|Forest Investment Account (FIA) - Land Base Investment Program|
|FIA Project 2806004|
|Pre Industrial Condition Report For The Dawson Creek TSA - Tembec Chetwynd|
|Project lead: Savage, Carole (FIA Coordinator for Tembec Chetwynd)|
|Author: Timberline Natural Resource Group Ltd.|
|Subject: Forest Investment Account (FIA), British Columbia|
|Series: Forest Investment Account (FIA) - Land Base Investment Program|
|A present philosophy in forest management planning is to emulate natural disturbances. This philosophy is based on the assumption that all living organisms have adapted to the patterns and process created by natural disturbances, and that if we can reproduce similar conditions, biodiversity will be maintained (Hunter 1993; Swanson et al. 1993; Bunnell 1995). Before the arrival of western civilization in the boreal landscape, natural disturbances played a leading role in shaping forest dynamics. The purpose of this report is to provide Tembec-Chetwynd Pulp Mill with a pre-industrial forest condition (PIC) analysis for the Dawson Creek Timber Supply Area (TSA) that may be used to guide forest management decisions. The PIC analysis includes a description of fire history and a comparison of species composition, age class and patch size between pre-industrial and current time periods.|
In the mid 1990ís, forest management in BC began to emulate natural disturbances. The Biodiviersity Guidebook (1995) was a first attempt at describing forest landscapes as they have been shaped by nature and was used to direct forest management in the Prince George Forest Region. As more information became available for the northeastern part of the Province, Natural Disturbance Units (NDU) began replacing Natural Disturbance Types (NDT) used by the Biodiversity Guidebook. NDUs were created based on differences in stand development, landscape pattern (temporal and spatial) and disturbance processes. A total of nine NDUs were created for the Prince George Forest Region (Delong 2002) and are used as the basis for describing the pre-industrial condition for the Dawson Creek TSA. Depending on the NDU, some disturbance factors have a stronger influence than others. Overall, wildfire is the most influential natural disturbance factor in the Dawson Creek TSA (Delong 2002). Of the six NDUís in the TSA, five have stand replacement fires as the foremost disturbance type. Only the Wet Trench Ė Mountain NDU is dominated by small-scale gap replacements caused by disturbance agents such as insects, disease and wind.
In the Boreal Foothills NDU, stand-replacing fire cycles are estimated to occur every 120 years for the valley portions and 150 years for the mountain portions. In the Boreal Plains NDU, fire cycles are estimated to be 100 years in the upland portions. In the Omineca NDU, fire is a key disturbance factor with stand-replacement disturbance cycle of 120 years for the valley and 300 years for the mountain portions. In the Wet Trench, the fire cycle varies depending on the site conditions with stand-replacement disturbance cycles estimated to be 800 years in the mountain portions. Data from the MOFR Fire Protection Branch for the Dawson Creek TSA indicate that, since 1922, the majority of all fires have been smaller than 100 hectares but that these fires make up less than five percent of the total area burned. On the other hand, there have been relatively few fires greater than 1000 hectares, yet these make up over 75% of the total area burned in the Dawson Creek TSA.
Results for species composition indicate that the current composition is quite similar to preindustrial species composition. Overall, the current TSA forest composition showed a slight increase in deciduous species and a slight decrease in coniferous species as compared to the preindustrial condition. These slight changes are likely due to the fact that less than 10% of the forested landbase has been harvested or silviculture management activities in the past 50 years. Slight changes in species could also be attributed to a variety of activities including natural fire patterns, fire suppression, and forest management practices.
Results for age-class distribution indicate that, in the current Dawson Creek TSA and Tembec operating areas, there are fewer stands 40 years and younger and 250 years and older than in preindustrial times. Currently, there are more stands older than 100 years of age than during preindustrial times. In the ESSF NDUís, there are now more stands over 140 years and in the BWBS NDUís, there are now fewer stands over 140 years. Contributing factors to this result may include a possible underestimation of the stand age in the deciduous stands in these NDUís, as well as fire suppression resulting in less area being burned and set back to a younger age class. Accurate age determination of deciduous stands over 100 years old can be difficult, especially with little deciduous field data to calibrate the VRI age estimates, which was usually the case in older inventories (Mike Sandvoss, pers. Comm.).
According to the analysis, patch size distribution has changed since pre-industrial times. The current Dawson Creek TSA forest patch-size distribution has more small and medium sized patches and fewer large patches than the pre-industrial condition for the Boreal Plains, Boreal Foothills, and Omineca Valley NDUís (BWBSmw1, BWBSwk1, and BWBSwk2), while the opposite was noted for the Mountain NDUís, the current amount of area in the very large (> 1000 ha) patch-size group was greater than expected. More large patches in the Mountain NDUís may be attributed to lower harvesting levels in these variants resulting in the creation of fewer small and mid-sized patches and more intact large patches, or a variation in the fire return interval and the average natural disturbance patch size. Reduction or fire suppression and reduced cutblock sizes may have attributed to current patch sizes the Boreal and Omineca NDUís, as both result in less larger patches and more mid to smaller patches.The Ominica Valley NDU (BWBSwk2 and SBSwk2) had fewer large patch sizes than was expected for the current condition. For the BWBSwk2 there is a very small amount of the variant in the forested landbase and the VRI shows that no harvesting has occurred in this variant outside of the TFL, therefore we assumed that the current patchsize distribution for this variant is due to the natural disturbance regime existing in that zone at this time. In the SBSwk2, the database shows that approximately 30% of the forested landbase had been harvested with an average block size of 30 ha, which would contribute to the creation of more small and mid-sized patches and a reduction in large patch sizes.
The current Tembec operating LUís forest patch-size distribution also had a similar trend to the Dawson Creek TSA, with more small and medium sized patches and fewer large patches than the pre-industrial condition. In the Boreal Plains Ė Upland NDU there were more 100-1000 ha patches than in the TSA and pre-industrial, and fewer >1000 ha patches than the TSA and preindustrial. A key consideration to managing boreal forests within the context of natural wildfire patterns is diversity. Boreal forests operate over wide temporal and spatial variability. In order to manage forests according to natural disturbance patterns, forest planning and operating should emulate similar ranges of time and space. Results of this PIC analysis show that Tembecís current forest management practices closely emulate pre-industrial species composition across the operating landbase. However, age-class distribution and patch sizes differ from pre-industrial times. To more closely emulate age-class distribution, Tembec may target fewer older stands for harvesting.
Creating some larger cutblocks to more closely emulate pre-industrial patch sizes may be difficult given current legistlative limits to cutblock sizes in BC.
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Updated August 16, 2010
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