Appendix 



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Forest Survey Methods 

 Areas 



FOUR methods were used in the forest survey in 

 Minnesota to collect the statistics on forest land 

 areas. 



1. One hundred percent mapping. — National 

 forests and a few smaller areas were mapped com- 

 pletely. 



2. Random-block sampling. — In nearly all the 

 northeastern division outside of national forests, the 

 area estimates were based on mapping of sample 

 blocks, either four 160-acre blocks or nine 40-acre 

 blocks selected at random in each township. The 

 type, size, and stocking classes were delineated and 

 classified on aerial photos before being checked on 

 the ground. 



3. Dot-block sampling. — In the southeastern divi- 

 sion and the northeastern parts of the western di\ision, 

 the dot-block method was used. The total forest 

 area proportions were determined by counting and 

 classifying as "forest," '"nonforest," and "water," 

 mechanically spaced dots on alternate aerial photo- 

 graphs. At every sixth forested dot, the legal 40-acre 

 description in which the dot fell was used as a sample 

 to break down the total forest land to type, size, and 

 stocking classes. On the aerial photographs of each 

 of these 40's, the type, size, and stocking classes were 

 delineated and classified, and the forested dot was 

 located. Every third 40 was ground checked to verify 

 or change the classifications of the forested dot and 

 the type, size, and stocking classes. These ground 

 checks were then used to adjust the data on the 

 samples that were not ground checked. 



4. Dot sampling. — In the thinly forested parts of 

 the western division, the number of forest and non- 

 forest dots counted and classified was increased. A 

 1-acre circle at every fourth forest dot was classified 

 as to type, size, and stocking class, and varying per- 

 centages were ground checked to reach a specified 

 lev el of accuracv. 



Ownership 



Information on forest area and timber ownership 

 was obtained by examination of ownership records for 

 the sample blocks at the various county offices. 



Volumes and Growth 



Volume and growth measurements were taken in 

 )^-acre circular plots located on a random pattern 

 within mapped areas. The resulting volumes and 

 growth per acre were used with the area data to 

 estimate total volumes and growth by species and 

 classes. 



Allowable Cut 



The allowable cut represents the timber volume 

 available for harvest under good forest management 

 practices. It does not equal the volume that would be 

 available under very intensive forest management, 

 but does presuppose a management level higher than 

 now exists statewide. It assumes forest protection 

 and management aimed toward a sustained yield on 

 all forest lands. It implies good forest practices such 

 as salvage cuttings, intermediate cuttings, and planned 

 controlled harvests. 



Where much of the forest land is not well managed 

 and consequently is either overcut or luidercut. the 

 allowable cut varies considerably from the amount 

 actually removed. Nevertheless, allowable cut is a 

 valuable guide for planning and evaluating progress 

 in improving the management of the timber resource. 



The appraisal of allowable cut was made as sys-. 

 tematic as possible in order to reduce bias and insure 

 uniformitN'. Field and office procedures, including 

 standard rotation periods for the \-arious types, were 

 worked out in conferences with the Minnesota Forest 

 Survey Committee, an advisory group composed of 

 public and private Minnesota foresters. 



Minnesota's Forest Resources 



