Adaptive variation in Pinus ponderosa from Intermountain regions. I. Snake and Salmon River Basins

Genetic differentiation of 64 populations from central Idaho was studied in field, greenhouse and laboratory tests. Analyses of variables reflecting growth potential, phenology, morphology, cold hardiness and periodicity of shoot elongation revealed population differentiation for a variety of traits. Regression models related as much as 61 percent of the variance among populations to the elevation and geographic location of the seed source. Clinal patterns of adaptive variation provide the basis for developing seed transfer guidelines that will control maladaptation in reforestation. In central Idaho, for example, seed transfer should be limited to within 180 m of the seed source.