LB 32-271 - Gas exchange and water potential of five hardwood species along a transect from the middle of a 0.4 ha circular gaps to the surrounding forest in the Southern Appalachian Mountains in North Carolina

Hardwood forests in the Southern Appalachians of North Carolina harbor many important tree species. Clearcutting greatly reduces the species composition of these forests. This is because the light seed of tulip poplar (now identified as LITU) which has a rapid growth rate as well as red maple (ACRU), which rapidly grows via stump sprouts, both quickly populate the site and dominate shade-tolerant hardwood species including Northern red oak (QURU), Eastern white oak (QUAL), and hickory (CARYA), all valuable for wildlife mast and timber. Our hypothesis is that starting from the center of gap and then extending into the full forest will progressively increase the regeneration of QURU, QUAL, and CARYA. The silviculture system Femelschag is being tested in a hardwood forest near Asheville, NC. Three 0.4 ha circular gaps (each now considered a Block) were cut on three areas of the forest with transects including edge (0 m), gap (-15m), and forest (+15 m) each of which are now considered Locations. One seedling (1-4 years old) per species at each block/location was selected for study. One block was measured over three days in the last three weeks of July 2002. Pre-dawn water potential (Ψpd) was measured on all study seedlings in each block. Statistical significance is considered p ≤ 050. Starting at approximately 10:30 AM through 1:30 PM, A (net photosynthesis), gwv (stomatal conductance), and Ψ (water potential) were measured at each species/location repeatedly. There was no variation among blocks in any ecophysiogical trait because of frequent thunderstorms. Pre-dawn water potential across all species/locations/blocks were approximately 0.0 MPa. There were minor relationships between both A and gwv with Ψ. There were several instances where a species had the significantly highest gas exchange measurement on very disparate conditions. Our results do not support our hypothesis however as the work was all conducted under saturated conditions may had each species performing at their highest capacity.