1 Why Use Count Plots? A Comparison of Various Count to Measure Ratios In the BC Interior Presented by: Jim Wilson RFT, ATE May 2008

2 Overview  Why are we sampling?  What are we sampling?  Why sample with count plots?  Variations of count plots  Study  Results  Recommendations

3 Why are we sampling?  Cost prohibitive to measure every tree  For appraisal purposes, we require cruise estimates to calculate the stumpage rate  Decision is based on:  What sampling error can we live with based on our budget?  unfortunately, the min 2SE is set for us

4 What are we sampling?  For appraisals – net volume ±15% 2SE  Sampling for net volume has two equal parts:  BA/ha (tree count)  VBAR (measure trees)  We could just as easily sample for any other attribute: $ value, stems/ha, etc.

5 What are we sampling? Questions:  Are the items to sample:  More or less variable?  More or less costly to collect?

6 Why sample with count plots?  More variability, more samples needed  Tree count is usually more variable than the measure trees  Counting trees is easy and cheap, measuring trees is costly  Measuring trees is 50% of the answer, getting tree count is the other 50%  You decide how much of each to sample

7 Variations of Count Plots

8  Which sample better covers the ground and covers the variability of the stand?  Selecting trees with a Big BAF better distributes measure trees – more efficient  Count:Measure plots clump measure trees into clusters – less efficient

9 Study  Selected 7 interior cutting permits  Northern and Southern Interior  Stand types: SB, FPyL, Pl(S)  All full measures:  Randomly selected plots to start  Ratios 0:1, 1:1, 2:1, 3:1, 5:1 (count:measure)  Graphed net vol/ha, ISR $/m3, cruising costs

10 Results : Net Vol/ha SB stand

11 Results: Stumpage Rate SB stand

12 Results : Net Vol/ha PlS stand

13 Results: Stumpage Rate PlS stand

14 Results Tree Count CV: SB stand: 0:1 – 5:1 86 plots - 39% PlS stand: 0:1 – 5:1 117 plots - 38%  Each of the runs by stand had the same number of plots and therefore the same CV

15 Results VBAR CV:  SB stand:  0:1 – 397 trees - 28%  1:1 – 195 trees - 28%  2:1 – 136 trees - 28%  3:1 – 107 trees - 29%  5:1 – 74 trees - 30%  PlS stand:  0:1 – 653 trees - 23%  1:1 – 337 trees - 24%  2:1 – 212 trees - 22%  3:1 – 161 trees - 24%  5:1 – 117 trees - 23%  Why are we measuring so many trees?

16 Results Trends :  Net vol/ha does not change using count plots  averaged within ± 2%  Stumpage rate does not change using count plots  averaged within ± 5%  CV is stable for VBAR (we are measuring too many!)  Cruising costs are 30% less using 1:1 ratio and 50% less using 5:1 ratio versus full measure plots

17 Results Optimal solution to reach 15% 2SE (using Kim Iles’ star_bar.xls): SB stand:  Using TC CV of 39% and VBAR CV of 28%  41 count plots & 41 VBAR trees  Equivalent to 3.5 counts to 1 measure plot PlS stand:  Using TC CV of 38% and VBAR CV of 23%  37 count plots & 31 VBAR trees  Equivalent to 7.2 counts to 1 measure plot

18 Recommendations  Use count plots in highly variable stands to meet sampling error (more counts)  Use count plots in homogenous stands to decrease effort (less measure trees)  Use count plots in partial reduction areas  Use Big BAF to select measure trees and increase efficiency  Use count plots and spread out the trees!

19 Acknowledgements Srdjan Kragulj, RPF Timberline - Vancouver  he helped provide all the stumpage calculations for each of the runs Kim Iles, PhD  for spoon feeding me time and time again  his STAR_BAR.xls program should be used by everyone to plan cruises John Bell, PhD  for his short course and newsletter ( Walter Bitterlich, PhD  for making cruising so much easier

20 Questions? Jim Wilson, RFT, ATE Cruise Compilation Manager Timberline Natural Resource Group Phone: Cell: