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Re: what are your thoughts on this?

To Lee and others,

I was also at the NAPC, but did not make it to that particular paper. 
However, I would agree that the premise regarding fine roots inhibiting
water uptake does not seem to have much weight given our observations over
the years.  What does seem apparent is that all these roots have created
pore space in the soil which was not present previously.  

We have an 8-year old reconstructed prairie on previously farmed land which
drains into a two-acre pond.  Inspite of 12 inches of rainfall this June the
pond raised only one foot.  I am not comparing it with a woodland, but it is
obvious that the prairies ability to retain water is phenomenal.  Only when
the soil is completely saturated by rainfall which exceeds 4 inches do we
get surface runnoff.  

There are also countless cases where woody vegetation is overtaking prairie
even in the Loess Hills of western Iowa on southwest facing slopes where
soil surface temperatures in the summer exceed 130 degrees  F.  

Carl Kurtz
Central Iowa

----------
>From: Lee Stone <leeprairie@austin.rr.com>
>To: prairie list serve <prairie@mallorn.com>
>Subject: what are your thoughts on this?
>Date: Mon, Jul 24, 2000, 7:36 PM
>

>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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