Diameter at Root Collar Measurement Guidelines Photo by

Diameter at Root Collar Measurement Guidelines Photo by Jim Stoltz. Copyright Walkin’ Jim Stoltz. 1

1 - DRC Variables 2 - Diameter Groupings 3 - Measuring DRC Stem Diameter 4 - Single or Multiple Stem Tree 5 - Unified or Distinct Crowns 6 - Computing DRC 7 - Estimations 8 - More Examples Topics Covered Photo by Ken De. Kamp. USDA Forest Service. 2

1 – DRC Variables • DRC Stem Diameter • Enter species code 66 and press Ctrl P on the PDR in order to open the DRC Calculator. • Enter the diameter for each stem. • The DBH variable on the PDR is shaded out and will auto populate once the DRC Calculator is complete and accepted. • DRC Stem Status • Enter a status of 1 for each live stem and a 2 for each dead stem. 3

1 – DRC Variables (continued) • Past Number of Stems • This is a hidden variable that will not show up on the PDR. • Current Number of Stems • This is a hidden variable that will auto populate at the bottom of the DRC Calculator once all data is complete and accepted. 4

2 - Diameter Groupings Saplings (microplot) • Single-stemmed trees between 1. 0 inch and 4. 9 inches in diameter. • Multi-stemmed trees with a cumulative DRC between 1. 0 inch and 4. 9 inches in diameter. Trees (subplot) • Single-stemmed trees 5. 0 inches in diameter or larger • Multi-stemmed trees with a cumulative DRC of at least 5. 0 inches or larger 5

3 - Measuring DRC Stem Diameter • remove loose material on the ground • DO NOT remove mineral soil • measure at ground line when reasonable • measure DRC just above any swells present • must be measured in a location that is a good representation of the volume in the stems • If excessive diameter exists at the base, measure the stems occuring above the base individually • stems must be at least 1 foot in length AND at least 1. 0 inch in diameter a foot up from the diameter measurement point • ignore cut or missing stems 6

Where should DRC stem diameter(s) be measured? C B D A E E is Judged NOT to be excessive. All non labeled stems in the picture are from a separate tree. Do measure E, NOT A, B, C and D individually 7

Where should DRC stem diameter(s) be measured? B C A D 8

Where should DRC stem diameter(s) be measured? Since this group of trees share both a unified crown and common root stock it is tallied as one tree with multiple stem entries Stems E and G are measured instead of measuring at location M because stems E and G best represent the volume of this tree E B H C A Location A represents the first stem, so location B is NOT measured. G D F M J I K L Ignore cut/missing stems that have deteriorated 9

DRC stem diameter measurement points. single tree – 3 stems with a unified crown single tree – 1 stem No unified crown 10

DRC stem diameter measurement points. These trees do not share a common crown……. . so they are tallied as 3 individual trees Ignore stem stubs that have deteriorated. B D is taken high to best represent the volume of the stem, accounting for the distortion in the bole caused by C. C D E F A Do not tally stumps. 11

4 – Single Multiple Stem Tree Is the tree Rocky Mountain Juniper 0066? Measure DBH, not DRC No Yes Does the clump of trees have both a unified crown AND common root stock? single tree – 3 stems Yes No Treat each tree in the clump as an individual tree. A B C Treat the clump of stems as a single tree. 12

5 - Unified or Distinct Crowns 3 distinct crowns This example shows: • 3 distinct crowns • 4 DRC measurement points • the two stems in blue are recorded as a single tree • the purple and orange stems are both single stemmed trees 13

Tree Individual Stem Diameters Number of Sapling or Which stems areand trees and which are saplings? Tree Number Status Stems 1 A - Live B - Live 2 Tree 2 C – Dead --- 1 Sapling 3 D - Dead --- 0 Not Tallied Single Crown A B C D Single Crown Single Unified Crown All are re-measurement trees growing on the micro plot. Stem Diameters A 3. 9 in B 3. 7 in C 1. 2 in D 0. 8 in With a Diameter of less than 1. 0 inch, D is too small to tally. 14

5 - Unified or Distinct Crowns Single unified crown 15

How many crowns are there? 16

How many distinct crowns are there? 17

How many distinct crowns are there? There are 2 crowns, but 4 trees (no common root stock) 1 2 3 4 18

6 - Computing DRC NRS will use the DRC Calculator by pressing Ctrl P on the PDR to compute DRC = SQRT [SUM (stem diameter 2)] round to the nearest 0. 1 inch Examples Tree Number Individual Stem Diameters and Status Number of Stems Tree or Sapling Computed DRC 1 12. 2 - Live 13. 2 - Live 3. 8 - Live 22. 1 - Live 4 Tree 28. 7 2 5. 6 - Live --- --- 1 Tree 5. 6 3 1. 4 - Live 3. 1 – Dead 2. 7 - Live --- 3 Sapling 4. 3 4 1. 1 - Live 1. 3 - Live 3. 0 – Old Stub 1. 3 - Live 3 Sapling 2. 1 19

How should DRC be computed for these stems? Stem Diameters Single Crown A B C D Single Crown Single Unified Crown A 2. 9 in B 2. 7 in C 1. 2 in D 0. 8 in Red tree DRC = SQRT [(A 2) + (B 2)] = SQRT [(2. 92) + (2. 72)] = SQRT [8. 41 + 7. 29] = SQRT [15. 7] = 3. 96232 = 4. 0 DRC Green tree DRC = SQRT [C 2] = SQRT [1. 22] = SQRT [1. 44] = 1. 2 20

7 - Estimations Whenever DRC is impossible or extremely difficult to measure with a diameter tape (e. g. , due to thorns, extreme number of limbs), stem diameters may be estimated and recorded to the nearest 1. 0 -inch class. 21

8 – More Examples 22

A Tree Number B C D Individual Stem Diameters and Status Number of Stems 1 A - Live B - Live C - Live 3 2 D - Live --- 1 23

Tree Number A Individual Stem Diameters and Status Number of Stems 1 A - Live --- 1 2 C - Live --- 1 B C D 24 purposes only. Photo by Robert Sivinski. Copyright 2004 Robert Sivinski and UC Regents. Used by permission for educational

Two Trees • the two stems appear to have a common root stock, but • have two distinct crowns Tree Number A Individual Stem Diameters and Status Number of Stems 1 A - Live --- 1 2 B - Live --- 1 B Photo by Larry Penington. Copyright Sierra Club. 25

Photo by Hunt Tec LLC. 26