ABSTRACT
Abies amabilis occurred only within the infestation, patchily and in small numbers. At the margin, the trees were small; larger trees occurred centripetally. This chapter discusses the developmental mechanisms of a forest in which a fungal pathogen and fire are major mortality factors. It shows how these mortality factors interact with the dominant tree species and physical factors to bring about different pathways of succession. The chapter describes how diversity and dominance among the trees are governed by these interacting factors and speculate about adaptiveness of indirect effects among species. According to the “intermediate disturbance hypothesis,” density-independent mortality at intermediate frequencies creates a mosaic of patches of biotic assemblages at various stages of succession such that, overall, maximum diversity is achieved. The root-rotting fungus, Phellinus weirri Gilbertson, grows radially outward, vegetatively, from points of initial establishment, into old-growth stands dominated by mountain hemlock, Tsuqa mertensiana Carr.
