Recovery status of a tupelo-cypress wetland seven years after disturbance: silvicultural implications

  • Published source details Aust W.M., Schoenholtz S.H., Zabest T.W. & Szabo B.A. (1997) Recovery status of a tupelo-cypress wetland seven years after disturbance: silvicultural implications. Forest Ecology and Management, 90, 161-169.


This study is summarised as evidence for the following.

Action Category

Use low-impact methods to harvest vegetation: freshwater swamps

Action Link
Marsh and Swamp Conservation
  1. Use low-impact methods to harvest vegetation: freshwater swamps

    A controlled study in 1986–1993 in a freshwater swamp in Alabama, USA (Aust et al. 1997) reported that a plot where logs were extracted by helicopter only contained fewer plant species and less plant biomass seven years later than a plot where logs were also extracted by ground vehicles, but that both treatments had a similar overstory tree density, diameter and height. Unless specified, results summarized for this study are not based on assessments of statistical significance. After seven years, helicopter-extracted plots contained 28 plant species, compared to 31 in vehicle-extracted plots. Helicopter-extracted plots contained only 46,748 kg/m2 dry above-ground plant biomass (overstory: 41,373; understory: 173; ground: 5,202 kg/m2), compared to 65,979 kg/m2 in vehicle-extracted plots (overstory: 60,222; understory: 108; ground: 5,649 kg/m2). For overstory trees, there were no significant differences between treatments in density (helicopter: 3,539; vehicle: 3,829 trees/ha), average diameter (helicopter: 6.2; vehicle: 6.9 cm) or average height (helicopter: 7.6; vehicle: 7.5 m). The study also compared all of these metrics for individual species. The main difference was that the overstory of helicopter-extracted plots contained significantly more swamp ash Fraxinus caroliniana and significantly less water tupelo Nyssa aquatica than vehicle-extracted plots (true for biomass and density; see original paper for data and full results). Methods: In summer 1993, vegetation was surveyed in two plots in a swamp. Both plots had been clear-cut (all trees felled) in autumn 1986. In one plot, some of the cut logs were removed by helicopter. In the other plot, after removing some cut logs by helicopter, other logs were dragged around the plot with a cable skidder to simulate extraction by vehicle.

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