<!doctype html public "-//W3C//DTD W3 HTML//EN">
<html><head><style type="text/css"><!--
blockquote, dl, ul, ol, li { padding-top: 0 ; padding-bottom: 0 }
--></style><title>A mistaken generalization about forest
dieoffs</title></head><body>
<div><font face="Arial" color="#1A1A1A"><i>Forest Ecology and
Management</i><b> </b> Volume 359, 1 January 2016, Pages
19-32<br>
<br>
<b>Do denser forests have greater risk of tree mortality: A remote
sensing analysis of density-dependent forest mortality</b><br>
K. Jane Van Gunst, Peter J. Weisberg, Jian Yang, Yuanchao Fan<br>
<br>
Keywords<br>
Forest disturbance; Landsat; Forest health; Drought; Sierra Nevada;
Tree mortality<br>
<br>
Highlights<br>
*25 years of Landsat data were used to relate forest mortality to
stocking level.<br>
*Stocking and mortality were positively related in xeric pine
forests.<br>
*Stocking and mortality were negatively related in red fir forests
during wet years.<br>
*Density reduction will yield disparate results depending on forest
type and climate.</font><br>
<font face="Arial" color="#1A1A1A"></font></div>
<div><font face="Arial" color="#1A1A1A">Abstract-<b> bold
added</b><br>
</font><font face="Arial"
color="#0040C2"><u
>http://www.sciencedirect.com/science/article/pii/S0378112715005277</u
></font><br>
<font face="Arial" color="#1A1A1A"></font></div>
<div><font face="Arial" color="#1A1A1A">In forests of the western
United States, high levels of forest stocking attributed to fire
exclusion and settlement-era logging practices have coincided with
periods of extensive forest mortality associated with extreme drought
and forest pest outbreaks.<b> This has led to the widespread but
largely untested generalization that increased stand density causes
increased levels of forest mortality</b>,<b> even for</b> uneven-aged,
multi-species, mature stands that are not actively undergoing
self-thinning. We used archival Landsat imagery to examine: (1)
variations in forest mortality among forest types and climate periods
from 1985 to 2010 in the mixed conifer forest of the Lake Tahoe Basin,
(2) relationships between stand density and mortality in the
subsequent year, and (3) the influence of environmental variables on
forest mortality. We found that positive density dependent
mortality,<b> where increased stand density is associated with
increased probability of mortality, is associated more with lower
elevation forests and drier climate periods. In mid- to
upper-elevation forests, increased density was more often associated
with decreased probability of mortality, especially during wetter
periods</b>. Results showed highest tree mortality during a drought in
the beginning of our 25-year time series, but not in a subsequent
drought period of similar severity.<b> Our study also found increased
risk of tree mortality on north-facing slopes across all forests and
all climate periods, even when stand density was controlled for.</b>
There is a nuanced relationship between stocking level, forest
mortality and drought effects, suggesting that<b> no single
density-reduction forest management strategy will increase forest
resilience under all climate periods and in all forest
types.</b></font><br>
<font face="Arial" size="-1" color="#1A1A1A"></font></div>
<x-sigsep><pre>--
</pre></x-sigsep>
<div><font face="Cambria" size="-1"
color="#000000"><b
>====================================================================<span
></span>===============<br>
</b></font><font face="Bookman Old Style" size="-1"
color="#000000">"The growth in CO2 emissions closely follows the
growth in Gross Domestic Product (GDP) corrected for improvements in
energy efficiency."<br>
<br>
P. Friedlingstein, et al. "Update on CO2 emissions."</font></div>
<div><font face="Bookman Old Style" size="-1"
color="#000000"><i>Nature Geoscience.</i> Published online: 21
November 2010</font></div>
<div><font face="Geneva" size="-1"
color="#000000"
>====================================================================<span
></span>===</font></div>
<div><font face="Geneva" size="-1" color="#000000">"An impressive
study across all of northern Russia from 1953-2002 showed a shift in
tree allometries. In areas where summer temperatures and precipitation
have both increased, a general increase in biomass (up 9%) is
primarily a result of increased greenery (33% more carbon in leaves
and needles), rather than woody parts (roots and stem). In areas that
have experienced warming and drying trends, greenery has decreased,
and both roots and stems have increased (Lapenis et al.
2005)."</font></div>
<div><font face="Geneva" size="-1" color="#000000"><br></font></div>
<div><font face="Geneva" size="-1" color="#000000">" ...
there is little theoretical or experimental support to suggest that
climate warming will cause absolute climatic tolerances of a species
to evolve sufficiently to allow it to conserve its geographic
distribution."</font></div>
<div><font face="Bookman Old Style" color="#000000"><br></font></div>
<div><font face="Bookman Old Style" color="#000000">Camille Parmesan.
"Ecological and Evolutionary Responses to Recent Climate
Change."<i> Annual Review of Ecol. Evol. & Systematics </i>
2006. 37:637-69</font><font face="Geneva" size="-1"
color="#FFFF00"><u><br>
</u></font><font face="Didot" size="-2" color="#FFFF00"><u><br>
</u></font><font face="Bookman Old Style" color="#000000"><br>
</font><font face="Geneva" size="-1" color="#000000"><br>
</font><font face="Verdana" size="-1" color="#000000"><br>
</font><font face="Times New Roman" color="#000000"></font></div>
<div><font face="Bookman Old Style" size="-1" color="#000000"><br>
</font><font face="Lucida Grande" size="-1" color="#000000"><br>
</font></div>
<div><font face="Lucida Grande" size="-1" color="#000000"><br>
</font><font color="#000000"><br>
</font></div>
<div><font face="Verdana" size="-1" color="#000000"><br></font></div>
<div><font face="Bookman Old Style" color="#000000"><br>
</font><font face="Times New Roman" color="#000000"><br>
<br>
</font><font face="Verdana" size="-1" color="#000000"><br>
</font></div>
<div><font face="Bookman Old Style" color="#000000"><br>
</font><font face="Verdana" size="-1" color="#000000"><br>
</font><font face="Geneva" color="#000000"><br>
</font></div>
<div><font face="Times New Roman" color="#000000"><br>
</font><font face="Verdana" size="-1" color="#000000"><br>
</font></div>
</body>
</html>