Understory vegetation response to post-tornado salvage logging

In an era of increasing natural disturbances, successful tree regeneration has grown more difficult to achieve. Disturbance notably alters forest microclimates, creating open canopy conditions that might promote growth of undesirable understory communities adept at outcompeting tree seedlings. Salvage logging, a common management response to disturbance, may further impede regeneration success. In 2013, a rare tornado in northcentral Maine, USA, and subsequent salvage operation created three clear ‘treatments’ for evaluation of post-disturbance understory regeneration: blowdown, blowdown followed by salvage logging and an undisturbed control. Ten years post tornado, we inventoried understory vegetation within each of these treatments. We used hemispherical photographs to characterize canopy openness and installed sensors to track temperature and soil moisture throughout a growing season. Results indicate distinct understory community differences among each of the treatments, with the salvage treatment supporting a higher richness and abundance of early successional, shade intolerant taxa, while the blowdown and control treatments were characterized by later successional, shade tolerant taxa. Abundance of conifer regeneration was notably lower in plots with high abundance of Rubus idaeus or Pteridium aquilinum. Ordination results suggest that canopy openness and surface temperature fluctuations were the primary factors associated with these compositional differences. This study furthers our understanding of the interactions among disturbance, microclimate, and understory communities, highlighting the need for increased consideration of long-term effects following salvage logging.