Factors influencing occurrence and impacts of fires in northern European forests

Abstract

The return interval and number of fires vary, depending on the geographical location in interaction with climate, topography and amount of fuel. During recent decades, in northern Europe the number and severity of fires have been insignificant compared with Mediterranean region, in which fire return intervals may be 15-35 years, compared to the average of 60-120 years for boreal forests. This is partly due to the efficient system of fire protection in northern Europe, but is mainly due to the less favourable climate for fire and the smaller human impact on ignition of forest fires.The consequences of fire are related to both site and stand characteristics, site being the most important factor controlling the stability of stands. Dry sites being more flammable and likely to ignite are associated with high risk of fire. In northern Europe, due to the interaction between species and site, the role of species difference in risk of fire damage is not clear. In southern Europe, fire risk cannot be explained by differences between tree species. There, other vegetation (shrubs, etc.) is of major importance for the risk of fire.Management of forests can, to some degree, alter the risk and the occurrence of fire. In northern Europe, logging may have compensated for fire occurrence by decreasing the amount of fuel. In addition, forest roads act as fire-breaks and facilitate fire-fighting. On the contrary, in southern Europe the risk of fire has been found to increase because the traditional forest uses and management have decreased, which increases the accumulation of fuel. However, it is not yet possible to quantify and compare the effect of management in absolute terms.Currently, some tools, such as fire-risk indices, remote sensing and GIS-based techniques, are available for prediction of fire risk in some areas. For example, fire-risk indices are most suitable for areas, like northern Europe, which have a low fire risk. In high-risk areas, such as southern Europe, more sophisticated techniques are needed for assessment of the risk. In the future, assuming global warming at northern latitudes (2 × CO 2 climate), the risk of fire damage could also increase in northern Europe. Therefore, to allow the various locational and silvicultural factors to be assessed on the European level, an integrated risk model is needed.

The forest fire regime in Latvia during 1922–2014

“…Fires affect climate through the change of vegetation structure, surface albedo, and release of aerosols, thus creating a feedback loop (Bowman et al 2009;Bowman et al 2014). In northern Europe, studies have reported strong S-N gradients in the length of fire cycles (Päätalo 1998;Drobyshev et al 2012), likely reflecting forcing of diverse climatic systems on regional fire activity (Drobyshev et al 2012). In the northern part of Sweden, fire activity has been clearly related to variations in Atlantic sea surface temperatures, while in the southern part, this pattern is weakly apparent (Drobyshev et al 2016); hence, fire activity has regional specificity (Drobyshev et al 2012).…”

Estimating aboveground biomass of broadleaved woody plants in the understory of Florida Keys pine forests

“…Biomass and its distribution within forest ecosystems vary with field conditions, e.g., with time since the fire or with fire intensity. At the same time, accumulation of fuel loadings in forest stands is an important determinant of fire frequency and severity (Paatalo, 1998;Cochrane et al, 1999). Therefore, information regarding the nature and distribution of fuels in relation to time elapsed since last fire has been used to project how rapidly fires will spread, their intensity, and ultimately their ecological effects (Rothermel, 1972;Kauffman et al, 1994;Paatalo, 1998).…”

“…At the same time, accumulation of fuel loadings in forest stands is an important determinant of fire frequency and severity (Paatalo, 1998;Cochrane et al, 1999). Therefore, information regarding the nature and distribution of fuels in relation to time elapsed since last fire has been used to project how rapidly fires will spread, their intensity, and ultimately their ecological effects (Rothermel, 1972;Kauffman et al, 1994;Paatalo, 1998). Unlike some southeastern pine forests, where flammable fuels are concentrated on the forest floor and/or in a continuous graminoid layer (Snyder, 1991), most burnable fuels in Florida Keys stands of Pinus elliottii var.…”

Influence of Fuel Load Dynamics on Carbon Emission by Wildfires in the Clay Belt Boreal Landscape

“…Few studies have compared CWD dynamics in different cover types [69]. Differences in DWD dynamics between coniferous forests and TA forests may be induced by the lower pre-fire tree productivity (Figure 2) and the presence of woody debris with higher flammability [83][84][85][86] in coniferous forests.…”