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Regeneration and growth following MPB-attack: synthesis of knowledge; a GYMP project
Hawkins, Chris D.B.
The lodgepole pine (Pinus contorta Dougl. Ex Loud. var. latifolia Engelm.) forests of British Columbia (BC) are currently experiencing the largest mountain pine beetle (Dendroctonus ponderosae Hopkins) (MPB) outbreak since the arrival of European settlers (Eng et al. 2005). The current infestation of lodgepole pine trees by the MPB has been estimated to have affected over 7 million hectares and killed nearly 600 million m3 of mature pine in British Columbia (BC). MPB mortality emulates a thinning from above. Forest changes will primarily be related to the MPB induced mortality (Hawkes et al. 2004, Stockdale et al. 2004) and abundance and condition of advanced regeneration (Heath and Alfaro 1990, Dale et al. 1998) or secondary structure (Coates et al. 2006). As attacked trees die and more light reaches the forest floor, advanced regeneration (Cole and Amman 1980, Waring and Pitman 1985) and understory vegetation (Stone and Wolfe 1996) should display enhanced growth rates. According to Thompson and Lewis (2007), release which results from sudden death of healthy canopy trees, as seen in the current MPB epidemic, should result in a more rapid and prolonged release response compared to release that occurs following slow death of canopy trees. There is no reason to believe that post MPB residual trees and secondary structure in the central BC interior will not release; however, the rates of release and subsequent stand dynamics are poorly understood (Veblen et al. 1991, Stockdale et al. 2004) and not documented. Through the use of dendroecological reconstruction, Alfaro et al. (2004) were able to show that in a period of 120 years 3 release events occurred in response to MPB attack, and these averaged 13.8 years in duration with 42.3 years in frequency between outbreak events. Response to release was similar for both pine and non pine species. It has been suggested that 25 ? 40% of MPB attacked stands will not be salvage logged (Pederson 2003). As a result, estimates of the amount of regeneration and rates of growth in stands following MPB attack (release) are critical for: (1) Forecasting the long term prospects of these stands; (2) Selecting stands for silvicultural treatments to improve yield; and (3) Forecasting impacts to hydrology, habitat, and vegetation types as a result of MPB attack. Following the most recent MPB epidemic, a number of research projects were initiated, in different areas of the northern and southern Interior of BC, to measure and model regeneration and growth following MPB attack (see project linkages). These projects collectively cover many of the Biogeoclimatic Ecological Classification (BEC) zones affected by MPB, as well as representing a geographical distribution of sampled sites. The research also covers a range of topics around regeneration and growth following MPB attack, including: (1) Estimating the number and types of regenerating trees based on residual overstory trees;(2) Modeling the light environments; and (3) Modeling recruitment and growth. For a number of these research projects, data collection is now being completed. Some continue with further measuring and monitoring beyond March 2008. There is a need to summarize the knowledge gathered by the many recent MPB research projects and identify the knowledge gaps on regeneration and growth following MPB attack. This information should be available to practitioners, managers, and researchers for: (1) use of research in management decisions; (2) identifying research needs; and (3) prioritizing further research in this area. Also, documentation on the data collected must be written, before this information is lost. We intend in part to achieve the above by holding a workshop and meeting where the proponents of these projects will bring colleagues up to date with their work
Report Number
Executive summary
Field tour notes - regeneration and growth following MPB attack
Summary of growth and yield workshop presentations

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