Effects of fire on ectomycorrhizal fungi in Fennoscandian boreal forests

Abstract

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-fi re adaptations, no succession of EM fungi following fi re is apparent after low intensity fi res, and only two EM fungal taxa exclusively fruit at post-fi re conditions. In this paper I review the present knowledge of effects of forest fi re 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 fi res 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 wildfi re. 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 wildfi re 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 fi res may be of signifi cance for yet unidentifi ed 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 wildfi res in temperate conifer forests differ considerably from those in boreal forests. Wildfi res in temperate conifer forests are typically high intensity stand-replacing fi res that cause a total combustion of organic layers. Subsequently, prefi re EM fungal communities are largely eradicated and a succession of post-fi re EM fungi is initiated.

Impact of fire on the macrofungal diversity in scrub jungles of south-west India

“…Some studies revealed that fruit body production in selected macrofungi will be stimulated by fire (Carpenter et al 1987; Duchesne & Weber 1993). According to Dahlberg (2002), some ectomycorrhizal fungi have adapted to low and high intensity of postfire conditions. Based on the traditional knowledge, the fire-impacted region yielded seven edible fungi against two in control region.…”

“…Pyrophylic (fire-dependent) fungi are cosmopolitan, often fruit in large numbers and valuable in ecosystem recovery and restoration (Robinson et al 2008; Bean et al 2009; Claridge et al 2009). According to Dahlberg (2002), in Swedish boreal forests, up to 40 species of pyrophylic fungi need postfire conditions for completion of their life cycles.…”

Benefit of permanent non-fire refugia for Lepidoptera conservation in fire-managed sites

“…In periodically burned landscapes such refugia offer persistent habitat diversity, as well as areas around unburned trees, logs, and surrounding litter where organisms averse to fire, such as specific spiders, ants, other arthropods, and fungi, are likely to persist (York 1999;Andrew et al 2000;Dahlberg 2002). When one management is dominant, establishment of areas consistently managed a different way adds beneficial diversity.…”

Post-fire, seasonal and annual dynamics of the ectomycorrhizal community in a Quercus ilex L. forest over a 3-year period

“…Many factors would influence the impact of fire on the ECM community, of which the intensity of fire could be important Dahlberg 2002;Grogan et al 2000). After a low-intensity fire, many trees survive, and the organic matter remains intact; in this situation, the effects of the fire on the ECM community are mostly small.…”