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Purpose:

The purpose of this on-line course is to introduce participants to the concepts and tools necessary for assessing windthrow hazard and developing prescriptions to reduce windthrow damage to opening boundaries and reserve trees or groups within cutblocks and within riparian management areas.

The increased use of partial cutting silvicultural systems has generated widespread interest in windthrow management. This on-line course introduces participants to the concepts and tools necessary for assessing windthrow hazard and developing prescriptions to reduce windthow damage to opening boundaries and reserve trees or groups within cutblocks and within riparian management areas. Course revisions include incorporation of new research results on tree responses to windloading, windflow within small openings and uniformly thinned stands, GIS-based techniques for building empirical models and mapping windthrow risk at the landscape scale, and windfirming techniques.

Target Audiences:

This on-line course is intended for government, industry and consulting practitioners who design, implement, supervise or audit development plans, silviculture prescriptions, logging plans, harvesting and stand tending operations.

Learners should understand and have experience with the development planning and silviculture prescription process including the assessment of soil properties, ecological site series and stand structure. Participants should be comfortable with the integration of site information with integrated resource managment objectives to produce stand management objectives.


Background:

Windthrow is complex and may appear random at first glance. Windthrow researchers break down this complexity by separating damage caused by endemic and catastrophic winds, and by evaluating the role of environmental factors separately.

The relative hazard assessment method presented here was developed for this workshop and uses environmental indicators with which managers are familiar. It has been adopted as the basis for the FS 712 Field Cards.

It uses an ecological/physiological model of windfirmness rather than a mechanistic model. The underlying premise is that trees can adapt to endemic peak winds, and that lack of windfirmness results from some site/stand limitation (see Mitchell, 1998 for details).

The environmental factors which contribute to endemic windthrow risk can be broadly grouped into topographic exposure, soil and stand properties. These factors are integrated to yield an estimate of 'biophysical hazard.'

Each component hazard (soils/topographic/stand) is assessed by asking a 'diagnostic' question (e.g., for soil hazard: 'is root anchorage restricted?'). 'Windthrow risk' is the combination of biophysical hazard and 'treatment risk.' Treatment risk refers to the change in windloading on residual trees caused by a particular treatment.

Treatments which result in major increases in wind loading on residual trees are high risk. Both assessment of biophysical hazard and treatment risk require an estimate of the damaging wind direction(s). Historic windthrow patterns are useful indicators of damaging wind direction and site influences.

Course Limitations:

Windthrow results from complex interactions of climate, site and management factors. While substantial progress has been made in developing predictive and management tools in recent years, these tools need to be tested and refined in different field locations throughout the province.

This course aims to provide learners with a basic understanding of windthrow concepts and evaluation methods, to bring them up to date on management techniques, and give them a systematic framework for making observations.

Following completion of the on-line course it will be necessary for participants to gain local experience with the tools introduced here through a process of assessment, experimentation and feedback.


Link to the Windthrow Handbook


Feedback:

Feedback from participants in previous workshop sessions has contributed greatly to the course revisions. The Ministry of Forests would appreciate comments from participants that would help to improve the on-line course.

Please forward your responses for material and course improvements to:

Forests.ForestPracticesBranchOffice@gems3.gov.bc.ca

 
Forest Renewal BC / Forest Service BC
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