Forest Investment Account (FIA) - Forest Science Program
FIA Project M075010

    Development of Residual Trees and Regeneration Following Mountain Pine Beetle Attack in Thinned Lodgepole Pine Stands
Project lead: Brockley, Rob
Contributing Authors: Brockley, Robert P.; Bealle Statland, Catherine A.; van Thienen, Frank J.; Staffeldt, Peter
Imprint: [BC] : B.C. Ministry of Forests and Range, 2007
Subject: Forest Investment Account (FIA), Dendroctonus Ponderosae, British Columbia
Series: Forest Investment Account (FIA) - Forest Science Program
By 2004, approximately seven million hectares of forests had been attacked by the mountain pine beetle (MPB) in British Columbia, representing about 40% of the area of susceptible pine (Eng et al. 2005). The annual volume of pine killed by the MPB is currently projected to peak in 2006, when 90 million m3 of merchantable wood may be lost in a single season. Significant pine mortality will continue until at least 2015, by which time 80% of the susceptible pine may have been killed or harvested (Eng et al. 2005). Older, mature lodgepole pine is most susceptible to attack by the MPB (Safranyik et al. 1974). However recent surveys by the proponent and others (Mitchell 2005) indicate that younger, smaller diameter lodgepole pine are also being attacked during the current epidemic. Previous studies have reported that thinning may reduce the susceptibility of mature pine stands to attack by endemic population levels of the MPB, either by increasing tree vigour or by altering stand microclimate (Mitchell et al. 1983; Waring and Pitman 1985; Amman et al. 1988; Whitehead and Russo 2005). However, thinned mature stands are apparently less successful at withstanding pressure from epidemic beetle populations (Whitehead and Russo 2005). The success of 'beetle proofing' in younger lodgepole pine stands has not been well documented, either at endemic or epidemic beetle population levels. Despite valiant salvage efforts, a large portion of the beetle-killed wood will not be harvested due to a variety of economic, management and environmental issues. Current estimates of provincial-scale non-recovered losses of dead pine by 2024 vary from 300 million m3 to 700 million m3 (Eng et al. 2005). Because young lodgepole pine stands contain little, if any, merchantable timber, there is little likelihood that salvage harvesting operations will be undertaken in them. For areas within the current harvesting land base, it is important that the productivity of unharvested, beetle-infected stands is maintained or rehabilitated as quickly as possible. The condition of the residual stand will depend on the proportion of pine in the stand, the percentage of pine mortality, and the abundance and condition of other species in the overstory and understory (Mitchell 2005). Regeneration success will largely depend on the amount and condition of non-pine species in the understory and the number of stand dead trees influencing light levels (Coates and Hall 2005). Mixed-species stands, and pine-dominant stands with an understory of non-pine species will likely recover quickly after MPB attack and will provide a reasonable yield without management intervention (Coates and Hall 2005). However, in pine-dominant stands with no advanced regeneration of other species, planting may be required to ensure successful regeneration. Coates and Hall (2005) modelled the light environment under MPB-attacked stands, and found that standing dead trees created low light levels for an extended period of time (until snags begin to fall in large numbers) and resulted in high levels of mortality in lodgepole pine natural regeneration. However, the post-attack health and growth of the residual overstory in thinned lodgepole pine stands, and the subsequent establishment and development of the pine and non-pine understory, has not been documented. Also, the fall down rate of dead trees under climatic conditions in the B.C. interior has not been well documented (Coates and Hall 2005), especially in thinned stands. In Oregon, Mitchell and Preisler (1998) found that 50% of the MPB-killed trees were on the ground after 8 years and 90% were down after 14 years. Beginning in 1982, a series of long-term thinning experiments (EP 922) were established by the B.C. Ministry of Forests, Forest Science Program to document the growth and yield impacts of a wide range of post-thinning stand densities in early- and mid-rotation, fire- and harvest-origin lodgepole pine stands in the B.C. interior. A total of 11 lodgepole pine installations are distributed among four biogeoclimatic (BEC) zones (IDF, MS, SBPS, SBS). Stand ages ranged from 7 to 60 years old at the time of trial establishment. The field installations test 4 or 5 post-thinning densities (500 to 3000 stems per hectare) plus an unthinned control. Each of the treatments is replicated two or three times at each of the study sites. A full description of the EP 922 study, including preliminary results from the 11 lodgepole pine installations, is provided in Johnstone and van Thienen (2004). In the early fall of 2005, several of the lodgepole pine EP 922 field installations were visited to determine whether they had been attacked by the MPB. During these visits, it was confirmed that a large percentage of the trees within treatment plots at several of the study sites had been attacked by the MPB in the summer of 2005 ('green attack'). The current ages of attacked stands range from 28 to 79 years. We believe the damaged EP 922 field installations provide an excellent opportunity to document post-attack stand dynamics in unsalvaged, thinned, pine-dominant lodgepole pine stands in the B.C. interior. We propose to document the pattern and progression of attack, mortality, and fall down rate of overstory trees, and the growth and development of surviving residual trees, in all of the thinned and control plots at two EP 922 study sites. We will also quantify, characterize, and measure the advance regeneration that exists at the time of beetle attack and the subsequent ingress and development of natural regeneration following attack
Related projects:  FSP_M086010


Executive Summary (90Kb)
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Updated August 16, 2010 

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