%0 Research article
%T Tree mortality agents in pristine Norway spruce forests in northern Fennoscandia
%A Lännenpää, Antti
%A Aakala, Tuomas
%A Kauhanen, Heikki
%A Kuuluvainen, Timo
%D 2008
%J Silva Fennica
%V 42
%N 2
%R doi:10.14214/sf.468
%U https://silvafennica.fi/article/468
%X We examined tree mortality agents in pristine old Norway spruce (Picea  abies (L.) Karst.) forests in northern Finland and northwestern Russia.  The data was collected on nine 40 m   400 m transects. The primary  mortality agents of recently dead trees were recorded and their  frequencies were calculated. The pattern of tree growth prior to death  was studied based on increment core samples and compared with the growth  of healthy dominant trees. Of all recently dead trees, 72% could be  associated with a primary mortality agent. In both study areas the most  common primary mortality agent was a Coniophora (Mérat) DC. -genus  fungi, which was found on average in 33% of trees sampled. The fungi  Phellinus chrysoloma (Fr.) Don and Onnia leporina (Fr.) H. Jahn as  mortality agents were more common in the Finnish area compared to the  Russian area. Analysis on the growth patterns indicated weak differences  between different pathogens’ influence on prior-to-death growth of  trees, so that fungi rotting the whole tree decreased tree growth more  rapidly than fungi rotting only the heart wood. The results demonstrated  that in old Norway spruce forests of northern Fennoscandia the most  common primary tree mortality agents were wood rotting fungi, which  weaken the mechanical stability of tree stems until they fall due to  snow or wind, which should be considered only as secondary mortality  agents. It is evident that tree death in pristine forest typically  results from a long-lasting process involving both biotic and abiotic  factors.