Nav: Home

Dying trees in cities? Blame it on the pavement

March 04, 2019

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 trees 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 natural areas 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.

Steven Frank, an NC State professor of entomology, and Lawrence Long, an NC State entomology graduate student, co-authored the paper along with Adam Dale from the University of Florida.

Funding for the study was provided by the U.S. Department of Agriculture National Institute of Food and Agriculture funded Southern IPM Center, under Agreement No. 2014-70006-22485, as well USDA NIFA award Nos. 2013-02476 and 2016-70006-25827. It was also supported by Cooperative Agreement G15AP00153 from the U.S. Geological Survey.

Note: An abstract of the paper follows.

"Urbanization drives unique latitudinal patterns of insect herbivory and tree condition"

Authors: Michael Just, Lawrence Long and Steven Frank, NC State University; Adam Dale, University of Florida

Published: Feb. 15, 2019 in Oikos

DOI: 10.1111/oik.05874

Abstract: Urban landscapes are characterized by high proportions of impervious surface resulting in higher temperatures than adjacent natural landscapes. In some cities, like those at cooler latitudes, trees may benefit from warmer urban temperatures, but trees in many cities are beset with problems like drought stress and increased herbivory. What drives patterns of urban tree health across urbanization and latitudinal temperature gradients? In natural systems, latitude-herbivory relationships are well-studied, and recent temperate studies have shown that herbivory generally increases with decreasing latitudes (warmer temperatures). However, the applicability of this latitude-herbivory theory in already-warmed urban systems is unknown. In this study, we investigated how the interaction of urbanization, latitudinal warming, and scale insect abundance affected urban tree health. We predicted that trees in warmer, lower latitude cities would be in poorer health at lower levels of urbanization than trees at cooler, higher latitudes due to the interaction of urbanization, latitudinal temperature, and herbivory. To evaluate our predictions, we surveyed the abundance of scale insect herbivores on a single, common tree species Acer rubrum in eight US cities spanning 10° of latitude. We estimated urbanization at two extents, a local one that accounted for the direct effects on an individual tree, and a larger one that captured the surrounding urban landscape. We found that urban tree health did not vary with latitudinal temperature but was best predicted by local urbanization and herbivore abundance. We did not observe increased herbivore abundance in warmer, lower latitudes cities, but instead herbivore abundance peaked in the mid latitudes of our study. This study demonstrates that urban landscapes may deviate from classical theory developed in natural systems and reinforces the need for research reconciling ecological patterns in urban landscapes.

North Carolina State University

Related Trees Articles:

Methane emissions from trees
A new study from the University of Delaware is one of the first in the world to show that tree trunks in upland forests actually emit methane rather than store it, representing a new, previously unaccounted source of this powerful greenhouse gas.
Scientists make plastic from pine trees
Most current plastics are made from oil, which is unsustainable.
Measuring trees with the speed of sound
Foresters and researchers are using sound to look inside living trees.
Seeing the forest through the trees
The University of Tennessee Institute of Agriculture is participating in a three-year, $3-million grant by the National Science Foundation to develop a user-friendly interface that will help forest scientists everywhere record and share their genomic data for various tree species.
How fungi help trees tolerate drought
In the transcriptome -- the set of its messenger RNA molecules that reflects actual biochemical activity by the organism -- of the most common ectomycorrhizal fungus Cenococcum geophilum, a team including DOE JGI researchers found specific adaptations that could help their hosts be more resistant to drought stress, a finding that could be useful in developing more plant feedstocks for bioenergy amidst the changing climate.
Researchers say trees could help strengthen auto parts
Srikanth Pilla of Clemson University announced Wednesday that he has received funding to work with the US Forest Service to develop fenders and bumpers that are less likely to break or distort on impact.
Droughts across Europe affect British trees most
Environmental scientists from the University of Stirling have found beech forests across western Europe are increasingly at risk from drought -- with areas of southern England worst affected.
Bacteria in branches naturally fertilize trees
A University of Washington team has demonstrated that poplar trees growing in rocky, inhospitable terrain harbor bacteria within them that could provide valuable nutrients to help the plant grow.
How do trees go to sleep?
Most living organisms adapt their behavior to the rhythm of day and night.
Which trees face death in drought?
William Anderegg and his colleagues looked for patterns in previous studies of tree mortality and found some common traits that characterized which species lived and which died during drought.

Related Trees Reading:

Best Science Podcasts 2019

We have hand picked the best science podcasts for 2019. Sit back and enjoy new science podcasts updated daily from your favorite science news services and scientists.
Now Playing: TED Radio Hour

Digital Manipulation
Technology has reshaped our lives in amazing ways. But at what cost? This hour, TED speakers reveal how what we see, read, believe — even how we vote — can be manipulated by the technology we use. Guests include journalist Carole Cadwalladr, consumer advocate Finn Myrstad, writer and marketing professor Scott Galloway, behavioral designer Nir Eyal, and computer graphics researcher Doug Roble.
Now Playing: Science for the People

#530 Why Aren't We Dead Yet?
We only notice our immune systems when they aren't working properly, or when they're under attack. How does our immune system understand what bits of us are us, and what bits are invading germs and viruses? How different are human immune systems from the immune systems of other creatures? And is the immune system so often the target of sketchy medical advice? Those questions and more, this week in our conversation with author Idan Ben-Barak about his book "Why Aren't We Dead Yet?: The Survivor’s Guide to the Immune System".