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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.

Lichens were cultured by attaching a thallus fragment to a nylon monofilament loop with silicone sealer. Two effective methods for adjusting lichen mass to a standard moisture content were developed (the ‘reference-sample’ and ‘sacrificial’ methods). These corrections for moisture content allow detection of very small changes in dry mass without having to oven dry (and kill) all transplants. Average annual biomass growth rates for non-fragmenting species were typically between 5 and 30%. Annual biomass growth rates of healthy, vigorous individuals, as indicated by the 75th percentile, were mostly between 10 and 40%. Alectoria sarmentosa was prone to fragmentation despite the maintenance of healthy thalli. The other species can be ranked by biomass growth rates as follows: Evernia prunastri> Lobaria pulmonaria=Usnea longissima> Pseudocyphellaria rainierensis=Lobaria oregano.

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