Community Tree Risk Management Conducting Tree Risk Assessments Modified From Presentation by: Donna Murphy, MACUCF Coordinator, USDA Forest Service, NA, State and Private Forestry Tod Ericson, Urban and Community Forester, Maryland DNR Forest Service Developed by Jill D. Pokorny, Plant Pathologist, USDA Forest Service, Northeastern Area -- Dudley Hartel, Center Manager Urban Forestry South Athens, GA

Community Tree Risk Management Conducting Tree Risk Assessments Systematic approach to examining trees, assessing defects and estimating the degree of risk to public health. - Modeled after recreational systems - No system is adapted to all situations-communities - Numerical or scaled --

Community Tree Risk Management Assessment is part of the 7- Step FS System Step 1: Locate and ID trees to be inspected Step 2: Inspect individual trees and their defects Step 3: Estimate the risk rating for each tree (num) Step 4: Prioritize defective trees for treatment Step 5: Conduct a public review Step 6: Take corrective actions on highest priorities Step 7: Document the process, actions recommendations to be taken. --

Community Tree Risk Management Post Storm Surveys  84 % of damaged trees have pre-existing defects that are preventable.  Most common pre-existing defects:  Decay  Weak branch unions  Codominant leaders  Stem girdling roots --

Community Tree Risk Management Systematically Inspect Trees Parts of the tree to inspect  Crown  Branch  Branch unions  Stem or trunk  Root flare  Rooting zone Examine all sides of the tree  From a distance  Close up  Use diagnostic tools --

Community Tree Risk Management Collect and Store Data   Use a standard form   Store so data is easy to assess, update and retrieve   Consider compatibility   Plan for update needs --

Community Tree Risk Management Risk Rating System 1-4 Prob. of Failure 1-4 Size of Part(s) 1-4 Prob. of Target + + = 3-12 Risk Rating 1- infrequent 2 – occasional 3 – frequent 4 – constant 1 - low 2 - possible 3 - likely 4 - imminent 1 - <3” 2 – 3-5” 3 – 6-16” 4 - >16”

Community Tree Risk Management Probability of Failure 1 – Low: Some minor defects 2 – Possible: 1 or more moderate defects 3 – Likely: Multiple or significant defects 4 - Imminent: Combination of significant defects 1 4

Community Tree Risk Management Probability of Failure (1-4) 1 - Low: some minor defects present  minor branch dieback  minor wounds or defects

Community Tree Risk Management Probability of Failure (1-4) 2 - Possible: several moderate defects present  stem decay or cavity within safe shell limits  crack(s) without extensive decay  major branch with weak union and included bark  defect(s) affecting 30-40% of tree’s circumference  girdling roots with > 40% of trees circumference  < 40% of roots damaged within the CRR

Community Tree Risk Management Probability of Failure (1-4)  stem decay or cavity at or approaching shell safety limits (<1” sound wood for 6” diameter)  cracks, particularly at soil line  weak union with crack or decay 3 - Likely: multiple or significant defects present  defect(s) affecting > 40% of tree’s circumference or roots in the CRR  leaning tree with recent root lifting or soil mounding, crack or decay  dead tree without significant defects

Community Tree Risk Management Probability of Failure 3 - Likely: multiple or significant defects present Silver Maple > 50% crown damage Included bark Stem decay evident

Community Tree Risk Management Probability of Failure  stem decay or cavity exceeding shell safety limits and severe crack  multiple deep cracks or a single crack which goes completely through stem  weak union with crack and decay 4 – Imminent: any combination of high defects  defect(s) affecting > 40% of tree’s circumference or roots within CRR and decay present  leaning tree with recent root lifting or soil mounding and other significant defects  dead branches: broken (hangers) or cracked  dead trees with other significant defects

Community Tree Risk Management Probability of Failure (1-4) 4 - Imminent: any combination of high defects American beech Excessive stem decay Defects affecting >40% of tree circumference Extensive hangers Failure could occur at any time

Community Tree Risk Management Size of Defective Parts 1 - Parts less than 3 inches in diameter 2 - Parts from 3 to 5 inches in diameter 3 - Parts from 6 to 16 inches in diameter 4 - Parts greater than 16 inches in diameter

Community Tree Risk Management Target Impacted 1 – Infrequent 2 – Occasional 3 – Frequent 4 – Always 1 2 3

Community Tree Risk Management 1 – Infrequent Use  low use roads and park trails, natural areas, riparian zones, industrial parks Probability of Target Impact

Community Tree Risk Management Probability of Target Impact 2 – Occasional Use  moderate to low- use parks  dispersed campgrounds and picnic areas  secondary roads  bus stops along moderate-use roads

Community Tree Risk Management Probability of Target Impact 3 - Frequent Use  High-use public buildings  High-use school playgrounds and parks  Primary roads: congested intersections and bus stops  Drive-in campsites in high-use parks

Community Tree Risk Management Probability of Target Impact 3 - Frequent Use

Community Tree Risk Management Probability of Target Impact 4 - Constant Use  Emergency access routes  Medical and emergency facilities  Structures  Playground equipment  Benches  Picnic tables

Community Tree Risk Management 10 3 Size of Defective Part 6-16” in diameter Risk Rating Probability of Failure Crack with extensive decay and cavity Outer shell width below shell safety limits (min. ratio: 2”per 6” stem diameter) 4 3 High-use area Target Impact

Community Tree Risk Management Trunk slit by major crack 2 inch rule: just meets shell limit > 16” diameter Public sidewalk and house Probability of Failure Size of Defective Part Target Impact Risk Rating

Community Tree Risk Management Probability of Failure 3 3 Size of Defective Part Target Impact 6-16” in diameter neighborhood street 3 9 Risk Rating

Community Tree Risk Management Probability of Failure 4 Size of Defective Part 3 Target Impact 2 Risk Rating 9 Silver maple with multiple cracks Decay and woodpecker damage From 6-16” in diameter High-use area

Community Tree Risk Management

Probability of Failure 3 Size of Defective Part 3 Target Impact 4 Risk Rating 10 Elm with closed crack in trunk >40% CRR compromised > 16” in diameter High-use area

Community Tree Risk Management Stem with cavity and crack. 2 inch rule: just meets shell limit Part from ” diameter Open area with fountain Probability of Failure Size of Defective Part Target Impact Risk Rating

Community Tree Risk Management Probability of Failure Size of Defective Part Target Impact Risk Rating Weak union with included bark Narrow crack is present 6-16” in diameter Parking lot adjacent to high use street 3

Community Tree Risk Management Probability of Failure Size of Defective Part Target Impact Risk Rating Flagging in upper branches from BLS No major structural defects 8-18” in diameter Intermittent use area 2

Community Tree Risk Management Discussion…