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--></style><title>USFS: Doug-fir drought tolerance varies by distance
from c</title></head><body>
<div><font face="Geneva">Graphic/map identifies areas where drought
tolerance is highest, lowest</font></div>
<div><font
face="Geneva">http://www.fs.fed.us/pnw/sciencef/scifi179.pdf</font></div
>
<div><font face="Geneva"><br></font></div>
<div><font face="Geneva">Some populations of Douglas-fir are more
drought tolerant than others. In an ongoing study, researchers are
testing how seed grown from different populations respond to
temperature and precipitation conditions that differ from current
local conditions.</font></div>
<div><font face="Geneva"><br></font></div>
<div><font face="Geneva">IN SUMMARY</font></div>
<div><font face="Geneva">Douglas-fir is an iconic tree in the Pacific
Northwest. Although individual trees may appear to be identical,
genetic differences within each tree have resulted from adaptation to
the local environment. These genetic differences over time have
resulted in differences among populations that are important to the
species' survival and growth in changing climates.</font></div>
<div><font face="Geneva"><br></font></div>
<div><font face="Geneva">Current climate models project that over the
next 50 years, the Pacific Northwest will experience an increase in
summer temperatures. Combined with less winter snowpack, warmer summer
temperatures will likely lead to more frequent and intense droughts,
and it is unknown how Douglas-fir will respond. Researchers with the
U.S. Forest Service Pacific Northwest Research Station tested how
seedlings from different populations of Douglas-fir would grow in
temperature and precipitation conditions unlike the climate of their
current seed source. By sampling 35 populations in three common garden
sites, researchers deter- mined how a combination of genetic factors
and environmental conditions influence drought-tolerant
traits.</font></div>
<div><font face="Geneva"><br></font></div>
<div><font face="Geneva">Trees grown in a warm, dry environment had
lower rates of water loss compared to seedlings grown in cooler
environments. Furthermore, researchers identified populations that had
high drought tolerance and relatively fast growth. This means that
although Douglas-fir as a species is relatively drought tolerant, some
populations are better adapted to future climate conditions than
others.</font></div>
<div><font face="Geneva"><br></font></div>
<div><font face="Geneva">LAND MANAGEMENT IMPLICATIONS</font></div>
<div><font face="Geneva">*By measuring an individual tree's
minimum transpiration rate, water deficit, and specific leaf area,
tree improvement programs can identify nursery stock that exhibits
relatively high drought tolerance.</font></div>
<div><font face="Geneva"><br></font></div>
<div><font face="Geneva">*Models relating drought tolerance to the
climates of seed sources may be used to predict which populations are
naturally more resistant to drought stress.</font></div>
<div><font face="Geneva"><br></font></div>
<div><font face="Geneva">*With this information, land managers can
plant seedlings that will be adapted to current and future climate
conditions. For example, populations that are more tolerant of drought
stress can be planted in drought-prone areas.</font></div>
<div><br></div>
<div>Full report here:</div>
<div><font
face="Geneva">http://www.fs.fed.us/pnw/sciencef/scifi179.pdf</font></div
>
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<div><font face="Cambria"
color="#000000">========================================<br>
"The broad pattern of these changes is clear enough."<br>
<br>
George Woodwell. The Energy Cycle of the Biosphere.</font></div>
<div><font face="Cambria" color="#000000"><i>Scientific American,</i>
September 1970, p. 36<br>
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