Canadian Forest Service Publications

Predicting mountain pine beetle impacts on lodgepole pine stands and woody debris characteristics in a mixed severity fire regime using prognosisBC and the fire and fuels extension. 2005. Hawkes, B.C.; Taylor, S.W.; Stockdale, C.; Shore, T.L.; Beukema, S.J.; Robinson, D. Natural Resources Canada, Canadian Forest Service, Pacific Forestry Centre, Victoria, BC. Mountain Pine Beetle Initiative Working Paper 2005-22. 17 p.

Year: 2005

Available from: Pacific Forestry Centre

Catalog ID: 25687

Language: English

Series: Mountain Pine Beetle Working Paper (PFC - Victoria)

CFS Availability: PDF (download)

Abstract

This paper examines the use of PrognosisBC (the BC variant of the Forest Vegetation Simulator) and the Northern Idaho variant of the Fire and Fuels Extension (FFE) to project changes in stand structure, fuel loading, snag density, and potential fire behaviour following a mountain pine beetle outbreak in a mixed severity fire regime on the Chilcotin Plateau in central interior British Columbia. Lodgepole pine stands on the dry cold Chilcotin Plateau have a complex structure (multi-age and size) because of previous mountain pine beetle (MPB) outbreaks, mixed-severity fires and as a result of lodgepole pine's ability to regenerate under its own canopy in dry ecosystems. To accommodate modelling this complex structure, stand inventory data were obtained from 15 stands in 1987, following an outbreak that lasted from approximately the late 1970s to 1985, and in 2001. Three model simulations were carried out for each of the 15 stands (45 total). Two scenarios were simulated using the 1987 data set: one including MPB mortality and one assuming no MPB mortality. A third scenario was carried out using 2001 base data and projected to 2031. The Stand Visualization System (SVS) was used to generate images of the condition of each stand. Quantitative and visual results clearly show that the PrognosisBC-FFE model is sensitive to differences in initial stand structure and composition, and that these differences persist over time. Projections with and without MPB mortality differ when there is significant MPB mortality in the sampled stands. Evaluation of the model's ability to simulate growth from the initial 1987 inventory to the 2001 remeasurement was confounded by additional mortality by MPB and Ips species, and evaluation of woody debris accumulation was limited by the absence of coarse woody debris in the 1987 inventory. PrognosisBC does not capture this mortality because attack from these bark beetles is not considered part of the "background" mortality used to calibrate PrognosisBC's mortality model. In stands with limited additional mortality, the model performs reasonably well for the live tree characteristics. Downed coarse woody debris accumulations projected by FFE due to fall down of standing dead trees are plausible in comparison to woody debris loads in 2001. Some calibration of the FFE will be necessary to better represent fuel dynamics, especially the snag dynamics for Chilcotin Plateau conditions. The FFE model predictions indicate that there is a need to increase the decay rate for small fuels and decrease it for large fuels.

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