Alternative Silvicultural Techniques for European Sub-alpine and Montane Protection Forests:Managing for community protection, disturbance resistance and resiliency, and timber production

Harold Zald, Dept. Forest Science, OSU

Chamonix, France

Protection forest overview

•Protecting from what?•Protective functions•Resistance and resiliency•Protective attributes•Alternative silviculture

Protecting from What?•Protection from rockfall, avalanches, and debris flows

•Engineered mitigation is expensive!!!

•The role of forests in reducing rockfall increasingly appreciated

Protective functions, resistance, and resiliency

Stability of protection forests over time requires managing for both resistance and resilience to rockfall and avalanche

Direct-protection functionsdirectly protect people, buildings, and infrastructureagainst the impacts of natural hazards such as rockfalland avalanches

Site-protection functionsprotect the site a forest occupies against processessuch as soil erosion and debris flows

ResistanceThe ability of a protection forest to slow or dissipate the energy and matter generated in a rockfall or avalanche.

ResilienceThe ability to recover direct-protection resistance characteristics following a natural hazard (or other) disturbance event.

Protection forest attributes: Stem Density

Simulated rockfall patterns (rockfall accumulation in black)a) current forest, b) 50% stem reduction, c)100% stem reduction.

Dorren et al. 2004. Geomorphology

Increased stem densities increase resistance to rockfall and avalanches

Protection forest attributes:

•Increased stem diameters increase resistance to rockfall and avalanches

•However importance of diameter varies

•Long live crowns

Protection forest attributes: Forest Floor/Understory

•Regeneration (for resistance and resiliency)

•Large down wood

•Shrubs

•Ground structure (rocks)

Alternative Silvicultural Applications

Density/Size Management

Developmental Stage

Regeneration

Understory/Forest Floor Management

Silvicultural Application Layout

Landscape Considerations

Density, Diameters, and Developmental Stages

•Greater resistance at the cost of lower resilience Implication: manage for earlier developmental stages

•Especially important for older Norway spruce plantations

•Best balance between resistance and resilience may occur at what is roughly analogous to the understory reinitiation stage - at the stand level

Ott 1989 Schonenburger 2001. For. Eco. Man.

Regeneration

•Clumped planting•Coppice method when possible•Regeneration slits

Harvest Layout and Landscape Considerations

•Conserve forest floor structure

•Position harvest units with respect to hazards, areas to protect, and surround forests, non- forest vegetation, and any engineered mitigation structures

Dorren et al. 2004. For. Eco. Man.

When you look at these two forests, which is better for:•Timber production?•Protection function resistance?•Protection forest resilience?

Changing Objectives, Changing Perceptions