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 Roanoke Tree Care Workshop • March 15, 2023 Source: indygrit.community/blog Creating Storm-Resilient Urban Forests
02 26 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 urban forests Goal: Raise awareness about future climate threats to urban forests and highlight best practices of creating storm-resilient urban forests Roanoke Tree Care Workshop • March 15, 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 03 26 Premises of Presentation Source: www.channel3000.com/news/local-news Roanoke Tree Care Workshop • March 15, 2023
Source: www.theglobeandmail.com/news/toronto 04 26 The Conundrum We Face Trees and Urban Forests Help Us Mitigate and Adapt to Climate Change Climate Change Makes Sustaining Urban Forests More Difficult Roanoke Tree Care Workshop • March 15, 2023
05 26 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 Roanoke Tree Care Workshop • March 15, 2023
06 26 Climate Change and Extreme Weather Source: nca2018.globalchange.gov/chapter/2 Source: en.wikipedia.org/wiki/Representative_ Concentration_Pathway Roanoke Tree Care Workshop • March 15, 2023 Observed and Projected Changes in Carbon Emissions and Temperature
07 26 Climate Change and Extreme Weather Observed and Projected Changes in Annual Average Temperature Roanoke Tree Care Workshop • March 15, 2023 Source: nca2018.globalchange.gov/chapter/2
08 26 Climate Change and Extreme Weather Observed and Projected Change in Heavy Precipitation Source: nca2018.globalchange.gov/chapter/2 Roanoke Tree Care Workshop • March 15, 2023
09 26 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 Roanoke Tree Care Workshop • March 15, 2023
Source: www.purdue.edu Source: theloopny.com Source: www.gfc.state.ga.us UPROOTING STEM FAILURE BRANCH FAILURE 10 26 How Do Trees Fail During Storms? Roanoke Tree Care Workshop • March 15, 2023 Failure is loss of structural integrity in tree parts that compromises tree stability and jeopardizes people and property
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 11 26 Why Do Trees Fail During Storms? Roanoke Tree Care Workshop • March 15, 2023
12 26 Why Do Trees Fail During Storms? Roanoke Tree Care Workshop • March 15, 2023 Branch & Trunk Failure Windthrow Source: www.tdworld.com/vegetation-management/article/21120419/effect-of-wind-in-the-utility-forest
Source: www.theday.com Source: www.rynolawncare.com Source: www.bartlett.com 13 26 COMPROMISED ROOTS WEAK BRANCH UNIONS DECAYED/CRACKED WOOD What Defects Predisposes Trees to Failing? Roanoke Tree Care Workshop • March 15, 2023 Trees with defects fail with higher frequency and under milder storm conditions than sound trees
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 14 26 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 Roanoke Tree Care Workshop • March 15, 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 15 26 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! Roanoke Tree Care Workshop • March 15, 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) Hackberry (Celtis occidentalis) Leyland cypress (Hesperocyparis leylandii ) Tulip-poplar (Liriodendron tulipifera) White pine (Pinus strobus) Poplar (Populus spp.) Callery pear (Pyrus calleryana) Basswood (Tilia americana) 16 26 Selecting Storm-Resilient Tree Species There is no perfect tree species! Every species has assets and liabilities: species selection is about tradeoffs! Roanoke Tree Care Workshop • March 15, 2023
17 26 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 Roanoke Tree Care Workshop • March 15, 2023
23 26 Source: edis.ifas.ufl.edu/publication/ep315 Before After Cultivating Storm-Resilient Urban Forests Roanoke Tree Care Workshop • March 15, 2023 Preventive Maintenance
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 26 26 Take Home Messages Source: unsplash.com/photos/UewgGfZgYj0 Roanoke Tree Care Workshop • March 15, 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 Roanoke Tree Care Workshop • March 15, 2023 Creating Storm-Resilient Urban Forests
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