Environmental factors affecting the montane range of red spruce
Red spruce (Picea rubens Sarg.) is a dominant tree species in regions having cool-temperate rainforest climates. These areas extend from the upper elevations of the Appalachians to the northeastern parts of Maine and New Brunswick and are characterized by perhumid moisture regimes and low potential evapotranspiration rates. Within these regions, the occurrence of red spruce is further modified by additional factors, giving it a unique distribution when compared with otherwise sympatric species. This paper examines some of the major components which define the range of red spruce in the montane spruce-fir forests of the Appalachian mountains. Several experiments were conducted to examine the extent to which temperature extremes and mist presence and chemistry affect the physiology and biochemistry of montane red spruce. Various aspects of the trees biology are discussed in relation to its range. High temperature effects were examined directly by raising temperatures in small cuvettes. Branch sized environmental exclosures were developed to examine the affect of cloudwater and air chemistry on mature, montane trees. Pruning experiments were used to explore the consequences of injury to branch development. In summary, the lower elevational and latitudinal boundaries for red spruce occur at the 27$\sp\circ$C mean summer maximum isotherm. The results of the cuvette heating study support this observation, as the trees experience poor carbon gain above 30$\sp\circ$C. The northern and upper elevational boundaries occur where the mean winter low is 40$\sp\circ$C. Pests, pathogens and competition probably have not greatly influenced the range of red spruce. In particular, the species' shade tolerance and strong historical presence in hardwood forests suggest that competition has not played a role. In the montane and coastal regions, the frequent occurrence of clouds or fogs does not appear to be vital based on the data collected. This interpretation is, however, limited to the effect of cloudwater interception. Cloud chemistry is important to the trees' physiology. The presence of acidic cloudwater alters the pigment content of shoots and affects winter hardiness and susceptibility to winter injury. Selective pruning indicated that injuries affecting buds had the most serious consequences for branch architecture.
Vann, David Reid, "Environmental factors affecting the montane range of red spruce" (1993). Dissertations available from ProQuest. AAI9321493.