City Trees

May/ June 2012

City Trees is a premier publication focused on urban + community forestry. In each issue, you’ll learn how to best manage the trees in your community and more!

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Page 19 of 39

R O U N D T A B L E Urban Forestry in the Drought Zone I have been involved with trees and urban landscape management for over 30 years now and have a few thoughts about drought in the southeast- ern U.S. It seems that our summers are getting hotter and drier. Weather events are getting more extreme. Just last year, for example, we had killer tornadoes in April, a severe drought in August combined with temps in the mid- to upper-90s every day, followed by 10 inches (254 mm) of rain and floods on Labor Day. Other locales around the Southeast have experienced similar conditions in recent years. Although my experi- ences are only one tile in a larger mosaic, I suspect that when you fit all of the tiles together, it creates a picture of climate change with which all of us are now trying to cope. So what's a poor city forester to do? I have elected to plant those trees that are both drought tolerant and heat resistant. In my area that includes 'Princeton' American elm (Ulmus), and some of the sweetgum (Liquidambar) cultivars. But it also includes some of the non-native trees that do particularly well here, including Chinese pistache (Pistachia chinensis), ginkgo (Ginkgo biloba), crape myrtle (Lagerstroemia indica), and lacebark elm (Ulmus parvifolia). As part of an effort to counter the impacts of climate change, I have adopted a policy of planting trees that will develop the largest canopy possible for a given site. In this way our trees can provide the maximum benefits for their ecological services of reducing the heat island effect, absorbing air pollut- ants, and intercepting rainfall for stormwater deten- tion. If your City is in the process of developing a climate adaption plan, this type of action would fit in very well. In Chattanooga, we typically use a 20-gallon (76- liter) irrigation bag for watering. We chose this item for practical reasons because it allows us to quickly fill the bags with a watering truck. It also offers a broad flat side onto which we paint the logo for our tree planting initiative, "Take Root." I instructed the employees to always face the logo toward oncoming traffic so that drivers can see the logo hundreds of times as they drive down the street. This is our form of guerilla marketing, and it works well. —Gene Hyde, City Forester, Chattanooga, Tennessee 20 A tree irrigation bag in Chattanooga, Tennessee publicizes the City's Take Root program to passersby. Photo by Preston Roberts Last year, the Great State of Texas suf- hottest June, July, and August on record seared Texas to a crisp. In August 2011, Texas was brutalized with the hottest month recorded for any state ever in U.S. history. fered the most severe drought ever recorded. The Parts of Texas experienced 20 inches (510 mm) less- than-normal rainfall from October 2010 to September 2011. Many Texas cities set new records for number of 100-degree days and consecutive 100-degree days. Fort Worth recorded 71 days over 100 degrees F (32 C) during the summer of 2011. Texas Forest Service esti- mated that 5.6 million urban shade trees were killed by drought across the state, as much as 10% of the total Texas urban forest. Estimated cost of removal state- wide is $560 million. Estimated loss in environmental benefits provided by drought stricken trees is roughly $280 million per year. High temperatures and low humidity caused wildfires to rage across Texas, burning 3,993,716 acres (1,616,199 ha). Severe drought can have a long-lasting effect on trees. As wood tissues dry, they separate, creating internal checks and shanks. Trees lack the ability to close internal wounds. These hidden faults become points where limbs will break under load-bearing stress such City Trees

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