P. Eric Wiseman, PhD Associate Professor of Urban and Community Forestry Dept. of Forest Resources and Environmental Conservation Virginia Tech [email protected] linktr.ee/EricWiseman @vtarborist VCE Master Gardener Tree Stewards • June 8, 2023 Source: indygrit.community/blog Creating Storm-Resilient Urban Forests
01 25 Presentation Outline o Future climate and extreme weather events o How and why trees fail during storms o Characteristics of storm-resilient trees o Selecting storm-resilient tree species o Cultivating storm-resilient trees Goal: Raise awareness about future climate threats to urban forests and highlight best practices of creating storm-resilient urban forests VCE Master Gardener Tree Stewards • June 8, 2023
o Regardless of human causes, extreme weather events are occurring more frequently and with greater severity o Extreme weather events cause stress on trees and predispose them to failure o Falling trees endanger lives, damage property, and diminish ecosystem services o Likelihood of storm damage can be greatly reduced through proper species selection, planting, maintenance, and protection Source: www.apg- wi.com/sawyer_county_record/f ree 02 25 Premises of Presentation Source: www.channel3000.com/news/local-news VCE Master Gardener Tree Stewards • June 8, 2023
Source: www.theglobeandmail.com/news/toronto 03 25 The Conundrum We Face Trees and Urban Forests Help Us Mitigate and Adapt to Climate Change Climate Change Makes Trees and Urban Forests More Vulnerable and Dangerous VCE Master Gardener Tree Stewards • June 8, 2023
04 25 The Responsibility We Bear Source: www.thespec.com/news/hamilton-region/2021/04/30 Source: twitter.com/SanJoseDOT The Urban Forests We Create Today Will Face the Climate of Tomorrow VCE Master Gardener Tree Stewards • June 8, 2023
05 25 Climate Change and Extreme Weather Source: nca2018.globalchange.gov/chapter/2 Source: en.wikipedia.org/wiki/Representative_Concentration_Pathway Observed and Projected Changes in Carbon Emissions and Temperature Radiative Forcing (W/m2) in 2100 VCE Master Gardener Tree Stewards • June 8, 2023
06 25 Climate Change and Extreme Weather Observed and Projected Changes in Annual Average Temperature Source: nca2018.globalchange.gov/chapter/2 VCE Master Gardener Tree Stewards • June 8, 2023
07 25 Climate Change and Extreme Weather Observed and Projected Change in Heavy Precipitation Source: nca2018.globalchange.gov/chapter/2 VCE Master Gardener Tree Stewards • June 8, 2023
08 25 Fitzpatrick, M. C., & Dunn, R. R. (2019). Contemporary climatic analogs for 540 North American urban areas in the late 21st century. Nature Communications, 10(1), 614. Source: fitzlab.shinyapps.io/cityapp Climate Change and Extreme Weather VCE Master Gardener Tree Stewards • June 8, 2023
Source: www.purdue.edu Source: theloopny.com Source: www.gfc.state.ga.us UPROOTING STEM FAILURE BRANCH FAILURE 09 25 How Do Trees Fail During Storms? Failure is loss of structural integrity in tree parts that compromises tree stability and jeopardizes people and property VCE Master Gardener Tree Stewards • June 8, 2023
o Trees fail when mechanical stress (referred to as load) exceeds root anchorage or wood fiber strength o Gravity acting on the mass of the tree exerts internal load on tree parts o Ice, snow, and rain add mass and exert external load on tree parts o Wind intensifies loading stress on tree parts o Moisture decreases soil strength and root adhesion to soil particles 10 25 Why Do Trees Fail During Storms? VCE Master Gardener Tree Stewards • June 8, 2023
11 25 Why Do Trees Fail During Storms? Branch & Trunk Failure Windthrow Source: www.tdworld.com/vegetation-management/article/21120419/effect-of-wind-in-the-utility-forest VCE Master Gardener Tree Stewards • June 8, 2023
Source: www.theday.com Source: www.rynolawncare.com Source: www.bartlett.com 12 25 COMPROMISED ROOTS WEAK BRANCH UNIONS DECAYED/CRACKED WOOD What Defects Predisposes Trees to Failing? Trees with defects fail with higher frequency and under milder storm conditions than sound trees VCE Master Gardener Tree Stewards • June 8, 2023
WOOD STRENGTH PHYSICAL CONFORMATION DEFECT VULNERABILITY Density Modulus of Rupture/Elasticity Decay Resistance Root Architecture Growth Habit Branch Angle, Aspect, & Taper Girdling Roots Codominant Leaders Included Bark 13 25 Tree Characteristics and Storm Resilience Tree species are quite variable in their wood strength, physical conformation, and vulnerability to defect development Source: doi.org/10.1039/D0NJ06234K VCE Master Gardener Tree Stewards • June 8, 2023
o Roots well in confined, compacted, and hypoxic soils o Slow to moderate growth rate with dense wood and decay resistance o Tendency to develop dominant central leader and broad branch angles o Coarse branch architecture o Moderate foliage and fruit density 14 25 Traits of a Storm-Resilient Tree Species Selecting Storm-Resilient Tree Species There is no perfect tree species! Every species has assets and liabilities: species selection is about tradeoffs! VCE Master Gardener Tree Stewards • June 8, 2023
SPECIES THAT SHOULD BE IN YOUR URBAN FOREST SPECIES YOU SHOULD PONDER BEFORE PLANTING Japanese cedar (Cryptomeria japonica) Ginkgo (Ginkgo biloba) Ky. Coffeetree (Gymnocladus dioicus) East. Redcedar (Juniperus virginiana) Blackgum (Nyssa sylvatica) Hophornbeam (Ostrya virginiana) Swamp white oak (Quercus bicolor) Baldcypress (Taxodium distichum) Silver maple (Acer saccharinum) Yellowwood (Cladrastis kentukea) Leyland cypress (Hesperocyparis leylandii ) Tulip-poplar (Liriodendron tulipifera) White pine (Pinus strobus) Poplar (Populus spp.) Callery pear (Pyrus calleryana) Basswood (Tilia americana) 15 25 Selecting Storm-Resilient Tree Species There is no perfect tree species! Every species has assets and liabilities: species selection is about tradeoffs! VCE Master Gardener Tree Stewards • June 8, 2023
16 25 Species Selection Nursery Quality Landscape Placement Planting Practices Preventive Maintenance Tree Protection 1 2 3 4 Cultivating Storm-Resilient Urban Forests The Nursery to Woodpile Continuum of Care VCE Master Gardener Tree Stewards • June 8, 2023
o Future climate is likely to bring increased frequency and intensity of storms o Storms increase risk of tree failure, especially for defective trees o Tree species selection is foundational to storm resilience o Urban forests need a continuum of care to endure lifelong threats from storms 25 25 Take Home Messages Source: unsplash.com/photos/UewgGfZgYj0 VCE Master Gardener Tree Stewards • June 8, 2023
P. Eric Wiseman, PhD Associate Professor of Urban and Community Forestry Dept. of Forest Resources and Environmental Conservation Virginia Tech [email protected] linktr.ee/EricWiseman @vtarborist Creating Storm-Resilient Urban Forests VCE Master Gardener Tree Stewards • June 8, 2023
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