Paleo-fires and climate changes in northern European boreal forests during the Holocene

• Main Author: Magne, Gwenaël
• Other Authors: Montpellier, Ali, Ahmed Adam, Gandouin, Emmanuel
• Format: Thesis
• Language: French
• Published: 2019
• Subjects: Forêt boréale; Paléo-feux; Paléoclimatologie; Charbons lacustres; Chironomes subfossiles; Dendrochronologie; Boreal forest; Paleo-Fires; Paleoclimatology; Lacustrine charcoals; Subfossil chironomids; Dendrochronology; envir; geo; Fennoscandian; Lapland
• Online Access: http://www.theses.fr/2019MONTG068

Boreal forest ecosystems represent almost 30% of the world forest area. These regions characterized by a complex forest mosaic are mainly structured by climate (temperature and precipitations) and fire regime. The predictive ability of forest fires is essential to mitigate their impacts on forest ecosystem dynamics, considering related ecological and social-economic aspects. Under global warming (IPCC, 2014), changes in climatically-driven fire regime (frequency and severity) are expected, which could represent a potential threat to boreal ecosystems. Consequently, it is necessary to better investigate the link between fire and climate in order to apprehend the natural variability of ecological processes. But before looking at future changes with the use of models, it is essential to understand the changes in the past with palaeoecological proxy. Paleoecological studies use time series of physical or chemical properties of paleontological, geological and glaciological records, thus allowing understanding of climatic variability even in the absence of direct meteorological observations. With this study, different methods were used to reconstruct the paleo-fires history (lacustrine charcoals and dendrochronology) and past climates (subfossil chironomids and pollens) in order to study the fire-climate link in Northern Europe during Holocene. Firstly, he was shown here that it was possible to detect surface fires in Fennoscandian boreal forests from sedimentary records. Climate change in Lapland has also been reconstructed over the last 9500 years using chironomid and pollen inferred-temperatures. These results were compared with the local fire history to study the link between fire dynamics and climate oscillations. The data resulting from the charcoal analysis indicate an increase in fire frequency since 3500 cal. BP. This dynamic seems to be linked to climate changes, as evidenced by the temperatures decrease observed during the past 4000 years. The colder and wetter climatic and environmental conditions have ...