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Future productivity of lodgepole pine stands following mountain pine beetle outbreaks
Alfaro, René I.
As a natural agent of disturbance, mountain pine beetle (MPB) outbreaks play an important functional role in directing ecological processes and maintaining biological diversity of forest ecosystems (Roe & Amman 1970, Veblen et al. 1991). However, having infested 9.2 million hectares of lodgepole pine forests to date (BC Ministry of Forests and Range 2007) the current beetle outbreak is unprecedented in scale. As lodgepole pine comprises around one quarter of the provincial timber supply, socioeconomic impacts of this outbreak are enormous. A variety of silvicultural tools and management strategies can be used to reduce the effects of timber losses, the most important tool being salvage logging. In the short-term, adjusting harvest scheduling to remove standing beetle-killed trees can compensate some of the timber losses. However, due to market, operational, legal, and ecological constraints, the proportion of the beetle-killed forests that can be salvage-logged is limited. As the outbreak continues, and especially after its eventual collapse, forest managers will need to develop strategies to manage the large areas left unsalvaged. For this they will need to quantify the basic stand dynamics processes associated with MPB outbreaks, such as level of tree mortality by age class, post-outbreak stand growth, recruitment rates and species composition following MPB outbreaks. Currently, this information is scant and our ability to estimate the long-term impacts of beetle outbreaks on BC forests is, therefore, limited. Fundamental to achieving the goal of sustainable forest management in areas infested by MPB, are reliable decision support tools, such as stand and whole forest dynamics models that incorporate the impacts of beetle outbreaks into forecasts of future stand conditions and projections of future timber supply (Mitchell 1975, Mitchell & Cameron 1985, Goudie et al. 2005). However, we still lack the information necessary to reliably implement these tools in some forests, particularly uneven-aged lodgepole pine forests. This proposed research is aimed at understanding and quantifying how unsalvaged stands will develop following MPB attacks in the Cariboo region of central BC. For this we propose, in the first year of research, to re-measure a number of existing permanent plots in the Chilcotin Plateau, to determine past disturbance history of the area (fire and previous beetle outbreaks) and assess current beetle impacts. These plots are unique in the Province of BC, in that they have been maintained for 20 years (since 1988). In the second year we will project future stand development using the BC Ministry of Forests TASS model. In 1987, during the previous (1980s) MPB outbreak, the CFS established 10 plots in each of 30 stands in the Chilcotin Plateau, to determine beetle impacts. In 2001, 15 of these stands were re-measured for growth impacts, mortality, and succession following the 1980s MPB outbreak. Unfortunately, logging and wildfires eliminated the possibility of re-measuring the remaining stands. These stands are now undergoing yet another MPB outbreak. In this project we propose to re-measure all remaining plots (a 21-year re-measurement) and, using these data, estimate future growth of the residual stands and regeneration, and analyze and model the future stand structure and species composition of these stands. The stands to be studied are located in the heart of the current MPB outbreak, in the Chilcotin Plateau range, and consist of even-aged and uneven-aged, complex stands in the Sub Boreal Pine-Spruce (SBPS) and Interior Douglas-fir (IDF) BEC zones. Currently, there is a knowledge gap in our understanding succession and growth in beetle impacted areas, and there is uncertainty regarding the growth and release of advance regeneration in unsalvaged MPB-attacked stands (Griesbauer & Green 2006). To fill this gap, we will use the techniques of dendrochronology to develop in-depth stand histo ...
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