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The Forest Service specialist also explained that the current Timber Type Map in the TLMP 

 Revision GIS "will not provide reliable location specific information." 



The Forest Service is attempting to improve the reliability of the Timber Type Map by 

 correlating the timber information with other resource data in the GIS. However, that effort 

 can only make slight improvements, at best. With regard to this effort the same Forest Service 

 specialist's report states: 



For the Tongass situation no great expectation of success is justified. 1 



The upshot of the timber database inaccuracies is that: 



The Forest Service cannot locate timber stands of different volume classes on the 

 ground. 



The Forest Service cannot distinguish between the three most important timber stand 

 volume classes on the Tongass. 



Site specific evaluation, analysis, and planning is impossible given the TLMP Revision's poor 

 timber maps; the GIS machinery will be drawing maps that are long on beauty but devoid of 

 meaning. As an example of how inaccurate the Timber Type Maps are: 



Among the most valuable timber stands for timber and Sitka black-tailed deer are those 

 stands with more than SO thousand board feet per acre (50+ mbf/a). These stands are 

 classified as Volume Class 7. 



When the Forest Service compared their GIS timber maps of volume class 7 stands to 

 their on-the-ground, measured inventory, they found that only 15% of the areas 

 mapped as volume class 7 were measured as volume class 7 in the field, [see graph and 

 explanatory notes on the following two pages] Even worse, there was no statistically 

 valid basis for comparing the two sets of data. 



As an example of how inaccurate the field timber inventory for the TLMP Revision is: 



On the Ketchikan administrative area of the Tongass the field inventoried, calculated 

 average stand volume for stands in the three important volume classes were totally 

 inconsistent with the mapped volume classes in the GIS. 



Volume Class # Volume Class Definition Average Volume 



5 20-30 mbf/a 33.6 mbf/a 



6 30-50 mbf/a 31.2 mbf/a 



7 50+ mbf/a 35.6 mbf/a 



1 Review of Forest Inventory Methodology and Results, 

 Tongass National Forest, by J.R. Brickell, Forester, TCFPM R-l, 

 1989. 



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