VEGETATION, BIOMASS, AND NITROGEN POOLS IN A SPRUCE-FIR FOREST OF THEGREAT-SMOKY-MOUNTAINS-NATIONAL-PARK

Unlike most forests, Picea rubens-Abies fraseri forests of the Great S moky Mountains appear to be saturated with nitrogen (N). However, stud ies of N cycling in these forests have been carried out only in a few small plots. To expand these data to a landscape scale, studies of N d ynamics were initiated in 1991 in an unlogged 17.4 ha watershed. An in itial phase of these studies, presented here, was the estimation of ov erstory species composition, biomass, and standing N pools, and their spatial distributions, in that watershed. Picea comprised most live ba sal area and biomass and showed no obviously unusual mortality or heal th symptoms. Abies, although formerly abundant, was a minor overstory component, consisting mostly of small individuals at the highest eleva tions. Most Abies have been killed by an exotic insect pest, Adelges p iceae. Biomass of Betula alleghaniensis was high on low-elevation east -facing slopes near streams. Picea contained 71% of the live overstory N, while Abies contained less than 2%. Although Picea foliage compris ed only 6% of live biomass, 37% of the total N content was in Picea ne edles. Overall, some species distributions reflect well-known landscap e patterns (e.g., increasing Abies importance with elevation); distrib utions of other species (e.g., Picea and Betula) reflect smaller-scale topographic and possibly disturbance-oriented patterns. The watershed is large enough to encompass vegetation patterns at several spatial s cales, all of which will influence N storage and dynamics.