Abies grandis, Taxus brevifolia, Thuja plicata, or any combination of these may dominate old-growth mesic forests of the Bitterroot Canyons, western Montana. Similar sites need not develop similar, relatively stable forests. This is shown by (i) anomalous distributional patterns of tree species, (ii) broad overlap of tree species abundance in environmental space (shown by ordination and discriminant analysis of stands in environmental space), and (iii) weak or undetectable correspondence of species × stand and site factor × stand matrices (multiple regressions of compositional dissimilarity against environmental differences; also, canonical correlation and Mantel tests). Since a one-to-one mapping from site factors to species composition in old-growth vegetation is a fundamental tenet for applications of the climax concept, caution is warranted where the concept is to be applied within a narrow range of site factors or to insular communities.

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Abstract. Conventional levels of organization in ecology can be hierarchically ordered, but there is not necessarily a time or space scale‐dependent difference between the classes: cell, organism, population, community, ecosystem, landscape, biome and biosphere. The physical processes that ecological systems must obey are strictly scaled in time and space, but communities or ecosystems may be either large or small. Conventional levels of organization are not scale‐dependent, but are criteria for telling foreground from background, or the object from its context. We erect a scheme that separates scale‐ordered levels from the conventional levels of organization. By comparing landscapes, communities and ecosystems all at the same scale, we find that communities and ecosystems do not map onto places on the landscape. Rather, communities and ecosystems are wave interference patterns between processes and organisms interfering with and accomodating to each other, even though they occur at different scales on the landscape, and so have different periodicities in their waved behavior. Population members are usually commensurately scaled and so do not generally interact to give interference patterns. Populations are therefore tangible, oratleastcan be assigned a location at an instant in time.

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