DEEP ROOTS RESEARCH UNRI Webcast – 08/13/08 “ Dysfunctional Root Systems and Brief Landscape Lives” Gary Johnson, Department of Forest Resources, University of Minnesota
University of Minnesota Urban Forestry and Horticulture Institute Chad Giblin, Research Scientist Jeff Gillman, Associate Professor Dave Hanson, Research Specialist Gary Johnson, Professor and corresponding presenter. [email_address] , 612-625-3765. Rebecca Koetter, Research Fellow Patrick Weicherding, Ext. Educator and Professor
University of Minnesota Urban Forestry and Horticulture Institute
Criteria for Condition Rating Trees: Canopy and Stem Conditions ~ 10% cambial loss. One crack and/or one seam. 3.0 ~ 10-25% Dieback, or Loss of Density, or <50% L.C.R., or Loss of Symmetry. No cambial loss*. No decay. No cracks/seams. 4.0 No Dieback. Characteristic Density for the species. 60%+ Live Crown Ratio (L.C.R.). Symmetrical. Stem Pts Canopy
Premature Failure in Loading Events* III. Most common pre-existing conditions : For all damage, separating preexisting conditions : CONDITION % OF TOTAL Decay Only 13 Stem Girdling Roots (SGR) 12 Included Bark Only 4 Root Problems (other than SGR) 3 Codominant Leaders Only 4 Construction Damage Only 1 *Storm Damage 1995-2005; University of Minnesota
Storm Damage in Minnesota: SGRs below ground with compression Norway Maple ( Acer platanoides )
Storm Damage in Minnesota: 1998 n=564 1995-2005 n=1584 Total Tree Failures In Boulevards Most Commonly Damaged Size (d.b.h.) ranges 1998 1995-2005 Size (d.b.h.) Range % of Total % of Total 6-10 inches 28.6 29.0 >25 inches 25.7 26.0 20-25 inches 15.7 16.0 10-15 inches 14.3 14.0 15-20 inches 14.3 14.0
Storm Damage in Minnesota: Failures due to Stem Girdling Roots 1995-2005 n=1584
32% of all tree failures , located on the edges of storms
26% of all boulevard total tree failures (53% of 6-10” category)
68% of Little-leaf Lindens that failed in boulevards (#3 rd most common species)
> 90% of trees that had SGRs had stems buried 4” or more.
Storm Damage in Minnesota: 1998 n=564 1995-2005 n=1584 Commonly Damaged Species with Chronic Problems 1998 1995-2005 Little Leaf Lindens: 73% of all 76% that failed were 4”+ deep and had stem girdling roots causing stem compression. These trees failed below the stem compression points.
Decline in Stem Condition Associated with SGR’s and Tilia