Forest Investment Account (FIA) - Forest Science Program
FIA Project M086024

    Mountain pine beetle impacts on young age class pine leading stands in the SBS biogeoclimatic zone
Project lead: Hawkins, Chris (University of Northern British Columbia)
Contributing Authors: Hawkins, Chris D.B.; Pousette, John; Runzer, Kyle; Rakochy, Patience
Subject: Forest Investment Account (FIA), British Columbia
Series: Forest Investment Account (FIA) - Forest Science Program
British Columbia’s lodgepole pine (Pinus contorta Dougl. Ex Loud. Var. latifolia Engelm.) forests are experiencing a mountain pine beetle (Dendroctonus ponderosae Hopkins) (MPB) epidemic. It is predicted that 80% of the susceptible pine (age class 5 and older) will be killed and the Prince George TSA AAC will fall below 75% of the pre – MPB AAC. The post beetle mid-term AAC is dependent on there being no attack in stands =60 years old (age classes 1, 2 and 3) and only 50% attack in age class 4. The Chief Forester has predicted a significant timber supply fall down in the mid-term (1). This prediction is based on the above attack assumptions as well as stands first attacked are first to the mill for processing and the attacked trees have a shelf life of 10 years (5 years for saw logs (13)). We have been assessing (sampling) the impact of MPB in young to mature (age classes 1 to 8) pine leading stands in the: southern portion of Prince George Forest District [SBS dw2, dw3, mk1, wk1, mw, and vk]; the south – central part of the Vanderhoof District [SBS dw2, dw3, mc2, and mc3], and the southeast portion of the Lakes TSA (SBS dk). This work is and has been supported by FSP – MPB projects Y061021, M065002, and CFS MPBI projects 8.23 and 8.59. We sampled 50 mature (age class 6 to 8) stands (303 plots) in 2004, 201 stands (1005 plots across all age classes) in 2005 and 140 stands (640 plots across all age classes) in 2006. An additional 10 stands will be sampled by the end of March 2007. More than 125 stands (600 plots), in the SBS dk, dw2, dw3, mc2, and mc3 will be re-measured by the end of March 2007. All re-sample data is combined with initial data to allow both temporal and spatial analysis. Initial findings show attack rates in older stands are at or above the predicted 80% level (2). Attack rates far exceed 80% when only pine is considered. From our observations, age class 4 stands have attack rates similar to the older mature stands: 80% rather than the assumed 50%. In 2005, pine leading age class 1 to 3 stands located in the southwest portion of the Prince George TSA had attack rates of approximately 10% in age class 1 and about 25 and 30% in age classes 2 and 3 respectively. A subset of the 2005 stands was re-measured in 2006. We found that re-sampled attack rates changed to 22, 24 and 49% in age classes 1 to 3 respectively. Clearly the MPB is more successful in young stands than previously thought: at the landscape level at least 25% of the largest trees have been attacked. Attack rates in stands first sampled in 2006 (Bowron and Willow drainages) were 20, 38 and 43% for age classes 1 to 3 respectively: considerably higher than that observed in the drier sub-zones to the west. Preliminary findings from young age classes indicate substantial attack rates in all younger age classes; however the variability among stands is large which makes management recommendations more difficult. Our findings are contrary to the published literature (3,4) and timber supply assumptions (5,6). The attack of younger age class stands will further exacerbate the mid-term timber supply fall down referred to by the Chief Forester (1,7). In addition to MPB mortality and attack, we have sampled: tree layer dbh (diameter at breast height) and height, regeneration height [species <1.4 m tall], advanced regeneration height and dbh [species =1.4 m in height and <7.5 cm at dbh], shrub, herb and moss cover, tree hierarchy (dominant, co-dominant, etc), and crown closure. Attack is generally focused on trees with a dbh =15 cm but about 10% of the trees between 7.5 and 10 cm have been successfully attacked. Regardless of age class, except in the SBS dk, many stands have a stocked regeneration layer. Characterizing stand dynamics and landscape patterns temporally and spatially across the affected area will identify the key variables (assumptions) which need to be incorporated into a viable up-to-date timber supply analyses in the central BC interior (Prince George Timber Supply Area). Furthermore, the data will allow us to describe i) residual stand structure after MPB attack, ii) regeneration in MPB affected stands in a range of SBS sub-zones, and iii) MPB attack levels in young (age class 1 to 3), transitional (age class 4) and mature (age classes =5) stands. Our preliminary findings indicate that regeneration and advanced regeneration differ by sub-zone and site series. As a result, when the mature layer is killed by the beetle, some stands may be satisfactorily stocked and others will not be stocked. The critical unknown is in which stand structures the regeneration will release. This is particularly important for the younger age class stands that are the ones most likely not to be logged (economically unviable). Given the limited resources available for post MPB restoration, knowing which stands in each sub-zone that will likely have adequate regeneration and release provides a ranking of the need for intervention in a stand. This will allow for allocation of fiscal resources in the most efficient fashion. The speed at which the regeneration component releases also has a significant impact on future timber supply, particularly the mid-term. As a result of the high levels of MPB activity observed in young pine stands, in 2007, we will continue to re-sample age classes 2 to 4 (older age class 1 in areas with extreme attack) (areas first sampled in 2005 and 2006 or re-sampled in 2006) in the SBS dk, mc2, mc3, dw2, dw3, mk1, wk1, mw, and vk in order to understand some temporal effects of MPB dynamics within these stands. There is a paucity of information on MPB dynamics in young age class pine leading stands. Collection of this data will also allow better parameterization of timber supply analysis in the Prince George and Lakes TSA and better management of attacked but unlogged stands. In 2007, we propose to sample young pine leading stands and some adjacent mature stands in the Salmon and Fraser River drainages and the Bear Lake area. This will further facilitate our understanding of MPB dynamics in young stands in the sub-boreal, improve timber supply analysis, assist restoration activities, and detail stand development projections in the Prince George TSA. The extent to which the MPB is attacking younger stands (age class 1 to 4) with smaller trees is a crucial component for: timber supply considerations, planning for restoration activities on unlogged stands, and determining and planning for social impacts on affected communities (Pers. Com. J. Snetsinger, BC Chief Forester, December 2004). Without the young stand data, plans to deal with these issues will not be complete and will potentially fail.


Executive Summary (99Kb)
MPB Workshop Presentation (0.9Mb)
Projected Pine Growth (Presentation) (2.7Mb)
Lodgepole Pine Stands After MPB Attack (Presentation) (5.5Mb)
Stand Dynamics (Presentation) (0.4Mb)
Summary of MPB Field Tour (16Kb)
Data Tables (65Kb)

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Updated August 16, 2010 

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