Long-term effects of helicopter and ground-based skidding on site properties and stand growth in a tupelo–cypress wetland

Ground-based timber harvesting operations in forested wetlands have the potential to cause soil disturbances. Soil disturbances on upland sites have been linked to reduced site productivity, but the effects of such disturbances on the long-term site productivity of bottomland hardwoods is not well documented. In 1986, a long-term research project was established to compare the effects of helicopter and skidder timber harvesting on the regeneration, growth, and development of naturally regenerated water tupelo (Nyssa aquatica)–baldcypress (Taxodium distichum) stands. At stand age 16-years, both treatments have well-stocked, vigorously growing stands composed of coppice-regenerated water tupelo, Carolina ash (Fraxinus caroliniana), baldcypress, and seed-origin black willow (Salix nigra). Although both treatments are well stocked, the skidder treatment favored the establishment and growth of water tupelo, while the helicopter treatment had greater densities and growth rates for Carolina ash. Apparently, the initial effects of the skidder traffic puddled the soils and resulted in more reduced soil conditions, which favored the very flood tolerant water tupelo rather than the less flood tolerant species. Stand growth parameters suggest that both treatments will produce stands that will be similar to the previous stand in terms of species and volumes. Recovery in this area was speeded by annual inputs of nutrient rich sediment, the shrink-swell nature of the soil, and rapid growth of the coppice regeneration.