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Integrating Historical Air Photo Data for Cedar Analyses Forest, Marguerite S.E.
Abstract: The main forest management object of this project is growth and regeneration of sufficient red and yellow cedar of monumental quality for Haida cultural uses. First Nations in coastal British Columbia make extensive use of large, high-quality cedars for long-houses, canoes, totem poles, planks, and other objects. On Haida Gwaii, evidence suggests that there are now very few red and yellow cedar in second growth stands, that cedar regeneration is impeded in part due to severe over-browsing by introduced deer, and that remaining cedars are not of as good quality. Large high quality cedars are now a key focus for First Nations consultation and accommodation on Haida Gwaii. They are also a critical indicator in the co-managed Land Use Plan. This research will help determine changes in the distribution, abundance, and quality of red and yellow cedar on Haida Gwaii between 1937 and 2007, as well as the best sites for future growth of high quality cedar. Project results will be used to develop a registry of monumental cedar for Haida cultural use and to establish a series of age graded sites for long-term regeneration of high quality cedar. The registry and regeneration sites will bring a higher level of certainty to local timber harvests. Time series data are the key to more precise understanding of long-term forest cover changes and resulting variation in timber growth and value. Sources of time series data include historical records, field surveys, and remote sensed data. Haida Gwaii is fortunate to have all three. Despite the availability of these data, long-term changes such as shift in species composition, reduction in tree sizes, and deterioration in wood quality have not been rigorously quantified for cedar on the islands. Some of the first air photos in coastal British Columbia were flown for Haida Gwaii in 1937 at ~1:15,000. The photos are of good quality and provide detailed information. They are now being scanned, orthorectified, and mosaiced in a series of projects funded by the South Moresby Forest Replacement Account (SMFRA), Gwaii Trust, and other sources. A trial has been done on using these photos to interpret forest cover and pinpoint locations of individual large trees on Lyell Island. No other sites have been examined so far. The method for that project was desktop stereo pair interpretation. Forest cover polygons and attributes were delineated by hand on mylar overlays. Mylar overlaid photos were scanned, georeferenced, and orthorectified, then the polygons were digitized on screen and their attribute data entered into GIS files. Results were checked against 1960s forest cover maps and cruise data, but not against any field data. It was a time-consuming procedure, involving much duplication of effort, and without any of the field samples now required for accuracy assessment. New forest cover interpretation methods focus on 3D digital stereo viewing using specialized software and equipment, such as the PurView extension for ArcGIS. On-screen digitizing is done from scanned photos. The need to scan, georeference, and orthorectify both original and mylar overlaid photos, and to delineate polygons both on mylar overlays and on screen, is eliminated. Use of these techniques would speed up historical forest cover interpretation significantly. The first goal of this project is to test if these new methods can be used effectively on the 1937 air photos. In 2004, Vegetation Resource Inventory (VRI) mapping standards were updated to reflect use of digital ?softcopy? technology and the RISC format. The new standards will be followed as much as is practicable for the 1937 air photos, and Haida Mapping technicians will be trained in these interpretation methods. Timber cruise data and forest cover maps for Haida Gwaii date back to the 1960s. Subjective back-casting is needed to compare these data to interpretations from the 1937 air photos. So far, no other method has been used to check the Lyell Island sample 1937 fores ...
Forest, Marguerite S.E., Fortier, Jean-Marc. 2008. Integrating Historical Air Photo Data for Cedar Analyses. Forest Investment Account (FIA) - Forest Science Program. Forest Investment Account Report. FIA2008MR206
Topic: FLNRORD Research Program
Keywords: Forest, Investment, Account, (FIA), British, Columbia
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