For trees, carbs are key to surviving insect defoliation, study finds


Date:
August 13, 2021
Source:
Harvard University
Summary:
Research reveals that a tree's carbohydrate reserves are crucial
to surviving an onslaught of hungry caterpillars.



FULL STORY ==========================================================================
A recent multi-year outbreak of an invasive moth killed thousands of
acres of oak trees across southern New England. But interspersed among
the wreckage were thousands of trees that survived. A new study published
today in Functional Ecology sheds light on why. Research by scientists
from Harvard, UMass Amherst, Boston University, and MIT reveals that a
tree's carbohydrate reserves are crucial to surviving an onslaught of
hungry caterpillars.


==========================================================================
The biology of trees makes them resilient to even the most severe
stressors.

"Oak trees are planners, in a way," says Meghan Blumstein, NSF
Post-doctoral Research Fellow at MIT and a co-author of the study. "Some
of the food they make during the growing season is used immediately for
energy and some is stored in the stems and roots for a rainy day. With
stored carbs, they are able to immediately create a new flush of leaves
after an insect outbreak." But trees are not invincible, and the new
study reveals the specific threshold of reserves necessary for them to
survive: 1.5 percent carbohydrates in their dried wood- or about 20-25%
of their normal storage capacity. The repeated emergence of Lymantria
dispar (an insect formerly known as "gypsy moth") from 2016 to 2018
challenged trees' resilience by defoliating them year after year.

"The trees that died were the trees that were out of reserves," says
lead author Audrey Barker Plotkin, a Senior Scientist at the Harvard
Forest. But the location of the trees mattered, too. The research team
found that trees growing along forest edges tended to have more reserves,
even at the same level of defoliation, making them more resilient than
interior forest trees. The research team posits that forest edge trees
may have simply experienced less severe defoliation in the years before
2018. And, because edge trees get lots of light, they may also be able
to rebound without drawing down their reserves as much as their interior
forest counterparts.

The new study provides direct evidence, that had until now been lacking,
that trees can indeed starve to death when insects invade. This more
nuanced understanding will help improve forest resilience models as new
pests and a shifting climate continue to drive change in the region.

The Harvard Forest, founded in 1907 and located in Petersham,
Mass., is Harvard University's outdoor laboratory and classroom
for ecology and conservation, and a Long-Term Ecological Research
(LTER) site funded by the National Science Foundation. Its 4,000-acre
property is one of the oldest and most intensively studied research
forests in the U.S. More information can be found at: http:// harvardforest.fas.harvard.edu/ More information Read a blog post
about the study, written by lead author Audrey Barker Plotkin, at: https://functionalecologists.com/2021/08/13/audrey-barker-plotkin-trees- can-starve-to-death-from-insect-defoliation/ ========================================================================== Story Source: Materials provided by Harvard_University. Note: Content
may be edited for style and length.


========================================================================== Journal Reference:
1. Audrey Barker Plotkin, Meghan Blumstein, Danelle Laflower,
Valerie J.

Pasquarella, Jennifer L. Chandler, Joseph S. Elkinton, Jonathan R.

Thompson. Defoliated trees die below a critical threshold of stored
carbon. Functional Ecology, 2021; DOI: 10.1111/1365-2435.13891 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2021/08/210813152017.htm

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