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--></style><title>When drought follows fire, tree seedlings
die</title></head><body>
<div><font face="Geneva">When and where a forest fire is followed by
drought, recovery from fire becomes harder, thanks to seedling
failure, a loss of the youngest age class (Kueppers et al 2016, Harvey
et al 2016, and Welch et al 2016).</font></div>
<div><font face="Geneva"><br>
Kueppers and colleagues approached the question of seedling survival
in a common garden experiment, using limber pine and Engelmann spruce
to test outcomes. Harvey et al looked at post-fire conifer seedling
survival in the US Rockies. Welch et al eyed post-fire conifer
seedling survival in the Sierra Nevadas.<br>
<br>
A basic finding was common to all three 2016 studies: Seedlings need
water.<br>
<br>
Drought makes a difference to the forest's youngest trees in any
circumstance, and now including the difference drought makes to the
young when it comes on the heels of a fire.<br>
<br>
These three findings of 2016 look all the more compelling because they
confirm an earlier, 2013 finding:</font></div>
<div><font face="Geneva">"We examined conifer regeneration a decade
following complete stand-replacing wildfire in dry coniferous forests
spanning a 700 m elevation gradient where low elevation sites had
relatively high moisture stress due to the com- bination of high
temperature and low precipitation. Conifer regeneration varied
strongly across the elevation gradient, with little tree regeneration
at warm and dry low elevation sites" (Dodson and Root
2013).</font><br>
<font face="Verdana" size="-1" color="#000000"></font></div>
<div><b>References</b></div>
<div><font face="Verdana">Dodson and Root. Conifer regeneration
following stand-replacing wildfire varies along an elevation gradient
in a ponderosa pine forest, Oregon, USA. Forest Ecology and Management
2013</font></div>
<div><br></div>
<div><font face="Verdana">Harvey, Donato, and Turner. High and dry:
post-fire tree seedling establishment in subalpine forests decreases
with post-fire drought and large stand-replacing burn patches. Global
Ecology and Biogeography 2016</font></div>
<div><font face="Verdana"><br></font></div>
<div><font face="Verdana">Kueppers et al. Warming and provenance limit
tree recruitment across and beyond the elevation range of subalpine
forest. Global Change Biology (2016)</font></div>
<div><font face="Verdana"><br></font></div>
<div><font face="Verdana">Welch, Safford, and Young. Predicting
conifer establishment post-wildfire in mixed conifer forests of the
North American Mediterranean-climate zone. Ecosphere
2016.</font></div>
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<div><font face="Verdana" size="-1"
color="#000000"
>=-------------------------------------------------------------------<span
></span>-------------------------------------=</font></div>
<div><font face="Geneva" size="-1" color="#000000">"Oxygen in the
atmosphere might be reduced several percent below the present level
without adverse effects."</font></div>
<div><font face="Geneva" size="-1" color="#000000"><br></font></div>
<div><font face="Geneva" size="-1" color="#000000">"Free oxygen
not only supports life; it arises from life. The oxygen now in the
atmosphere is probably mainly, if not wholly, of biological
origin."<br>
<br>
Preston Cloud and Aharon Gibor. The Oxygen Cycle. </font></div>
<div><font face="Geneva" size="-1" color="#000000">Scientific
American, September 1970</font></div>
<div><font face="Verdana" size="-1"
color="#000000"
>=-------------------------------------------------------------------<span
></span>-------------------------------------=</font></div>
<div><font face="Verdana" size="-1" color="#000000">"We found
that tree mortality rates increased by an overall average of 4.7%yr
from 1963 to 2008, with higher mortality rate increases in western
regions than in eastern regions (about 4.9 and 1.9% yr ,
respectively). The water stress created by regional drought may be the
dominant contributor to these widespread increases in tree mortality
rates across tree species, sizes, elevations, longitudes and
latitudes. Western Canada seems to have been more sensitive to drought
than eastern Canada" (Peng et al 2011).</font></div>
<div><font face="Verdana" size="-1"
color="#000000"
>********************************************************************<span
></span>****</font></div>
<div><font face="Verdana" size="-1" color="#000000">"We contend
that traditional approaches to forest conservation and management will
be inadequate given the predicted scale of social-economic and
biophysical changes in the 21st century."</font></div>
<div><font face="Verdana" size="-1" color="#000000"><br></font></div>
<div><font face="Verdana" size="-1" color="#000000">Forest Ecology and
Management Accepted 7 October 2015</font></div>
<div><font face="Verdana" size="-1" color="#000000">Review and
synthesis<br>
Achievable future conditions as a framework for guiding forest
conservation and management</font></div>
<div><font face="Verdana" size="-1" color="#000000">S.W. Golladay,
K.L. Martin, J.M. Vose, D.N. Wear, A.P. Covich, R.J. Hobbs, K.D.
Klepzig, G.E. Likens, R.J. Naiman, A.W. Shearer </font></div>
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