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what are your thoughts on this?

Hello, Everyone,

I just got back from a very pleasant and memorable 17th North American
Prairie Conference in Iowa.  Iowa did a GREAT job hosting it.  It was
the best of the four NAPCs I have attended.

There was one paper which took me by surprise and I would like your
comments on it.  The title and abstract are below.

"The control of infiltration as a mechanism for the self-regulation of
prairie ecosystems: Preliminary studies at Rolling Thunder Prairie State
Preserve, Warren County, Iowa."  Steven H. Emerman, Dept. of Biology and
Environmental Science, Simpson College, Indianola, Iowa 50125

"All of Iowa's prairie preserves are subject to invasion by woody
plants.  Most studies see the movement of the prairie / forest boundary
as a passive response to the external forces of climate change,
overgrazing and fire suppression.  An alternative hypothesis is that the
prairie ecosystem actively repels woody invasion by growing in such a
way as to keep the soil moisture too low for woody plants.  The soil
moisture is kept low by inhibiting the infiltration of water which is
controlled by the thickness of the plant roots and the activity of
burrowing animals." (Note by me:  no evidence was provided for this
statement.)  "The hypothesis was tested at Rolling Thunder Prairie State
Preserve in southern Warren County in a portion of the prairie which had
not been burned for two years.  At 8 widely-separated sites, the
field-saturated hydraulic conductivity Kfs was measured 5 m upslope and
5 m downslope from the prairie / forest boundary.  In five cases, Kfs
was greater within the woody invaders than within the prairie; in three
cases, Kfs was the same within the woody invaders as within the
prairie.  Mixed results were obtained from the burned portion of the
prairie."


I don't think highly of this study or the hypothesis.  Doesn't seem like
rigorous science.

Please note where the speaker states that the finer roots of the grasses
make it harder for water to penetrate.  Yet prairie people here in Texas
have been saying that grasslands are one of the finest plant communities
for capturing and moving rainwater into the ground.  This is based on
work done in the Seco Watershed in western Texas by the Agri Extension
Service and Tx A&M where prolific junipers were removed from portions of
a watershed, replaced by native grasses whose seeds were in the soil
bank, and where springs began to flow again, etc. etc.

Comments?

lee stone
Austin, TX


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