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 (Princ ...
Hawkins, Chris D.B., Pousette, John; Runzer, Kyle; Rakochy, Patience. 2008. Mountain pine beetle impacts on young age class pine leading stands in the SBS biogeoclimatic zone. Forest Investment Account (FIA) - Forest Science Program. Forest Investment Account Report. FIA2008MR209
Topic: FLNRORD Research Program
Keywords: Forest, Investment, Account, (FIA), British, Columbia
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