Woodlands - Fall 2017 - 7

PROJECT LEARNING TREE HAS A NEW HOME
We are pleased to announce that the national
sponsorship of Project Learning Tree (PLT) has officially
been transferred to the Sustainable Forestry Initiative
(SFI). We are excited about this new home for PLT and
the many opportunities that it provides for PLT. We

look forward to the program's continued growth and
success with SFI.
If you wish to support PLT, please contact
Nadine Block, SFI's chief operating officer at
Nadine.Block@sfiprogram.org.
A

DROUGHT-AFFECTED TREES DIE FROM HYDRAULIC FAILURE AND
CARBON STARVATION

New Study Improves Predictive Models of How Trees Die in Response to
Heat, Drought, and Other Climate Stresses
Hydraulic failure, which is the inability of a plant to
move water from roots to leaves, is almost universally
present when trees die during a drought, while carbon
starvation is a contributing factor roughly half of the time,
a new report finds.
"Droughts are increasing in frequency and severity,
and their impact on plants and humans is becoming more
intense," says research co-author, Melanie Zeppel of
Sydney University's Charles Perkins Centre.
"The discovery of how droughts cause death in trees,
regardless of tree type, will let us make better regionalscale predictions of the effects of droughts on forests."
As the number of hot droughts increases globally,
scientists are looking to make more consistent predictions
of what will happen to plants and vegetation in the future.
This matters for models used to predict climate change
because plants take up a big portion of the carbon dioxide
humans pump in the atmosphere. Therefore, the effect
of tree death and die-off, as observed globally in recent
decades, could affect the rate at which climate changes.
"Current global vegetation models have a hard time
producing consistent and accurate estimates of plant
carbon dioxide-uptake, and their predictions vary widely
based on the assumptions they use about how plants
respond to climate," says Zeppel.
"Trees and forests are particularly important because
they take up and store a lot of this carbon dioxide, and
also affect their environment in other ways."
"Understanding drought is critical to managing our
nation's forests," says Lina Patino, section head of the
National Science Foundation's Division of Earth Sciences,
which funded the study.

"This research will help us more accurately predict
how different plant species respond to different types of
environmental stress such as drought, insect damage
or disease."
The paper's lead author, Henry Adams at Oklahoma
State University, explains that 99 percent of the water
moving through a tree is used to keep stomata open,
the pores that let in carbon dioxide, allowing it to carry
out photosynthesis.
Trees respond to the stress of drought by closing
those pores that let in carbon dioxide. At that point, they
need to rely on their stored sugars and starches to stay
alive, and could die from carbon starvation if they run
out before the drought is over.
On the other hand, if the tree loses too much water too
quickly, an air bubble (embolism) will form and the tree has
hydraulic failure. It cannot transport water from the roots to
the leaves, which becomes lethal as the whole tree dries out.
Adams and his colleagues saw that in many cases, both
carbon starvation and hydraulic failure appeared to occur
as trees died.
This makes sense, because the stored sugars and
starches that could be reduced in carbon starvation are
also important for preventing hydraulic failure. When
converted to sugar, these can act as "osmoprotectants,"
increasing the tree's ability to hold on to
its water.
"It's kind of like antifreeze in a
car that keeps the engine from
overheating," Adams says.
A
Source: University of Sydney

Potapove Alexander/Shutterstock

Fall 2017 * WOODLAND 7



Table of Contents for the Digital Edition of Woodlands - Fall 2017

Overstory
Tools and Resources
Forests and Families
A Legacy to Keep
From Forests to Fermentation
Feathering a Forested Nest
Woodlands - Fall 2017 - intro
Woodlands - Fall 2017 - cover1
Woodlands - Fall 2017 - cover2
Woodlands - Fall 2017 - 3
Woodlands - Fall 2017 - Overstory
Woodlands - Fall 2017 - 5
Woodlands - Fall 2017 - 6
Woodlands - Fall 2017 - 7
Woodlands - Fall 2017 - 8
Woodlands - Fall 2017 - 9
Woodlands - Fall 2017 - 10
Woodlands - Fall 2017 - 11
Woodlands - Fall 2017 - 12
Woodlands - Fall 2017 - 13
Woodlands - Fall 2017 - 14
Woodlands - Fall 2017 - 15
Woodlands - Fall 2017 - 16
Woodlands - Fall 2017 - 17
Woodlands - Fall 2017 - Tools and Resources
Woodlands - Fall 2017 - 19
Woodlands - Fall 2017 - Forests and Families
Woodlands - Fall 2017 - 21
Woodlands - Fall 2017 - 22
Woodlands - Fall 2017 - 23
Woodlands - Fall 2017 - A Legacy to Keep
Woodlands - Fall 2017 - 25
Woodlands - Fall 2017 - 26
Woodlands - Fall 2017 - 27
Woodlands - Fall 2017 - 28
Woodlands - Fall 2017 - 29
Woodlands - Fall 2017 - From Forests to Fermentation
Woodlands - Fall 2017 - 31
Woodlands - Fall 2017 - 32
Woodlands - Fall 2017 - 33
Woodlands - Fall 2017 - Feathering a Forested Nest
Woodlands - Fall 2017 - 35
Woodlands - Fall 2017 - 36
Woodlands - Fall 2017 - 37
Woodlands - Fall 2017 - 38
Woodlands - Fall 2017 - cover3
Woodlands - Fall 2017 - cover4
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https://www.nxtbook.com/naylor/AFOQ/AFOQ0316
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