Forest Investment Account (FIA) - Forest Science Program
FIA Project Y092048

    Estimating Natural Regeneration and Yield in Pine-Dominated Stands Following Mountain Pine Beetle Attack Using SORTIE-ND and PrognosisBC in a Hybrid Modelling Approach
Project lead: LeMay, Valerie (University of British Columbia)
Contributing Authors: Sattler, Derek F.; LeMay, Valerie M.; Marshall, Peter L.
Subject: Forest Investment Account (FIA), British Columbia
Series: Forest Investment Account (FIA) - Forest Science Program
The amount of timber affected by the current Mountain Pine Beetle (MPB) epidemic is beyond the industrial capacity to extract and process. Thus, a large portion of these stands will go unsalvaged, and much of the Province’s mid- to long-term timber supply will originate from these stands. This has placed considerable importance on the need to develop quantitative growth and yield models that capture the natural dynamics of MPB-affected stands. As a result, there is a need to develop quantitative growth and yield models that capture the natural dynamics of MPB-affected stands, beginning with the estimation of regeneration following attack.
PrognosisBC is an empirical, tree-level, growth and yield model that has proven to be an effective forest management tool that can simulate a variety of silvicultural applications and can be used to provide operational estimates of growth and yield. Several approaches to estimating regeneration have been examined for use with PrognosisBC including using a set of probability models in partially cut stands (e.g., Boisvenue 1996) and using nearest neighbour imputation in partially cut and MPB-affected stands (e.g., Boisvenue 1996; Hassani et al. 2004; LeMay et al. 2006). However, the dynamics of natural regeneration recruitment and growth under MPB affected stands is markedly different than regeneration in thinned or partially cut stands, since dead trees remain standing for a long period of time, and remain on site once they fall. Ideally, regeneration estimations following MPB-attack should take into account the variable rates of mortality, snag decay and subsequent fall-down, and light transmission that are observed following MPB attack. SORTIE-ND is a process-based forest ecology model that simulates growth, mortality, recruitment, and resource availability. Model strengths lie in the spatially explicit light submodel and the ability to simulate the establishment and growth of natural regeneration. However, SORTIE-ND has had limited use in forest planning and forest operations. To this extent, regeneration estimates from SORTIE-ND coupled with projections using PrognosisBC could result in improved growth and yield projections in unsalvaged stands. Preliminary tests of SORTIE-ND to obtain regeneration indicated that this approach showed considerable promise (LeMay et al. 2006).
In this project, we will use a hybrid modelling approach to estimate growth and yield following MPB-attack in pine-dominated forests of the central and southern interior of BC, by linking SORTIE-ND and PrognosisBC. To examine this hybrid modelling approach, first, the strengths of each of these two models will be examined in terms of providing accurate growth and yield estimates, from seedlings through to adult growth stages. Second, modifications to components of each model will be proposed and developed to strengthen the accuracy of regeneration and yield predictions for the application areas. In the third step, alternatives for linkages between the two models will be examined, including when the regeneration estimates are passed from SORTIE-ND to PrognosisBC. Data from the Cariboo-Chilcotin area gathered in 1987 and remeasured in 2001 by Natural Resources Canada, as well as data collected in the summer of 2006 from the Williams Lake area (FSP Project M07-5015), will be used in this project. A third dataset will be available from the Kamloops/Kelowna area in 2008. These data will also be used to examine other approaches to estimate regeneration following MPB-attack (MMPI MPB Standard Contribution Agreement, PO # 8.35).
A hybrid model that combines the strengths of the processed-based and empirically-based functions of SORTIE-ND and PrognosisBC would be a very useful tool for the projection of mid- to long-term yields. By focusing on the accurate prediction of natural regeneration, this study represents an important step in the development of a hybrid model that could be used to make informed management decisions. For example, stands expected to have low natural regeneration densities following MPB attack could be a priority for salvaging or under-planting. Although the project focus will be on MPB-affected stands, the hybrid model could be extended for use in other complex and disturbed stands of BC.
The project is proceeding according to the objectives, work schedule, and extension plan in the original proposal. In Year 1 of this project, progress was been made towards meeting the project objectives. An extensive literature review was conducted into the origins of SORTIE-ND and PrognosisBC to document model developments. Tests using the two models to predict the amount of natural regeneration via a simple linkage with no changes to either model have been conducted using a sample of stands from the Caribou-Chilcotin (data collected by Natural Resources Canada via a separate research project) and the Williams Lake data (gathered by UBC under a separate FSP project). This included reformatting SORTIE-ND and PrognosisBC output files for compatibility, and passing regeneration estimates from SORTIE-ND to PrognosisBC. The transfer of SORTIE-ND estimated regeneration files to PrognosisBC were tested at five and ten years post-MPB attack and compared to the results obtained when using SORTIE-ND or PrognosisBC alone. The results indicate that the use of the combined models provide better estimates that each model separately, but changes to models are needed to improve estimates using the linked model. In terms of modifications to model components, work to date has focused on adjusting parameter estimates for several SORTIE-ND behaviours. More specifically, data from the Williams Lake area were used to calculate species-specific parameters related to crown allometry, height-diameter relationships, and snag fall-down rates. The findings from each of the project components described here have been presented at conferences and will be included in the publication of conference proceedings (Sattler et al. in press). In the remainder of Year 1, the modifications to models will be incorporated into SORTIE-ND, and the linked models tested again using the changes in SORTIE-ND behaviors. Results will be presented at a conference for researchers and professionals in Smithers, BC in February, Further modifications and testing is scheduled for Year 2, using data from Williams Lake and Kamloops/Kelowna (gathered via a separate FSP funded project), along with data from Natural Resources Canada. Extension of final project results to BC forestry professionals and to the research community and BC and elsewhere is planned for Year 2.

References Cited
Boisvenue, C. 1999. Early height growth and regeneration: Applicability of Prognosis components to the Southern Interior of British Columbia. M.Sc. Thesis, Univ. of B.C., Vancouver, BC. 193 p.

Hassani, B., V.M. LeMay, P.L. Marshall, H. Temesgen, and A.A. Zumrawi. 2004. Regeneration imputation models for complex stands of Southeastern British Columbia. For. Chron. 80:271-278.

LeMay, V., T. Lee, R.E. Scott, D. Sattler, D. Robinson, A-A. Zumrawi, and P. Marshall. 2006. Modeling Natural Regeneration Following Mountain Pine Beetle Attacks in the Southern and Central Interior of British Columbia: Results for Year 1. Internal report for Natural Resources Canada, MPB Standard Contribution Agreement, PO # 8.35. 70 pp.

Sattler, D.F., V. LeMay, and P. Marshall. In press. Estimating natural regeneration using a linked-model approach. In Proceedings of the IUFRO conference on process models to wood processing, Portland, US, Aug. 6 to 10, 2007.
Related projects:  FSP_Y081048


Complex_Stand_poster (0.3Mb)
Presentation (0.9Mb)
Estimating Natural Regeneration Following Mountain Pine Beetle Disturbance (0.7Mb)
Hybrid Modelling Abstract (12Kb)
Linked model_abstract (9Kb)
Prognosis_Poster (0.1Mb)

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Updated August 16, 2010 

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