FWF Silviculture Lab Exercise 2018 Spring Semester. Comparison of Thinning Methods

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1 Page 1 of 10 FWF Silviculture Lab Exercise 2018 Spring Semester Comparison of Thinning Methods Introduction Thinning is the technique that more than any other distinguishes intensive silvicultural practice and is the primary means by which productivity of stands can be adjusted beyond what might be achieved under purely natural conditions. Thus, appreciation and understanding of thinning procedures requires knowledge of many fundamentals basic to silviculture. Recognition of crown classes and evaluation of relative crown position are components of many silvicultural practices. The crown classes most commonly used are dominants, codominants, intermediates and overtopped. You should know the definitions and be able to interpret and distinguish crown classes from previous discussions. Objective The objective of this exercise is to compare thinning methods as to the material removed and effect on the residual stand (trees retained or left) Field Location 16-year old loblolly pine plantation (planted in 2002), Oak Ridge Forest Resources Research and Education Center, Chestnut Ridge Equipment Field data forms (columnar paper), diameter tape, flagging, reel tape, clinometer, prism Field Procedures Be cognizant of safety while in the plantation. Week 1 1. Divide into field crews as designated by the instructor, and work in locations designated by the instructor. 2. Lay out a square one-fifth acre plot (93.3 by 93.3 )

2 Page 2 of Designate a corner of your plot for re-identification with flagging, i.e., be able to find that corner if you need to return during the next lab period 4. Determine plantation spacing average spacing within and between rows. How many rows are within your 1/5 acre plot? Rows extend across the slope direction 5. Measurement of trees a. Make a preliminary determination of basal area using a prism (number of in trees x 10). Ten factor prisms have a plot radius factor of 2.75 for determining if borderline trees should be counted. b. Map present and missing trees on your plot with columnar paper. Live trees receive measurements on the graph/columnar paper and dead or missing trees receive an x. Orient one corner with a cardinal direction using a compass so that it will be easy to pick up work where you left off in week 2. c. Record diameter (nearest inch --- i.e., 6-inch size class are trees from 5.5 to 6.4 inches in diameter) and crown class (overstory or subordinate) for each tree. Indicate whether the tree has poor form (forks, crooked, etc) and should be removed during a thinning. Estimate a diameter threshold to distinguish between subordinate and overstory trees d. Record crown position for each tree, either overstory or subordinate. Why? e. Select a subsample of any 3 overstory trees and measure: total height and height to base of live crown Accurate and efficient collection of data this week will facilitate your work next week! If you are efficient in data collection during the first week, you may be able to accomplish some of the field work for second week below into the first week --- we have two weeks scheduled for collecting data. Week Thinning by Different Methods --- (for more context on thinning methods, refer to pages in your text) Relocate your one-fifth acre plot. A. Conduct a low thinning (thinning from below) by designating cut stems. Description: Trees are removed from the lower crown classes, some

3 Page 3 of 10 codominants can be removed, especially those of poor form with sweeps, cracks, cankers, and forks. They can also have small live crowns. Remaining trees should be in the overstory. 1. Record removal trees from the low thinning on your tally sheets. B. Conduct a free thinning. Description: A combination of low and crown thinning to release potential crop trees; residual basal area should be about 80 square feet/acre. 1. Record removal trees from your free thinning on your tally sheets. These should include all trees from your low thinning conducted in #1 above and the trees removed as a crown thinning C. Conduct a mechanical or row thinning. Description: Remove every 3 rd row. This can be solely done from the tally sheet and field marking is not necessary. D. Conduct a row/combination thinning. Description: After the row thinning, trees are thinned from remaining rows following free thinning techniques, primary to leave evenly spaced dominant and co-dominant overstory trees. 1. Survey trees in the rows on each side of the row thin and determine other trees to be thinned based on spacing. With the row thin, 33% of the trees are removed (1 of 3 rows). Generally with a row/combination thin, another 20% of the trees are thinned/removed such that approximately the total thinning is removing about 50% of the original trees. Office Procedures A. Stand parameters 1. Construct a stand table (1.0-inch diameter classes) for the original stand and the residual stand after each of the 4 thinning methods/procedure (on a per acre basis). A stand table contains # of trees by diameter class. 2. For each thinning method and the original stand, calculate the (a) number of stems, (b) basal area, (c) diameter of a tree of mean basal areas, (d) volume (per acre basis). Do calculations for cut material and residual stand (remaining trees).

4 Page 4 of 10 B. Crown Classes 3. For each thinning method, calculate the mean diameter of the remaining trees and the mean diameter of the cut trees. 4. The information calculated in 2 and 3 above should be compiled into a single summary table. 1. Calculate the percentage of stems in each crown class (overstory and subordinate) for the original stand, the cut material in each thinning method, and the residual material after each thinning method. Calculate # in each crown class and get % of total. 2. Compile this information into a single table for comparison. C. Diameter Distributions 1. For each thinning method, draw on a common set of axes the diameter distribution curve for the original stand and that of the residual stand after thinning. 2. Indicate the removed material on each of the four illustrations. 3. Figure captions go below the figure D. Other measurements 1. Determine the average height and average live crown ratio for the overstory trees. 2. Determine site index from the table that will be given to you. 3. Determine a. Mortality per acre based on the original planting b. Basal area per acre --- add BA for each tree measured in the plot, then put on a per acre basis (Section A2b above). Compare to your prism measurement.

5 Page 5 of 10 Report A. Content B. Format 1. Discuss each thinning method as to the material removed and the effect on the residual stand. Discussion should include: (a) stand parameters, (b) crown classes, (c) diameter distribution, (d) expected growth response, and (e) economic considerations. Data should be presented on an ACRE basis, NOT on a plot basis. 2. Compare thinning methods as above. In your comparison of thinning methods, discuss the advantages and disadvantages of each method based on your data. Example --- low thinning did not reduce BA enough to release crop trees; low thinning might not be economical, etc. 3. Since we did not thin to a prescribed diameter, volume or basal area, use the stocking charts to determine stocking of the present stand and the stocking of the stand following each of the thinnings. Based on your data for each thinning method, should more trees be left or more trees be cut. 4. In light of the description and comparison of thinning methods, recommend the method you feel is best suited to the current stand conditions and assuming a sawlog rotation. Give adequate justification for your selection. 5. Give hypotheses on how the plantation could have been more efficiently managed. What regeneration options are available if objectives are to (a) convert to hardwoods or (2) remain in loblolly pine? 1. The report should be presented in acceptable format. 2. Crew leaders will include field tally sheets in their report. 3. All figures and tables must be adequately labeled. 4. Your main objective should be to interpret the data and discuss the results in relation to the principles we have discussed. Use

6 Page 6 of 10 your textbook as a reference! Your report will be evaluated for accuracy, neatness, completeness, interpretation and understanding of the data you have collected. Other Info in this handout 1. Loblolly Pine Stocking Table (Westvaco) 2. Site Index Curve for Loblolly Pine Plantations (Smalley) 3. Basal Area Table Basal Area = x DBH 2 DBH in inches, Basal area in ft 2 4. Loblolly Pine Volume Table (in cubic feet ft 3 ) by total height and 4-inch top Source: Alexander and Souter 1994 Forest Service, SE Forest Experiment Station Research Paper SE Tally Sheet for mapping EWP stems (additional EXCEL file) Due Date: Target Date is March 7 and 8, 2018 (week before spring break)

7 Volume equations (ft 3 ) Page 7 of 10

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10 BA = x D 2 Page 10 of 10