Ponca State Park, NE

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Jess Riddle
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Ponca State Park, NE

Post by Jess Riddle » Mon Nov 11, 2013 7:41 pm

NTS,

You can see the outline of the Laurentide Ice Sheet in the state lines of the Midwest. The eastern quarter of the South Dakota-Nebraska state line follows the edge of the ancient ice sheet. To the north of that line, the land is flat, planed down by the ice. To the south, rolling hills. However, that contrast in history and topography has not led to a contrast in land cover. Corn fields to the north. Corn fields to the south. Before the corn fields, prairie to the north, prairie to the south. The exception lies along the contact. The Missouri River has cut a valley along the ancient edge, and the valley’s moisture supports forests. The river waters the floodplain forests, and acts as a natural fire break for the bluffs on either side. Deep ravines dissect the forest covered bluffs and create shaded, moist habitat.

In 1934, Nebraska set aside a chunk of the bluffs and a little of the floodplain as Ponca State Park. Roads run by campgrounds and overlooks on the ridge lines 200’ above the river, and past little cabins on their way straight down the middle of the larger ravines.

The forests on the slopes and smaller ravines remain largely intact, but erosion acts as a significant disturbance. Running water easily cuts through and carries away the deep loess soils that make up the bluffs. Even run-off from a parking lot will leave a line of holes running down a slope as each mini-waterfall bores into the loose silt. The ravines typically have flat bottoms in their upper reaches, but a steadily enlarging ravine within the ravine in their middle reaches. Trees with exposed roots cling to the upper lip of those nested ravines. Chunks of the slopes also occasionally break loose and expose the underlying limestone. The limestone has layers packed with fossilized mussels and occasional vertebrae of plesiosaurs, large marine reptiles.
Slump on ravine slope
Slump on ravine slope
Nested ravine cutting headward
Nested ravine cutting headward
Typical nested ravines
Typical nested ravines
I visited Ponca State Park yesterday to: measure trees in a disjunct population of rock elm; measure Kentucky coffee-tree at the edge of its range; and fill in the gaps in the spread of measurements for black walnut and a few other species. Bur oak is probably the most common species in the park, and covers the drier south and west facing slopes as well as the upper slopes and ridges. Eastern red cedar and green ash mix in on the upper slopes and ridges in the central part of the park, but not near its edges. On more moist slopes and in the middle of ravines, American basswood dominates. Hackberry also mixes in on the lower slopes, and deep soiled, moist sites also support black walnut and scattered Kentucky coffee-tree, rock elm, and slippery elm. Rock elm seems especially common around the rim of the nested ravines.
Lower slope forest with trail
Lower slope forest with trail
Upper ravine forest
Upper ravine forest
In the spring, Dutchman’s breeches carpets the moist slopes and gives way to Virginia water leaf as the season progresses. Sedges and Virginia wild-rye cover the drier slopes under the oaks. Scattered clumps of Missouri gooseberry and chokecherry rise out of the herbs on moist slopes, and colonies of prickly ash grow on the ridges. Between them and the overstory, hophornbeam covers the slopes, but generally avoids the ravine bottoms. Young hackberries and elms make up the midstory on those sites.
Dutchman's Breeches
Dutchman's Breeches
PoncaMeasurements.JPG
PoncaMeasurements.JPG (76.3 KiB) Viewed 1684 times
Surprisingly, at least to me, these are the first rock elms NTS has measured. There are none in the database and I came across none in going through old posts to compile the Maxlist. These rock elms are much larger than the ones in the other population I’ve seen in the region or ones growing on the eastern edge of their range. They also crush the current state champion, a 128 point coppice growing along one of the roads in the park. However, given that none of the other species approaches their maximum dimensions, I’m sure rock elm reaches much larger sizes in other parts of its range.
The largest rock elm, 6’3” cbh x 78.2’
The largest rock elm, 6’3” cbh x 78.2’
Jess

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bbeduhn
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Re: Ponca State Park, NE

Post by bbeduhn » Tue Nov 12, 2013 8:48 am

I'm impressesd with the hophornbeam and the redcedar. I would have expected them to be understory rather than midstory. The walnuts are solid. Those elms I've seen in guides but never in person. I would have guessed black gum in the "nested ravine cutting headward" shot. I guess that is an elm.

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Larry Tucei
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Re: Ponca State Park, NE

Post by Larry Tucei » Tue Nov 12, 2013 5:19 pm

Jess- Nice posting. I don't believe I have seen Rock Elm in any of our Forests. Your photos of the loess hills look like they could have been taken in the Ms. Delta. Lots of hills just about 15 miles east of the Delta NF. The hills run From Natchez to way north of Greenwood, lots of cool trees in there. Your post makes me want to check those areas in the future. Larry

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Jess Riddle
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Re: Ponca State Park, NE

Post by Jess Riddle » Tue Nov 12, 2013 6:38 pm

Brian,

Hophornbeam and red cedar were the species that jumped out at me too. I expected their heights to drop off more than than that relative to trees in the southeast.

The rough barked tree is a walnut.

Larry,

Rock elm, also known as cork elm, is widespread in Tennessee, but doesn't make it any farther south.

There's a long line of loess hills along the eastern side of the Mississippi River. Your area in Mississippi probably looks similar because the soils area very similar.

Jess

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wrecsvp
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Re: Ponca State Park, NE

Post by wrecsvp » Sun Mar 30, 2014 12:11 pm

Hi Jess,
I just noticed this thread and will comment a bit late in the game. Very interesting to see Rock Elms you found in Nebraska, at the far western part of its range. You are correct that Rock Elm is capable of much larger dimensions. I note this species wherever I find it (mainly looking in eastern Ontario) and it attains large size on good soils; 80+' by 3' DBH seems easily attainable. A few months ago I posted a 92' tall by 128" CBH one I found in Merrickville on the Ontario page (I lazily haven't entered this in the NTS database yet). There's a few large ones in Ottawa in the 80' by 3' range. There aren't many old ones left which have escaped logging or Dutch Elm Disease, but the species when found seems to keep up with or surpass many of its associates such as Sugar Maple, Basswood, Bitternut Hickory, Slippery Elm, Butternut, Red Ash, Bur Oak, etc.
Owen

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