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With about 1.5 million acres of lodgepole pine trees in Colorado
already infested with the mountain pine beetle, researchers at the
Fraser Experimental Forest are studying how all those dead trees will
affect watersheds that serve as the source for much of the West's water
supplies.
The 36-square-mile Fraser Experimental Forest lies in the heart of
the central Rocky Mountains about 50 miles west of Denver. About
three-quarters of the forest lies above 10,000 feet and about one-third
is above timberline, including the forest's highest point, Byers Peak,
which reaches 12,804 feet.
St. Louis Creek, the main drainage
on the Fraser Experimental Forest, is typical of the headwater streams
that provide 85 percent of the 20-million-acre feet of water that
drains from the Colorado Rockies, according to the Forest Service. In
fact, water from the Fraser Experimental Forest trickles throughout the
West -- from Los Angeles to Las Vegas to Phoenix -- since about
three-quarters of the West's water comes from snowmelt captured in the
Rockies.
"When you open the tap in Denver, you're drinking
Fraser water," said Kelly Elder, the administrator of the Fraser
Experimental Forest.
n fact, the 6-mile-long Moffat Tunnel brings water from St. Louis
and Vasquez creeks across the Continental Divide to supply water for
the city of Denver. The tunnel is just one of more than 40 diversions
that bring West Slope water to the growing cities along Colorado's
Front Range and farms in the eastern plains.
The Fraser
Experimental Forest is also one of two major headwater basins to the
Colorado River, which provides water for Arizona, California, Colorado,
Nevada, New Mexico, Utah and Wyoming. St. Louis Creek flows into the
Fraser River, which is a tributary of the Colorado River.
The
Fraser Experimental Forest was established specifically because of the
recognition of the importance of the production of water from Forest
Service land, said Chuck Rhoades, a biogeochemist with the Forest
Service. "During some of the initial work going on here, we were kind
of in competition with the folks that were putting the tunnels in," he
said.
"It's pretty unique," Rhoades added. "There's nothing
else like this in the southern central Rockies. In terms of the data
record, it's also the longest for these Western conifer forests."
The
forest was set up to research the effects of timber harvest and forest
management on water yield. That research revealed that selected,
well-planned cuts of timber could increase the yield of the amount of
water that comes out of the subalpine forests. The removal of the trees
allows more snow to fall on the ground, where it can make its way into
the water drainages rather than evaporating from the canopy into the
atmosphere, and keeps water in the ground during the summer that
otherwise would have been used by trees.
The manipulation of
snowpack is important because the snowpack is essentially a huge water
storage system for the western United States. "It's a reservoir you
don't have to build, but we don't have complete control over it. It's
not like the floodgates on a reservoir, where when you need water you
open them," Elder said.
"Augmenting or manipulating that snowpack is the biggest way we can manipulate the amount of water that comes out," Elder said.
A tiny beetle's impact to a massive watershed
One of the
big questions surrounding the mountain pine beetle attack is how the
loss of all that canopy cover will affect the watershed. Researchers
suspect the loss of canopy cover will increase the amount of water
coming out of the forests, but they do not know how much or for how
long.
The early research on the forest reveals that it takes
a long time for these forests to recover. Data collected from the
forest indicates it takes about 60 years before a logged area achieves
hydrologic recovery, Elder said.
"Areas that were cut in the '50s still haven't returned to the way
they were functioning in terms of interception and water use," Rhoades
said. "The trees grow so slow here, we still haven't regained the leaf
area. The trees are still quite small."
Because these
subalpine environments are so slow to recover, disturbances in them,
such as the beetle outbreak, may have effects for several decades.
"When
we're talking about why the beetle is so important and why the beetle
outbreak is important to water, it's because it could have an influence
that could go on for decades," Rhoades said.
Researchers
first started seeing the beetle in the forest in 2003. The beetles
swept through the forest, chomping on trees in areas that had been
thinned, as well as ones that hadn't.
"Very quickly, we realized, you know this is going to be catastrophic," Elder said.
The
beetles kill the trees by boring through the bark into the phloem
layer, the living tissue that carries organic nutrients to all parts of
the plant. The trees respond to the attack by increasing their resin
output to discourage or kill the beetles, but the beetles carry blue
stain fungi that can block the tree resin response. Over time, the
trees are overwhelmed as the phloem layer is damaged enough to cut off
the flow of water and nutrients, essentially starving the trees to
death.
Beetles are native to the western forests of North
America, but they have spread in recent years, as trees stressed by
drought became more susceptible to attack. In the past, such outbreaks
have typically been halted by cold spells that lasted long enough to
kill the beetles. That is a concern for forest managers, since the
minimum annual daily temperatures have increased over the past 50
years, making such a cold spell less likely now.
Impacts to research, management
The beetle's arrival
changed the focus of research in the seven watersheds of the Fraser
Experimental Forest. So far, researchers have not detected any changes
in the hydrologic system as a result of the beetles, but they are
already looking at ways to manage the forests after the beetle attack.
Elder said the experimental forest is in a unique position to conduct
such studies because of its long-term data.
"The public's
demanding that we treat these forests for a fire perspective and for
all kinds of other reasons from aesthetics to safety, and so the Forest
Service has to manage that post-beetle scenario, so a big part of our
research now is to look at the effects of management and make sure
we're doing management in the best way possible," Elder said.
"Part of the problem is we know how to do clearcuts and we know how
to apply riparian buffers to protect watersheds and stream systems, but
we don't know how that works when we're talking about base loads with
90 percent mortality."
For example, logging operations
typically leave trees within 100 feet of riparian areas to maintain
water quality and habitat in the watershed, but there are concerns that
leaving dead trees in these areas may simply increase the risk for fire
to move through the watershed. When the dead trees fall over, they will
also provide coarse wood and structure in the stream, but researchers
do not yet know how the streams will respond to so many dead trees
falling in a relatively short time period.
"We have no idea
in terms of the natural range of variability, whether this huge
increase in wood going into the stream, whether that's going to be
something streams have seen normally, whether that's going to be good,
whether that's going to be bad, how that would affect aquatic
invertebrates or fish," Rhoades said. "We don't know."
Researchers
on the forest are currently conducting experiments looking at what
happens when these riparian buffers are left in place versus thinning
the areas in a way that reduces the fuel loads without impacting water
quality.
The pine beetle is also not the only problem in the
riparian areas, since most of the riparian areas also contain spruce,
which is battling a beetle infestation of its own. "That could really
hammer the lower part of the landscape," Rhoades said.
The
researchers are also looking at the results of different management
techniques. For example, they are comparing logging projects that aim
to maximize the amount of water coming off the forests with projects
that aim primarily to reduce fuel loads and projects that encourage the
growth of new trees.
Although the Healthy Forests Restoration
Act allows for exemptions from the National Environmental Policy to
speed up timber sales in areas like the Fraser Experimental Forest that
are facing timber loss of epidemic proportions, Forest Service
officials said the infrastructure simply is not there to remove trees
in infected areas on a large scale. Aside from the sheer magnitude of
the task, with 1.5 million acres affected, there is a lack of roads to
access many of these areas and Colorado only has one operating timber
mill.
Another open question is what the forest will look like
in the future. There are millions of young trees that are now
benefiting from the beetle outbreak. The loss of canopy cover once
provided by the mature trees allows more sunlight to reach them, and
the big trees are no longer hogging up the water supply either.
Because
many of the areas affected by the pine beetle outbreak have been logged
in the past, creating a monoculture of even-aged lodgepole pines, the
beetle outbreak also provides an opportunity for the forest to return
to something closer to what it looked like before humans started
managing the forests, with greater species and age diversity.
"When
people hear 90 percent mortality, they're visualizing Craters of the
Moon or southern Nevada. It's not going to be like that," Elder said.
"There's a really health understory in a large portion of the forest
that's really taken off."
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