A.P.E.S. “Cruising” the Forest: Estimating Basal Area and Assessing Forest Composition Introduction: Timber cruising is a kind of surveying done by foresters to ascertain the value of a forest, its species composition, age, etc. In this activity you will use a special kind of a prism to determine the basal area of different tree species in the local forest. Basal area is the cross-sectional area of the tree trunk – the roughly circular area of the stump if the tree were cut down. Procedure: ● Measure 37 feet (or 11.3 meters) with your tape measure. A circle with this radius has an area equal to one-tenth of an acre ● Identify the tree species present using a field guide ● Standing at the center of a 37-foot radius circle, hold the prism at arm’s length so that you are looking through it as illustrated below ● Look at each tree in the circle ● The prism will cause the tree trunks to appear offset. If they are completely offset, do not count them. If they are not completely offset, count them “in” In Out ● Chart the number of “in” trees of each species ● For each species, multiply the number of “in” trees by the number on the prism (probably 10) to find the basal area in square feet/acre ● If time allows, move to a second point and repeat ● Average the class data for each species Group data: NA for remote learning Species Number “in” Basal area Class data: to convert average basal area to board feet (the unit by which we measure lumber) assume 2 logs per tree and use this graph to make the conversion: Species Chestnut oak Northern red oak White oak Sugar maple Red maple Birch Hickory Total basal area, all groups 50 ft2/acre 120 ft2/acre 20 ft2/acre Average basal area (ft2/acre) 16.7 40 6.7 50 ft2/acre 50 ft2/acre 16.7 16.7 Thousand board feet/acre Conclusions: 1. Which species were most dominant? 2. How could you check on the accuracy of the prism method we used to measure basal area? 3. Using the average basal area/square acre from the class data, research the timber value of the forest. “Forest value per acre” is a good starting search term or use provided links: https://www.dec.ny.gov/docs/lands_forests_pdf/sprwinter20.pdf - use the Hudson/Mohawk average price range median price if possible) https://extension.psu.edu/pennsylvania-timber-market-report-2nd-quarter-2020 Report your results here: (don’t add the example to your total!) Species Average basal area (ft2/acre) Thousand board feet/acre (mbf) Median value $/thousand board feet Value per acre ($) ex: Sugar maple Total: 30 3.6 390 1404 4. Try searching “ecosystem service value per acre” or something similar, or use these two websites that give an estimate for the ecosystem services value of the forest, and report your findings here: a. https://www.sierraforestlegacy.org/Resources/Conservation/FireForestEcology/Fo restEconomics/EcosystemServices.pdf (see table 2 for $/acre estimate): b. https://www.njkeepitgreen.org/wp-content/uploads/2019/05/Valuing-NJs-nat-cap1.pdf (see table 5 on page 17 for $/acre/year): 5. In three to four sentences, state and defend what you think the best use of this part of the forest might be: logging or forest preserve (keep in mind that the timber value is a cash value while the ecosystem service value benefits the community but may not give you money):
