Dendrochronological investigations of forest fire, tree ring growth and climate west of Puostijärvi lake, northern Sweden

Abstract

How trees respond to climatic factors such as temperature and precipitation is well documented but can be locally different when other factors play a part in the process. Forest fires have had a large influence in boreal zones around the world and in the boreal zone in Sweden where the study area between Överkalix and Övertorneå is located. The methods inherent to dendrochronology are adapted in this thesis to answer how climatic factors and forest fires influence tree growth and to build three chronologies. 26 samples were used to create a chronology without fire scars spanning the years 1352 - 1983 and a total of 9 samples for the fire scar chronology with documented fires spanning between the years 1567 - 1922. The use of TSAPWin and COFECHA softwares for measuring and dating the samples was implemented with further analyses using a Pearson correlation and a first difference estimator for climate correlation and superposed epoch analysis used in ring width and fire scar variance to examine changes in growth after and before a fire event. The resulting chronology without fire scars showed statistical detectable results while five fires had confirmed matching years dated. Running the statistical analyses presented no significant correlation, not against climatic factors or effected growth patterns in relation to fire event years. The results presented in this study does however show that more research in the field is necessary and that a multitude of factors could influence tree growth locally making it difficult to pinpoint a single limiting factor.