To: Larry Caldwell,
I hadn't heard the buffalo hypothosis before. Interesting. As for
forest expansion in Arizona goes, I doubt that there has been any
influence of that kind. I'd be more inclined to believe that
topography is the ruling factor. The ponderosa pine forest there
parallels the Mogollon Rim. Mostly ON the rim, but much of it below
it. Here, prevailing winds from the SW, S, and SE bring warm moist
weather which rises at the rim to meet the cool (cold) weather on top
which is a gain of about 2000 feet in 3 to 5 miles distance. Average
elevation on top is about 7000' but some of it is 9000'. This produces
snow and rain. Of course in Arizona this "wet" area is still very dry
by standards elsewhere. Thus the stage is set for PP growth. On the
North side of the rim, or ON the rim, (It's the Colorado Plateau) the
trend is a decrease in elevation and within 10 to 20 miles of the rim
the forest gives way to Juniper, then grasses and then mostly bare
dirt and rock (The later is "Navajo type country".) Elevations have
dropped to 3500 to 4000 feet. It is very dry and moisture soaks into
the sandstone very rapidly with almost none remaing near the surface
to support vegetation. Since the PP forest in Arizona is the largest
PP forest in the world it is important to understand how it grows.

I certainly agree with you regarding Juniper. It can and has become a
weed. There are numerous places where ranchers plow it up and burn
the piles and hope it goes back to grass. But putting cattle back on
it will prevent the grasses from becoming dominant unless the Junipers
are "managed" over time.

By thew way. BEAUTIFUL dogs on your web site!



Larry Caldwell wrote in message nk.net...
(Le Messurier) writes:

I'm not aware that "much of the present day Ponderosa
forest occupies what used to be grassland in the late 1800's. Stopping
fire and grazing changed that." The grasslands were IN the forests,
and were the prevalent ground cover. This is what allowed the low
intensity fires to "work" in keeping this forest type free of
excessive fuel loading. I don't believe that the area covered by the
ponderosa forests have grown.

There has been a substantial encroachment of forests into grasslands
since the buffalo were eradicated at the end of the last century.
Buffalo have an instinctive antipathy toward trees. A buffalo will go
out of its way to kill small trees. Maybe they just like to run without
running into anything, but the absence of trees on the Great Plains is
primarily due to the historic large herds of buffalo. Urban sprawl has
introduced tree species with landscaping, and existing forests have
encroached from both the east and west. If the plains ever revert to a
natural state, they will become a great central forest in North America.

Another, quite separate issue is the encroachment of Juniper and Pinon
Pine forests into grasslands in the more arid parts of the west. Juniper
is a water thief that will eradicate competing vegetation. If an area
develops a 40% juniper canopy, the destruction is so complete that the
ecology of the land can not recover naturally.