Spatial aspects of structural complexity in old-growth forests

Abstract

Old-growth forests typically have complex structures, including heterogeneous spatial arrangements as well as a diversity of individual structures. Two aspects of this spatial complexity are discussed and illustrated: (1) vertical distribution of foliage, often apparent as multiple layers; and (2) horizontal heterogeneity, often evident as canopy gaps and dense reproduction patches. Shifts in mortality processes from competitive-based mortality in young stands to agent-based mortality (i.e., insects, diseases, and wind) in older stands play an important part in the development of structural heterogeneity. Old temperate forests can be viewed as fine-scale structural mosaics in which all stand development processes are simultaneously present within the stand. An additional definition of forest stand that incorporates the entire structural mosaic of old-growth is needed.