Ash Management Guide for Private Forest Landowners
Ash Management Guide for Private Forest Landowners Ash Management Guide for Private Forest Landowners
Chapter 7Other Implicationsof EAB and Ash TreesEpicormicbranchingDefects in ash treesThere are as many ways for trees tofail as there are trees. An ice storm canoverload all the branches on a tree, ablustery wind can blow down a tree if itsroots are restricted or a cracked tree canfail just under its own weight.Trees are designed to easily withstandthe normal windstorms and winterstorms that occur, yet we have all seentrees that have failed. Trees fail when theload (weight and motion of the crown)exceeds the mechanical strength of theirbranches, stems or root systems. This istrue for both sound and defective trees,Photo: Ed Czerwinskibut defective trees can only withstand afraction of the load that sound trees canwithstand. Defective trees fail soonerthan sound trees.A sound tree becomes potentiallydangerous when the tree’s woody structureis weakened by one or more defects.Most defects can be linked to pastwounding and decay, pest infestations,severe storms, or to growing conditionsthat limited the root system. Sincedefects, the old injury sites and nearbywood, are structurally weaker thanuninjured wood, the tree is predisposedto fail at the location of the defects.Defective trees can be found growinganywhere. Management of a defectivetree is at the landowner’s discretion. It issuggested that if defective trees or deadtrees could fall onto structures, yards,fences, driveways or recreational trails,a landowner might consider removingthem. On the positive side, defective andfallen trees provide wildlife habitat andother important ecological services. Asa species group, ash are susceptible totwo main defects; root system failureand branch failure. In many soil types,ash root systems are quite shallow,making the trees prone to windthrow.Commonly the entire tree and much ofits root system tip over during strongwinds, especially in exposed locations.Branches are likely to fail at the junctionof the branch and the stem due to thepresence of bark growing inside the treeand/or the presence of serious decay inthe same location. Branch failure is moreprevalent in large diameter trees.For information on where to find the full resourceon defects in ash trees see Appendix D, page 66.58
Windthrow MortalityAll hardwood forests in their latesuccessionstages (older ages) can beperpetuated where a closed canopy ismaintained over decades. Regenerationis by seedling release in canopy gaps(chronic windthrow), or by thinningoverstocked stands. Thinning removestrees to where remaining tree canopiesoccupy 50 to 80% of the land area. Forprotection against excessive windthrowand provision of favorable riparian andstream attributes, thinning down to acanopy closure of 80% is recommended.Exposure of stands along long edgeswill greatly increase the likelihood ofexcessive windthrow. Studies of strip cutforests in Minnesota show the balancebetween stand growth and tree mortalityis a function of the total stand edgeand the height of the trees. Along streamcorridors the stream produces one standedge and cutting of forests landward ofa forest next to the stream produces asecond edge. Maintaining continuouscanopystands along the stream or riverat least 125 feet wide will ensure that normalwindthrow mortality will not exceedstand growth over time. A wider standwill maximize stand growth. Many riparianforests in the Lake States have poorstocking (low canopy closure and notenough trees); though studies of the causeof this poor stocking are needed, excessivewind mortality is a prime candidate.Chapter 7Other Implicationsof EAB and Ash TreesGLOSSARYwindthrow: A tree uprootedor broken by wind; also called“blowdown”.Blowdown in theBoundary Waters CanoeArea Wilderness, 1999Photo: Eli Sagor59
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Chapter 7Other Implicationsof EAB and <strong>Ash</strong> TreesEpicormicbranchingDefects in ash treesThere are as many ways <strong>for</strong> trees tofail as there are trees. An ice storm canoverload all the branches on a tree, ablustery wind can blow down a tree if itsroots are restricted or a cracked tree canfail just under its own weight.Trees are designed to easily withstandthe normal windstorms and winterstorms that occur, yet we have all seentrees that have failed. Trees fail when theload (weight and motion of the crown)exceeds the mechanical strength of theirbranches, stems or root systems. This istrue <strong>for</strong> both sound and defective trees,Photo: Ed Czerwinskibut defective trees can only withstand afraction of the load that sound trees canwithstand. Defective trees fail soonerthan sound trees.A sound tree becomes potentiallydangerous when the tree’s woody structureis weakened by one or more defects.Most defects can be linked to pastwounding and decay, pest infestations,severe storms, or to growing conditionsthat limited the root system. Sincedefects, the old injury sites and nearbywood, are structurally weaker thanuninjured wood, the tree is predisposedto fail at the location of the defects.Defective trees can be found growinganywhere. <strong>Management</strong> of a defectivetree is at the landowner’s discretion. It issuggested that if defective trees or deadtrees could fall onto structures, yards,fences, driveways or recreational trails,a landowner might consider removingthem. On the positive side, defective andfallen trees provide wildlife habitat andother important ecological services. Asa species group, ash are susceptible totwo main defects; root system failureand branch failure. In many soil types,ash root systems are quite shallow,making the trees prone to windthrow.Commonly the entire tree and much ofits root system tip over during strongwinds, especially in exposed locations.Branches are likely to fail at the junctionof the branch and the stem due to thepresence of bark growing inside the treeand/or the presence of serious decay inthe same location. Branch failure is moreprevalent in large diameter trees.For in<strong>for</strong>mation on where to find the full resourceon defects in ash trees see Appendix D, page 66.58
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