Dying trees in cities? Blame it on the concrete

Dying trees in cities? Blame it on the pavement
Scale insects accumulate on a maple tree in Raleigh. Scale insects wreak havoc on maples in the midrange of studied cities in the Southeast. Credit: Adam Dale

A North Carolina State University study examining urbanization, scale-insect abundance and latitudinal warming on tree health in the Southeast captured a few surprising results.

The study showed more scale insects on red maple in the midrange of eight cities within a 10-degree latitudinal difference, from Newark, Delaware, to Gainesville, Florida.

Cities in that midrange, including Raleigh and Asheville, showed poorer tree health, due mostly to these high volumes of tree-destroying gloomy scale insects (Melanaspis tenebricosa), which appear as tiny bumps on tree branches and leaves.

"Impervious surfaces—basically concrete and pavement—near trees was a better predictor of scale-insect abundance than temperature, and thus a better predictor of poor tree health in the study area," said Michael Just, an NC State postdoctoral entomology researcher and corresponding author of a paper describing the research.

The finding was surprising, Just said, as the study's original hypothesis predicted higher scale-insect abundance at lower latitudes—the study's southernmost areas.

"What we've learned over the years in like forests didn't translate in this study, which means we may need to consider if other natural-system theories can be used in urban areas," Just said. "That's important if we want to have reliable predictive ecological models."

The study appears in the journal Oikos.


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More information: Michael G. Just et al, Urbanization drives unique latitudinal patterns of insect herbivory and tree condition, Oikos (2019). DOI: 10.1111/oik.05874
Journal information: Oikos

Citation: Dying trees in cities? Blame it on the concrete (2019, March 4) retrieved 20 October 2020 from https://phys.org/news/2019-03-dying-trees-cities-blame-concrete.html
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