The goal of this project was to explore various patch size options for NDT 3 forests within the TFL 15 area. In the first section of this report, historical fire distribution patterns were examined to identify the size range of openings that occur naturally in the area. Fire size distributions were calculated for the southern Okanagan area as well as for the TFL 15 area, and included summaries for both NDT 3 and NDT 4 forests. Most fires were less than 1 ha, but fires larger than 1,000 ha, although numerically rare, had the biggest effect on the landscape. This information was incorporated into a harvesting scenario in the second part of the project. In the second section of the report, the range of patch sizes available prior to extensive harvesting in the TFL 15 area was examined by 'back-dating' the landscape to 1970 conditions by removing the effects of recent fires and harvesting. This landscape was then compared to current conditions. Conditions on the 1970 landscape, the 2004 landscape, and openings created by historical fires did not meet the patch size recommendations of the Biodiversity Guidebook (1995) for NDT 3 forests. Multiple harvesting strategies were explored using TELSA, a landscape-level simulation model. The strategies included: conventional harvesting (0-40 ha cutblocks); a mixture of conventional harvesting and 41-100 ha aggregated harvesting areas (AHAs); a mixture of conventional harvesting and 100-600 ha AHAs; and a mixture of conventional harvesting and historical fire-sized cutblocks ranging from 2-6,000 ha. Two scenarios without harvesting were also run to assess the lingering constraints of current conditions on the future landbase and the effects of unsuppressed wildfires. Indicators measured included harvesting volume, seral condition, patch size, 'core' mature forest area and active roading. The volume removed by all harvesting scenarios was similar, differing at most by 3.7% over 100 years, suggesting that harvesting pressure was applied evenly across the scenarios. Despite the very different harvesting strategies, seral conditions were also similar when summarised for the NDT 3 landbase. Differences among the harvesting approaches appeared, however, when seral condition was examined spatially by grouping similarly-aged stands into discreet patches. Conventional harvesting and the hybrid strategy with 100-600 ha AHAs created the most fragmented landscape with proportionately more area in < 40 ha patches. Conversely, the mixture of conventional harvesting with 41-100 ha AHAs and the larger, fire-emulating approach, both created proportionately more area in larger patches. None of the harvesting approaches successfully maintained a significant amount of 'core' mature forest, partly reflecting the intensity of harvesting on the NDT 3 landbase as well as the constraints of current conditions (only 7% of the NDT 3 is currently in mature 'core' habitat). Active roading did not differ substantially among scenarios, although conventional harvesting and the hybrid strategy with 100-600 ha AHAs maintained the most active roads. The range of harvesting scenarios used and their outcomes provide options for managers to consider when implementing harvesting strategies in this area. As the results indicate, some indicators can be influenced by management approaches while others may be difficult to change given current constraints in the landbase. All results should be interpreted with a thorough understanding of the model's assumptions and rules.
Walton, Russ. 2004. Patch size study in the TFL 15 area: draft report. Forest Investment Account (FIA) - Forest Science Program. Forest Investment Account Report. FIA2004MR152
Topic: FLNRORD Research Program
Keywords: Forest, Investment, Account, (FIA), Fire, Ecology, British, Columbia
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