Forest Science Program

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The ecological role of coarse woody debris: an overview of the ecological importance of CWD in BC forests

Author(s) or contact(s): V. Stevens
Source: Forest Science Program
Subject: Ecosystems
Series: Working Paper
Other details:  Published 1997. Hardcopy is available.


The approach taken by the Forest Practices Code Biodiversity Guidebook is that given our incomplete knowledge of the quantity and identification of species in the ecosystems of B.C., biodiversity is more likely to be sustained if managed forests are made to resemble those forests created by the activities of natural disturbance agents such as fire, wind, insects, and disease. There is wide realization that the preservation of species and the ecological functions that link them must take place both inside and outside of reserves and that it is more efficient than a species-by-species conservation effort (see Walker 1994). This paper describes what is known about the contribution to ecosystems of large pieces of dead down wood. Much of this information was compiled by Harmon et al. (1986).

The living parts of a natural forest can be viewed as having two important phases--the building phase during which available elements are assembled into structures we know as plants and animals, and the deconstruction phase during which these structures are disassembled into pieces available for rebuilding. We call these the living and decaying parts of the whole life-and-death cycle; however, both the living and decaying processes involve living organisms. One of the roles of the growing organisms is to build structure, while one of the roles of the decay organisms is to break down structure. Both phases are essential to the ecological processes that have evolved in forests. These processes include the life cycles of vertebrates and invertebrates (wildlife), fungi and bacteria, and the strategies used by plant structures to accumulate nutrients. All living organisms in forests have finite life spans after which they become part of the decaying portion of the ecosystem. Soft-bodied organisms and small plant structures generally decay rapidly and provide a quick turnover of nutrients, an addition to the forest floor, and/or a meal for forest wildlife. Large woody material contains very significant stores of carbon and energy and is the foundation of an important forest food web. This large material usually decays more slowly and therefore provides a more steady input of energy and nutrients and longer-lasting structures. For example, approximately half of the time that a mature Douglas-fir tree is in an ecosystem, it is dead wood. This paper describes the ecological role of the larger, down pieces of wood in both the living and decaying processes in the forest. These pieces are referred to as coarse woody debris (CWD).

Keywords: ecosystems, biodiversity, coarse woody debris

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Updated November 05, 2009