Fontenelle Forest

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#1)  Fontenelle Forest

Postby Jess Riddle » Sat Dec 19, 2015 4:22 pm

Nts,

Omaha, Nebraska may be one of the most unlikely places to look for old-growth forest in the United States.  The state’s largest conglomeration of asphalt and concrete, the city sits in the middle of a corn belt hundreds of miles wide, much of it growing out of old prairie soils.  Omaha perches on a far narrower band of forest and woodland that the Missouri River’s floodplain and bluffs supported.  Agriculture has eaten away most of that floodplain forest while the bluff woodlands have grown back and thickened following harvest.  Concurrently, the Gateway to the West grew into the state’s largest city, and pavement replaced local forest.  

However, Omaha also brought together a group of individuals who were both concerned about the loss of nature in the area and had the means to do something about it.  They began Fontenelle Forest with a purchase of over 300 acres of forests on the bluffs in 1920. Much of that initial purchase was logged only selectively from the mid-1850’s to mid-1870’s, and dendrochronological investigations suggest that a couple of small, ridge top patches were never cut at all. Some later additions were farmed up until the 1960’s, but on a walk through the forest early tracts blend imperceptibly into the original purchase.  Now tucked between the Omaha suburb of Bellevue and the Missouri River, Fontenelle Forest and Nature Center has grown to 1400 mostly forested acres split roughly evenly between the bluffs and the floodplain.

Twenty-six miles of trails run through the preserve’s upland and floodplain, and take visitors to oxbow lakes, foundations of Native American shelters, and rotating educational exhibits such as structures built from recyclables and life-size fiberglass dinosaurs detailed down to the wrinkles in their skin.  Those shelters were built on the ridge tops in what would have been bur oak woodlands.  The current trees’ woodland origins can still be seen in the branch structure of some of the oaks, and they have been dated back to 1732, but fire suppression has converted the woodlands into forest.  American basswood, hackberry, shagbark hickory, and white ash have grown up around the old oaks in recent decades and hophornbeams filled in the understory.

               
                       
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Oxbow lake and bluffs at Fontenelle Forest
               
               

Deep in the tallgrass prairie region, forest requires more than the fire-break provided by the Missouri River to survive.  In the floodplain, the high water table counteracts the semi-arid climate, and on the bluffs deep deposits of wind-blown silt provide the moisture buffer.  Those loess soils erode easily to produce narrow ravines that further concentrate moisture.  Moving downslope, the bur oak quickly gives way to more drought sensitive northern red oak, and basswood and hackberry become more prominent in the overstory.  Black walnut often dominates on the toe slopes and ravine bottoms, which also occasionally harbor colonies of Kentucky coffeetree.  The herbaceous layer, while quite mixed on the ridges and mid slopes, undergoes a parallel transition down the moisture gradient.  Drier slope positions feature many grasses and sedges while white snakeroot and finally wood nettle dominate the more moist and sheltered sites.  While experiencing less fire than the ridges, that disturbance was not unknown in the ravines, and its absence may contribute to the complete lack of red oak and walnut regeneration and abundance of hackberry in the understory.

               
                       
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Typical bluff forest.  The large tree is a black walnut and most of the understory trees are hackberries.
               
               

Altered disturbance regimes have also dramatically affected the floodplain forests.  A patchwork of cottonwood, cottonwood-sycamore, and silver maple-green ash-white mulberry forests and oxbow lakes covers the floodplain.  Those forests cover a continuum of ages from 60 to over 125 years, but younger forests are conspicuously absent.  No logging occurred in the floodplain, so instead that distribution of ages reflects riverine processes.  Historically, meandering of the river continually recycled the floodplain creating a patchwork of not only age, but also soil texture, and flooding frequency.  In the 1950’s, hundreds of miles of the river in the Dakotas were converted to reservoir, and much of the main channel was lined with wing dikes.  As intended, the river hasn’t moved since, and went 60 years between floods.  An unintended consequence has been a scarcity of young cottonwood forest, which requires moist bare sand to establish, and the species associated with them are scarce up and down the river.

               
                       
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Dense cottonwood stand adjacent to an oxbow lake.  The tree with the tape around it is 12’6” cbh by 132.6’ tall.
               
               

Flood control has also altered the species composition of the floodplain forests by allowing flood-intolerant species to colonize.  While cottonwoods have persisted in the canopy, many species from the adjacent bluffs, especially hackberry, have filled in the understory and midstory.  At least until 2011.  That spring, a rain event in Montana triggered a flood that inundated much of the forest to depths of over five feet for two months.  So many hackberries died that some pockets of forest were converted to woodland and other areas lost their midstory and understory.  However, the flood also deposited enough sediment to spur patches of cottonwood and sycamore regeneration.

I didn’t know what I would see or measure when I visited Fontenelle Forest.  Having only as much data about tree size across broad parts of the Midwest as Lewis and Clark did severally hampered NTS ability to look at east-west height and size gradients, and Fontenelle appeared to be a good place to start gathering data on many species.  I had spent the entire summer sampling forests along 100 river-miles of the Missouri. Out of all those we sampled, Fontenelle looked like the most promising site for large trees, but I had seen only a small part of the floodplain and only driven through the bluffs.  Several species, including sycamore and shagbark hickory, reach their northwestern range limit in the vicinity of Fontenelle, so the site would also help explore north-south size gradients.

Long time science manager Gary Garabrandt gave me a wonderful introduction to the site by taking his time on a drizzly fall day to guide me to the largest trees he knew of for several upland species.  In each case, the trees he showed me were the largest I would see on my whole trip.  In between trees, Gary shared his wealth of knowledge on the site’s history (and prehistory), and described ongoing efforts to preserve the site including erosion control, planting poorly regenerating species with local seed, and managing invasive species.  Throughout the day, well-formed Kentucky coffee-trees kept catching my eye, but Gary just mentioned a large one further down the trail.  When we finally reached that tree, I understood why Gary had shrugged at those other coffee-trees.  This tree with picture-perfect form dwarfed every other coffee-tree I have seen, and set a new NTS diameter record for forest grown coffee-trees.

               
                       
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A rather poor photo of the 9’2” cbh by 98.2’ tall Kentucky coffee-tree
               
               

I spent the following two days exploring the ravines and floodplain trying to locate the largest diameter and tallest individual of each native tree species.  Measuring on the bluffs turned out to be a bit of an adventure as walnuts would accelerate through 100’ of canopy space and then I would hear them crater into the duff a few feet away with a resounding thud.  

               
                       
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A good year for walnuts
               
               

The oldest section of floodplain forest impressed me the most.  For work I had visited sites along the river that were mapped as forest in the 1890’s, but all of those other sites appeared more disturbed and less productive than this stand.  Sycamores, growing in the harshest climate in their extensive range, matched the cottonwoods in height, and were gradually taking over the stand.  The scattered cottonwoods, in the twilight of their lives, reminded me of tuliptrees in the Southern Appalachians with their massive branches and trunks commonly five feet thick.  While measuring the cottonwoods and larger sycamores I was perplexed by a ridge of sediment about a foot high that extended south 10 to 20’ from the base of each trunk.  I eventually realized that the trees were large enough that during the flood their trunks created an area of slack water downstream where sediment dropped out of suspension.

               
                       
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One of the old declining cottonwoods: 17’3” cbh by 124.2’ tall
               
               

               
                       
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The same tree from a distance
               
               

               
                       
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Maximum dimensions found for each species at Fontenelle Forest
               
               

               
                       
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Rucker Height Index
                       
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Rucker Girth Index
                       
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Black walnut 9’3” cbh by 113.8’ tall
               
               

               
                       
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The tallest tree found at Fonetelle Forest, an 11’4” cbh 137.5’ tall sycamore
               
               

By expanding the range of NTS measurements, all of these numbers should help NTS investigate how climate and other broad scale factors influence tree height and growth.  Paw paw, bitternut and shagbark hickories, redbud, white ash, sycamore, northern red oak, and rock elm in particular should prove valuable, because all of those species are growing near their northwestern range margin at the site.  Of those, sycamore particularly impresses me for how tall the species is relative to other species and how little the height drops off approaching the species cold and arid range limits.  Similarly, black walnut seems remarkable for the height the species can reach without access to a perennial source of water and relative to what the species reaches in more southern parts of its range.  In addition to the coffee-tree, the downy hawthorn, peachleaf willow, and cottonwood are new forest grown diameter records for NTS.

               
                       
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The largest diameter cottonwood 20’11” cbh by 111.2’ tall
               
               

However, the tallest cottonwood, 135.8’, made an even greater impression on me that the diameter record tree.  The tree matches that height with an 18’3” cbh trunk, but what sets the tree apart is the massive crown.  While dead branches and greatly reduced crowns show the decline of most of the older cottonwoods, the tallest tree’s crown remains full and healthy.  The branch volume in that crown makes the tree clearly the largest at Fontenelle and a good candidate for largest tree by volume in the state.

               
                       
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18’3” cbh by 135.8’ tall cottonwood
               
               

I left feeling Fontenelle Forest is one of the great regional forests, like Cook State Forest in Pennsylvania or Congaree National Park in South Carolina.  Those old-growth forests give us a window into the past.  Parks named for the Lewis and Clark line the Missouri, but few if any of them can show what vegetation the explorers saw as well as Fontenelle can.  The forest still faces pressures from fire suppression, flood control, and invasive species, and will change.  However, managers are taking practical approaches that incorporate recent science to tackle these issues.  Those efforts should help Fontenelle Forest retain its stature and integrity, and ensure future generations can still glimpse what Lewis and Clark saw.

Jess

For this message the author Jess Riddle has received Likes - 7:
bbeduhn, ElijahW, Erik Danielsen, jamesrobertsmith, Larry Tucei, tsharp, Will Blozan
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#2)  Re: Fontenelle Forest

Postby bbeduhn » Tue Dec 22, 2015 10:15 am

Sycamore is very drought resistant and pollution resistant. Its tolerance of weather and climate extremes makes it a resilient tree even when nutrients are sparse.

The walnuts are unexpected. Those are not heights I'd expect from Omaha. The understory trees are solid as well. Farming has erased most of the forest in the Midwest but the rivers still hold exceptional pockets.
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#3)  Re: Fontenelle Forest

Postby Larry Tucei » Tue Dec 22, 2015 10:36 am

Jess-  Fantastic report.  The Black Walnut heights are really something and those Cottonwoods are huge. I am surprised that Omaha would have such a Forest thanks for sharing. Congrats on the records. Larry
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#4)  Re: Fontenelle Forest

Postby Rand » Tue Dec 22, 2015 12:59 pm

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#5)  Re: Fontenelle Forest

Postby Matt Markworth » Tue Dec 22, 2015 8:02 pm

Jess,

Excellent report. Reports like this are extremely educational for me since I don't have a formal background in a related field (I'm a Financial Services major). Your efforts are greatly appreciated!

It's cool to see more numbers for bur oak and really cool to see the big gaps in the Midwest get some attention. I periodically visit family in Missouri and want to do some measuring in the southern half of the state. Other than Big Oak Tree State Park and away from the floodplain, surely there is a large block of forest there than can be a signature forest for the region, similar to the role that Fontenelle plays for that region.

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#6)  Re: Fontenelle Forest

Postby dbhguru » Wed Dec 23, 2015 10:59 am

Jess,

  Ditto to what the others said. Like you, I am very interested in understanding what a species can do at the margins of its range. The eastern cottonwood has always been of particular interest to me. The 18.2 x 135-footer is an example of the extroverted nature of this species. Because lumbermen shun the cottonwood, it is allowed to mature, especially in wetland areas, and reveal to us its growth potential more fully than most other species we track.

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#7)  Re: Fontenelle Forest

Postby Joe » Wed Dec 23, 2015 1:12 pm

dbhguru wrote:I am very interested in understanding what a species can do at the margins of its range.
Bob


I suspect we hardly know what the potential range is for most species since the biota of North America is so disturbed from that most invasive species on the planet, white people.
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#8)  Re: Fontenelle Forest

Postby Lucas » Wed Dec 23, 2015 3:09 pm

Joe wrote:
dbhguru wrote:I am very interested in understanding what a species can do at the margins of its range.
Bob


I suspect we hardly know what the potential range is for most species since the biota of North America is so disturbed from that most invasive species on the planet, white people.
Joe


disturbance measured


http://www.sciencedaily.com/releases/20 ... 135820.htm



A study published today finds a surprising and very recent shift away from the steady relationship among species that prevailed for more than 300 million years.

The study, published in the journal Nature, offers the first long-term view of how species associated with each other for half of the existence of multicellular life on Earth, says co-author Donald Waller, a professor of botany at the University of Wisconsin-Madison. "We did not expect, or predict, that we would see continuity in the fossil record for such a long time. The fraction of plant and animal species that were positively associated with each other was mostly unchanged for 300 million years. Then that fraction sharply declined over the last 6,000 years," says Waller, a plant ecologist.

Species are 'positively associated' if they are found in the same place and time.

Starting about 6,000 years ago, negatively associated species were preponderant, meaning plants and animals are seldom found in the same place and time, a sign that longstanding relationships have been disturbed.

In assessing the cause of the dramatic change they found, the researchers first eliminated five possible sources of error. "Senior author Nicholas Gotelli, of the University of Vermont, developed careful methods to guard against false positive results," Waller says. "With a result as unexpected as this, we wanted to be very careful to make sure that the pattern was real and not an artifact of the methods we were using, or the particular datasets we looked at."

The most likely cause for the shift, the researchers state, was rapid human population growth, with ensuing effects from plant and animal agriculture. "The conclusion we reluctantly came to is that there have been systematic changes around the world in ecological conditions, prompting changes in the pattern of species coexistence," Waller says. "This is an aspect of global change that has never been noticed, or documented before."

Although the researchers do not have direct evidence for the cause of any particular species assemblage, patterns of species living together form an intricate ecological web involving predation, symbiosis, disease, nutrition, habitat and evolution, Waller points out.

The situation on continents, often recognized as having more stable species assemblages, is now starting to resemble the situation on islands, Waller says. "In general, island habitats are fragmented, and species are vulnerable and declining. Islands are models for conservation biology because they indicate what happens in the end game" as species go extinct and biodiversity declines.

The study, supported by the National Science Foundation, is more evidence that humans have substantially changed the planet, Waller adds. "The Paris accord on climate signed last week reflects a global recognition that humans have fundamentally changed our planet's climate. Now we present evidence that humans are changing the Earth in another fundamental way: how species are associated with one another. It's fossil evidence that we have entered the 'anthropocene,' a geologic era marked by human dominance of the planet. In fact, the study even provides a way to date the start of the anthropocene."
We travel the Milky way together, trees and men. - John Muir
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#9)  Re: Fontenelle Forest

Postby Joe » Wed Dec 23, 2015 3:21 pm

"It's fossil evidence that we have entered the 'anthropocene,' a geologic era marked by human dominance of the planet."

Though that dominance is currently a very negative feature- it could become a positive one.
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