Forest Investment Account (FIA) - Forest Science Program
FIA Project Y093167

    Coarse Woody Debris in the East Kootenays: Understanding Sources and Dynamics to Guide Targets for Sustainable Forest Management
Project lead: Daniels, Lori (University of British Columbia)
Contributing Authors: Daniels, Lori D.; Cochrane, Jared D. (Jed); Gray, Robert W.; Thorne, Susan; Soverel, Nicholas; Welton, Maria; Tiffany, Sarah; Uppal, Victor; Theroux, Nicci; Davis, Reg; Forsite Consultants Ltd.
Subject: Forest Investment Account (FIA), British Columbia
Series: Forest Investment Account (FIA) - Forest Science Program
Rationale, Purpose and Research Questions
Ecosystem management aims to conserve biodiversity and maintain ecosystem function while sustaining renewable resources. To achieve these goals, patterns of variation resulting from natural disturbances can be used to guide management. The premise of this approach is that management that maintains historic forest structures and functions will maintain the habitat suitable for the biota adapted to the ecosystem. Based on literature reviews, field research, and modeling, Tembec and Canadian Forest Products (Canfor) have been developing criteria and indicators for sustaining biodiversity of the managed forests of the East Kootenay region of southeastern British Columbia. Specific indicators include important habitat elements, such as snags, logs, large live trees, and stand structure classes. Preliminary targets for these indicators provide recommendations such as snag densities and volumes of logs to be maintained in managed stands. However, current targets may not represent the historical range of variation for these attributes. Many of the dry forests on southern British Columbia have been subject to substantive human impacts during the past century, including widespread fires associated with mining and logging at the end of the 19th century followed by fire exclusion, indirectly due to land use that has altered forest fuels and directly due to active fire suppression. The resulting contemporary forests may lie outside the range of historic variation and targets based on current composition and structures may not be appropriate or achievable over the long term. To be sustainable and achievable on the ground, targets for indicators of biodiversity must include a measure of the historic range of variability and measures of departure from this range.

Knowledge of the processes that historically generated CWD and the age, decay rates, and residence time of snags and logs of different species is critical to ensure that appropriate quantities of CWD suitable for wildlife use are maintained in managed stands over the short and long terms. This proposal requests funds to support an ongoing investigation of coarse woody debris dynamics in the context of fire regime changes in the mountain forests of southeastern British Columbia. We address the following four questions about coarse woody debris (CWD) in the dry forests of southeastern British Columbia:
• How much CWD is present in old, mixed-conifer forests in absence of human disturbances such as 19th century fires associated with mining and industrial logging?
• How old are the snags and logs in these forests? Did this CWD originate as a result of historic fires or did it originate during the fire-exclusion era?
• How will the quantity and quality of CWD in these stands change through time?
• How does improved understanding of CWD dynamics and fire regimes influence existing tools for wildlife habitat modeling?

Research Progress
There are four parts to this research. Parts 1 and 2 provide the spatial and temporal framework for our analysis of CWD dynamics and are now complete. Part 3 was the major focus of our 2007-8 workplan. Part 4 of the project is a modeling exercise that will be completed in 2008-9, once all lab analyses have been accomplished.
In 2006-7, we completed (1) landscape-level GIS analysis, (2) fire history reconstructions at 30 sites in the Southern Rocky Mountain Trench (20 of which will be included in J. Cochrane’s MSc thesis) and (3) a pilot study of stand structure and CWD dynamics at 10 sites. In 2007-8 we completed (4) fire history reconstructions at 10 additional sites (40 total), (5) sampled stand structure and CWD dynamics at 20 sites, and (6) J. Cochrane completed his MSc thesis and published one manuscript in BC JEMS. Summaries for work completed for parts 1 and 3 follow; part 4 is described in the “Experimental Design and Methods section of this proposal since that work is ongoing and is the major focus of our 2008-9 workplan.

Part 1. Identification of structurally complex stands
This research was conducted for the montane forests in the Interior Cedar Hemlock and Montane Spruce zones of the southern Rocky Mountain Trench in British Columbia in the Invermere and Cranbrook TSAs and TFL14. Using GIS, we stratified the landscape according to historic land use and biophysical attributes (BEC zone, elevation slope aspect, forest composition and age). This analysis serves two purposes: (1) provides regional context to inform/constrain extrapolations from the study sites to the broader study area and (2) identifies study sites in the ICH and MS zones. Potential study sites were structurally complex stands with ?2 age classes, multiple canopy strata dominated by western larch and Douglas-fir veterans. From these locations, we randomly selected our study sites.

Part 2. Fire History and Time Since Last Fire
Using results from Part 1, we selected 20 study sites using a stratified-random approach. Sites were evenly distributed on slopes with warm (225±60º) and cool (45±60º) aspects. An additional 20 sites were sampled to represent old-growth forests. At the centre of each polygon we searched a 1-ha circular plot for fire-scarred trees, snags and logs. From that area, we collected up to 15 partial- or cross-sectional disks, preferentially selecting large trees with multiple fire scars to maximize the period of analysis and number of scars.
Fire scar samples have been dried and sanded (Stokes and Smiley 1968). Species-specific, regional chronologies were used to visually and statistically crossdate ring-width series of fire scar disks to (1) check for missing or false rings in samples from live trees, (2) establish years of death of snags and logs, and (3) determine the exact year ± season of historic fires recorded as scars in both live and dead trees (Holmes 1983, Grissino-Mayer 2001). Seasonality of fires was determined by assessing the position of the tip of fire scars within the annual ring (Brown and Swetnam 1994). Only the fire scars dated to an annual resolution were included in subsequent analyses.

Data analysis of fire intervals at the site and regional spatial scales is complete for 30 sites and lab work is underway for the remaining 10 sites. Fire intervals were calculated for each site using composite fire chronologies. Fires that scar at least 10% of recorder trees and include =2 scarred trees at the site will be considered "major" fires. Minimum, maximum and Weibull median intervals (WMI) were calculated for all fires and major fires using the computer program FHX2 (Grissino-Mayer 2001). When computing fire intervals, we will include only scar-to-scar dates and exclude the interval between the pith and the first fire scar on each disk as our pilot study showed that trees do not always established as part of a post-fire cohort (Baker and Ehle 2001). Using logistic regression, we have modeled fire intervals and tests for the influences of topographic factors (aspect, elevation, slope angle and solar insolation) on fire intervals. To quantify changes in regional fire frequency over time, we calculated fire intervals for three 50-year intervals corresponding to the pre-settlement (<1860), Euro-settlement (1860-1910), and fire exclusion (>1910) eras. The number of years since the last fire and major fire have been determined for each site.
Related projects:  FSP_Y071167FSP_Y082167Tree Ring Lab at UBC


various articles in BC Forest Professional 14(4) (2.7Mb)
Technical Report Part 1 (0.5Mb)
Technical Report Part 2 (0.9Mb)
Field Trips and Presentations (90Kb)
Education Package (3.9Mb)
Link Article (1.0Mb)
Presentations (0.2Mb)

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Updated August 16, 2010 

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