Zobel, Donald B. 1975. Local variation in intergrading Abies grandis-Abies concolor populations in the central Oregon Cascades. 3: Timing of growth and stomatal characteristics in relation to environment. Botanical Gazette. 136(1): 63-71.
Temperature, humidity, and timing of growth were observed for a population of Abies grandis saplingsand three populations intermediate between A. grandis and A. concolor. The typical A. grandis population,which experienced the greatest moisture stress, had a more favorable temperature regime and less evapora-tive stress than populations on the other sites and began growth earlier. Two intermediate populationseast of the Cascades, which never experienced severe plant moisture stress, grew in a cooler environmentwith drier air and started growth later. A third intermediate population experienced both high moisturestress and cool temperatures. For the typical A. grandis population, daily and seasonal stomata] closurein summer appears to be necessary to prevent fatal desiccation, but assimilation lost due to stomatal closurecan probably be made up during the mild weather of other seasons. East-slope intermediate populations,without severe moisture stress, maintain open stomata, which would maximize assimilation during theshort growing season; this is possible due to abundant soil moisture. The third intermediate population,in a cool habitat where soil water is limited, probably maximizes assimilation early in the season by main-taining open stomata but closes them more in late season to avoid fatal water deficits. Large numbers ofadaxial stomata, characteristic of A. concolor and some intermediate populations, may provide an advantagein habitats where the season suitable for assimilation is short.