Of the 14.9 million ha of pine in BC of various ages, there are approximately 1.96 million ha of young pine (natural regeneration and managed plantations) in between the ages of 20-55 years. Over 1.1 million ha of these are over 80% pine. Within this inventory of young pine, over 1 million ha is between ages 20-35 years (MOFR 2005). These stands represent future harvests, habitat and forest structure. Many of these young stands are currently being impacted by the mountain pine beetle (MPB) and associated bark beetles (e.g. Ips pini). The risk to our future forest inventory from MPB is a major concern of forest industry and government alike. Approximately 8.5 million ha of mature pine were attacked by MPB in 2004, as represented in the 2005 Provincial Aerial Overview results (BCMOFR 2004, 2005) and it is estimated that number will increase about 1.5-fold as a result of the 2005 beetle flight. Assessments conducted in 2005 (Maclauchlan 2005, FSP Y072003) showed that close to 50% of young stands in the core area of the MPB outbreak had some level of 2004 MPB attack. Stands over 45 years of age that are spaced, or pruned, are generally not discriminated from mature stands by the MPB and are being attacked at the same frequency and intensity as adjacent mature stands (Maclauchlan 2005). Therefore the highest future risk is to stands younger than 45 years or of smaller diameter (<12 cm). Young or small diameter pine has often become a 'sink' for MPB during past outbreaks. A beetle 'sink' describes the phenomenon of MPB attacking and killing trees in stands that are not thought of as susceptible because of age or size, and generally few, or no brood result from these attacks. The decline of the South Okanagan MPB outbreak (1984-1992) was in part due to the MPB being pushed into these sub-optimal stands of very dense, small and often younger age pine (L. Maclauchlan personal observations). However, even if beetle production out of these young stands is minimal in this current outbreak, the local and landscape level conditions of this MPB outbreak are very different from anything recorded in the past. The beetle pressure, the size of the outbreak (>8.5 mill. ha) and the mixing and dispersal of beetles over the landscape is unprecedented. Attack levels in stands surveyed in 2005 ranged from <1% to >90%. This level of attack renders the stand NSR (non-satisfactorily restocked) and therefore must be scheduled for reforestation. Forest for Tomorrow (FFT) has initiated extensive reforestation plans for fire-killed and MPB-killed stands (primarily mature) but has not yet accounted for the potential mortality in young stands. In these stands, as little as 25% mortality (e.g. less than 700 sph live) (M. Madill, personal communication) would cause a stand to be classified as NSR. Given the MPB pressure and levels of attack observed in 2004 and 2005, this could occur over 2-3 years. As with mature stand risk (Safranyik et al. 2004; Shore and Safranyik 1992; Safranyik and Linton 1985; Safranyik and Jahren 1970) risk to young stands is highly dependent upon the status of adjacent stands or land. This status has been quantified in terms of beetle risk to the young stand (low-high levels of attack), temporal risk (e.g. whether the MPB population in the adjacent stand is low, static or declining) and if the young stand is adjacent to cutblocks, or other bare land (low risk) (Shore and Safranyik 1992; McGregor et al. 1981). Other trends that are becoming evident is the classic 'oldest and largest' first rule with the MPB, although the largest trees are not always the oldest in young treated stands. The geographic location is also a key factor. Fewer young stands have as yet been impacted by the MPB in the southern portion of the SIR (Southern Interior Region, e.g. south of Kamloops). The highest mortality to date is in the 'core outbreak area (Prince George, Vanderhoof, Quesnel and Central Cariboo Districts). It is imperative that forest managers, ...
Maclauchlan, Lorraine E., Rankin, Leo; Hodgkinson, R.S.; White, Ken. 2007. Integration of GIS analysis and field evaluation to identify young pine at risk to mountain pine beetle: Phase 1: Analysis of risk factors associated with ?when? MPB attacks young stands. Forest Investment Account (FIA) - Forest Science Program. Forest Investment Account Report. FIA2007MR436
Topic: FLNRORD Research Program
Keywords: Forest, Investment, Account, (FIA), Dendroctonus, Ponderosae, British, Columbia
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