Forest Investment Account (FIA) - Forest Science Program
FIA Project Y091188

    The release of secondary stand structure in immature and mature pine stands following MPB attack
 
Project lead: Hawkins, Chris (University of Northern British Columbia)
Contributing Authors: Hawkins, Chris D.B.; Balliet, Nicole; Runzer, Kyle
Subject: Forest Investment Account (FIA), British Columbia
Series: Forest Investment Account (FIA) - Forest Science Program
Description:
The lodgepole pine (Pinus contorta Dougl. Ex Loud. var. latifolia Engelm.) forests of British Columbia (BC) are currently experiencing the largest mountain pine beetle (Dendroctonus ponderosae Hopkins) (MPB) outbreak since the arrival of European settlers (Eng et al. 2005). It is predicted that by the end of the epidemic 80% of the susceptible (mature, >80 years old) pine will have been killed. Timber supply analysis conducted by the British Columbia Ministry of Forests and Range (MFR) predicts that the mid-term timber supply in the Prince George timber supply area (TSA) will have fallen from a pre MPB AAC (allowable annual cut) of 9.1 million m3 to about 6.9 million m3 35 years from today (Eng et al. 2005, Pousette and Hawkins 2006, Pousette 2006). The post MPB epidemic AAC is based on several timber supply modeling assumptions 1) oldest attacked stands are harvested first, 2) mature stands have attack rates of about 80 % while transitional aged stands (61-80 years old) will have attack rates of about 50 %, 3) there is no attack in immature stands (=60 years old), 4) there is a regeneration delay of 15 years in areas not logged, and 5) product shelf life is 15 years with 5 years for saw logs (Eng et al. 2004, 2005).

It appears that 61 – 80 year old stands are being attacked at rates similar to those observed in mature stands (>80 years old) and that immature pine leading stands (=60 years old) are also being attacked at significant levels (MacLauchlan 2006, Hawkins unpublished data). MPB induced mortality in immature and transitional aged stands will cause a significant reduction (2.2 million m3) in the merchantable volume available for the mid-term timber supply in Prince George TSA (Eng et al. 2005, Pousette and Hawkins 2006). The current cut level is expected to be reduced within 5 years and will continue to be reduced until the projected mid-term AAC is reached in approximately 35 years. Given the hypothesized drop in future AAC by timber supply models, regeneration or secondary structure (Coates et al. 2006) in immature age classes and unlogged mature age classes has the potential to contribute to the mid-term timber supply and reduce the effect of the mid-term timber supply fall down (Rakochy 2005).

MPB mortality emulates a thinning from above. Forest changes will primarily be related to the MPB induced mortality (Hawkes et al. 2004, Stockdale et al. 2004) and abundance and condition of advanced regeneration or secondary structure (Heath and Alfaro 1990, Dale et al. 1998). As attacked trees die and more light reaches the forest floor, advanced regeneration (Cole and Amman 1980, Waring and Pitman 1985) and understory vegetation (Stone and Wolfe 1996) should display enhanced growth rates. According to Thompson et al. (2007), release which results from sudden death of healthy canopy trees, as seen in the current MPB epidemic, should result in a more rapid and prolonged release response compared to release that occurs following slow death of canopy trees.

It is essential for forest managers to consider the contribution that release of advanced regeneration can make towards meeting the mid-term timber supply in MPB killed stands (Veblen et al. 1991; Archibald and Arnup, 1993), especially as it is anticipated that
25 - 40% of the 582 million m3 of MPB affected wood (post 2006 flight) will not be salvage harvested.

There is no reason to believe that post MPB residual trees and secondary structure in the central BC interior will not release; however, the rates of release and subsequent stand dynamics are poorly understood (Veblen et al. 1991, Stockdale et al. 2004) and not documented. Through the use of dendroecological reconstruction, Alfaro et al. (2004) were able to show that in a period of 120 years 3 release events occurred in response to MPB attack, and these averaged 13.8 years in duration with 42.3 years in frequency between outbreak events. Response to release was similar for both pine and non pine species.

Considering the complexity of species composition, abundance, spacing, health and vigor, as well as other stand level attributes including light intensity and hydraulic cycling, it is not an easy task to predict how advanced regeneration will respond to release (Griesebauer and Green, 2006). These factors do suggest that 1) residual stands should be those which have significant levels of healthy secondary stand structure, can be restored economically and will contribute to the mid and long term timber supply or 2) logged stands should be those that do not have adequate levels of secondary stand structure and will be costly to restore or have low potential to contribute to the mid-term timber supply.

Since 2004, we have conducted MPB attack surveys in approximately 525 polygons: 235 in immature (age class 1 to 3); 80 in transitional (age class 4); and 210 in mature stands (age class 5 to 8). They are located in the southern portion of the Lakes Timber Supply Area (TSA), and the southwest, southeast and west-central portions of the Prince George TSA. The survey data, collected in previous MPB research projects, allows description of MPB attack and stand structure, quantification of regeneration by stand attributes, and tree lists for use in stand level growth and yield (G&Y) models. A temporal component has been added for stands initially surveyed in 2005 and 2006. This project will use stands initially sampled in 2005 and 2006. The focus will be on age class 2 to 4 (21 to 80 years) stands with a lesser emphasis on age class 5 to 8 (81 to 250 years) stands. Stands with moderate to high levels of MPB attack will be the study focus.

This project will consider six forest management questions identified by industry and government. 1) What is the quality and quantity of regeneration in MPB affected stands? 2) What are the growth and yield implications of treating or leaving MPB attacked stands and allowing the secondary stand structure to develop? 3) What is the release potential of these stands? 4) Which trees will release and when? 5) What are the economics of treating or leaving MPB attacked stands with varying amount of secondary stand structure? 6) What are the medium and long-term impacts of residual and secondary structure on timber supply? The answers-outcomes of the project will help to improve harvest scheduling, identify stands most suitable for retaining or restoring, and guide stand activities that positively affect the growth and quality of secondary stand structure.

Stand level G&Y modeling which incorporates the response of secondary structure to MPB attack is required to develop sound MPB mitigation strategies. SORTIE-ND is well suited for modeling post MPB stand dynamics in the central BC interior. We plan to incorporate the release response of secondary stand structure found from data collected by this project, into the model assumptions in order to reflect “on the ground” post MPB stand dynamics. This will improve SORTIE-ND simulations, growth and yield projections, and timber supply analyses. Several SORTIE-ND simulations will be conducted for each sampled stand: 1) leave the stand alone; 2) under plant the attacked stand; 3) remove only the pine; 4) remove the pine and under (fill) plant; and 5) clear cut or clear the stand and plant. Each scenario will also include an economic analysis. The scenarios and accompanying economic analyses will be put into a decision matrix to help forest managers choose appropriate stands for harvest or retention, as well as helping to select the most cost effective management strategies.
Related projects:  FSP_Y102188

    Deliverables:

Executive summary (0.2Mb)
Identification of Problem Stands Report (80Kb)
The Forest is Alive after MPB Attack- Presentation (12.0Mb)
Response of Secondary Stand Structure Report (0.8Mb)
Presentation - Mountain pine beetle attack in immature lodgepole pine stands (9.8Mb)
Confirmation of Completion of Deliverables (0.1Mb)

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Updated August 16, 2010 

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