JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org. This content downloaded from 128.235.251.160 on Sun, Abstract. Mature Pinus contorta var. latifolia in the Bitterroot watershed of western Montana bear either predominantly serotinous cones (cone scales sealed by a resin bond and requiring a heat treatment for opening) or nonserotinous cones. This study investigated the extent to which amongstand variation in serotiny could be explained by environmental variables, estimated fire frequency, and the nature of the stand-initiating disturbance. The frequency distribution of serotiny at the stand level was bimodal, with peaks near 25 and 75% serotinous cones. Stand-level serotiny was not related to measured environmental variables and was only weakly related to estimated fire frequency. In contrast, much of the among-stand variation in serotiny could be explained by the nature of the standinitiating disturbance, with a predominance of serotinous trees in stands that had originated from stand-replacing burs and of nonserotinous trees in those that had originated from disturbances not related to fire. The disturbance regime is highly variable in time and space, and this variability, coupled with gene flow, is an important factor maintaining the polymorphism of cone type in stands.

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Mature serotinous and nonserotinous trees of Pinus contorta Dougl. var. latifolia Engelm. in the Bitterroot Watershed of western Montana do not differ in most life-history characteristics (reproductive or vegetative). No differences between trees of the two cone types were found in height, basal area, basal area growth rates over the lives of the trees, or crown ratio. Cone number, weights of individual cones and seeds, and estimates of reproductive effort were similar in serotinous and non-serotinous trees. Reproductive characteristics were either independent of tree age, or related similarly in trees of the two cone types. Nonserotinous trees may, however, have more seeds per cone than serotinous trees. This difference in seed numbers may be adaptive if serotinous trees invest relatively heavily in cone materials to protect seeds (which are retained in cones for many years), while nonserotinous trees (which shed seeds each year) invest relatively heavily in seeds. Trees of the two cone types differ mainly in the particular types of disturbance favoring their regeneration, but they often grow in the same stands where there are similar selective pressures on most aspects of their biology. Gene flow between them probably homogenizes all but those differences maintained by strong selective pressures.

His research has focused primarily on the ecology, stand development, and silviculture of young coniferous forests of the Intermountain and Northern Rocky Mountain West.