3.7-9 Site Quality Index of Pine Woodland. 



(A) Site quality index refers to the domi- 

 nant tree heights at 50 years of age. The rela- 

 tive higher tree indicates more productive soil 

 with consequent greater earning value of the 

 land under appraisal. Reasonably accurate de- 

 termination of site index is the most important 

 appraisal step. It is a one-time task — site index 

 does not change. 



Methods available in the order of preference 

 include: 



Method 1 — Sample borings to determine 

 age and measurement of tree height. Ref- 

 erence to site index curves, Exhibits 42 

 a-c, will give the index for the specific 

 parcel. An increment borer and hypsom- 

 eter are the tools to be used. This is the 

 preferred method for sites having suffi- 

 cient trees of adequate diameter. 



Method 2 — For use in the absence of a re- 

 cent soil survey. Gain familiarity with the 

 area's terrain, representative! soils, and 

 pasture sites, as described in Exhibit 40. 

 Site index may then be determined by 

 reference to Exhibit 41. This method is 

 used for sites recently clear-cut and those 

 having seedlings and small saplings. 



Method 3 — If a recent Soil Survey Report 

 exists, reference to it will reveal site in- 

 dices for the entire county, identifiable by 

 detailed maps. 



3.7-10 Density of Stocking. 



(A) Stocking is a measure of the degree to 

 which growing space is effectively utilized by 

 trees. It is defined as follows: 



A — Well stocked — areas 70% or better 



stocked with growing stock. 



B — Medium stocked — areas 40 to 70% 



stocked with growing stock. 



C — Poorly stocked — areas 10 to 40% 



stocked with growing stock. 



(B) Density of stocking is best estimated by 

 aerial photo interpretation in conjunction with 

 ground observation. Crown closure percent, 

 also referred to as crown cover or crown den- 

 sity, is the proportion of the forest canopy 

 occupied by tree crowns. Measurements of 

 crown closure percent are made by viewing 

 aerial photos under stereoscope, using a crown 

 density scale similar to the examples shown 

 here. Exercise care not to overestimate crown 

 closure by overlooking small stand openings 

 or including portions of crown shadows. 



(C) A second method is measurement of basal 



CROWN DENSITY SCALE 



PERCENT CROWN COVER 

 1:15840 

 FOREST SURVEY- CENTRAL STATES FOREST EXPERIMENT STATION 



TIMBER SURVEY AID NO 5 



GUIDE FOR ESTIMATING DEGSEE OF STOCKING ON AERIAL PHOTOS 



BASED ON CROWN DENSITY OF DOMINANT AND CODGMIMANT TREES 



£5 % 



• . •■ Y: 



f .Til ' 



• ? ' . .' «" 



:*- : f. 



May be ordered f*om 



Director, Racihc Northwest Forest 8. Range Experiment Station 

 ot not- Regional Forester, US Forest Service Portland, Oregon 



area by the use of a prism calibrated to a 

 factor of 10. Step by step procedure is as fol- 

 lows : 



Step 1 — Select an observation point in the 

 stand that is representative of average stand 

 density as estimated by general observation. 



Step 2 — Observe all surrounding trees 

 through the prism, regardless of distance, and 

 tally them according to the following schedule : 



DBH Tally 



1.0 — Any tree where the image is with- 

 in the balance of the tree : 



24 



