and evaluated using data from multiple sites in Scandinavia and from Mer Bleue, Canada. It was subsequently applied across the pan-Arctic to advance the existing knowledge on carbon accumulation rates at different spatial and temporal scales, and also to demonstrate the potential implications of current warming on these climate sensitive ecosystems. Both of the models developed in this thesis performed satisfactorily when confronted with experimental data.LPJ-GUESS is quite robust in capturing ...