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fire</title></head><body>
<div><font face="Lucida Grande">Drought alters recovery of Rocky
Mountain forests after fire</font><br>
<font face="Lucida Grande"></font></div>
<div><font face="Lucida Grande">UNIVERSITY OF
WISCONSIN-MADISON</font></div>
<div><font
face="Lucida Grande"
>http://www.eurekalert.org/pub_releases/2016-03/uow-dar032116.php</font
></div>
<div><font face="Lucida Grande"><br>
MADISON, Wis. -- A changing climate is altering the ability of Rocky
Mountain forests to recover from wildfire, according to a new study
published in the journal<i> Global Ecology and
Biogeography</i>.</font></div>
<div><font face="Lucida Grande"><br>
When warm, dry conditions lead to drought in the years following
fires, it impedes the growth and establishment of vulnerable new
post-fire seedlings. The study also shows that forest recovery has
been negatively affected by increased distances between burned areas
and the sources of seeds that typically replace trees lost to
fire.</font></div>
<div><font face="Lucida Grande"><br>
"Fires that are followed by warm, dry conditions offer us a
window into the future," says Brian Harvey, lead author of the
study and a former University of Wisconsin-Madison graduate student in
the laboratory of Monica Turner, E.P. Odum Professor of Ecology and
Vilas Research Professor of Zoology. Harvey is now a postdoctoral
Smith Fellow at the University of Colorado Boulder.</font></div>
<div><font face="Lucida Grande"><br>
"From all the best available data and modeling, and expectations
about future climate, these are the kinds of fires and post-fire
climates that we're going to see more of in the future," he
says.</font></div>
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The new data positions researchers to better understand how forests
could change in coming decades and may yield valuable information for
the development of robust simulation models. Turner says the dataset
-- which is the first to comprehensively demonstrate the impact of
drought on forest recovery in the context of a changing climate --
"provides unambiguous evidence that the climate conditions
following fires are really going to matter."</font></div>
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The forests of the Rocky Mountains are well-adapted to fire. For
instance, lodgepole pines, a dominant species in the Mountain West,
possess seed cones that are opened by fire, with each tree releasing
thousands of seeds when burned. However, how the forests will adapt to
a changing climate is still unknown.</font></div>
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"Fires that are followed by drought -- which we are very likely
going to see more of with climate change -- really do set a new
context in which these forests are not recovering as quickly,"
says Harvey. "It's a double whammy because even if seeds can get
to a burned patch, they still need to survive once they get there.
That may be much harder to do in a warmer, drier
climate."</font></div>
<div><font face="Lucida Grande"><br>
The Turner lab's interest in how forest recovery after fire may change
in the future began in the summer of 2000, when large wildfires raged
across the southern portion of Yellowstone National Park in Wyoming.
Thousands of acres of forest burned.<br>
Turner had previously studied the massive 1988 Yellowstone Fires and
in the summers following the 2000 Glade Fire, she and collaborators
visited the forest to collect as much data as possible. They were
surprised to see that tree density in the years after the 2000 fire
was 10 times lower than comparable forests recovering from the fires
of 1988.</font></div>
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A plausible explanation? The year following the Glade Fire was
unusually hot and dry, with just 30 percent of normal summer
precipitation. But one fire followed by a dry summer could not provide
the data to rigorously test the theory.</font></div>
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By 2013, however, multiple well-documented fires had burned throughout
the Rockies and that summer, Harvey conducted field studies in
Yellowstone and Glacier national parks.</font></div>
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He and the research team visited 184 sites where 11 wildfires burned
between 1994 and 2003. The work was exhilarating, but also grueling,
he says, as most sites were well off trail in the backcountry of some
of America's wildest places and the research team was on its hands and
knees examining nearly 10,000 individual tree seedlings.</font></div>
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The team collected data on the overall character of the forest before
fire and the number, species, size and age of trees after fire; the
ground cover on the forest floor (for example, the presence of shrubs
or grasses) following fire; and other qualities of the site, such as
whether the forest stands were on cooler/moister north-facing slopes
or warmer/drier south-facing slopes.</font></div>
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The researchers also turned to existing climate records to assess the
drought severity of each location in the three years immediately
following each fire and examined the distance from each plot to the
nearest source of seeds -- other still-living trees typically outside
the burn patch.</font></div>
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"By going into areas that had burned at least 10 years ago --
enough time for many post-fire tree seedlings to establish -- we were
able to characterize how these forests will likely look for some time
in the future," says Harvey.</font></div>
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They found that overall, fewer post-fire tree seedlings established in
years when fire was followed by severe drought and when seed sources
were farther away, compared with cooler, wetter years and when burned
areas were closer to seed sources.</font></div>
<div><font face="Lucida Grande"><br>
Subalpine tree species, including Engelmann spruce and subalpine fir,
were more negatively affected by drought after fire than species that
grow at warmer, drier low elevations -- Douglas-fir and quaking aspen,
for instance -- and those at the upper tree line, such as whitebark
pine.</font></div>
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"The warm/dry post-fire climate conditions really hammered the
species that currently dominate subalpine forests," Harvey
says.</font></div>
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One exception, however, was the lodgepole pine, which was less
impacted by drought or seed source distance. However, these and the
other species from lower elevations have not moved quickly enough into
higher-elevation burned areas to replace the more sensitive subalpine
tree species.</font></div>
<div><font face="Lucida Grande"><br>
This means that in addition to shifts in the composition of
post-burned forests in the Northern Rockies, forest densities will
also likely be lower in areas where fires are followed by drought,
Harvey says -- at least in the near and medium term.</font></div>
<div><font face="Lucida Grande"><br>
Turner hopes the findings are valuable to land managers who routinely
work with wildfires, which often leave behind a mosaic of burned and
unburned trees. These islands of live, unburned trees in a burnt
desert may serve as valuable seed sources for forest recovery and
should likely be left intact, she says.</font></div>
<div><font face="Lucida Grande"><br>
Harvey and Turner's larger goals are to understand the conditions
under which forests can or cannot recover after fire and to anticipate
what the forest landscape might look like over the next few decades or
centuries.</font></div>
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"Trees grow slowly, and we can't just wait 100 years to get
enough opportunities to study forest recovery from fire," says
Turner.</font></div>
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With the study data, Turner and her collaborators will try to create
models to predict future change. She is also involved in experimental
efforts to understand the moisture thresholds various tree species
require to germinate and become successfully rooted. She hopes to
better understand forest recovery in the context of climate
projections through mid-century.</font></div>
<div><font face="Lucida Grande"><br>
"We want to tease this apart so we can anticipate what the
ecosystem services (like carbon storage and wildlife habitat) will be
in the future, what the landscape will look like, what it means for
people's ability to recreate and where their communities are,"
she says. "There are a lot of human dimensions that come from the
character and distribution of these forests."<br>
###<br>
Daniel Donato, a former member of Turner's lab now with the Washington
Department of Natural Resources, is a co-author on the study, which
was funded by the U.S. Joint Fire Science Program and the National
Park Service.</font></div>
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"Our results indicate that future reductions in Arctic sea ice
cover could significantly reduce available water in the American
west...."<br>
<br>
Jacob O. Sewall and Lisa Cirbus Sloan. Disappearing Arctic sea ice
reduces available water in the American west<br>
<i>GEOPHYSICAL RESEARCH LETTERS</i> VOL. 31,<b> 2004<br>
<br>
</b>******************************************************<br>
"Linkages between northern high-latitude climate and precipitation
in the Sierra Nevada suggested here could indicate that, under
conditions of continued global warming, this drought-prone region may
experience a reduction in Pacific-sourced moisture."<br>
<br>
Jessica L. Oster et al. Late Pleistocene California droughts during
deglaciation and Arctic warming.<i> Earth and Planetary Science
Letters</i><b> 2009</b></font></div>
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" Š the proportion of the land surface in extreme drought is
predicted to increase from 1% for the present day to 30% by the end of
the twenty-first century." <br>
<br>
Eleanor J. Burke et al. "Modeling the Recent Evolution of Global
Drought and Projections for the Twenty-First Century with the Hadley
Centre Climate Model."<i> JOURNAL OF HYDROMETEOROLOGY</i> OCTOBER<b>
2006</b></font><br>
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