City dwellers rejoice: spring greening comes earlier for urban plants


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The first signs of spring occur earlier in cities than surrounding rural areas, new research found (via Creative Commons).

Julia Poska | February 27, 2020

Vegetation starts turning green earlier in cities than surrounding rural areas, but urban plants are less sensitive to unseasonable warmth, new Iowa State University-led research found. The authors attribute the difference to the urban “heat island” effect.

Cities typically have somewhat higher temperatures than surrounding rural areas because materials like asphalt and brick absorb heat more readily than natural landscapes. For example, New York City is about 7 degrees Fahrenheit warmer than surrounding areas in summer, according to NASA’s Climate Kids site.

Researchers found this “heat island” phenomenon causes urban vegetation to perceive the start of spring and begin greening an average of six days earlier than surrounding rural plants.

As climate change progresses, however, plants in both rural and urban areas are responding to unseasonably warm temperatures by beginning growth earlier and earlier over time. Pollinators and last frosts have failed to keep up, which has damaged the early bloomers’ ability to survive and reproduce.

The study found that rural vegetation is more sensitive to early spring weather than urban vegetation, perhaps due to the urban heat island effect as well.

ISU Ph.D. student Ling Meng led the research team, which included CGRER member Yuyu Zhou, an ISU geological and atmospheric scientist, among others. The study, published this month in Proceedings of the National Academy of Sciences, was based on satellite images from 85 large U.S. cities from 2001 to 2014.

Zhou told the Iowa State News Service that this sort of research can help predict how plants will respond to climate change and urbanization.

On The Radio – Leaves drop early due to fall drought


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Some leaves in Iowa fell to the ground before changing color this year due to drought. (Liz West/flickr)
Jenna Ladd | October 9, 2017

This week’s On The Radio segment discusses how drought conditions in late September pushed some trees into early dormancy.

Transcript: Tree leaves in Iowa began changing colors and falling to the ground earlier than usual this year due to drought conditions.

This is the Iowa Environmental Focus.

Leaf color change is closely tied to weather conditions. During the last week of September, the U.S. Drought Portal reported that about thirty percent of Iowa was experiencing abnormally dry conditions and about twenty-five percent of the state was in a moderate drought.

Officials from the Iowa Department of Natural Resources explained that if trees do not have enough moisture, they can be pushed into dormancy earlier than usual. As a result, many leaves died and fell from trees before they bursted into autumn’s hues of red, yellow and orange this year.

In a typical year, leaves change color in northern Iowa between the last week of September and the second week of October, from the first to third weeks of October in central Iowa and from the second to fourth weeks of October in southern Iowa.

For more information, visit iowa-environmental-focus-dot-org.

From the UI Center for Global and Regional Environmental Research, I’m Betsy Stone.

Alliant energy offers trees at significant discounts to costumers


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Maple trees make up one-third of all trees in Iowa, making them more susceptible to disease and pest problems. (Dee McIntyre/flickr)
Jenna Ladd | October 4, 2017

Alliant Energy’s Operation ReLeaf tree distribution program will continue this week and into October. During this time, the company provides landscape-quality trees to their customers at a significant discount. Thoughtful placement of trees can cut energy costs for homeowners by providing shade in the warmer months and wind blocks during colder months.

Customers can buys trees that typically retail for $65 to $125 for just $25 each. Residential tree distributions will be held in Buena Vista, Fayette, Lee, Linn, Lucas and Story counties this October.

The Iowa Department of Natural Resources provides several resources for homeowners looking to select the appropriate tree for their yards. In one of the DNR’s publications, “Rethinking Maple: Selecting Trees For Your Yard,” officials point out that maple trees make up more than one-third of all trees in Iowa, which increases their risk for disease and pest problems. The pamphlet encourages homeowners to consider other tree species based on desired qualities such like vibrant fall color, storm resistant, salt tolerant and others.

Trees will be distributed on a first-come, first-serve basis at the following locations on the following dates:

Buena Vista County – Storm Lake

Partner: City of Storm Lake

Location: Kings Point Park

Date: Oct. 4, 4:30 p.m. to 6 p.m.

Lee County – Montrose

Partner: Lee County Conservation

Location: Lee County Conservation Center

Date: Oct. 5, 5 p.m. to 6:30 p.m.

Tree planting and care workshop: 5:45 p.m.

Linn County – Marion

Partner:  Linn County Conservation Board

Location:  Squaw Creek Park

Date: Oct. 7, 7:30 a.m. to 9 a.m.

Tree planting and care workshop:  8:15 a.m.

Story County – Ames

Partner: Story County Conservation

Location: East Petersen Park

Date: Oct. 19, 4:30 p.m. to 6 p.m.

Tree planting and care workshop: 5:15 p.m.

Tips for watering trees during the drought


Photo by iowa_spirit_walker, Flickr.

The Iowa Department of Natural Resources has released a set of tips for watering trees during drought conditions.

They advise using buckets of water or a hose instead of sprinklers, since sprinklers are less efficient.

An area within and just beyond the canopy should be watered with one gallon of water per square foot. This should be done in the evening or early morning to avoid evaporation.

On weeks with no rainfall, trees should be watered one to three times.

Read more tips on watering trees here.

Cedar Rapids increases funding for new trees


Emerald ash borer. Photo by USDAgov, Flickr.

Cedar Rapids will double their spending on new trees for this upcoming fiscal year. However, the city will still likely remove more trees than they plant during that time.

During 2011, the city removed 1,200 trees while adding about 500.

Part of the issue is that 30 percent of Cedar Rapids’ trees are ash trees. Many of these ash trees are being removed every year in preparation for the expected arrival of the emerald ash borer – a beetle that has killed millions of ash trees around the nation.

Read more about Cedar Rapids’ trees here.