Harvest and dispersal syndromes influence the probability of tree seedling establishment in the eastern United States

Abstract

AbstractAimThe goal of this work was to investigate the influence of disturbance, in particular tree harvesting, on seedling establishment rates both within and beyond the range extent of individual species. In addition, we considered how disturbances differentially affect seedling establishment depending on the dispersal syndromes and shade tolerance of species.LocationThis project covers the eastern forests of the USA.Time periodData for this project extend from 1996 to 2019.Major taxa studiedTree species of the eastern USA.MethodsWe used the US Forest Service's Forest Inventory and Analysis (FIA) data for tree species of the eastern USA to investigate the influence of disturbance, the dispersal mechanism and shade tolerance of species on the establishment of seedlings. We ran generalized linear models for seedling presence/absence and the number of seedlings as the response variables. Disturbance categories were no disturbance, natural disturbance, harvest, and both harvest and natural disturbance.ResultsThe probability of seedling establishment increased in response to harvest within FIA plots but not in response to natural disturbances. Harvest increased the probability of seedling presence the most for shade‐intolerant species; however, intermediately shade‐tolerant and ‐intolerant species also increased in harvested plots. Additionally, bird‐dispersed species had a higher probability of colonizing new plots outside their range, in comparison to mammal‐dispersed or wind‐dispersed tree species.Main conclusionsOur results suggest that stand competition is an important limiting factor for seedling establishment in the dense, secondary forests of the eastern USA. Harvesting creates sizeable gaps that promote seedling establishment and species turnover. Harvesting especially facilitates the establishment of tree species with bird dispersal outside of their range. Thus, timber harvesting can be a useful management tool when the goal is to assist range shifts for certain species. We recommend that future research should include harvested plots when looking for evidence of recent tree migration.