The latitude-elevation relationship for spruce-fir forest and treeline along the Appalachian mountain chain

Spruce-fir forests extend along the Appalachian Mountains of eastern North America from 35° to 49° N. This montane vegetation differs from boreal spruce-fir forest in that it is dominated by Picea rubens, has a higher vascular species richness, has wind, rather than fire, dominated dynamics, and has a mean annual temperature above 2 °C. Using field reconnaissance, remote sensing, and literature review we described and modeled the latitude-elevation relationship for Appalachian spruce-fir. The elevation of the sprucefir/deciduous forest ecotone decreases from 1,680 m at 35° N to 150 m at 49° N, while the elevation of treeline (spruce-fir/tundra ecotone) decreases from 1,480 m at 44° N to 550 m at 55° N. Linear regressions gave latitude-elevation relationships of –100 m/l^o Latitude for the spruce-fir/deciduous forest ecotone and –83 m/l^o Latitude for treeline. These values compare to literature reports of –54 to –230 m/l^o Latitude and are most similar to values reported from eastern Asia. The latitude-elevation relationship for eman July temperature ( –94 to –121 m/l^o Latitude) was more similar to the slopes of these ecotones than is the slope for mean annual temperature ( –170 to –220 m/l^o Latitude). The spruce-fir/deciduous forest ecotone was correlated with a mean July temperature of approximately 17 °C. Treeline was correlated with a mean July temperature of approximately 13 °C.