Bulkley Valley Research Centre - Science in the Public Interest

Year 1 - Regeneration and Stand Structure Following Mountain Pine Beetle Infestation in the Sub-boreal Spruce Zone

Project Reference Number: 2005-08

Project Status: Complete

Led by: Dave Coates, PhD, Research Silviculturist, Ministry of Forests and Range, Smithers

Erin Hall, Assistant Research Silviculturist, Ministry of Forests and Range, Smithers; Jacqueline Prior, Smithers; Tlell Glover, Smithers

Funder: Forest Investment Account - Forest Science Program

Due to the overwhelming magnitude of the Mountain Pine Beetle (MPB) epidemic, management emphasis has shifted from efforts to control the epidemic to efforts to mitigate its impact on communities and the environment. The Allowable Annual Cut has been increased in most management units which may lead to a fall-down in timber supply in the medium to long term. It is likely that significant areas of infested forest will never be salvaged due to the large area that is impacted. Forest managers must now make decisions about which stands should be salvaged, which should be left to regenerate naturally, and which stands may require rehabilitation.

Managers are using a variety of modelling tools to assist with these decisions, to predict the long-term consequences of the beetle infestation, and to explore possible management responses to it. These modelling efforts face two barriers: incomplete data on regeneration and stand structure following Mountain Pine Beetle, and models are not available for these ecosystems to predict growth and yield in complex stands.

The mountain pine beetle outbreak is leaving residual stand structures consisting of scattered or clumped surviving lodgepole pine trees, interior spruce and subalpine fir of different sizes and ages, and patches of assorted hardwood species. As many of the heavily hit stands (especially the remote ones) will never be salvaged, the future dynamics of these stands and their ability to contribute to the timber supply is largely unknown. There is little or no data on how these complex, unmanaged stands will regenerate. Where forest managers do harvest stands following MPB, they are frequently leaving behind significant amounts of in-stand structure, in order to mitigate the possible environmental impacts of salvage operations, and to mimic the stand structures that would follow a natural disturbance. The regeneration in these complex managed stands is not well understood.

Existing forest growth models (e.g. TASS/TIPSY) were developed for contemporary forest management; largely even-aged stands with little or no in-stand structure; they were not designed to deal with the complex stands that will regenerate after Mountain Pine Beetle. In contrast, SORTIE is specifically designed to simulate the development of irregular multi-species stands (Coates et al. 2003).

This project will prepare a comprehensive data set that describes stand structures and regeneration found following pine beetle attack, across diverse site types, from one to ten years following attack, and across several biogeoclimatic subzones in the north-central Interior. The data will be collected so that it can be applied in various modelling environments, including further development of SORTIE. This dataset will be used to refine tree recruitment models for use within SORTIE.

The objectives of this project are to:

1. Quantify tree seedling recruitment across the full range of stand types affected by MPB. Two critical factors affecting recruitment success will be assessed: abundance of parent trees and seedbed substrate favourability.

2. Develop, test and parameterize non-spatial recruitment models for MPB damaged forests that can be incorporated into stand and landscape dynamics models.

3. Determine the relative importance of long-distance versus local dispersal.

Related Reports

Publication Date Report Title Authors
2006 Regeneration and Stand Structure following Mountain Pine Beetle infestation in the sub-boreal spruce zone Dave Coates and Erin Hall