Conservation value of the early stage of succession in western U.S. forests

Background/Question/Methods

The early stage of succession on forest sites has received increasing attention from scientists and forest managers in the last decade.  This emphasis is partly due to the current rarity (relative to historical conditions) of naturally-structured examples, despite their potentially disproportionate contribution to the maintenance of biodiversity and other values.  How do the variety of conditions found in this stage contribute to biodiversity and ecosystem function in the western USA?  What species rely on them for at least part of their requirements or life cycle?  What types of early seral forest ecosystems (ESFEs) are found in western US forests, and how can their characteristics be incorporated into management strategies and silviculture?  The peer-reviewed literature, state and federal species conservation lists, and other relevant sources are evaluated to produce a synoptic understanding of ESFEs in the western USA. 

Results/Conclusions

ESFEs provide habitat for a wide diversity of plants (such as many important flowering and fruiting plants, including members of the Compositae, Salicaceae, Ericaceae), invertebrates (including many Coleoptera and Lepidoptera), mammals (including game animals and large carnivores), birds (passerines, raptors), bryophytes, and many other organisms.  A substantial proportion of the organisms on state and federal conservation or protection lists use early-seral habitat for some or all of their life cycle.  Functional attributes of early-seral habitat in the western U.S. include abundant (but variable) down woody debris and snags, spatially and temporally variable conifer regeneration, a period of broadleaf tree/shrub abundance, and high diversity of vascular plants (including ecologically and culturally important taxa such as Vaccinium).  Case studies are drawn from early seral habitats created by high severity fire, windstorm, snow avalanche, and volcanic eruption, all of which have been studied in western U.S. forests.  Incorporation of the characteristics of naturally occurring ESFEs into silviculture in western forests will involve recognition of differences between traditional timber harvest methods and natural disturbance in terms of in spatial scale and pattern, biological legacies, and regeneration strategies.  ESFEs with complex structure and high diversity, whether created by natural disturbance or via deliberate silvicultural treatments, are necessary elements in western forest landscapes of the 21st century for the maintenance of biodiversity and many other values.