Using The ISA Basic Tree Risk Assessment Form

12Occupancyrate1– rare2 – occasional3 – frequent4 – constantRestrictionpractical?Target within1.5 x Ht.Target descriptionTargetwithin 1 x Ht.Target withindrip lineTargetnumberTarget zonePractical tomove target?Target AssessmentSection 3—Site Factors34Site FactorsHistory of failures Topography Flat Slope % AspectSite changes None Grade change Site clearing Changed soil hydrology Root cuts DescribeSoil conditions Limited volume Saturated Shallow Compacted Pavement over roots % DescribePrevailing wind direction Common weather Strong winds Ice Snow Heavy rain DescribeTree Health and Species ProfileVigor Low Normal High Foliage None (seasonal) None (dead) Normal %Chlorotic %Necrotic %Pests AbioticSpecies failure profile Branches Trunk Roots DescribeFactorsSite factors may influence the likelihood of tree failure. ThisLoadsectionprovides a list of common site factors that should be considWindexposureProtected Full areWindfunnelingRelativeSmallare notMedium ered.Theremay beother sitePartial factors thatcriticalon a givensite, or which you shouldnotecrownevensizeif theyon thisLargeform.densitySparse Normal Few Normal Dense paper.Vines/Mistletoe/Moss AnyCrownof thesefactorscan befurther Dense describedInteriorin thebranchesspace providedor on additionalOther site factorsaffecting wind loadRecent or planned change in load factorsshould be noted. These may include the site elevation, surface roughness, and hilltop locations.Tree Defects and Conditions Affecting the Likelihood of Failure— Crown and Branches —History of failures—note and describe evidence of previousSoil conditions—factors that can affect the ability of the rootUnbalancedLCRestimate% the time frame forCracks systemLightningwhole-treefailures crownon the site, andto mechanically support the tree,as welldamageas the generalDead twigs/branches % overall Max. dia.Codominant Included bark how recentlythey occurred.Previousbranchfailuresshouldhealth and vitality of the tree; check all that apply:Broken/HangersNumberMax.dia.Weak attachments Cavity/Nest hole % circ.be notedOver-extendedin the CrownandBranchesbox(locatedintheTreebranches Limited volume—soil volume limited by rocks, waterDefects andConditionsAffecting the Likelihood of Failure Previous branch failures Similar branches present Pruninghistoryfoundations,of a container,or otherDead/Missingtable,bark buildingCankers/Galls/Burls sizeSapwooddamage/decaycleaned Thinned Raised section ofCrownthe form).factors.Conks Heartwood decay Reduced Topped Lion-tailed Flush cuts OtherTopography—checkboxes forflat or sloping topography; Response growthSaturated—soil saturated due to poor drainage, high wateran estimatethe slope percentage may be included.Mainofconcern(s)table, excess irrigation, or location in a low area. May besaturated now or have a history of inundation.Aspect—thecompassfacing.Load ondefect directionN/A that the slopeMinor is Moderate Significant Likelihood of failure Improbable Possible Probable ImminentShallow—rootingdepth limited by one or more factorsSite changes—factors affecting the root system of the tree orincludinghighwatertable,rockCollarledges, —compacted layers,Trunk— check all that apply:— Roots andRootthe change in exposure of the—treeto wind;or undergroundstructuressuch as parkingDead/Missing bark Abnormal bark texture/color Collarburied/Not visible DepthStem decks.girdling None—noevidenceof recentIncludedsite changes.Codominantstems bark Cracks Dead Decay Conks/Mushrooms Compacted—soil is severely compacted, limitingtheSapwooddamage/decay Cankers/Galls/Burls Sapooze Ooze spread,Cavity% circ. of the root system.Grade change—soil was added or removed from the site.depth,and distributionLightning damage Heartwood decay Conks/Mushrooms Cracks Cut/Damaged roots Distance from trunkSite Cavity/Nestclearing—adjacenttrees, which may havePoorblockedPavement over roots—concrete, asphalt, pavers, or otherhole % circ. Depthtaper Root plate lifting Soil weakness the ls restricting root growth or water movement intoLean Corrected?the rootgrowthzone. If present, enter the percentage of the areaResponseChangedsoilgrowthhydrology—changes have been made thatResponsewithinthe drip line that is paved.concern(s)Mainconcern(s)affectMainwaterflow in or out of the site.RootLoadcuts—theroot system has been cut or otherwiseon defect N/A Minor Moderate Significant significantlydamaged.Likelihood of failure Additional information on root Possible RootsProbable CollarImminent cuts Improbablewill be includedin theand Rootbox.Prevailingwind direction—aconsistent,moderate-toLoad on defectN/A Minor typical,Moderate Significant strongwind,ofusuallyLikelihoodfailure from a single direction, which has affected rootPossible development.Probable Imminent treeImprobablecrown andsystemPage 1 of 2Common weather—trees will adapt to a number of climaticconditions if they occur regularly; check all that apply.Copyright 2013 International Society of Arboriculture. All rights reserved.125

RprPrmwiTaTa4 – constant1234Site FactorsSection 4—Tree Health and Species ProfileHistory of failures Topography Flat Slope % AspectSite changes None Grade change Site clearing Changed soil hydrology Root cuts DescribeSoil conditions Limited volume Saturated Shallow Compacted Pavement over roots % DescribePrevailing wind direction Common weather Strong winds Ice Snow Heavy rain DescribeTree Health and Species ProfileVigor Low Normal High Foliage None (seasonal) None (dead) Normal %Chlorotic %Necrotic %Pests AbioticSpecies failure profile Branches Trunk Roots DescribeLoad FactorsWind exposure Protected Partial Full Wind funneling Relative crown size Small Medium Large Crown density Sparse Normal Dense Interior branches Few Normal Dense Vines/Mistletoe/Moss Recent or planned change in load factorsThis section provides the opportunity to note any species specific failure patterns that you suspect may influence likelihood ofTreeisDefectsand Conditionsof Failurefailure. Any species information you feelimportantshould beAffectingnoted inthethisLikelihoodsection. Anyof these factors can be further described— Crown and Branches —in the spaces provided or on additional paper.Unbalanced crown LCR %Cracks Lightning damage Dead twigs/branches % overall Max. dia.Codominant Included bark Broken/Hangers Number Max. dia.hole%becausecirc.Vigor—an assessment of overall tree health; classify as low, Weak attachmentsNone (dead)—atree that has Cavity/Nestdropped itsleavesitOver-extended branches Previous branchfailures Similar branches present normal, or high:is dead.Pruning historyDead/Missing bark Cankers/Galls/Burls Sapwood damage/decay Crown cleaned growingThinned and/orRaised Normal—foliage size and color are normal for the speciesLow—treeis weak,slowly,under stress.Conks Reduced Topped Lion-tailed in the area.Heartwood decay Normal—treevigor for its species and the siteResponse growthFlush cuts has averageOtherconditions.Main concern(s)Chlorotic—yellowish-green to yellow.Necrotic—dead foliage in part of or the entire crown.High—tree is growing well and appears to be free ofLoad on defectN/A Minor Moderate Significant significanthealthstressfactors.Pests—insectsand diseases that may significantly affect tree Likelihood of failure Improbable Possible Probable Imminenthealthorstability.Foliage—size and color are indicationsof tree health; compare— Trunk —— Roots and Root Collar —with a healthyspecimenspecies inbarkthetexture/colorarea. Lines Dead/Missingbark of the same AbnormalCollar buried/Not problemsvisible DepthStem girdlingAbiotic—abioticthat may significantlyaffect treeand boxesin this sectiondataIncludedcollectionCodominantstems allow barkof the percentageCracks Deador Conks/Mushrooms healthstability. Decay of each category,or simply a checkmark for presence:Sapwood damage/decay Cankers/Galls/Burls Sap ooze Ooze Cavity % circ.Species failure profile—any known failure problems with theLightning damage Heartwood decay Conks/Mushrooms Cracks Cut/Damaged roots Distance from trunkNone (seasonal)—a deciduous tree that has dropped itsspecies in the branches, trunk, or roots.Cavity/Nest hole % circ. DepthPoor taper Root plate lifting Soil weakness leavesfor the winter.Lean Corrected?Response growthMain concern(s)Response growthMain concern(s)Load on defect N/A Minor Moderate Significant Likelihood of failureImprobable Possible Probable Imminent Load on defect N/A Minor Moderate Significant Likelihood of failureImprobable Possible Probable Imminent Page 1 of 2126Copyright 2013 International Society of Arboriculture. All rights reserved.

4Site FactorsHistory of failures Topography Flat Slope % AspectSite changes None Grade change Site clearing Changed soil hydrology Root cuts DescribeSoil conditions Limited volume Saturated Shallow Compacted Pavement over roots % DescribePrevailing wind direction Common weather Strong winds Ice Snow Heavy rain DescribeTree Healthand SpeciesFactorsProfileSection5—LoadVigor Low Normal High Foliage None (seasonal) None (dead) Normal %Chlorotic %Necrotic %Pests AbioticSpecies failure profile Branches Trunk Roots DescribeLoad FactorsWind exposure Protected Partial Full Wind funneling Relative crown size Small Medium Large Crown density Sparse Normal Dense Interior branches Few Normal Dense Vines/Mistletoe/Moss Recent or planned change in load factorsTree Defects and Conditions Affecting the Likelihood of Failure— Crown and Branches —Unbalanced crown LCR %Cracks Lightning damage Deadtwigs/branches need%Max. dia.Generally,twotypes of loadtooverallbe consideredwhen evaluatingtree risk.Dynamic load is from wind as it impactsthe tree, andCodominantIncluded barkBroken/HangersNumberMax.dia.static loadis from gravityactingon the tree.Thesetwo loads Weakcan interact.attachments Cavity/Nest hole % circ.Over-extended branches Pruning historyCrown cleaned Thinned Reduced thatTopped Wind exposure—factorsaffect windFlush cuts Othercheck all that apply:Main concern(s)Raised Previous branch failures Similar branches present Dead/Missing bark Sapwood damage/decay Cankers/Galls/Burls Conks Interior branches—increaseHeartwood decay Lion-tailed loadon the tree;windresistance but ��trees or structures in the area significantlyFew—little wind resistance and damping.Loadwindon defectMinor to wind.Moderate Significant reducevelocity orN/Athe tree’s exposureNormal—moderate wind resistance and damping.Likelihood of failure Improbable Possible Probable Imminent Partial—other trees, or buildings near the tree, moderatelyDense—significantand —damping.— Trunk —— Rootswindand resistanceRoot Collarreduce the impact of wind on the tree.Dead/Missing bark Abnormal bark texture/color Collar buried/Not visible Depth Stem girdling Vines/Mistletoe/Moss—checkbox if present at moderate toCodominantstemsexposed Cracks Full—treeis fullyto Includedwind. bark Dead Decay Conks/Mushrooms high levels that increase weight or wind resistance. Moss refersSapwood damage/decay Cankers/Galls/Burls Sap ooze Ooze Cavity % circ.Windfunneling—wind may be “funneled” orto Spanish or ball moss (epiphytes).Lightning damage Heartwood decay Conks/Mushrooms Cracks Cut/Damaged roots Distance from of trees)Cavity/Nest hole% circ.Depthlargetaper Recentor plannedin weaknessload factors—recordanyRoot platelifting changeSoil towardtreeso that windvelocity experienced by theLeanthe Corrected?factors, recent or planned, that may significantly affect thetree Responseis increased.Responsegrowthloadon anygrowthdefects.Main concern(s)Main concern(s)Relative crown size—comparison of the tree’s crown size tothe trunkdiameter; classify as small, medium, or large.Load on defect N/A Minor Moderate Significant of failureCrown Likelihooddensity—therelative wind transparency of the crown:Improbable Possible Probable Imminent Sparse—crown allows a large degree of wind and lightpenetration; varies with species.Load on defect N/A Minor Moderate Significant Likelihood of failureImprobable Possible Probable Imminent Page 1 of 2Normal—indicates moderate wind and light penetration.Dense—crown does not allow much light or wind penetration.Copyright 2013 International Society of Arboriculture. All rights reserved.127

Soil conditions Limited volume Saturated Shallow Compacted Pavement over roots % DescribePrevailing wind direction Common weather Strong winds Ice Snow Heavy rain DescribeTree Health and Species ProfileVigor Low Normal High Foliage None (seasonal) None (dead) Normal %Chlorotic %Necrotic %Pests AbioticSpecies failure profile Branches Trunk Roots DescribeLoad Factorsand Conditions AffectingSection 6—Tree Defectsthe Likelihood of FailureWind exposure Protected Partial Full Wind funneling Relative crown size Small Medium Large Crown density Sparse Normal Dense Interior branches Few Normal Dense Vines/Mistletoe/Moss Recent or planned change in load factorsTree Defects and Conditions Affecting the Likelihood of Failure— Crown and Branches —Unbalanced crown LCR %Dead twigs/branches % overall Max. dia.Broken/Hangers Number Max. dia.Over-extended branches Pruning historyCrown cleaned Thinned Raised Reduced Topped Lion-tailed Flush cuts OtherCracks Lightning damage Codominant Included bark Weak attachments Cavity/Nest hole % circ.Previous branch failures Similar branches present Dead/Missing bark Sapwood damage/decay Conks Response growthCankers/Galls/Burls Heartwood decay Main concern(s)Load on defectN/A Minor Likelihood of failure Improbable Possible Moderate Significant Probable Imminent — Trunk —— Roots and Root Collar —Dead/Missing bark Abnormal bark texture/color Collar buried/Not visible Depth Stem girdling Codominant stems Included bark Cracks Dead Decay Conks/Mushrooms Sapwooddamage/decay Cankers/Galls/Burls Sap oozeThis sectionprovidesa systematicchecklist for assessingthe tree, dividingitinto“CrownandBranches”,Ooze Cavity % circ. “Trunk”, and “Roots andLightningdamage Heartwooddecay Conks/Mushrooms Root Collar”. Check only factors that apply to the assessed tree. These factorsor may notrootscontributeto yourMainconcern(s),Cracks mayCut/Damaged Distancefrom trunkCavity/Nesthole% circ.Poor taper Load ondefect, orLikelihoodof Depthfailure.Root plate lifting Soil weakness Lean Corrected?Response growthMain concern(s)Response growthMain concern(s)Crown and BranchesLoad on defectLoad on defect N/A Minor Moderate Significant Topped—inappropriatepruning technique used to reduceLikelihoodof failuretree size; characterizedImprobablePossible by internodalProbable cuts. Imminent N/A Minor Moderate Significant Unbalancedcrown—checkbox if foliage is not uniformlyLikelihoodof failuredistributed.Improbable Possible Probable Imminent Live crown ratio (LCR)—the ratio of the height of the livecrown to the height of the entire tree [LCR (crown height/treeheight) 100].Page 1 ofan2Lion-tailed—inappropriate pruning practice removingexcessive number of inner and/or lower lateral branches.Flush cuts—pruning cuts through (or removal of ) thebranch collar, causing unnecessary injury to the trunk orparent branch.Dead twigs/branches—small diameter, dead branches; checkbox if present and indicate percentage and maximum size(s) indiameter.Broken/Hangers—broken or cut branches remaining in thecrown; record the number and size (maximum diameter).Over-extended branches—check box if there are branchesthat extend beyond the tree’s canopy or that are excessivelylong with poor taper.Pruning history—check appropriate boxes if pruning isknown and relevant:Crown cleaned—pruning of dead, dying, diseased, andbroken branches from the tree crown.Thinned—selective removal of live branches to reducecrown density. Other pruning types include, but are notlimited to, structural, pollarding, espalier, and vista, andmay be included in your notes.Raised—removal of lower branches to provide clearance.Reduced—pruning to decrease tree height or spread bycutting to lateral branches.128Other—note any other pruning history that may affect thelikelihood of failure.Cracks—separation in the wood in either a longitudinal(radial, in the plane of ray cells) or transverse (across thestem) direction; check box if present and describe briefly.Lightning damage—often evidenced by a centrally locatedline of sapwood damage and bark removal on either side in aspiral pattern on the trunk or branch; check box if present.Codominant—branches of nearly equal diameter arising from a common junction and lacking a normal branchunion. Check box if present and describe.Included bark—bark that becomes embedded in a unionbetween branch and trunk, or between codominant stems,causing a weak structure. Check box if present.Weak attachments—branches that are codominant or thathave included bark or splits at or below the junctions. Checkbox if present and describe.Copyright 2013 International Society of Arboriculture. All rights reserved.

Cavity/Nest hole—openings from the outside into the heartwood area of the tree; record the percentage of the branchcircumference that has missing wood.Conks (mushrooms, brackets)—fungal fruiting structures;common, definite indicators of decay. Check box if presentand describe under Main concern(s).Previous branch failures—check box if there is evidence ofprevious branch failures and describe briefly. Note “similarbranches present,” if relevant.Heartwood decay—check box if present and describe.Dead/Missing bark—check box if branches are dead or ifareas of dead cambium are present where new wood will notbe produced.Cankers/Galls/Burls—check box if relevant and circle whichone(s) are of concern:Canker—localized diseased areas on the branch; oftensunken or discolored.Gall—abnormal swellings of tissue caused by pests; mayor may not be a defect.Burl—outgrowth on the trunk, branch, or roots; notusually considered a defect.Sapwood damage/decay—check box if there is mechanical orfungal damage in the sapwood that may weaken the branch,or decay of dead or dying branches. If checked, you may circle“damage” or “decay” to indicate which one is present.Response growth—reaction wood or additional woodgrown to increase the structural strength of the branch;note location and extent.Main concern(s)—conditions in the crown and branchesthat may affect likelihood of failure. Note the mainconcern(s); if there are no concerns, write “none.”Load on defect—a consideration of how much loading isexpected on the tree part of concern. Record as N/A (notapplicable), minor, moderate, o

Tree Risk Assessment Form This form is provided with the ISA Tree Risk Assessment Manual and is intended to act as a guide for collecting and recording tree risk assessment information. This form is for trees receiving a basic (Level 2) risk assessment. It is not intended for use with li