Recent conceptual advances address forest response to multiple disturbances within a brief time period, providing an ideal framework for examining the consequences of natural disturbances followed by anthropogenic management activities. The combination of two or more disturbances in a short period may produce “ecological surprises,” and models predict a threshold of cumulative disturbance severity above which forest composition will be drastically altered and regeneration may be impaired. Salvage logging (the harvesting of timber after natural disturbances; also called “salvaging” or “sanitary logging”) is common, but there have been no tests of the manner in which salvaging after natural wind disturbance affects woody plant regeneration. Here we present findings from three years after a moderate‐severity wind disturbance in west‐central Tennessee, USA. We compare two unsalvaged sites and two sites that had intermediate‐intensity salvaging. Our approach demonstrates the calculation of cumulative severity measures, which combine natural windthrow severity and anthropogenic tree cutting and removal, on a plot‐by‐plot basis. Seedling/sapling density and species richness were not influenced by cumulative disturbance severity, but species diversity showed a marginal increase with increasing cumulative severity. The amount of compositional change (from pre‐disturbance trees to post‐disturbance seedlings/saplings) increased significantly with cumulative severity of disturbance but showed no evidence of thresholds within the severity range examined. Overall, few deleterious changes were evident in these sites. Moderate‐severity natural disturbances followed by moderate‐intensity salvaging may have little detrimental effect on forest regeneration and diversity in these systems; the ecological surprises and threshold compositional change are more likely after combinations of natural and anthropogenic disturbances that have a much greater cumulative severity.

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.

The risk of extreme events due to weather and climate change, such as winds of unprecedented magnitude, is predicted to increase throughout this century. Artificial ecosystems, such as coniferous plantation forests, can suffer irreversible deterioration due to even a slight change in environmental conditions. However, few studies have examined the effects of converting natural forests to plantations on their vulnerability to catastrophic winds. By modelling the 2004 windthrow event of Typhoon Songda in northern Japan using the random forest machine learning method, we answered two questions: do Abies plantation forests and natural mixed forests differ in their vulnerability to strong winds and how do winds, topography and forest structure affect their vulnerability. Our results show that Abies plantation forests are more vulnerable to catastrophic wind than natural mixed forests under most conditions. However, the windthrow process was common to both types of forests, and the behaviour of wind inside the forests may determine the windthrow probability. Future management options for adapting to climate change were proposed based on these findings, including modifications of plantation forest structure to reduce windthrow risk and reconversion of plantations to natural forests.