Cottonwood Range   dbhg-@comcast.net
  Aug 08, 2003 16:35 PDT 

ENTS:

   The Connecticut River corridor from Springfield, MA to Hartford, CT holds
great promise to add splendid cottonwoods to my cottonwood database. Today on a
trip to Hartford, I saw many large specimens that have gone unnoticed by just
about everyone, including yours truly. They are on the radar scope and now John
Knuerr, Gary Beluzo, and I are tuned into Populus deltoides. I'm especially
anxious to add Connecticut trees to the list, not so much because they
represent a different political entity, but because they are a little further
south and more under the influence of Long Island Sound. They grow in a
slightly warmer climate, albeit only marginally so from that of Springfield,
MA. However, starting from a spot in northern Vermont and working down to
Biloxi, Miss, it is hard to understand why the cottonwood is excluded from much
of the central Appalachian corridor. It isn't temperature or precipitation.
Consider the temp range


Location  Jan   Jul Cottonwood
St. Johnsbury, VT  17 69 Y
White River Junction,VT  18 69 Y
Brattleboro,VT   21 71 Y
Northampton,MA     22 71 Y
Hartford,CT        26 74 Y
Bridgeport,CT    30 74 Y
New York, NY   32 76 Y
Boone, NC 29 68 N
Asheville,NC  36 74 N
Black Mtn,NC   35 72 N
Knoxville,TN  38 79 Y
Biloxi,MS 51   51 82 Y

Appalachian range restrictions are neither from cold or precipitation.

Bob

More on Cottonwood Range   dbhg-@comcast.net
  Aug 10, 2003 12:25 PDT 

ENTS:

   Looking at the conspicuous Appalachian gap in the east-west and north-south
range of Populus deltoides makes me ever more curious about the explanation.
Nobody questions the ends of the range, but a gap in the middle? The gap is not
related to extremes of temperature since cottonwood territory includes very
cold places like Minnesota, Montana, Saskatchewan, and Alberta. The range
includes hot regions like south-central Texas. Temperature is not a factor. Nor
is the Appalacian restriction range based on moisture since the range of the
cottonwood includes very wet to vary dry climates. The Appalachian range
restriction doesn't include all the Appalachians since the species is found in
the Berkshires of Massachusetts and in other northern Appalachian areas.

    Perhaps the range maps are wrong or perhaps the species is just absent in
upper elevations of the Appalachians. That is a definite possibility, but if
so, it isn't the temperature component of altitude. If to get established in
abundance, the cottonwood needs large areas that stay flooded for considerable
time periods, that would exclude upper elevations in mountainous terrain where
flooding is brief for obvious reasons. So is does the answer to the Appalachian
exclusion lie in land form? Or are the range maps simply outdated, or both
explanations? Lee, any thoughts on the Appalachian restriction? Anybody?

Bob
Re: More on Cottonwood Range   lef
  Aug 10, 2003 16:10 PDT 

Bob:

Cottonwood does not require flooded areas to survive, but it can only
compete against other tree species in areas that flood or are disturbed in
some other way. However, I doubt that the lack of floodplains would totally
exclude the species, there would still be a few around.

That brings us back to temperature, but a different aspect of temperature
than you were considering. Cottonwood drops out in northeastern MN, even
though it grows in areas like North Dakota with winter extremes just as
low. That is because it is not only winter temperatures that limit
species. Summer temperatures also limit a lot of tree species. Cool summers
exclude a lot of species, and that is likely part of the explanation.

Lee
Re: The ENTS go marching on   Lee E. Frelich
  Dec 22, 2004 11:26 PST 


Bob:

Sounds like you had a good time teaching people to measure trees in
Vermont. We could use more heights and Rucker indexes from the northern
areas. The more latitude we span the better.

Speaking of cold spots, the junction of the Minnesota and Mississippi
Rivers, which is in a valley below the Minneapolis-St.Paul International
Airport (where the temperature data you cited came from), is quite a bit
colder than the plateau the airport is on (in fact the whole city is quite
a bit colder than the official readings at the airport). Yet, I keep
finding more 15 and 20' cbh cottonwoods in the relatively wild forests
lands of the river valley every time I look. I also found one within
walking distance of my place last week that is probably 16-18' cbh, but I
didn't measure it since it was -10 with a 40 mph wind when I was there. You
gotta keep moving under those conditions. If you pause for more than 3
seconds, you will turn into a pillar of ice.

On the other hand, 150 year old cottonwoods near Lake Michigan in Chicago
are only 10' cbh, even though winters there are quite mild. As one moves
inland in Chicago, the cottonwoods get bigger by the mile--about 1 foot cbh
for every mile from Lake Michigan, until they reach the same 15-20' cbh
range as in Minneapolis. My conclusion is that cottonwoods are not
influenced by winter temperatures, but they have a large response to summer
temperatures. They grow big as long as the summer is warm and humid, hence
the 20' cbh cottonwoods in Minneapolis, where daytime temperatures are
above 80 degrees for several months, and relatively diminutive cottonwoods
on the Chicago lakefront, where it rarely reaches 80 degrees during the summer.

Lee
Lee and Ernie   Robert Leverett
  Dec 22, 2004 13:17 PST 

Lee:

   That's fascinating. I was wondering when you would spawn a plausible
theory on cottonwood growth in the areas where you are finding the
whoppers. Beyond your explanation for the growth characteristics, it
sounds to me like you can lay absolute claim to the largest collection
of cottonwoods in the 15 to 20-foot circumference range. How many do you
currently have cataloged?

   Here are some interesting climate statistics.

Location               Jul Hi    Jul Lo   Precip

Springfield, MA      85.4     62.9      3.60

Minneapolis, MN     83.0     63.0      4.04

   On the surface, it appears that Springfield and Minneapolis have very
similar climates in July. Other than the severity of thunderstorms, what
do you suspect is different? What isn't revealed by these statistics?
Maybe Ernie can weigh in on this one also.

Bob    
Re: Lee and Ernie   Lee E. Frelich
  Dec 22, 2004 14:08 PST 

Bob:

I probably have 25 cottonwoods in the 15 to 20' cbh range, and there are
still several sites I have heard about that I haven't visited yet, so I
expect that total to double.

Regarding the climate, we probably have more warm weather in the spring
than you do out east, although I am not sure that would make a big
difference. You do seem to have big cottonwoods there, so the difference
may lie in how much of the right type of floodplain habitat exists in MA
versus MN and WI. We have several vast floodplains along slow moving
rivers (a mile or more wide and hundreds of miles long) on the Minnesota,
Mississippi, and Wisconsin rivers. If you combine that much habitat with
the right climate, it leads to a lot of big cottonwood trees.

Lee
RE: Lee and Ernie   Ernie Ostuno
  Dec 22, 2004 22:49 PST 

Bob,

Climate-wise, a good indicator to compare might be "growing degree
days". These are calculated from daily high and low temperatures and are
used by agricultural interests in the same manner that "heating degree
days" are used by energy companies. Generally, the more growing degree
days during the season, the more plant growth there was (provided
sufficient moisture was available of course). Here's the explanation
from the climate prediction center web page on corn growing degree days:

"A corn growing degree day (GDD) is an index used to express crop
maturity. The index is computed by subtracting a base temperature of
50F from the average of the maximum and minimum temperatures for the
day. Minimum temperatures less than 50F are set to 50, and maximum
temperatures greater than 86F are set to 86. These substitutions
indicate that no appreciable growth is detected with temperatures lower
than 50 or greater than 86."

Now how well this applies to cottonwood trees is debatable, and there is
the issue of moisture stress (Minneapolis may be a bit wetter in the
summer than Springfield) but this could be a good overall indicator of
growing conditions for most plants. Looking at the climate prediction
center stats:

http://www.cpc.ncep.noaa.gov/products/analysis_monitoring/cdus/degree_days/grodgree.txt


Unfortunately, normals for Minneapolis (MSP) and Hartford (BDL, the
closest site to Springfield) were not available, but looking at last
years totals MSP had 2,909 and BDL had 3,195. It's hard to say what the
departures from normal were at those two sites, but looking at nearby
sites: Albany, NY had about 100 more GDD than normal and Eau Claire, WI
had about 60 GDD more than normal. So it seems (as the average July
temps would indicate) that climatologically, there isn't a big
difference between Springfield and Minneapolis.

Which would point towards habitat as being the more important variable
here, as Lee indicated.

Ernie

RE: Lee and Ernie Continued   Lee Frelich
  Dec 23, 2004 08:40 PST 

Bob:

The amount of growth a tree can put on is probably correlated to growing
degree days within a certain range of other important variables. For
example, red oak can be severely injured by extreme winter cold and spend
most of the summer repairing the damage, so that more GDD would not
necessarily mean more growth as compared to another site with a cooler
summer, but that does not have extreme cold during the winter. When Paul
Jost and I saw the red oaks at Muskegon MI, after crossing Lake Michigan on
the ferry, it was obvious that was the case. Their oaks in MI grow faster
and get bigger even though they have less GDD than WI, because there is
less winter injury.

Northern conifers cannot tolerate extreme summer warmth and dryness, but
they would grow more with more GDD as long as extreme summer temperatures
were within their tolerance. Winter cold is not a problem for them, except
for those trees transplanted from the southern edge of their range to the
northern edge (i.e. a white pine from Cataloochee would have died last
night in northern MN--minimum at Embarrass, MN last night, which is near my
Hegman Lake and Kawishiwi white pine stands, was -42).

Lee