6 Cut block size designed to emulate natural disturbance The Alberta approach

6 cut block size designed to emulate natural

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6. Cut block size designed to emulate natural disturbance. The Alberta approach to cut block size, shape, distribution, tree and residual structure retention and age class is that the FMA holder must establish targets in the FMP, but what those targets are is not prescribed. The targets are supposed to be set based on patterns of natural disturbance and EBM. The benefits of not prescribing specific targets for patch size and distribution are that 1) FMPs can be tailored to emulate the varying natural patterns (e.g. fire regimes) in different ecoregions of the province; 2) the province can evaluate how successful companies are at innovating different approaches; and, 3) the approach supports innovation. This approach is a significant improvement on the two-pass system that was in place before, which set out an average, maximum and minimum cutblock size. It was noted that cut blocks are not the appropriate measurement unit for EBM; rather, aggregations of cutblocks more analogous to natural disturbance events are appropriate. Cut blocks are analogous to burn patches. Alberta has pioneered a spatial language and approach through the fRI Healthy Landscapes Program. 58 Alberta Environment and Sustainable Resources Development. 2005. Alberta Vegetation Inventory Interpretation Standards. . Accessed on March 8, 2013.
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46 Companies would not have the social license to log blocks as large as the area a large wildfire event could burn in some areas of the province. That said, companies do have the license for large events, which are combinations of aggregated blocks. Some historical harvest events are greater than 20,000 hectares. It is easier to approximate natural conditions than events, which can be achieved with multiple events instead of a few large ones. The Performance Standards within the Forest Management Planning Standard require FMA holders to establish “a distribution of harvest area sizes that will result in a patch size pattern over the 200 year planning horizon approximating patterns created by natural disturbances.” The objective associated with this target is to maintain biodiversity by avoiding landscape fragmentation. The target “ shall be based on sound science, ecological considerations, wildlife zones, and disturbance regimes. Target shall ensure representation of natural range of ecosystem attributes (e.g. cover class and productivity class ).” According to the Ground Rules, “ unless otherwise approved by Alberta, the size distribution of harvest areas within a compartment shall be representative of the natural variation of the landscape, which for the purposes of harvest planning, is the range of stand polygon sizes prior to harvest within the compartment boundary.” The Ground Rules require an FMP holder to abide by a 10-year spatial harvest sequence. There are spatial constraints on block size in the Ground Rules that do not apply as long as a Spatial
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