Grand Canyon Cottonwood   Don Bertolette
  Feb 18, 2005 22:52 PST 

Bob-

Well, I haven't been searching the internet on cottonwoods, but I can now
tell you about what happens when they grow fast at Phantom Ranch, down in
Grand Canyon alongside Bright Angel Creek. Last summer, myself and a forest
pathologist evaluated the cottonwoods at Phantom for soundness...we
identified 33 trees that either needed pruning or removal (7)...this winter
we went down to Phantom Ranch. Every tree we treated had significant rot,
some more than we anticipated, and some where we hadn't anticipated.
These trees were planted in two waves, the first in 1920s at the Park's
inception, and the second in 1930s with the Harvey concessionaires creation
of the 'dude ranch' now known as Phantom Ranch. Some 75 and 85 years later,
they clearly are reaching the far end of their time here on earth. Not
normally a problem, but virtually all of them were planted where they would
create shade for guests and historic structures...and habitat for bald
eagles and other denizens of the Park.
Not being an arborist by trade or training, I would welcome input from any
of the arborists who grace this listserve...replacing cottonwoods with a
hardier more windfirm species that still provides quick shade AND is native
to the Park, has been the challenge.

-Don
Grand Canyon Cottonwoods    Edward Frank
   Feb 20, 2005 22:22 PST 

Don,

I am curious about the time frame in which the cottonwoods will need to be
replaced?   Have you ever been to McKittrick Canyon in Guadalupe National
Park in Texas? In the park are some of the most spectacular fall colors
from an isolated pocket of maples growing there.

http://www.nps.gov/gumo/gumo/mckittrick.htm

http://www.nps.gov/gumo/gumo/trees.htm

I wonder how much genetic drift has taken place in this isolated pocket
from the main body of the tree population? It is likely that a similar
situation has occurred with the tree and shrub populations native to the
floor of the canyon.

First I would look at historical records of the early expeditions down the
canyon, John Wesley Powell kept notes during both his first and second
expedition down the canyon. What trees did he and other early explorers
find before the landscape was altered by ranching, and before invasive
species arrived from elsewhere? What do some of the other explorers say?
What trees are shown in the photographs of Timothy O'Sullivan? What trees
lived at the bottom of the canyon before the arrival of settlers? Or even
before the native Americans? Once you knew what species were present, or
at least commonly present in the pre-settlement days, then you could choose
one that provided the best shade for structure and adequate wind tolerance.

Journal of Powell's second trip can be found at this address:

http://www.library.unt.edu/gpo/powell/publications.htm

http://www.library.unt.edu/gpo/powell/exploration2.pdf 25.5 MB

From what I read cottonwoods were the most commonly mentioned tree in the
canyon. Perhaps the problem is that the cottonwoods planted in the area
were not native to the canyon itself?

p. 94 (Bright Angel Canyon) Early in the afternoon, we discover a stream,
entering from the north, a clear, beautiful creek, coming down through a
gorgeous red canon. We
land, and camp on a sand beach, above its mouth, under a great, overspreading
tree, with willow shaped leaves.

p. 100 Our way to day is again through marble walls. Now and
then we pass, for a short distance, through patches of granite, like hills
thrust, up into the limestone. At one of these places we have to make
another portage, and, taking advantage of the delay, I go up a little stream,
to the north, wading it all the way, sometimes having to plunge in to my
neck; in other places being compelled to swim across little basins that have
been excavated at the foot of the falls. Along its course are many cascades
and springs gushing out from the rocks on either side. Sometimes a cottonwood
tree grows over the water.

I would like to see trees originally native to the canyon. Maybe you need
cottonwoods native to the canyon rather than from elsewhere. If there is
time, it might be better to transplant specimens of these natives from
locations elsewhere in the canyon. These should be locations where the
populations are sufficient that it will not strain the local ecosystem. If
there is time, seedlings could be grown from local seed.

The second option would be to replace the cottonwoods with another species,
such as willow, originally native to the canyon, but from commercial
sources from areas outside of the canyon. There is some concern that they
might not thrive as the local original trees may have become better adapted
to growing on the canyon floor over time than plants from other localities.
Trees from more southerly areas when transplanted here in Pennsylvania
tend to bud and flower earlier than do local native trees.

Another consideration might be that this age range is as long as a typical
cottonwood will grow in the area without problems given the current
environmental conditions. Certainly the flood regime of the canyon itself
has changed dramatically with the Glen Canyon Dam. Trees are being impacted
by pollution and ozone levels higher than pre-industrial days. I don't
think this is the case, but in any marginal situation, even small changes
in climate can affect species viability.


Ed Frank
Re: Grand Canyon Cottonwoods   Don Bertolette
  Feb 21, 2005 18:22 PST 

Ed-

Most of the studies on cottonwoods in the Southwest don't wax very
optimistic on longevity...The conditions that make them grow fast (people
out here want shade NOW) don't lend the tree much in the way of strength
(unlike say, an oak, which the wider the annual ring the stronger).
The cottonwoods at Phantom Ranch are on a side tributary (Bright Angel
Creek). Bright Angel Creek still retains a "natural" flood regime. There
certainly are cottonwoods along the Colorado, but the disturbance regime
there generally prevents anything getting rooted for long. Regarding air
quality, we have a long running air quality program and the records of our
air quality are fairly extensive, both in the canyon and on the rim... to
monitor regional power generating plants.

The effects of these on a species not known for its longevity could have a
"disproportionate" effect, although to date, no one has yet done a study to
confirm this.

Tomorrow, we go down to Indian Garden to prune/remove a half dozen "hazard
trees"...3 miles down the trail, 3000 feet elevation loss...better shift off
my low carb diet and consume some carbs!

-Don
Re: Grand Canyon Cottonwoods   Don Bertolette
  Feb 21, 2005 18:49 PST 

Ed-

I have done some preliminary research on the role of cottonwoods
historically in the Southwest, and in the Canyon in particular. Your posted
accounts are new to me, and I'm sure I have much more to peruse.
We are in the initial stages of putting together an EIS for our vegetation
program, and reference conditions will be fully researched...local
publications recording the 1910 to 1930's are fascinating (Native Americans
were employed to carry the suspension cables for the 1920s suspension
bridge, down a trail, with individuals every 12 foot "winding" down the
trail...photographs of the time show short, freshly planted cottonwoods,
with none of any size in view. To date the source of their genes are
presumed to be imported from outside the immediate region, but one of the
methods of propagation in sufficiently moist sandy soils was to stab a
branch off a nearby cottonwood into the selected site.

I do recall, from my role in the research permit review process, a study
proposed to investigate the gene source of Canyon cottonwoods, but that was
just last spring, and results are still forthcoming.

We have been looking at velvet ash and boxelder as they are both native to
the region and the canyon, at different locations. However, velvet ash is
slow growing and boxelders share a lack of windfirmness with cottonwoods.
The Park has with the cottonwoods a precedent in importing shade trees from
outside regions. Given choices, we'd prefer not to follow that precedent,
but our missions sometimes conflict...those who have been down there from
June-August will vote shade and shade NOW...for more than it would seem
possible, these can be life or death decisions. Last July, I left the rim
at 5PM, and when I checked the thermometer at Phantom Ranch upon my arrival
at 11PM at night, it was 109 degrees...

Thanks for the literature tips, I look forward to reviewing them soon!

-Don