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forests?</title></head><body>
<div><font face="Geneva">Drought implicated in slow death of trees in
southeast's forests<br>
DUKE UNIVERSITY<br>
Public Release: 19-Aug-2015</font></div>
<div><font face="Geneva"><br></font></div>
<div><font face="Geneva">Damage suffered by trees during a drought can
reduce their long-term survival for up to a decade after the drought
ends, a new study of tree mortality in southeastern forests finds. By
identifying the symptoms that mark a tree for later death and the
species that are at highest risk, the study's findings may give
managers and scientists a way to recognize and reverse drought-induced
declines before it's too late.</font></div>
<div><br></div>
<div><font face="Geneva">Aaron Baird Berdanier and James S. Clark<i>
In press.</i> Multi-year drought-induced morbidity preceding tree
death in Southeastern US forests.<i> Ecological Applications.</i><u>
http://dx.doi.org/10.1890/15-0274.1</u><br>
<br>
<b>Multi-year drought-induced morbidity preceding tree death in
Southeastern US forests</b></font></div>
<div><font face="Geneva"><b>Aaron Baird Berdanier1,* and James S.
Clark2</b><br>
1Duke University<br>
2Duke University, Nicholas School of the Environment<br>
<br>
Recent forest diebacks combined with threats of future drought focus
attention on the extent to which tree death is caused by catastrophic
events as opposed to chronic declines in health that accumulate over
years. While recent attention has focused on large-scale diebacks,
there is concern that increasing drought stress and chronic morbidity
may have pervasive impacts on forest composition in many regions. Here
we use long-term, whole-stand inventory data from Southeastern US
forests to show that trees exposed to drought experience multi-year
declines in growth prior to mortality. Following a severe, multi-year
drought, 72% of trees that did not recover their pre-drought growth
rates died within 10 years. This pattern was mediated by local
moisture availability. As an index of morbidity prior to death, we
calculated the difference in cumulative growth after drought relative
to surviving conspecifics. The strength of drought-induced morbidity
varied among species and was correlated with drought tolerance. These
findings support the ability of trees to avoid death during drought
events but indicate shifts that could occur over decades. Tree
mortality following drought is predictable in these ecosystems based
on growth declines, highlighting an opportunity to address multi-year
drought-induced morbidity in models, experiments, and management
decisions.</font><br>
<font face="Geneva"></font></div>
<div><font face="Geneva">*To whom correspondence should be addressed.
E-mail:<u> aaron.berdanier@gmail.com</u></font></div>
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<div><font face="Lucida Grande" size="-1"
color="#000000">"</font><font face="Lucida Grande" size="-1"
color="#141413">Here, we examine the physiological basis of a recent
multiyear widespread die-off of trembling aspen (Populus tremuloides)
across much of western North America. Š. We test whether
accumulated hydraulic damage can predict the probability of tree
survival over 2 years. We find that hydraulic damage persisted and
increased in dying trees over multiple years and exhibited few signs
of repair Š. Contrary to the expectation that surviving
trees have weathered severe drought, the hydraulic deterioration
demonstrated here reveals that surviving regions of these forests are
actually more vulnerable to future droughts due to accumulated xylem
damage."<br>
<br>
WILLIAM R. L. ANDEREGG et al. Drought's legacy: multiyear hydraulic
deterioration underlies widespread aspen forest die-off and portends
increased future risk. Global Change Biology (2013) 19, 1188-1196,
doi: 10.1111/gcb.12100<br>
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