WALNUT CREEK NATIONAL WILDLIFE REFUGE
AND PRAIRIE LEARNING CENTER
RESTORING A LARGE-SCALE TALLGRASS PRAIRIE
AND SAVANNA ECOSYSTEM IN SOUTH CENTRAL IOWA
Diane R. Witte
INTRODUCTION
Walnut Creek National Wildlife Refuge and Prairie
Learning Center (Walnut Creek NWR), located 20 miles east of Des Moines in the
southwestern corner of Jasper County, Iowa is an ambitious, large-scale
restoration project by the U.S. Fish and Wildlife Service. Established in 1991
with the purchase of 3,600 acres from Iowa Light and Power, the refuge now owns
5,000 acres and will total 8,654 acres when finished, all bought from willing
sellers. Most of the fifteen square miles that make up the refuge have recently
been agricultural land used for corn, soybean and cattle production. Some of
the land not yet purchased, approximately 1,500 acres, and some that has been
purchased is still farmed today.
The refuge was glaciated, but not during the
most recent ice age. The relief of the rolling landscape is approximately 100
feet, the uplands being remnants of an old glacial plain. Loess caps on the
uplands over more impervious glacial till or paleosols allow the water to
percolate down; it then moves laterally until it reaches a hillside and is
released to the surface, thus creating seeps. The lowest elevations are in the
southern portion of the refuge in and around Walnut Creek and its tributaries,
which have cut deeply into the landscape.
The northern portion of the refuge
was used mostly for row crop production. While some of the southern portion has
been used for crop production, it was more suited to pasture use. Small,
isolated remnants of the original vegetation are left in areas that were
unsuitable for agricultural or pasture use.
The pre-settlement ecosystems in
Walnut Creek NWR were determined by studying the General Land Office (GLO)
surveyors' notes of the 1840s and soils information. Pauline Drobney, Refuge
Biologist, surveyed existing vegetation on remnants and compared the information
to GLO surveyors' notes. Dr. Darryl Smith from the University of Northern Iowa
studied the soils and the surveyors' soils maps . From the information they
gathered, they determined that the northern two-fifths of the refuge was
probably open prairie. No trees were recorded in this area on the GLO
surveyors' notes. The southern three-fifths are believed to have been a mosaic
of prairie, savanna and sedge meadow or wet prairie. The existing remnants of
prairie, oak savanna and sedge meadow, together with the surveyors' notes of the
mid-1800s, local anecdotal information, soils information and pertinent research
of others provide the models for this restoration. The models are not static,
however; they evolve as new information is learned.
The idea for the refuge
began with former Iowa Congressman Neil Smith, who was interested in an
ecological restoration. Iowa has lost to agriculture over 99.9% of its original
35 million acres of prairie and savanna. Congressman Smith wanted to see a
large area of the tallgrass prairie and savanna ecosystems of Iowa
reconstructed. He garnered Congressional support and appropriations for
purchase of the land and construction of the necessary buildings. GOALS The
primary goals of Walnut Creek National Wildlife Refuge and Prairie Learning
Center are:
- to restore the refuge landscape, as nearly as possible, to the
natural condition that existed prior to Euro-American settlement, about 150
years ago;
- to do scientific research to support and guide the process of
tallgrass prairie and savanna ecosystem recovery; and
- to develop a strong
and innovative environmental education program.
To achieve the first goal,
answers were needed to such questions as: What was on the site? What is on the
site? What are the limitations to the restoration? How is it to be done? How
will it be determined successful or unsuccessful? The first two questions were
answered by P. Drobney and Dr. Smith when they researched old records and
identified what is in the remnants and on the farmed and pastured land.
The third question is about learning what cannot be done. For example, the area is
too small to reintroduce predators such as the wolf that once roamed the area.
Some species, such as the passenger pigeon, will never return because they are
extinct. Plant and animal species that were not in the historic landscape may
be impossible to eradicate. Soil conditions are far different now than what
they were in the 1800s due to farming practices and topsoil erosion. The
impossibility of creating an exact replica of the historic landscape is an
important understanding of this restoration. The fourth and fifth questions
deal with interventions and monitoring and will be addressed in the following
sections.
INTERVENTIONS
Using a comprehensive approach to ecosystem recovery,
the restoration is being done gradually, for practical reasons. First, some of
the land has yet to be purchased; but they are not in a great hurry to purchase
it because sufficient local ecotype seed is not available yet to seed all the
land they currently own. If all the land had been purchased in the first year,
it has been estimated that it would have taken 20 years to seed the entire
refuge using local ecotypic seed. Except for species no longer available
locally, introduced biota will be only from natural community remnants within a
38-county range in central and southern Iowa. Second, funding is inadequate to
provide the necessary labor and equipment to restore, maintain and perform
research on the entire 8,654 acres. Third, animal species will return on their
own and will be reintroduced when the proper vegetation structure and food
sources are available, which may take some years to establish.
Because of
limited funding and resources, the first priority was to enhance the quality of
the remnants currently existing. This enhancement involved seeding, weeding and tree
cutting. With the help of volunteers and some ingenuity, in 1992 refuge staff
began harvesting seed from existing remnants located on and off the refuge land.
Purchased seed, together with the harvested seed, was planted in remnants
needing enhancement and in areas that are being reconstructed from farm fields.
Ingenuity came in the form of adapting farm equipment for use in collection of
seed, in seedings and in maintenance. For example, a 1930s Kentucky bluegrass stripper was modified by a
local citizen to harvest prairie seeds from tall and short plants
simultaneously. Seedings were done using a
mulcher-blower, bale shooter, fertilizer wagon, Truax broadcast seeder and
drill, and hand seeding. Currently, 1,100 acres have been planted with well over 100
species, including Andropogon gerardii, Schizachyrium scoparium, Sorghastrum
nutans and Rudbeckia hirta. The goal is to plant a minimum of 300 acres per
year. Agricultural land that is not yet scheduled for planting is rented out
and continues to be farmed.
Other interventions include plugging or breaking
tiles and removing roads. Tiles were found and plugged during construction of the seed handling and
maintenance buildings. Actively seeking out tiles is also being done. However, since no
maps of the tiles exist, finding them can be difficult. Some drainage ditches on
the refuge land have been bulldozed and recontoured to look more natural. Great
care must be taken, however, to keep intact the drainage systems used by
upstream farmers; and to date, this has been done. Three and one half miles of
road within the refuge boundaries have been removed and contoured to fit with
the surrounding landscape. These areas were then planted.
As these kinds of
interventions are being done, others involving vegetation are also being done.
In addition to seeding, planting is done. Staff have begun some small-scale
production of plants on-site; and in the summer of 1996, with the addition of
three new, small greenhouses, greater plant production will begin. In 1995,
when a nearby savanna was going to be destroyed, volunteers organized a rescue
and transplantation of 15 truckloads of vegetation to savannas on refuge land.
In 1996, prairie remnants in a railroad right-of-way will be destroyed. Again,
volunteers are organizing a rescue of those plants. Other work involving
vegetation includes pulling Trifolium species, girdling trees and clearing
brush.
Most of the work done to date has been on prairie remnants and
restorations. Not as much has been done to restore the savanna landscape.
Fire-intolerant species of trees and shrubs, such as Ulmus, Gleditsia
triacanthos, and Morus rubra still need to be removed. Because information is
still incomplete about what plants currently exist and what plants need
reintroduction to the savannas, very little planting of these ecosystems has
been done. Even less has been done on the sedge meadows. Burns to help their
recovery are planned. Some hydrophilic species, such as Spartina pectinata,
Calamagrostis canadensis, and Eupatorium spp., have been planted in some of the more
moist farm fields.
Walnut Creek NWR has a management plan that will evolve
over time as the landscape matures. Currently, on the newly seeded areas, mowing is
done for the first one to three years. Upon reaching twelve inches in hieght, the plants
are mowed down to four inches to give the native prairie species a chance to become established.
Cutting trees and controlled burns are being done on the remnents and some older plantigs. Weeds
are pulled and spot treated with herbicides.
Work is also being planned to attract and reintroduce animal species.
The primary food of the larvae of the regal fritillary, Speyeria idalia is Viola spp. As part of a research program, several violets, including Viola pedata and V. sororia, are being planted. Bison bison will be reintroduced in the fall
of 1996. These animals will not be of local ecotype, however; they will come
from Kansas, Nebraska and Montana to be sure to have enough genetic variation in
the population. Plans to reintroduce elk, Cervus canadensis, are also underway.
Most of this kind of work is still in the very beginning stages for two reasons:
1) current efforts are mostly concentrated on the vegetation re-establishment;
2) more information is needed about the fauna of tallgrass prairie and savanna
ecosystems.
ASSESSMENTS OF SUCCESS
The second goal of Walnut Creek NWR, to do scientific to support and
guide the process of tallgrass prairie and savanna
ecosystem recovery, will generate data to help monitor the recovery. In 1994,
baseline data collection began on approximately 30 of the highest quality
natural remnants. Using transects with randomly-selected plots, staff and
researchers are studying plant species diversity and abundance. Researchers
from Iowa State University, University of Northern Iowa, other local colleges
and universities, as well as from out of state are performing these studies. In
1996, they hope to begin plant monitoring in the areas that have been seeded and planted.
Researchers are
also surveying the presence of birds, fish, terrestrial invertebrates,
amphibians and mammals. This will allow detection of trends in abundance of
these species. Already, they are seeing an increase of grassland birds, such as
shrikes, upland sandpipers and northern harriers in the plantings. A very
exciting event was the documentation of breeding short-eared owls on refuge
land. They have also seen an increase of fall migratory birds using the refuge.
Other species of significance that have been documented on the refuge are the
federally endangered Indiana bat, Myotis sodalis, five species of native
earthworms, and a new ant species.
Approximately two-thirds of the watershed
of Walnut Creek is on refuge land; the remainder is on private agricultural land.
Stream flow and sedimentation gauging stations are located in Walnut Creek at
the northern and the southern ends of the refuge. Information gathered from
these stations is compared to an equivalent stream in an entirely agricultural watershed.
During 1995, daily water samples were taken and sent to an off-site lab.
Periodically, these samples were analyzed for nitrates and pesticides. Five
deep wells, giving readouts every three minutes, are monitored for water table
fluctuations. After each rain, collections of the water from a precipitation
station are also analyzed for pesticides, and particulate matter. The ultimate
goal of Walnut Creek NWR is to restore the landscape as nearly as possible to
what it was 150 years ago. If progress is in that direction, it will be
considered successful. If it appears that the restoration is moving away from
that goal, adjustments will be made to correct the direction of recovery.
EDUCATION
The third goal of Walnut Creek NWR, to develop a strong and
innovative environmental education (EE) program, although not a direct part of
the restoration itself, will have an indirect effect on the restoration. The
purpose of the EE program is to instill in the participants an appreciation for
and understanding of the native ecosystems of Walnut Creek NWR.
Education of
local teachers and students has already begun. Among other things, they
participate in seed collection, stewarding natural remnants off refuge land, and
in planting local ecotype prairies or prairie gardens. These gardens are used
for teaching as well as for seed sources for the refuge.
Education of
volunteers is ongoing. Fifty volunteers regularly work at the refuge; in all,
approximately 450 people have volunteered over the past few years. Many
volunteers work with the researchers; and they learn from all their experiences.
Education of the public began when five seed-seeking volunteers identified 410
local remnant sites of varying quality and harvestability located on refuge land
and surrounding private land . When landowners were approached, they were
usually receptive and even intrigued when they learned they had land with
ecological significance. Many requested information about natural areas and
management techniques. If these and other people manage their natural areas for
quality, the restoration efforts at Walnut Creek NWR will go beyond its own
boundaries to other remnants; and this may ultimately create a network of
quality natural areas that will allow animals safe and easy movement from one to
another.
Currently, a 43,000 ft2 building that will house interpretive
exhibits, a research lab, volunteer space and administration is under
construction. When finished in the summer of 1996, more attention will be given
to active education of visitors through the exhibits and programs to be
developed.
SUGGESTIONS
It is somewhat difficult to assess the plans for this
restoration since they are not yet complete; and they will change and evolve
over the years as new information comes to light. However, I found a couple of
potential problems.
Due to the size of the restoration, many people actively
work in the restorations and comparatively few perform monitoring. This has
allowed an important source of information to be lost. To date, no monitoring
has been done on the plantings, and some of those are four years old. The
plantings have been done two different ways. Some had all the species planted
at once; some are being planted in stages. This restoration has the potential
to act as a model for others; yet valuable information about the first years of
the early plantings is not available.
The comparison of Walnut Creek to a
similar creek in an entirely agricultural watershed doesn't seem very useful.
Although that kind oof comparison will show similarities and differences between the creeks, it
wouldn't necessarily demonstrate the recovery of Walnut Creek. A
more useful comparison would be with a stream within a non-agricultural watershed. This kind of stream could be used as the model and as an asssessmeent tool for Walnut Creek's recovery.
COMMENTS
Although active restoration,
management and monitoring efforts have begun, Walnut Creek NWR is still only in
the planning phase. The staff of ten people has been working on this phase for
several years and expect to be finished by the end of 1996. On October 12,
1996, Walnut Creek National Wildlife Refuge and Prairie Learning Center will
have its official grand opening celebration.
Unlike many restorations, the
very comprehensive restoration effort of Walnut Creek NWR is attempting to
reconstruct not only the natural vegetation, but the animal populations, as
well. Considering all the aspects from plants to nutrient cycling to all the different animals that should be present in healthy tallgrass prairie and savanna ecosystems is a gargantuan effort. The refuge staff are considering all these facets, but are unable to act upon them all as yet.
Within the constraints of underfunding,
however, the staff, researchers, and volunteers at Walnut Creek NWR are doing a
superb job of considering all the various aspects of restoring the natural
landscape to their best approximation of what existed on the landscape 150 years
ago.
REFERENCES
Drobney, P.M. 1994. Iowa Prairie Rebirth: Rediscovering natural heritage at
Walnut Creek National Wildlife Refuge. Restoration & Management Notes (12)1:16-22.
Drobney, P.M. 1996. Personal communication
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