Salvage logging after windthrow alters microsite diversity, abundance and environment, but not vegetation

An increasing number of researchers propose that disturbance effects in forests are mediated through 'legacies', which are organisms or organically derived structures that persist after a disturbance. Much controversy currently surrounds the potential impact of post-disturbance salvage logging, in part, because of the potential for such actions to alter post-disturbance legacies and thus forest regeneration. Microsites (e.g. downed tree crowns, boles, stumps, treefall pits and mounds) created by natural disturbances are a subset of the broader concept of legacies, but the effect of windthrow + salvage logging on microsites and their environment and vegetation has not been previously examined. In a wind-damaged forest in western Tennessee, USA, we documented microsite diversity and abundance, environmental conditions, and initial vegetation regeneration in salvaged and unsalvaged areas. We found that salvaged areas had significantly greater variety of microsites, altered microsite abundance, higher soil temperature and greater canopy openness relative to unsalvaged areas. However, 2 years after the storm, herbaceous cover and species richness and tree seedling density and species richness did not differ between salvaged and unsalvaged areas. Soil moisture also was unaffected by salvaging. In contrast, environmental conditions and vegetation characteristics differed significantly among microsite types, with treefall mounds being warmer and drier than other microsites. This intermediate-severity wind disturbance, followed by moderate intensity of salvaging, created microsites that differed in environment and vegetation, and although the salvaging altered microsite diversity, abundances and conditions, the initial vegetation did not show detrimental effects of the salvage operations. We suggest that primary determinants of the consequences of salvaging after natural disturbance are the severity of the natural disturbance, and intensity of salvage operations. Detrimental effects of salvaging may accrue only if some combined severity threshold is exceeded.