Lesson 1: Windthrow and Forest Practices
In this lesson, participants will:
- To create awareness about the need for windthrow assessment and
management to achieve forest management objectives.
This lesson contains 5 pages. It starts with a review of windthrow
assessment and management. Links are provided to the relevant sources
for best practices. New forest practices that increase the need for
windthrow management are highlighted. The shift in emphasis from windthrow
salvage to windthrow management is presented.
Windthrow is a natural disturbance agent in British Columbia forests.
Windthrow can impact integrated management prescriptions that depend
on maintenance of residual trees within or adjacent to harvested areas.
Post-harvest windthrow can reduce the effectiveness of prescriptions
for riparian and biological reserves, visual quality and partial cutting.
In addition, salvaging windthrow can disrupt harvest planning.
Traditional methods of managing windthrow included locating block boundaries
to reduce windthrow and progressively salvaging windthrow in damaged
areas. The role of windthrow as a natural disturbance agent is recognized
and when windthrown areas are salvaged, retention of some structural
features is important.
Increasing emphasis on non-timber objectives makes windthrow management
more challenging. Smaller blocks with more complex boundaries, partial
cuts and reserve areas increase the number of trees at risk, and limit
a manager's ability to locate boundaries in windfirm locations. Pre-harvest
windthrow assessment procedures and new techniques such as feathering
and topping/top-pruning have been developed to assist managers.
Windthrow is a natural disturbance agent in BC's forests but can impact
integrated management prescriptions which depend on maintenance of residual
trees within or adjacent to harvested areas. Post-harvest windthrow
can reduce the effectiveness of prescriptions for riparian and biological
reserves, visual quality and partial cutting. Salvaging windthrow disrupts
The traditional methods of windthrow management were location of block
boundaries to reduce windthrow, and progressive salvage of damaged areas.
The Forest Practices Code (FPC) still provides flexibility for salvaging
windthrow, but requires enhanced prediction and management. The role
of windthrow as a natural disturbance agent is recognized and when windthrown
areas are salvaged, retention of some structural features is desired.
Current best management practices contain guidelines for the protection
of riparian and gully areas and biological diversity. This requires
windthrow assessments in specific circumstances. New management practices
make windthrow management more challenging. Smaller blocks with more
complex boundaries, partial cuts, and reserve areas increase the number
of trees at risk, and limit a manager's ability to locate boundaries
in windfirm locations. Pre-harvest windthrow assessment procedures and
new techniques such as feathering and topping/top-pruning have been
developed to assist managers.
Windthrow Management Guidance
Page 2 - Windthrow Best Practices
(Refer to the Silvicultural
Systems Handbook, Silvicultural
Systems Guidebook and the Biodiversity
- Windthrow needs to be recorded, evaluated and managed.
- Windthrow is a natural disturbance agent and as such, it periodically
occurs. As a result, flexibility to address salvage should be included
- Variation from cutblock size limits can be planned as required to
address windthrow risks.
- Harvesting adjacent to non-greened up stands, where it is necessary
to salvage windthrow, is allowed.
Best practices should include:
- a statement of windthrow management objectives
- consideration of windthrow risk
- inclusion of strategies to minimize and recover windthrow
- identification and evaluation of windthrow risk
- integration of windthrow risk into choice of silvicultural system.
Windthrow is a natural ecological process. Salvage should not compromise
site objectives. Plan cutblocks so that windthrow risk to wildlife patches
Page 3 - Management and Assessment Guidebooks
- The Riparian
Management Area Guidebook describes riparian assessment procedures
and best management practices by stream class.
- Reduction of wind damage in reserve zones is a major function of
- An assessment of windthrow risk is required in order to determine
which of the Best Management Practices is appropriate, and if necessary
to document your reasons for requesting RMA modifications.
- Crown modification treatments may be used in reserve zones. Removal
of windthrown trees must be as specified in an approved plan.
- The Gully
Assessment Procedures Guidebook [Acrobat PDF Format] describes
gully assessment procedures and management strategies.
- Windfirm boundaries must be designed if standing trees are left
in gullies. Where windthrow risk negates leaving standing trees, place
large woody debris (LWD) across the channel.
- The Mapping
and Assessing Terrain Stability Guidebook describes terrain
- Windthrow should be assessed during field work, and adequate protective
buffers should be left for deferred areas.
Page 4 - Windthrow Management Challenges
The new practices which are required or encouraged make windthrow management
more challenging by:
- requiring more within-block residual patches and individual trees
- increasing the ratio of edge to harvested area with smaller blocks
- requiring placement of treed reserves adjacent to riparian areas
- limiting the use of natural timber types or topographic changes
To respond to this challenge, managers must:
- be more observant and systematic in assessing windthrow risk
- be realistic about the likely outcome of prescriptions
- be more creative in designing prescriptions to reduce damage
- recognize that some windthrow in reserves may be non-harmful or
even beneficial, and to that end, include in prescription documents
a statement of what level of windthrow may be acceptable.