on commercial forest land during a specified year. 



Annual cut of growing stock. — The cubic-foot 

 volume of live sawtimber and poletimber trees cut or 

 killed by logging on commercial forest land during a 

 specified year. 



Forest Survey Methods 



Estimates of forest area, timber volume, and tree 

 growth in New Hampshire are based on data obtained 

 from sample plots that were first located on aerial 

 photographs. These plots were distributed uniformly 

 over the entire State. Trained photointerpreters ex- 

 amined the photos and classified each plot according 

 to stand size. Field crews then inspected enough plots 

 on the ground to attain a specified lev^el of statistical 

 accuracy. Species, volume, and growth data were col- 

 lected on these ground plots. 



Growth was computed from measurements of tree 

 rings on increment coies taken from sample trees. 

 These data were used in estimating the diameter dis- 

 tribution of each species 10 years hence. Future vol- 

 ume was predicted from this new distribution of 

 diameters. Growth was then detennined by subtract- 

 ing present net volume from estimated future net 

 volume and reducing the difference to an annual basis. 

 Allowances were made for ingrowth and for loss of 

 growth on dead and cut trees. 



Estimates of timber cut for sawlogs, veneer, cooper- 

 age, and pulpwood were derived from production data 

 largely supplied by the New Hampshire Forestry and 

 Recreation Commission (9). Fuelwood and fence- 

 post production was estimated from data obtained by 

 field surveys of farmers and other consumers. Output 

 of other products was estimated from field surveys of 

 producers or consuming mills. 



Special woods and mill studies were conducted to 

 determine the class of material being cut, i. e., whether 

 sawtimber or poletimber growing stock, and propor- 

 tion coming from cull and dead trees, mill residues. 



and other similar sources. Estimates of logging resi- 

 dues were derived from a special study of logging oper- 

 ations throughout the State. 



In order that all production from New Hampshire 

 timber would be accounted for, adjustments ^vere 

 made for shipments of sawlogs and pulpwood into the 

 State and for a small net export of veneer logs, cooper- 

 age bolts, and similar material. 



Reliability of the Estimates 



The estimates in this report inay contain t\\o kinds 

 of error. First, photointerpreters may make mistakes 

 in judgment and fieldmen may make mistakes in meas- 

 uring or recording. There is no practical way of find- 

 ing out just how often such errors occur. But they are 

 kept to a minimum by closely checking all phases of 

 the work. 



The second kind of error is inherent in sampling 

 procedures. The size of this possible error can be 

 measured. If there are no errors of the first kind, the 

 probabilities are 2 out of 3 that the estimated State 

 figures for areas and volumes do not vary from the 

 actual areas and volumes by more than the following 

 percentages : 



Percent 

 (plui ot minus) 



Forest land area 0. 6 



Sawtimber area 3. 9 



Poletimber area 5. 2 



Timber volume, board-foot basis 3. 9 



Timber volume in sawtimber stands, board-foot basis 5. 4 



Timber volume in poletimber stands, cubic-foot basis 6. 



Total timber volume, cubic-foot basis 2. 4 



Growth (board-foot basis) 8.0 



Growth (cubic-foot basis) 7. 1 



Timber cut (cubic-foot basis) 7. 2 



In every case, total figures are more reliable than 

 subtotals, subtotals are more reliable than any of their 

 component figures. Figures that are small in relation 

 to totals are subject to larger sampling errors. 



Species Tallied 



The \-arious tree species (7) tallied in New Hampshire are listed below. 



Softwoods 

 Spruce : 



Red spruce Picea rubens 



White spruce P. glauca 



Black spruce P. mariana 



Fir (balsam fir j Abies balsamea 



Hemlock (eastern hemlock) Tsitga canadensis 



32 Forest Resource Report No. 8, U. S. Department of Agriculture 



