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<h2><strong>5.3 ICE AND  WIND DAMAGE</strong></h2>
<h3><strong>BACKGROUND</strong></h3>
<p style="font-weight: bold">Tornadoes, hurricanes, ice  storms, and floods can damage the forest.</p>
<p>Although hurricane-size storms  rarely strike New England, expect damaging  wind storms every 15 to 30 years. Species and forest types vary greatly in  resistance to wind damage. White pine is most susceptible&mdash;as much as 80  percent of the volume was damaged in the 1938 hurricane. Hemlock trees also  were damaged. Spruce-fir (especially the fir) is next in susceptibility to  losses from wind. Northern hardwoods are least damaged; the 1938 hurricane  produced losses of about 10 to 20 percent, even in heavily damaged stands.  Factors other than forest type also affect vulnerability to wind. They include:</p>
<ul>
  <li>Exposure to wind. (Noticeable in the mountain  notches that characterize central and northern New Hampshire.)</li>
  <li>Soil depth and soil moisture. (Shallow and wet  soils are worst.)</li>
  <li>Stand age. (Large, overmature stands are most  susceptible.)</li>
  <li>Stand density. (Heavily thinned stands are most  at risk.)</li>
</ul>
<h3><strong>OBJECTIVE</strong></h3>
<p style="font-weight: bold">Prepare forests to  withstand ice and wind damage and when damage occurs, make informed forest  management decisions.</p>
<h3><strong>CONSIDERATIONS</strong></h3>
<ul>
  <li>Damage from natural factors such as wind, snow,  and ice regularly occur in New    Hampshire&rsquo;s forests. This damage is a normal part of  natural-ecosystem functioning and an important factor in creating a diverse  forest structure by providing dead and down woody material, wildlife trees, and  openings for regeneration.</li>
  <li>Microbursts, in-line winds, tornadoes,  hurricanes, and ice-forming events can cause economic damage. No amount of  silvicultural preparation can eliminate the risk of catastrophic damage.</li>
  <li>Healthy trees blown over with roots intact will  remain alive and free of insects and pathogens for many months.</li>
  <li>Ice storms cause most forest damage at  elevations between 1,000 and 3,000 feet and within hardwood stands. Softwood  branches naturally point down. Under extreme weight they sag down and in rather  than bend and break like hardwoods.</li>
  <li>It isn't necessary to quickly salvage standing,  live, ice-storm-damaged trees. It takes many years for previously healthy trees  to succumb to a single severe ice storm. Discoloration and decay travel from  the damaged branches into the stem of the tree only a few inches to a few feet  per year. Breaks in the main stem are more severe than breaks of the secondary  branches. Decay fungi and rot will affect the product quality and strength of  the tree.</li>
  <li>Salvaging trees damaged by an ice or wind storm  can be difficult and dangerous; often only a portion of the original timber  value is recouped.</li>
  <li>Fire hazard can increase with severe storms that  accumulate large amounts of debris, if followed by severe fire weather.</li>
</ul>
<h3><strong>RECOMMENDED PRACTICES</strong></h3>
<p style="font-weight: bold">Wind Damage</p>
<ul>
  <li>Maintain a diverse forest to spread the risk,  especially by limiting the acreage in susceptible types such as mature white  pine on wet soils.</li>
  <li>Consider the rooting depth, butt flair, crown  size and soil profile when planning a partial harvest in overstocked stands.  Trees growing for long periods in tight conditions or on shallow or wet soils  are at risk of windthrow from moderate to severe wind. Limit partial harvests  in susceptible stands to no more than one-third of the basal area, and perhaps  leaving an uncut buffer on the windward side of the stand.</li>
  <li>Position thin strip cuts so that prevailing  winds skip across the narrow width rather than down the full length of the  strip, orienting strips at right angles to the prevailing winds. Position  larger openings so that prevailing winds cross at the narrowest point.</li>
  <li>Remove high-risk trees that have stem cankers,  forking tops, or signs of internal decay such as visible rot, cavities, or  conks.</li>
  <li>Consider even-aged management in locations where  repeated occurrence of wind damage is evident, e.g., stands naturally growing  in mosaics of even-aged groups because of localized wet or shallow soils or  exposure to high winds are candidates.</li>
  <li>Post-windstorm actions:</li>
  <ul>
    <li>Determine the footprint of the storm.</li>
    <li>Determine the percentage of trees blown over  with roots intact versus trees broken above the stump, and salvage broken trees  first. There is no need to immediately remove trees blown over with tops and  roots attached.</li>
  </ul>
</ul>
<p style="font-weight: bold">Ice Damage</p>
<ul>
  <li>In forests with signs of previous branch breakage and top dieback,  remove trees with weak or hazardous branch structure. Trees with branches  forked in a V-shaped crotch are weaker than those with the stronger U shape.</li>
  <li>Post-ice storm actions:</li>
  <ul>
    <li>Determine the footprint of the storm.</li>
    <li>Inventory to determine the percentage of trees  damaged and the average amount of branch breakage by species; salvage according  to the following guidelines:</li>
    <ul>
      <li>Trees  with less than 50 percent branch breakage are likely to recover, except for  paper birch.</li>
      <li>Trees  with greater than 75 percent branch breakage and  trees with any bole breakage below the live crown are unlikely to  produce a high-quality tree for future harvest.</li>
    </ul>
  </ul>
</ul>
<h3><strong>CROSS REFERENCES</strong></h3>
<p>2.1 New Hampshire Forest  Types; 2.2 Forest Structure; 2.3 Regeneration  Methods; 6.2 Cavity Trees, Dens and Snags; 6.3 Dead and Down Woody Material.</p>
<h3><strong>ADDITIONAL INFORMATION</strong></h3>
<p>Hauer, R.J., M.C. Hruska, and J.O.  Dawson. 1994. <span style="font-style: italic">Trees and ice storms: The development of ice  storm&mdash;resistant urban tree populations</span>. Special Publication 94-1. Dept.  of Forestry, University   of Illinois at  Urbana-Champaign, Urbana, Ill. <a href="http://web.aces.uiuc.edu/vista/pdf_pubs/ICESTORM.PDF">http://web.aces.uiuc.edu/vista/pdf_pubs/ICESTORM.PDF</a> Accessed March 9, 2010.</p>
<p></p>
<p>Shortle, W.C., K.T. Smith, and  K.R.Dudzik. 2003. <span style="font-style: italic">Tree Survival and Growth Following Ice Storm Injury</span>.  USDA For. Serv. Res. Pap. NE-723. <a href="http://www.fs.fed.us/ne/newtown_square/publications/research_papers/pdfs/2003/rpne723.pdf">http://www.fs.fed.us/ne/newtown_square/publications/research_papers/pdfs/2003/rpne723.pdf</a> Accessed March 9, 2010.</p>
<p></p>
<p>Shortle, W.C., and K.T. Smith.  1998. <span style="font-style: italic">Tree Biology and Ice Storm '98</span>. UNH  Cooperative Extension, Durham,   N.H.<a href="http://extension.unh.edu/resources/files/Resource000987_Rep1127.pdf">http://extension.unh.edu/resources/files/Resource000987_Rep1127.pdf</a> Accessed June 7, 2010.</p>
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