PLOT SIZE CODES FOR TREES IN THE IDB

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Madeleine Johnson
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1 Trees per Acre and Trees per Hectare Calculations Every tree in an inventory is expanded to the number of trees it represents per-unit-area. The equation used to estimate the tree-level expansion factor depends on the size of the plot where the tree was sampled. s include variable radius plots sampled with a metric or English prism and fixed radius plots. sizes can differ among the many inventories in the IDB as follows: acre (1 hectare) plot, eastside acre (1 hectare) plot, westside 03 1/4 acre 04 1/5 acre or 1/5.3 acre, eastside 05 1/5 acre or 1/5.3 acre, westside 06 1/20 acre 07 1/8 acre 08 1/100 acre PLOT SIZE CODES FOR TREES IN THE IDB 10 variable plot, BAF 7 metric (FIACA, FIAWW, FIAWO) 11 variable plot, BAF 20 English (FIAEO, R5) 12 variable plot, BAF 30 English (FIAEO) 13 variable plot, BAF 40 English (FIAEW, R5) meter fixed plot (FIAWO) meter fixed plot (FIAEO), For plots using a 20 BAF meter fixed plot (FIAEO), For plots using a 30 BAF meter fixed plot (FIACA, FIAWW) meter fixed plot (FIAEW) meter fixed plot (FIAWW) Trees sampled in Northeast Quadrant SPECIFICS FOR EACH INVENTORY: FIA Inventories: Data Source Location Range of Diameters Sampled Type Size radius size code R6 & BLMWO seedlings Fixed 1/100 ac ft. 8 >= 1 and < 3 Fixed 1/100 ac ft. 8 R6 >= 3 and < 13 Fixed 1/20 ac ft. 6 BLMWO >= 3 and < 13 Fixed 1/24 ac 24.0 ft. 6 Eastside >= 13 and < 32 Fixed 1/5.3 ac ft. 4 Westside >= 13 and < 48 Fixed 1/5.3 ac ft. 5 Eastside >= 32 Fixed 2.5 ac. (1ha) Westside >= 48 Fixed 2.5 ac. (1ha) R5 seedlings Fixed 1/100 ac ft. 8 >= 1 and < 5 Fixed 1/100 ac ft. 8 >= 5 Fixed 1/8 ac ft. 7 >= 5 and < 30.4 Variable BAF >= 5 and <= 42.8 Variable BAF >= 20 fixed ¼ ac

s include variable radius plots sampled with a metric or English prism and fixed radius plots. sizes can differ among the many inventories in the IDB as follows: 01 2.

2 SPECIFICS FOR EACH INVENTORY: FIA Inventories: Data Source Range of Diameters Sampled Type Size (radius) BAF of Prism FIACA < 17.5cm Fixed 3.3m 17 >= 17.5cm and < 90cm Variable 7 m2/ha 10 >= 90cm Fixed 17.0m 10 FIAWO < 12.5cm Fixed 2.35m 14 >= 12.5cm and < 90cm Variable 7 m2/ha 10 >= 90cm Fixed 17.0m 10 FIAWW < 12.5cm Fixed ¼ of 3.3m 20 >= 12.5 and < 17.5cm Fixed 3.3m 17 >= 17.5cm and < 90cm Variable 7 m2/ha 10 >= 90cm Fixed 17.0m 10 FIAEW < 12.5cm Fixed 2.1m 18 >= 12.5cm Variable 9.18 m2/ha 13 size code FIAEO 2 BAF s were used in this inventory, depending on stand density. Other plot sizes differed based on the BAF used for the plot. FIAEO s that used a BAF 20: < 12.5cm Fixed 2.96m 15 >= 12.5cm and < 89cm Variable 20 ft2/ac 11 >= 89cm (none tallied) Fixed 16.95m 11 s that used a BAF 30: FIAEO < 12.5cm Fixed 2.41m 16 >= 12.5cm and < 89cm Variable 30 ft2/ac 12 >= 89cm Fixed 16.95m 12

5 and < 17.5cm Fixed 3.3m 17 >= 17.5cm and < 90cm Variable 7 m2/ha 10 >= 90cm Fixed 17.0m 10 FIAEW < 12.5cm Fixed 2.1m 18 >= 12.5cm Variable 9.

3 EQUATIONS FOR CALCULATING TREES PER UNIT AREA SUBPLOT LEVEL: TPH_SUBPLOT and TPA_SUBPLOT ** DBH_CM ** EQUATION Approx Size Value Code FIACA 17 < 17.5 TPH_SUBPLOT = 10,000 / (pi * (3.3^2)) >= 17.5 and < 90 TPH_SUBPLOT = 10,000 / (pi * ((DBH_CM * )^2)) 10 >= 90 TPH_SUBPLOT = 10,000 / (pi * (17^2)) FIAWO 14 < 12.5 TPH_SUBPLOT = 10,000 / (pi * (2.35^2)) >= 12.5 and < 90 TPH_SUBPLOT = 10,000 / (pi * ((DBH_CM * )^2)) 10 >= 90 TPH_SUBPLOT = 10,000 / (pi * (17^2)) FIAWW 20 < 12.5 TPH_SUBPLOT = (10,000 / (pi * (3.3^2))) * >= 12.5 and < 17.5 TPH_SUBPLOT = 10,000 / (pi * (3.3^2)) >= 17.5 and < 90 TPH_SUBPLOT = 10,000 / (pi * ((DBH_CM * )^2)) 10 >= 90 TPH_SUBPLOT = 10,000 / (pi * (17^2)) FIAEW 18 < 12.8 TPH_SUBPLOT = 10,000 / (pi * (2.1^2)) >= 12.8 TPH_SUBPLOT = 10,000 / (pi * ((DBH_CM * )^2)) FIAEO : BAF < 12.5 TPH_SUBPLOT = 10,000 / (pi * (2.96^2)) >= 12.5 and < 89 TPH_SUBPLOT = 10,000 / (pi * ((DBH_CM * )^2)) 11 >= 89 TPH_SUBPLOT = 10,000 / (pi * (16.95^2)) FIAEO : BAF < 12.5 TPH_SUBPLOT = 10,000 / (pi * (2.41^2)) >= 12.5 and < 89 TPH_SUBPLOT = 10,000 / (pi * ((DBH_CM * )^2)) 12 >= 89 TPH_SUBPLOT = 10,000 / (pi * (16.95^2)) Note that for FIA inventories, some plots were access denied and projected forward. The trees per unit area on these plots have been calculated in a different way and do not match the equations above. Access denied plots have a SAMP_KIND=2 found in the COND table. Condition Level trees per unit area TPH = TPH_SUBPLOT / SUBPLOT_COUNT_COND TPA = TPA_SUBPLOT / SUBPLOT_COUNT_COND

5 and < 90 TPH_SUBPLOT = 10,000 / (pi * ((DBH_CM * 0.18896)^2)) 10 >= 90 TPH_SUBPLOT = 10,000 / (pi * (17^2)) 11.014 FIAWW 20 < 12.5 TPH_SUBPLOT = (10,000 / (pi * (3.3^2))) * 4 1169.2 17 >= 12.

4 SUBPLOT LEVEL: TPH_SUBPLOT and TPA_SUBPLOT size ** DBH_IN ** EQUATION Approx Value R6 AND BLMWO 8 < 3.0 TPA_SUBPLOT = 43,560 / (pi * (11.8^2)) 100 R6: 6 >= 3.0 and <13.0 TPA_SUBPLOT = 43,560 / (pi * (26.3^2)) 20 BLMWO: 6 >= 3.0 and <13.0 TPA_SUBPLOT = 43,560 / (pi * (24 ^2)) 24 Eastside: 4 >= 13.0 and < 32.0 TPA_SUBPLOT = 43,560 / (pi * (51.1^2)) >= 32.0 TPA_SUBPLOT = (43,560 / (pi * (185.1^2))) * Westside: 5 >= 13.0 and < 48.0 TPA_SUBPLOT = 43,560 / (pi * (51.1^2)) >= 48.0 TPA_SUBPLOT = (43,560 / (pi * (185.1^2))) * R5 8 < 5.0 TPA_SUBPLOT = 43,560 / (pi * (11.8^2)) >= 5.0 TPA_SUBPLOT = 43,560 / (pi * (41.6^2)) 8 11 >= 5 and < 30.4 TPA_SUBPLOT = 20 / ( *(DBH_IN^2)) 13 >= 5 and <= 42.8 TPA_SUBPLOT = 40 / ( *(DBH_IN^2)) 3 >= 20 TPA_SUBPLOT = 43,560 / (pi * (58.9^2)) 4 Condition Level trees per unit area TPH = TPH_SUBPLOT / SUBPLOT_COUNT_COND TPA = TPA_SUBPLOT / SUBPLOT_COUNT_COND Variable Radius s The diameter used in the majority of TPA_SUBPLOT or TPH_SUBPLOT calculations was the DBH from the most recent inventory. However, for FIA inventories in Washington, a walkthrough inventory was conducted on some plots. Trees on these plots use the DBH from the previous inventory (PREV_DBH_CM) to calculate the subplot-level TPA or TPH.

0 TPA_SUBPLOT = (43,560 / (pi * (185.1^2))) * 5 2.023 Westside: 5 >= 13.0 and < 48.0 TPA_SUBPLOT = 43,560 / (pi * (51.1^2)) 5.31 2 >= 48.0 TPA_SUBPLOT = (43,560 / (pi * (185.1^2))) * 5 2.023 R5 8 < 5.

5 Level trees per unit area Note that these trees per unit area calculations are not stored in the IDB. TPH plot = TPH_SUBPLOT / (Count of subplots on the plot) TPA plot = TPA_SUBPLOT / (Count of subplots on the plot) Trees per Unit Area in the IDB In the IDB, the TPA and TPH are calculated and stored as condition class level trees-per-unit-area instead of a plot-level representation. The difference between the two is based on which subplot count is used to average the subplot level TPA or TPH. TPA condition = TPA_SUBPLOT / (Count of subplots in the condition) TPA plot = TPA_SUBPLOT / (Count of subplots on the plot) The decision to store the condition level TPA or TPH was for ease of use in the summary and analysis of data in the database. Although the primary sample unit is the plot and condition class is an attribute of a plot, each plot is essentially divided and stored as condition class records. The ACRES and ACRES_VOL are associated with a particular condition class, and represent the amount of acres covered by that condition on a given plot. Because the TPA in the IDB is weighted by the size of the condition class (i.e. divided by the number of subplots in the condition), all other per-acre tree variables such as volume/acre or biomass/acre are also weighted by the condition class area. When calculating standard errors please refer to the publication by T. Barrett entitled Estimation procedures for the combined 1990s periodic inventories of California, Oregon, and Washington (in press). A draft of this publication is available with the technical documentation and is called Alternative_Estimation_procedures.doc. Equations and programs used to calculate standard errors correctly require information about the primary sample unit (plot location) and the stratification scheme used in each inventory. It is important to know that the IDB stores TPA, TPH, all per-acre tree variables, ACRES and ACRES_VOL as variables weighted by the proportion of the plot in the condition (COND_WT).

as condition class level trees-per-unit-area instead of a plot-level representation. The difference between the two is based on which subplot count is used to average the subplot level TPA or TPH.

6 SEEDLINGS: When SEEDLING_YN=Y on R5, R6, and BLMWO plots, the live tree record represents a group count. The column TREE_COUNT is the count of the number of seedlings observed on a fixed radius plot in these inventories, which has a maximum count equal to 10. An adjustment must be made to the trees per unit area to account for the group: TPA=TPA*TREE_COUNT TPH=TPH*TREE_COUNT TPA_SUBPLOT=TPA_SUBPLOT*TREE_COUNT TPH_SUBPLOT=TPH_SUBPLOT*TREE_COUNT For each seedling group, the trees per unit area represent an estimate for the entire group. Note that treesper-unit area may appear larger than what you might expect at first glance, because the individual TPA has been multiplied by the TREE_COUNT. The group count was only done in the R5, R6, and BLMWO inventories and not in the FIA inventories. SMALL SAPLINGS The R5, R6, and BLMW inventories also include a group count for 2 saplings. The same procedure described above was done on the TPA and TPH for these trees.

An adjustment must be made to the trees per unit area to account for the group: TPA=TPA*TREE_COUNT TPH=TPH*TREE_COUNT TPA_SUBPLOT=TPA_SUBPLOT*TREE_COUNT TPH_SUBPLOT=TPH_SUBPLOT*TREE_COUNT For each

Lesson 10: Basic Inventory Calculations

Lesson 10: Basic Inventory Calculations Review and Introduction In the preceding lessons, you learned how to establish and take measurements in sample plots. You can use a program like LMS to calculate