Forest Service BC
Forest Renewal BC
 

Lesson 1: Windthrow and Forest Practices

Learning Objectives

Home Page

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.

 

Background

Background Page

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 harvest planning.

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 Guidebook)

  • 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 during planning.
  • 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 is minimized.

 

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 management zones.
  • 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 assessment procedures.
  • 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 and gullies
  • limiting the use of natural timber types or topographic changes for boundaries.

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.