Fire history and forest age distribution of an unmanaged Picea abies dominated landscape

Abstract

We examined fire history and forest age distribution in an unmanaged, Picea-dominated landscape in the Paanajärvi wilderness, located in northeastern Fennoscandia and northwest Russia. Maximum tree age was determined in 61 systematically located study plots in an area of about 6600 ha. Fire scars were examined in living and dead trees in the study plots and elsewhere in the study area. Charcoal and pollen analyses of peat were performed on samples from two locations. Fires had been rare in the landscape. Nearly half of the dendrochronologically dated fires occurred in a distinct and short period, from 1859 to 1889, in the northeastern part of the area. This nonrandom occurrence of fires, together with the observed signs of past human influence, suggests an anthropogenic origin for the majority of the fires. The fact that 95% of the study area consisted of forests older than 120 years reflects the end of the occurrence of fires in the 1880s. Pollen analysis from the southwestern part of the study area showed that the site had been dominated by Picea at least during the last millennium. Charcoal analysis from the same site indicated that likely more than 1000 years had elapsed since the last fire. In general, the results suggest that the abundance of old forests, with the oldest trees being approximately 300 years of age, belongs to the natural state of a Picea-dominated landscape.Résumé : Nous avons étudié l'historique des feux et la distribution de l'âge des forêts dans un paysage non aménagé dominé par Picea dans la région sauvage de Paanajärvi située dans le nord-est de la Scandinavie et le nord-ouest de la Russie. L'âge maximum des arbres a été déterminé dans 61 placettes-échantillons systématiquement réparties dans une zone d'environ 6600 ha. Les cicatrices de feu ont été examinées sur les arbres vivants et les arbres morts dans les placetteséchantillons mais aussi ailleurs dans la zone d'étude. Des analyses du charbon de bois et du pollen présents dans la tourbe ont été réalisées sur des échantillons provenant de deux endroits. Les feux ont été rares dans le paysage. Près de la moitié des feux qui ont été datés au moyen de la dendrochronologie sont survenus dans une période de temps pré-cise et assez courte, soit de 1859 à 1889, dans la partie nord-est de la zone. Le fait que ces feux ne soient pas survenus au hasard, ainsi que la présence d'indices de l'influence humaine passée, indiquent que la majorité des feux seraient d'origine humaine. Le fait que 95 % de la zone d'étude soit couverte de forêts âgées de plus de 120 ans correspond à la fin de la période de récurrence des feux dans les années 1880. L'analyse du pollen provenant de la partie sud-ouest de la zone d'étude montre que le site a été dominé par Picea pendant le dernier millénaire. L'analyse du charbon de bois provenant du même endroit montre qu'il s'est probablement écoulé 1000 ans depuis le dernier feu. En général, les résultats indiquent que l'abondance de vieilles forêts, où les plus vieux arbres ont environ 300 ans, correspond à l'état natu...

National circumstances in the international circumboreal community

“…Other research has indicated that changes in human influence have resulted in changes in fire regimes. The results of a study by Wallenius et al (2005) revealed the non-random spatial and temporal nature of forest fires in an unmanaged area of Fennoscandia and northwest Russia, suggesting that much of the historical fire activity in this area was human-caused, and that a change in human behaviour had resulted in a change in fire regime in this area (in contrast to other theories that climate change or a change in fire suppression activity were causal agents of changes in fire regimes).…”

Spatial tree community structure in three stands across a forest succession gradient in northern boreal Fennoscandia

“…We visually cross-dated the tree-ring series (Yamaguchi 1991), using master chronologies from northern Fennoscandia (Aakala et al 2009;Wallenius et al 2010), and verified measurement quality statistically, using the COFECHA-program (Holmes 1983). Since P. abies-dominated boreal forest stands are prone to severe forest fires, we assumed the oldest verified tree age within a stand to represent the minimum time since the last stand-replacing fire (Wallenius et al 2005). We added five years to the year of the innermost ring, as a conservative estimate of the time it takes to reach the sampling height.…”

Past human population history affects current forest landscape structure of Vodlozero National Park, Northwest Russia

“…Therefore, the human impact is the most plausible factor behind this pattern. Boreal forests were actively used for slash and burn agriculture for centuries in eastern Fennoscandia (Heikinheimo 1915;Taavitsainen et al 1998;Orrman 2003;Chernyakova 2014b) which could led to the increased fire frequency in the forest landscape (Zackrisson 1977;Lehtonen et al 1996;Lehtonen and Kolström 2000;Pitkänen et al 2002;Wallenius et al 2005). In addition to slash and burn agriculture, the other modes of human activity can increase the frequency of unintended fires in the forests near the villages.…”

“…Heath forests of southern boreal zone were largely affected by slash and burn agriculture (Heikinheimo 1915), and even in the mid boreal zone, the use of fire in agriculture has increased the fire frequency in the forest landscape (Zackrisson 1977;Lehtonen et al 1996;Lehtonen and Kolström 2000;Pitkänen et al 2002;Wallenius et al 2005). The extremely high fire frequency of the 19th century was followed by the current very low fire frequency because of the end of slash and burn agriculture and active fire prevention which is still carried out (Pitkänen et al 2002).…”

“…Rouvinen and Kuuluvainen 2001;Rouvinen and Kouki 2002;Lindbladh et al 2003;Erikson et al 2005;Jönsson and Jonsson 2007;Josefsson et al 2010) and the studies of larger current natural forest landscapes of over thousand hectares are rare (but see Lilja and Kuuluvainen 2005;Wallenius et al 2005). Another reason may be the great effort which such studies demand.…”