9407129 Nilsen Regulation of Seasonal and Spatial Water Use by R. maximum at Two Elevations at Coweeta (LTER) The understory of the Appalachian forest is dominated by two ericaceous shrubs Kalmia latifolia and Rhododendron maximum. In particular, R. maximum covers over half a million hectares of southern Appalachian forest. Dense thickets of this species, called "slicks", inhibit the growth of canopy trees. These dense growths are often close to streams making R. maximum a keystone species in the interface between terrestrial and aquatic ecosystems of the southern Appalachian mountains. Although R. maximum must have a significant impact on several ecosystem processes, the "role" of R. maximum in functions of the Appalachian forest have been only rarely studied. The influence of R. maximum on ecosystem hydrology may be one of the important impacts of this species on the Appalachian forest system. The objectives of this proposal are: 1. to determine the factors that regulate water use patterns in R. maximum; 2. to develop mathematical functions that predict water use patterns from environmental conditions; 3. to collect evidence for possible competition for water between R. maximum and an important canopy species. Experiments are designed to fit into the currently funded research program at the LTER site at Coweeta Hydrological Laboratory. Results from this proposal will clarify the importance of R. maximum in the ecosystem water budget for the regulation mechanisms therefore for R. maximum water use, and determine if competition for water between this important understory species and a canopy dominant species is likely. ***
