Soil Micro-Variability on Floodplains

Tree Root-Balls

Tree Root-Balls

These tree root-balls (in this case on the Angelina River Floodplain, TX, in the spring of 2006) are typically created when the wind load on a tree’s stem and canopy exceeds the anchorage capability of the tree’s root system.  The soil clinging to the root system is “excavated” and a small-to-large depression is created.

Root-Ball Depressions

Root-Ball Depressions

On floodplains subject to appreciable sedimentation rates, these root-ball depressions will eventually be re-filled such that the landscape surface is once again relatively flat.

Re-Filled Root-Ball Depression

Re-Filled Root-Ball Depression

If you sample the soils in one of these flat, somewhat “featureless” landscapes, you are almost certain to eventually encounter one of these re-filled root-ball depressions.  Depending on the mode and sequence of re-filling (i.e., root-ball soil fallback and/or alluvial sedimentation) and the types of sediments deposited, you may find dramatically different soil materials in samples that are quite close together (i.e., sometimes within 3 to 5 feet of each other).

It is entirely possible that these excavation / re-filling episodes have happened repeatedly over relatively long periods of time.  Thus the character of the soils below the currently visible surface may differ noticeably on a micro-scale as well as on a macro-scale.  Soil scientists who map these soils know this and are prepared to accept a certain amount of variability in what they group into soil mapping units in these areas.

Whereas soil scientists and wetland delineators can go home at night, the resident trees are rooted wherever they happened to establish as a seed.  It thus seems logical that the presence (i.e., survival) and relative vigor (i.e., competitive ability) of different tree species may give clues as to what the underlying soils are like.

I was introduced to these concepts in forestry school under the heading of forest site evaluation.  At the time I found the subject fascinating, and I continue to derive a good deal of professional satisfaction from learning more about these issues.  Thus, I suggest that you might want to not only learn to identify your plants, but you may want to learn about their ecological requirements.  I suspect that such a course of study will pay ample professional dividends for you.

If you really want to learn about the soils and plants, as well as delineate wetlands accurately in these areas, you should plan on carrying an ample supply of “elbow grease” with you.  You’ll need it, or an eager assistant “Auger Boy” to avoid soil surprises.

Post a comment.

Post a Comment

Your email is never published nor shared. Required fields are marked *

*
*

You may use these HTML tags and attributes: <a href="" title=""> <abbr title=""> <acronym title=""> <b> <blockquote cite=""> <cite> <code> <del datetime=""> <em> <i> <q cite=""> <strike> <strong>