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Natural-Stand-Dynamics

  • Stand dynamics describe the processes of change over time in forest stand structure, including the disturbance (start and end).

For example: Forest burns down then regeneration then phase where the forest density increases then old growth

Terms and Definitions

What matters most in BC?

  • Fire
  • Wind
  • Insects

Disturbance Regime:

  • Describes the temporal and spatial characteristics of a disturbance agent, and its impact on the landscape.
    • Temporal Characteristics
    • Spatial
    • Impact
  • Frequency of stand-initiating events varies with ecosystem type
  • Return interval is key to stand development and landscape level heterogeneity

Stand Initiation

  • Growing space is available
  • Early pioneer species dominate
  • Trees establish until all growing space is occupied

Stem Exclusion

  • All growing space is in use
  • Competition among trees
  • No regeneration
  • Branch mortality - Living crown moves up
  • Number of trees declines due to mortality

Understory re-initiation

  • Overstory is less dense
  • Self-thinning occurs
  • Growing space becomes slowly available
  • Shade tolerant species regenerate and form a new understory

Old Growth:

  • Trees can grow large
  • Over time, trees in the overstory die and are replaced
  • Gap phase:
    • Mortality of old trees creates space for regeneration
  • Pioneer species are rare

Consequences for silviculture

  • Silviculture practice aims at imitating natural disturbances
    • Important for biodiversity and habitat quality
    • Natural stand dynamics automate processes with desirable outcomes, for example:
      • Branch mortality
      • Increased diversity and flexibility through stratification
  • Knowledge about how tree species can make use of the growing space is key
    • Silvics
    • Competitiveness
    • Facilitation

Key Takeaways:

  • Stand dynamics depend on the ecosystem with its species and disturbance regime
  • Over the long term, structurally rich, uneven-aged stands form when disturbance is rare
  • Disturbance regimes differ strongly across ecosystems
  • Trees compete for growing space
  • Knowledge about successional stage is key for developing silvicultural prescriptions that utilize natural processes for your objectives

Up Next: Silvics and Tree Growth