Fire in boreal forests : climatic influences on the number and sizes of fires in recent Canadian forests and the size-area relationship in a Swedish site over the last 800 years

To assess if the fire regimes in Sweden before the strong human intervention are comparable to the recent Canadian fire regime I compared two datasets of fire numbers. A likeness could be found when comparing the Swedish and Canadian fire regimes, but due to the differences in study area (Canada: the whole state; Sweden 608km2) and time span (Canada: 41 years, Sweden: 800 years), no significant result could be determined. The effective fire size (definition p. 27) were calculated for the four forest types in Canada (coniferous, broadleaf, mixed and transitional), a significant difference in the effective fire size is present when assessing the broadleafed and the coniferous forests with the other forest types. The weather is often used to predict the fire danger, using fire indices such as the Nesterov fire index. In this analysis the correlations between the daily weather and the number of fires and the fire size were assessed over Canada. No relationship between the fire size and the weather was detected. An envelope pattern was assessed, in which the weather limits the maximum size of the fires but has no effect on the minimum size. This is most probably due to a number of additional factors limiting the spread of the fires (e.g. fire barriers). A GLM regression model was carried out to assess if a more significant result was detected when not using a linear correlation for the correlation between the burnt area and the fire indices, but no good correlation could be found. To test whether large scale climate pattern influence the fire pattern, a correlation was carried out between the teleconnections NAO, PNA, TNH, PT, AO, ENSO and the effective fire size, standard mean fire size, number of fires and total burnt area per year. A significant correlation was found between the standard mean fire size and the teleconnections NAO and TNH. When assessing the whole of Canada there is no correlation between the teleconnections in the northern Hemisphere and the effective fires size, number of fires and total burnt area. Compared to other areas (e.g. Africa), the link between fires and large scale weather conditions is rather weak due to the randomness in the ignition pattern, which cannot be assessed using the available climate data.