Northern peatlands are terrestrial ecosystems that provide specialized habitats in which biomass production exceeds decomposition, resulting in accumulation of organic matter. Understanding what factors drive species changes in future climate conditions in these systems is of high importance since this has the potential to affect ecosystem functioning and biodiversity, and by extension carbon sequestration. In ecology, a common method for investigating species’ relationships with climate variation, linked with spatial information, is species distribution modelling (SDM). This method typically uses information about current climate conditions tied to locations of species occurrences, forecasting the effects of change on future geographic distributions based on the implicit assumption that temporal variation can be substituted by contemporary spatial variation. 

This assumption might not be met for several reasons, namely (1) species changes often occur over much longer time-scales than the ones involved in contemporary ecology, and therefore (2) responses to climatic changes are time-lagged. Incorporating paleo-records of actual (past) changes in species distributions and climate conditions therefore provides a much more direct way to model species responses to climate change. In this project, a combination of methods from the fields of paleoecology and ecology were employed to create a novel approach to explore species distribution changes over time in boreal peatlands. This was done by first reconstructing the vegetation of two proximal peatlands (Store Mosse and Dala Mosse bogs; Paper I and III) in south-central Sweden, followed by statistical modeling of the species data and climatic parameters over time (obtained from independent paleoclimate data; Paper II and III), creating Temporal Paleo-Species Distribution Models (Temporal Paleo-SDMs). 

Paper I identifies factors driving species changes in Store Mosse bog based on internal (successional steps and biotic interactions) and external (climatic) processes. This study tests the assumption that climate has been the main driver of species change by producing a high-resolution postglacial vegetation reconstruction using macrofossil analysis, which is assessed against a set of independent proxy records representing changes in local and regional hydrology, nutrient input, and temperature. Paper II uses the same high-resolution plant macrofossil dataset from Store Mosse and pairs this with independent information about local and regional climate conditions, nutrient input and fire incidence during the same period to create the first Temporal Paleo-SDM and thereby assess the relationships between bog species and climate variability over time (reaching ~10 000 cal yr BP). Paper III tests the repeatability of the Temporal Paleo-SDM method by applying it to a new high-resolution species dataset from Dala Mosse, using the same climate parameters as in Paper II. This thesis bridges across paleoecology and ecology and shows the power of interdisciplinary collaborations and demonstrates the useful contributions they can make in future peatland research.