Choctaw Island Wildlife Management Area, AR

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#1)  Choctaw Island Wildlife Management Area, AR

Postby Jess Riddle » Mon Dec 28, 2015 4:14 pm

NTS,

A long growing season and rich moist soils give the lower Mississippi River floodplain great potential for producing diverse and productive forest.  Those same conditions create great agricultural potential.  As reservoirs and levees have disconnected the floodplain from the river, corn and soybeans have replaced flood tolerant hardwoods.

Forest still dominates only the batture lands, the area between the levees. Timber companies, which take advantage of the easy transportation, and hunting clubs own most of these lands.  In Arkansas, aside from a few small city parks, there are only three areas of public land along the Mississippi.  At 9,431 acres, Choctaw Island Wildlife Management Area is by far the largest of the three.

Choctaw Island WMA consists of a point bar on the Mississippi River split by a side channel.  The island portion is all sandbar and sandbar recently colonized by forest.  A mix of forests, fields, and ponds covers the older land in the rest of the WMA.  Sugarberry and pecan dominate the main block of forest on the WMA, usually mixed but tending towards pure sugarberry in the lower areas and pure pecan on the highest ground.  Oaks are conspicuously absent; in two days of traversing the area, I saw only a single overcup oak and a single nuttall oak, neither of them mature.  The lack of oaks probably reflects a combination of unfavorable soils conditions and limited availability of acorns.  Below the sugarberry and pecans are more sugarberries and box elder with scattered pecans and green ash.  Swamp privet, its clustered and arching stems reminiscent of its relative the olive, is the main understory species, and it sometimes forms thickets in the wettest areas with few or no other tree species.

The southern end supports a different mix of species, which may be due to some of the land being deposited within the last century.  Sycamore and cottonwood are often components of the overstory, and cottonwood forms pure stands in some areas.  Those stands have a sugarberry midstory and sparse understory.  The wettest areas contain extensive pure black willow forest with little understory.

               
                       
IMG_4335.JPG
                       
Cottonwood forest with sugarberry understory
               
               

Choctaw Island came on my radar by being one the scattered areas in southern Arkansas with available LiDAR.  I also wanted to check out the composition of the forests, since river front forests are always distinct from surrounding forests. I had also read about black willow becoming a large canopy species along the lower Mississippi, in contrast to the species’ behavior in the rest of its vast range, and willows are one of the primary groups of trees that colonize bare sediment deposited by rivers.  

               
                       
ChoctawIslandMeasurements.JPG
                                               
ChoctawIslandMeasurements.JPG (81.4 KiB) Viewed 597 times
               
               

In addition to the trees above, I stopped immediately on the other side of the levee to measure the largest yard tree in Arkansas City.  The 16’5” cbh by 127.3’ pecan gives a hint at what used to grow in the floodplain.

The gum bumelia is the first NTS has reported.  The lower Mississippi seems to be much better habitat for swamp privet than the other parts of the species range where we have measured them previously.  These trees dwarf our previous records for both height and girth.  Several of them also easily exceed the national champion.  The Sandbar willows are similarly larger than the few we have measured previously and the current national champion.  The cottonwoods, while within 10 feet of the current height record, may not be exceptional at all.  The site does not seem extraordinary, and I suspect most point bars along the lower Mississippi would produce 140’ cottonwoods if left alone for 100 years.

               
                       
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The two largest swamp privets, potential national champions
               
               

               
                       
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The two largest swamp privets, potential national champions
               
               

               
                       
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The tallest sandbar willows displaying the species typical narrow crown growth habit and common habitat on edge of high flow channel
               
               

               
                       
IMG_5117.JPG
                       
The largest sandbar willow, 3’4” cbh by 43.4’ tall, a potential national champion
               
               

               
                       
STA_4343_stitch.JPG
                       
145.7’ tall cottonwood with wad of grape vines collapsed around the base
               
               

These black willows give credence to the claim that the species develops best in the lower Mississippi.  These trees dwarf any we have found in other regions of the country, and this stand easily bests the previous height record.  Given that the stands are still dense and most of the trees are healthy, 140’ seems possible for the species.  In a way, these trees have already reached that height.  They sprouted on moist sediment within a few feet of the river level.  Since then, the river has dumped sand on the groves, and the tree bases are now 15 to 20 feet above the river level.

               
                       
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Black Willow on eroding river bank showing roots that germinated from the trunk after burial
               
               

               
                       
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Dense grove that contains all of the tallest black willows
               
               

               
                       
STA_5094_stitch.JPG
                       
6'2” cbh by 118.0’ tall black willow
               
               

               
                       
STA_5107_stitch.JPG
                       
5’10” cbh by 115.7’ tall black willow
               
               

               
                       
STA_5104_stitch.JPG
                       
7’3” cbh by 121.3’ tall black willow
               
               

Jess

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#2)  Re: Choctaw Island Wildlife Management Area, AR

Postby Erik Danielsen » Mon Dec 28, 2015 5:54 pm

Those Black Willows are incredible! Reminds me of what surprising things black locust can do on an ideal site. I wonder how many species known for just moderate size will be observed to achieve exceptional growth in particular habitats as our eastern landscapes get into further stages of regrowth?

You may well be right that tall cottonwood (125+) might properly be the norm anywhere with enough moisture and competition to stimulate a tall trunk. There are enough of them at high latitude in NY state, why not the rest of their range? Cottonwood underscores the degree to which our perception of tree character and growth is, for many species, heavily shaped by the effects of our early efforts to clear the landscape.
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#3)  Re: Choctaw Island Wildlife Management Area, AR

Postby Bart Bouricius » Tue Dec 29, 2015 3:21 pm

Jess,

The Gum Bumelia Sideroxylon lanuginosum caught my eye, as we have at least 4 species of that genus here in Costa Rica, 2 of which are large emergent trees.  This genus in the family Sapotaceae, extends down through Mexico and Central America into South America.  Great to have documentation of species in this rare ecosystem.

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#4)  Re: Choctaw Island Wildlife Management Area, AR

Postby Matt Markworth » Tue Dec 29, 2015 7:56 pm

Jess,

Very, very cool. It really shows the importance of at least having some public lands set aside because of the unknown important discoveries that can be made in the future, like you have found at this site.

Matt
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