Effects of post‐windthrow salvage logging on microsites, plant composition and regeneration

AbstractQuestions: How does windthrow influence plant diversity and composition aswell as regeneration and microsite characteristics? What are the consequencesofpost-windthrowsalvageloggingonthesekeyattributes?Location:Easternblackspruce–mossforest,Quebec,Canada.Methods:Atotalof92plotsweresampled,eachwitharadiusof11.28 m;49ofthese plots were salvaged while 43 were unsalvaged. Regeneration density,plantdiversityandseedbedswerecharacterized.Wetestedtheeffectofmicroto-pography and windthrow severity on species richness and Shannon diversityindex for salvaged and unsalvaged windthrows using a mixed model. Partialredundancyanalysis(RDA)determinedwhichenvironmentalandstandcharac-teristicsweremostimportantinexplainingdifferencesinplantspeciesandforestfloortypesamongthetreatments.Theeffectsof treatments(salvaged and unsal-vagedwindthrows),microtopographyattributes,windthrowseverityandregen-eration species on seedling and sapling abundance were tested using a linearmixedmodel.Results:Salvagedwindthrow,withalargeproportionofskidtrails,deadmossesand Sphagnum, had a lower degree of seedbed heterogeneity. Also, some under-storey species present in the unsalvaged ecosystem were absent from the sal-vaged windthrow. Sphagnum and other moss species were clearly associatedwith the unsalvaged treatment. White birches were positively associated withmoundmicrotopographyintheunsalvagedwindthrow.Conclusion: From an ecosystem-based forest management perspective, naturalpost-windthrow understorey conditions and microsite heterogeneity can be inpart maintained in salvaged cut blocks by incorporating retention patches thatinclude downed and standing dead wood and living trees of diverse sizes. Thesestepsshouldfavourplantregenerationandaugmentdiversityforsalvageloggingafterwinddisturbance.IntroductionIn many parts of the world, major disturbance episodesoften lead to salvage logging (often called sanitary loggingin Europe; Lindenmayer et al. 2004, 2008). Functionally,salvage logging can be distinguished from other harvestoperations in that, with salvaging after natural distur-bance, the ecosystem is subjected to two sequential distur-bances within a short period (Lindenmayer et al. 2008).Peterson & Leach (2008) suggest that multiple disturbanceimpacts need to be understood on the basis of cumulativeseverity. Indeed, recent conceptual advances (e.g. the cuspmodel of Frelich & Reich 1999; the three-axis model ofRoberts 2004, 2007) have begun to address the potentialfor multiple disturbances to change the trajectory of com-munity development, sometimes in undesirable directions(Paine et al. 1998). Because of the potential for thecombined severity of natural disturbance followed bysalvaging to yield unwanted ‘ecological surprises’ (Paineet al. 1998), guidelines are needed for the planning of