DRAINAGE EFFECTS ON PLANT DIVERSITY AND PRODUCTIVITY IN LOBLOLLY-PINE (PINUS-TAEDA L) PLANTATIONS ON WET FLATS

Silvicultural practices are under increased scrutiny with respect to environmental impacts and intensive forestry is often cited as a contributing factor in the decline of biodiversity. However, there are few studies which evaluate the long-term impact of forest operations on plant diversity and production. The objective of this project was to determine the rotation age effects of three site preparation methods on plant diversity and productivity in wet pine flat plantations. The study area consisted of three wetland sites in the coastal plain of Virginia, Treatments were originally established in 1969 to study the effects of site preparation on loblolly pine (Pinus taeda) growth. The three site preparation treatments applied were: chop and burn, bedding between windrows (windrow-bedding), and secondary ditching. This study was conducted in 1991 when stands were near rotation age (22 years). Plant diversity was lowest and total biomass highest on the windrow-bedding treatment. Windrow-bedding appeared to increase pine growth by providing seedlings with more available soil volume and by reducing the vegetative regeneration of hardwoods and shrubs, thereby decreasing diversity. Secondary ditching increased pine growth by lowering water table levels, but had little effect on plant diversity.