Module 3 — Stand level components
of biodiversity
British Columbia
Ministry of Forests
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Module 3

Module 3C — Coarse woody debris
coarse woody debris drawing
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Learner outcomes



On completion of Part 3C, you will be understand the role that the stand level component — coarse woody debris — plays in forest biodiversity and you will be able to:

  1. Describe coarse woody debris

  2. Identify forest management applications for coarse woody debris
  1. Describe the role of coarse woody debris in forest biodiversity


General information about CWD


Define coarse woody debris

For more information

Coarse woody debris (CWD) consists of fallen trees, sloughing bolewood, and other woody material on the forest floor.

It is generally considered to be sound and rotting logs, stumps and branches greater than 10 cm in diameter that provide, among other things, habitat for plants, animals and insects, and a source of nutrients for soil development.

Maintaining CWD after harvesting is a critical element of managing for biodiversity.

In most cases, non-merchantable logs, breakages, short pieces, stumps, tops and branches left on the forest floor after harvesting provide the major source of CWD in managed stands. Ensuring that large pieces of CWD are maintained through several rotations is a significant forest management challenge.


icon Explain each of these reasons.

  CWD is important for three reasons:
  1. Nutrient cycling
  2. Seed beds
  3. Habitat for insects, small mammals, and amphibians




icon Are there other roles? If so, list them

CWD roles

CWD plays numerous functional roles in natural and managed forest and aquatic ecosystems, including:

  • Contributes to stand level structural diversity of old growth and mature forests

  • Provides feeding, breeding, and shelter substrate for many organisms (invertebrates, small mammals, amphibians) 

  • Provides habitat for many forest plants, animals, (both vertebrates and invertebrates), and microorganisms

  • Provides nutrients source and growing substrates for various bacteria and fungi (including beneficial mycorrhizal fungi), as well as saprophytic plants, lichens, and mosses that are important in decay, nitrogen production, and other nutrient and moisture cycling

  • Carbon storage

  • Erosion control

  • Buffered microclimates suitable for seedling establishment

  • Shelter and access routes for small mammals in periods of heavy snow cover

  • Serves as a refugium for organism after disturbance, and through its persistence across disturbances

  • Influences slope and stream geomorphology

  • Influences forest floor microtopography and microclimate

  • Contributes to nutrient and organic matter dynamics of forest ecosystems

  • Influences stream habitat quantity by dispersing stream energy, releasing nutrients, and creating gradual steps, gravel bars and pools for resident and spawning fish (Caza, 1993)

  • Shapes and stabilizes stream banks, and in aquatic habitats. It increases channel complexity and habitat quality by creating pools and riffles (disperse stream energy and create fish habitats).

  • In streams, CWD increases litterfall retention (up to 70%), which is then decomposed by stream organisms




See Selected Literature

In turn, CWD levels will be influenced by forest management objectives and practices, and site-specific conditions and operational constraints, (fuel/residue loading concerns, type of silvicultural system, harvesting method, site preparation, and slope and soil stability [Radcliffe et al., 1994]).

Log decomposition stages are shown in Figure 13.

  next Next: Maintaining CWD

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