FR 3218/5218 Spring 2007

Due March 28, 2007

This assignment covers summarizing a variable-radius plot, computing stand and stock table entries from variable-radius plots, "height-only-tally" of variable-radius plots, and double sampling with variable-radius plots.

It is important that you show your work. Credit cannot be given if answers are not accompanied by intermediate calculations that demonstrate how you arrived at the final solution. The TA will use the intermediate calculations to determine the level of partial credit to be granted for wrong answers. If you turn in a printout of a spreadsheet be sure to include the formulas you used to calculate all intermediate and final estimates (see Excel insert in the solution set for Assignment 1). You may also use a statistical package if you wish. If you do, turn in printouts that are annotated so that the TA can follow the calculations. All data for this assignment are in the Excel workbook hw5Data_07.xls.

1. Ten (10) trees were "in" on a 15BAF variable-radius plot. The tally results are in worksheet VarPlot. Compute the plot observations of trees/acre, basal area/acre, and volume per acre BY SPECIES (since there are two species you will compute six numbers). The volume unit of interest is board-feet (International 1/4-inch rule) and Table 2 of Bulletin 1104 (class handout) has been determined to be appropriate.

2. A stand was cruised using 15, 20BAF variable-radius plots. Tally results for three DBH/species combinations are given in worksheet StndStck (41 trees total). Find the per acre stand and stock table entries for the DBH and species combinations that appear in the worksheet (compute six numbers total). You don't need to lay out formal stand and stock tables. The volume unit of interest is cords and Table 6 of Bulletin 1104 has been determined to be appropriate.

3. If the tally in 1. had been "by height only" (no DBH observed), what would have been the estimate of volume per acre for the two species combined (compute one value)? Use trees 10- to 22-inches DBH in your calculation of average VBAR (tree volume to basal area ratio) by height (don't go beyond using a separate VBAR by height class); the data necessary to compute the average VBARs are in worksheet Vols. How does the "by height only" volume per acre compare to what you obtained in 1.? Does the shortcut seem adequate (realize this is only one plot!)?

4. Double sampling with a 25BAF instrument was used to cruise a jack pine pulpwood stand. Twenty (20) total plots were used with trees measured on four (4) plots. The results are in worksheet Double. Calculate tree volumes using Table 6 of Bulletin 1104. Compute volume per acre using the standard ratio-of-means estimator. Compute volume per acre using the formula (average G) * (average VBAR), where G is basal area per acre (show each calculation separately even though you should get the same answer). Finally, estimate the standard error of your cords per acre estimate (using the standard error formula for double sampling with a ratio-of-means estimator).