article id 551,
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                        Review article
                    
        
                                    
                                    
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                            Fire, the primary natural disturbance factor in Fennoscandian boreal  forests, is considered to have exerted major selection pressure on most  boreal forest organisms. However, recent studies show that few  ectomycorrhizal (EM) fungi appear to have evolved post-fire adaptations,  no succession of EM fungi following fire is apparent after low  intensity fires, and only two EM fungal taxa exclusively fruit at  post-fire conditions. In this paper I review the present knowledge of  effects of forest fire on EM fungal communities in Fennscandian boreal  forests, put into perspective by a comparison from other parts of the  world. Characteristically, these boreal forests consist of less than a  handful of tree species, e.g. Scots pine and Norway spruce, while the  below ground communities of EM fungi is impressively species rich with  presently more than 700 known taxa. Commonly, forest fires in  Fennoscandia have been of low intensity, with a considerable portion of  the trees surviving and the organic humus layer partly escaping  combustion. Hence, EM fungi appear to largely have evolved under  conditions characterised by a more or less continuous presence of their  hosts. In fact, the composition of EM fungi within a forest appear be  more variable due to spatial variation than due to wildfire. However, in  areas with high intensity burns and high tree mortality, most EM fungi  may locally be killed. Thus, the legacy of EM fungi following wildfire  depends on the survival of trees, which determine the potential for  mycorrhizal growth, and the combustion and heating of the organic soil,  which directly correlate to mortality of mycorrhizas. The questions if  and to what degree fires may be of significance for yet unidentified  spatiotemporal dynamics of EM fungal populations and communities are  discussed. Recent experiments indicate a few EM fungi are favoured by  high intensity burn conditions whereas others disappear. The  consequences of wildfires in temperate conifer forests differ  considerably from those in boreal forests. Wildfires in temperate  conifer forests are typically high intensity stand-replacing fires that  cause a total combustion of organic layers. Subsequently, pre-fire EM  fungal communities are largely eradicated and a succession of post-fire  EM fungi is initiated.
                        
                
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                            Dahlberg,
                            Department of Forest Mycology and Pathology, Swedish University of Agricultural Sciences, P.O. Box 7026, SE-750 07 Uppsala, Sweden
                                                        E-mail:
                                                            anders.dahlberg@artdata.slu.se