Adaptation and Dimorphism in Eastern Hemlock, Tsuga canadensis (L.) Carr
Kessell SR. 1979. Adaptation and Dimorphism in Eastern Hemlock, Tsuga canadensis (L.) Carr. The American Naturalist. 113(3):333-350
The habitat distribution of T. canadensis along environmental gradients in New England is notably bimodal, for it is found in abundance in mesophytic ravines, draws, and stream bottoms, and on more xerophytic exposed slopes, but is rare or absent at intermediate habitat. This paper reports studies which attempt to test this dimorphism hypothesis by quantifying (1) the habitat distribution of the species, (2) correlations between radial growth rates and macroclimatic variation, (3) sensitivity of the populations to climatic and topographic variation, and (4) gross morphological variations. This work was conducted in eight major geographical areas throughout T. canadensis' range, including western Massachusetts, the eastern edge of the White Mountains in western Maine, the Allegheny Mountains of West Virginia, the Great Smoky Mountains of Tennessee, the southern Blue Ridge of western North Carolina, the Cumberland Mountains of Kentucky, the Cumberland Plateau of northern Alabama, and areas of disjunct populations in central Indiana.