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Re: Infiltration of Prairie Soil

The process the researcher was referring to occurs when many roots and
hyphae become so densely intertwined that they function as a claypan.

Linda Adair
----------
>From: Chris Hauser <cehauser@uiuc.edu>
>To: prairie list serve <prairie@mallorn.com>
>Subject: Infiltration of Prairie Soil
>Date: Thu, Jul 27, 2000, 1:27 AM
>

>I'm inclined to agree with you.  Many fine roots in the soil usually
>increases infiltration due to improved soil structure.  If prairies
>prevented infiltration of rainfall, we'd see a fair amount of runoff from 
>prairies, which we don't.
>
>I believe that the researcher was correct in finding that the prairie soil
>is generally dryer than forest soil, and this probably negatively
>affects the germination of woody plants, but that doesn't mean
>that rainfall infiltrates prairie soil more slowly than forest soil.  In
>fact, the opposite may be the reason:  Is it possible that prairie soil
>is dryer than forest soil partly because the water moves quickly down into
>the subsoil/groundwater, out of the reach of the young woody plants?  Of
>course the soil is dryer for other reasons too, like more exposure to
>wind, sunlight, etc.
>
>Chris.
>
>On Mon, 24 Jul 2000, Lee Stone wrote:
>
>>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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