Assessing the Soil Composition and Quality in Virgin and Restored
Tallgrass Illinois Prairie
By
Amy Wille
An Undergraduate Thesis Proposal
Submitted in Partial Fulfillment for the Requirements of
Bachelor of Arts
In
Geography and Earth Science
Carthage College
Kenosha, WI
March 2012
Assessing the Soil Composition and Quality in Virgin and Restored
Tallgrass Illinois Prairie
Amy Wille
Abstract
The North American prairie landscape is the natural environment of the Midwest, yet few
have seen its existence. Over the course of time as humans continue to sculpt the land, this flat
grassland has dramatically decreased in size. With the hopes of maintaining the bits of prairie left
and restoring heavily degraded areas, understanding the landscape and its ecosystem is crucial.
The soils, in particular, create insight to the types of plant and animal species that inhabit the
area. This study focused on the soil quality and composition in virgin and restored prairies.
Based on management practices, the soils are expected to be fairly similar. Air Station Prairie
and James Woodworth Prairie were the sites of study, in which soil was obtained through coring.
The soil samples were collected and analyzed through various tests determining the texture,
porosity, water holding capacity, and available nutrients for composition. The results suggest that
the soil compositions are similar and may be in part due to variables that were unaccounted for.
The land use of agriculture and urbanization surrounding both prairies has similar effects on the
natural environment, which includes erosion along its edges. The results show that additional
research would be beneficial in producing more effective restoration practices.
1
Table of Contents
Abstract…………………………………………………………………………………...…1
List of Figures……………………………………………………………………………......3
Introduction……………………………………………………………………….…......…..4
Literature Review…………………………………………………………………...............4
Prairie Environment History…………………………………………………......4
Illinois: The Prairie State………………………………………………………...7
European Settlement: Introduction to Agriculture……………………………….8
Importance of Fire and Grazing………………………………………………….8
Soil Composition………………………………………………………………...11
Virgin and Restored Prairies……………………………………………………..12
Restoration Efforts………………………………………………………………12
Purpose of Study………………………………………………………………...13
Methodology.………………………………………………………………………….…….13
Site Description…...................…………………………………………………..13
Soil Sampling ……….…………………………………......................................16
Soil Analysis……………………………………………………………………..16
Soil Tests……………………………….………………………………………..18
Statistical Analysis……………………………………………………………….20
Results……………………………………………………………………………….............21
Discussion……………………………………………………………………………............24
Future Recommendations………………………………….………………………...27
Acknowledgements................................................................................................................28
References…..........................................................................................................................29
2
List of Figures
Figure 1: Map of North American Grasslands
5
Figure 2: Aerial Map of James Woodworth Prairie
14
Figure 3: Aerial Map of Air Station Prairie
15
Figure 4: Soil Survey of James Woodworth Prairie
17
Figure 5: Soil Survey of Air Station Prairie
18
Figure 6: Texture of Each Soil Type
21
Figure 7: Porosity of Each Soil Type
22
Figure 8: Water Holding Capacity of Each Soil Type
22
Figure 9: pH Levels of Each Soil Type
23
Figure 10: Nutrients in Each Soil Type
24
3
Introduction
Central North American grasslands have greatly evolved since their natural state before
the Europeans arrived in 1820. The three grassland types are the shortgrass prairie in the west,
mixed prairie in the central region, and the tallgrass prairie covering the east. The prairie was
home to several plant and animal species with some being endemic to this environment. Many
migratory bird species relied on the grasslands for nesting grounds. Naturally, fire and grazer
disturbances occurred in harmony with the landscape by adding nutrients and organics to the
soils, making these soils among the most productive in the world. When the Europeans settled
and understood its productivity, the land quickly converted to agricultural fields and pastures.
Much of the natural prairie land was destroyed, which negatively impacted the plant and animal
species relying on it for habitat. Now, the coverage of these landscapes has significantly reduced
to the point where major restoration efforts have to be made in order to maintain and preserve the
land that once thrived. Present-day prairies are categorized by virgin, or remnant, prairie where
the land has never been plowed or cultivated and restored prairie where the land has been
plowed, but has since been reseeded with native grass and wildflower, or forb, species.
Management processes to restore these areas have been put into practice more in the last few
decades. Assessment of the soil composition by testing certain soil properties will help
understand the virgin and restored prairie ecosystem and possibly create better management.
Literature Review
Prairie Environment History
Grasslands, or prairie landscape, are the largest vegetation type in North America with a
coverage of nearly 15% within the central region. Nearly 1.4 million square miles of grasses
form the Great Plains, reaching as far north as the Canadian provinces to southern Texas and
then eastward slightly into Indiana to the western foothills of the Rocky Mountains. Throughout
the world, approximately 32 to 40% of the entire land surface was grasslands. Now, those
grasslands have been converted to farmlands to provide humans with nearly 70% of the world’s
food production, making these lands extremely important to maintain (Robertson 2008).
4
Figure 1 is a map of the coverage of North American grasslands, or prairie, before the European
settlement in 1820 (Mason 2011).
Three types of prairie landscape are located in the continental United States: shortgrass,
mixed, and tallgrass. Each is distinguished by the herb layer growth, as their names suggest.
Generally, the average annual precipitation that each prairie type receives is correlated to the
height of their herb layers. Shortgrass prairie receives the least amount of rainfall and has the
shortest herb layer. Mixed prairie is the transition to the tallgrass prairie, which receives the most
rainfall during the summer months and consists of the tallest herb layer.
The shortgrass environment covers the western region of the United States (Figure 1) and
accounts for the driest of the prairies with about ten to twenty inches of average annual
precipitation. Since nearly all of the rain falls during the growing seasons of April to September,
the vegetation tends to have a short root system in order to obtain as much moisture before the
dry winter season. Grasses growing in this region are characteristically short and sparsely
dispersed within one herb layer that is generally about a foot tall (Henderson 2003). Specifically,
species found in this prairie are western wheatgrass (Agropyron smithii), fringed sedgebrush
5
(Artemisia frigid), blue grama grass (Bouteloua gracilis), prickly pear (Opuntia polyacantha),
and needle and thread grass (Stipa comata) (Vinton 1995). In the more mesic areas, grasses will
grow in bunches, forming a sod layer. Due to a generally flat topography and low rainfall, the
soil develops hardpans, or impervious topsoil layers, of calcium carbonate and higher levels of
salt in the poor drainage areas (Henderson 2003).
The mixed prairie is centralized in the United States (Figure 1) as the transition between
shortgrass and tallgrass. It contains two herb layers with the shortest at one foot and the tallest at
about four feet. This intermediate region has a semiarid climate and an average annual
precipitation of about twenty-three inches. Both bunch grasses and forbs are present with roots
that reach depths of about five feet. These roots are within the silty clay loam soil that has a
darker brown color than the shortgrass prairie (Albertson 1937). This prairie type is characterized
by blue grama grass (Bouteloua gracilis), obtuse sedge (Carex obtusata), porcupine grass (Stipa
spartea), and little bluestem (Andropogon scoparius) (Wilson et al. 1990).
Tallgrass prairie, otherwise known as “true prairie”, is located on the eastern edge of the
North American grasslands (Figure 1). This landscape has a more humid climate that changes its
characteristics in comparison to shortgrass prairie. Three herb layers define this region with each
being high in species diversity. The two layers are topped by the tallest herb layer, reaching
heights of six feet or more. Both sod-forming and bunch grasses are present, as well as numerous
forb species blooming at various times during the growing season (Woodwar 1996). Dominant
grass species include big bluestem (Andropogon gerardii), switchgrass (Panicum virgatum),
indiangrass (Sorghastrum nutans), and little bluestem (Andropogon scoparius). Common forbs
present are the mints of the Lamiaceae family (including species of Monarda and
Pycnanthemum) and the sunflowers of the Asteraceae family (including species of Aster,
Helianthus, Silphium, Solidago) (Howe 1994). In general, the tallgrass prairie is defined by
dominants of the late-flowering phenological guild of grasses and forbs (Howe 1994). More
important than the plant biomass aboveground, the extensive root systems found below the
surface play a vital role in the success of this environment. Roots have been recorded to reach
depths of about nine feet (Woodwar 1996). Some specific species can even reach depths of about
fifteen feet, such as the plant species in the Silphium genus of the Asteraceae family. These roots
help enrich the soils with nutrients and organic matter since the aboveground plant biomass dies
6
every winter season. Soils found in this region are the darkest brown, even black sometimes, and
are referred to as “black earth” (Eyre 1963).
This grassland region has been known for its productive soils that have shown very
beneficial to the agricultural realm, but it also has many benefits to the animal kingdom as well
as being the habitat for some of the Midwest’s rarest species according to The Nature
Conservancy (Robertson 2008). High species diversity in plants provides a vast amount of
habitats and nursing grounds. Many native and migratory birds rely on the grasses for nesting
and mating during the spring and summer months. North American bird species dependent on
the grasslands have declining populations by more than 40% as the landscape continues to be
fragmented (Gerrity 2011). The fragmentation of prairie causes an edge effect, in which the
outside boundaries become heavily eroded and tend to be the most degraded. Also, woody shrubs
tend to invade into the prairie landscape from the forests or urbanized landscapes surrounding the
prairie (Robertson 2008). According to the North American Breeding Bird Survey, the grassland
birds have a higher proportion of declining species than any other avian guild in North America
(Cunningham et al. 2006). Many grassland birds are area-sensitive, in which they will not be able
to acquire the proper space for nesting grounds when the prairie size is limited. A specific study
by Cunningham and Johnson found that grassland species respond negatively to the presence of
trees and the presence of some species can be determined by the proximity to the woody
vegetation (Cunningham 2006). Wetland-dependent species are even scarcer as the prairies
present today do not all include wetlands within their landscape or the area of open water is too
minute. This wetland loss contributes to the reduction in quality of available breeding habitats
(Cunningham 2006).
Illinois: The Prairie State
Illinois was once dominated by tallgrass prairie, which covered 55% of the landscape.
Being located on an area known as the “prairie peninsula” due to the eastward bulge in the
general prairie coverage in North America, this tallgrass region was referred to as true prairie
with a landscape dominated by tall grasses (Robertson 2008). These central-eastern, species-rich
grasslands stretched for miles (Sivicek et al. 2011). Big bluestem (Andropogon gerardii), a
perennial bunch grass, used to be the most widespread and abundant of the grasses in the true
prairie. In 1989, it became a state symbol as Illinois’s official prairie grass. Apart from the
7
variety of grasses present, wildflowers also grow abundantly, giving the landscape a beautiful
palette of color amongst the greenery. These wildflowers, called forbs, add to the diversity
(Robertson 2008). These plant species are among those that die every winter season, collecting
as a plant litter layer, which is naturally or purposefully burned to allow space for new growth.
This unique process increases the decomposition rate and provides the soil with nutrients,
making it extremely productive.
European Settlement: Introduction to Agriculture
When the Europeans travelled west, they discovered this sea of grass and settled due to
the expansive flat lands that provided ideal agricultural opportunities. Originally, the soils of this
land were thought to be infertile, considering the settlers were not accustomed to prairies, but
rather forests with their naturally acidic soils (Taft et al. 2009). Soon, however, these settlers
realized the importance of the productive soils to provide the populations with food. The only
obstacle, seemingly, was the extensive network of roots that penetrate deep into the soil. It was
extremely difficult to plow evenly, so when John Deere’s invention of the steel plow occurred in
1837, the impact of agriculture on the prairie changed the lands quickly and permanently (Eyre
1963). Since the discovery of the highly productive soils located in this region as well,
agriculture boomed and made Illinois presently known for its vast farms of corn and soybeans
(Robertson 2008). Now, only 0.01% of the original nine million hectacres of tallgrass prairie
remains in Illinois that has not been degraded. Expanding agriculture and intensive livestock
grazing are the primary issues regarding the precious prairies by drastically reducing the
grassland vegetation, which heavily exposes the soil to wind erosion (McKinley 2001).
Importance of Fire and Grazing
Before settlement, grazers were among the naturally occurring disturbances that
maintained a symbiotic relationship with the prairie environment, providing benefits to the soil.
Various grazers roamed the land, the largest in size and population being the American Bison.
These mammalian herbivores were considered keystone species as they freely grazed about twothousand years ago before any Europeans arrived, but records of fossils and Native American
history provides knowledge of their existence (Taft et al. 2009). The prairie grasslands had
adapted to these dominant species and had grown a tolerance to the pressures the animals put on
8
the land. Overall, the prairie landscape benefitted from the grazers’ elimination of trees and
shrubs that would invade. Trampling over the young saplings of woody vegetation or defoliation
of fully grown vegetation were both controls to naturally manage the prairie’s quality. Over time,
the bison were moved out of the region and many prairies naturally converted to woodlands due
to Europeans’ neglect in understanding the environment (Hobbs et al. 1992).
Another introduction to the grassland region, post European settlement, was the large
numbers of livestock. Europeans created pastures for cattle, in which grazing became more
concentrated in certain areas. The magnitude of cattle invading on the prairie landscape increased
degradation of the once natural relationship among flora and fauna. These animals were linked to
the decline of native perennial grasses and the replacement of non-native annual grasslands (Taft
et al. 2009). Cattle are more selective in foraging than bison, therefore more native species,
especially forbs, are consumed rather than a mixture of native and non-native as seen in the
bison’s diet. The choice in diet further adds to the degradation by lowering the species diversity
and allowing for the nonnative to outcompete the fragile forb species (Damhoureyeh et al. 1997).
Now, White-tailed Deer are vastly impacting the tallgrass prairie, causing negative
effects on plant diversity, composition, and structure, which therefore affects the soil
composition and structure. They are quickly overpopulating the area due to high reproductive
rates and an easily adaptive herbivore lifestyle with humans being their only serious predator.
Prairies greatly suffer from these grazers, since the deer tend to favor the native plant species
(Taft et al. 2009).
Overall, present-day grazers found in this region cause detrimental effects to the soil
through trampling and digging. These disturbances change the conditions of prairies and the
relationships among the plant species. With trampling of the grasses, the soil becomes
compacted and does not receive sufficient oxygen and water to its roots, therefore stunting the
growth of the grasses (Towne et al. 2005). The soil texture is affected during compaction, in
which the pore spaces (intended for holding water to be taken up by roots) are reduced. Another
effect that grazers have on soil is an increased mineralization of nitrogen from dead plant
material due to the trampling, which produces an increase in litter and faster decomposition rates.
Negatively, the grazers create an increased loss in nitrogen as well through volatilization and
direct removal (Risser et al. 1982).
9
One of the largest reasons for the prairies’ long-term success is the periodic fires set off
naturally by lightning and purposefully by the Native American tribes. These fires allowed for
new growth with the removal of excess plant litter. The high decomposition rates increases the
grassland productivity and soil fertility (Taft et al. 2009). In one particular study done by Alan K.
Knapp, two dominant grass species (big bluestem and switchgrass) and their net photosynthesis
response to burned and unburned prairies were compared. Following a spring burn, the big
bluestem showed significantly greater net photosynthesis than in the unburned plot by greater
than 1 mmol/𝑚2 s. This was as a result of fire exposure due to the considerably higher
availability of solar radiation from the removal of dead biomass (Knapp 1985).
There are no accurate records before European settlement on the frequency of these
prairie fires, but estimates have claimed them to be occurring in the prairie every five to ten years
(Gibson 1988). This estimate is at a much lower frequency than the occurrence of prescribed
burns on prairies that are post-European settlement, typically being restored once the settlers
understood the prairie environment. Now, prairies are being restored with prescribed, carefully
managed, burns that occur annually or biennially (Gibson 1988). With annual prescribed fires in
the late spring, grasses are typically favored and will accentuate their dominance the following
season. Forbs typically occur less since the emergent seedlings do not survive the prairie burns.
As for prescribed fall burns, most legumes, or common forbs that are found in tallgrass prairie,
will be favored (Towne et al. 1996).
The plant species associated with frequent fires have been able to adapt, having the
underground roots safely insulated by the impenetrable soil (Taft et al. 2009). Also, these species
have specifically adapted to having tough-shelled seeds that require scarification to germinate.
Fire provides the trigger to stimulate germination and therefore creates substantial dominance in
areas more prone to fire (Towne et al. 1996). Typically, short-lived annuals and biennials occur
in disturbed or open habitats, which is much more commonplace in the highly industrial and
continuously urbanizing United States (Gibson 1988). Therefore, these plants will regularly die
and collect into a biomass layer that can easily be removed from frequently prescribed burns
(Gibson 1988).
Periodic fires across the prairie recycle nutrients, which promote the re-growth of
vegetation. The accumulation of dead litter and increased rate of decomposition provide a higher
10
organic content to the soil’s surface layer. Therefore, the nutrient availability and light are
increased after a fire disturbance. Especially in grassland ecosystems, nitrogen has been shown
to play a vital role in affecting the structure and function of these systems. It affects the rates of
primary productivity as well as organic matter decomposition through rapid utilization and
immobilization by vegetation and decomposers (Risser et al. 1982). Nitrogen is usually the only
nutrient that promotes vegetation growth. In a study performed by Smith and Owensby, higher
moisture content has been recorded after spring burns as the dead biomass burned up, leaving
availability for the precipitation to penetrate into the soil (Smith et al. 1970).
Soil Composition
Prairie soils are unique within this landscape with two-thirds of the plant biomass as the
roots networked below ground to form thick prairie sod. The parent material is the loess, or
wind-deposited sediment, accumulated in this area post floodplains of the intricate glacial rivers
(Taft et al. 2009). The dark enriched soil gave this most widespread prairie soil the name black
earth based on the World Reference Base for Soil Resources (Eyre 1963). In the United States,
based on USDA soil taxonomy, the proper soil order is mollisols, which form in semi-arid to
semi-humid areas. Mollisol soils are defined by their large, highly fertile A horizons, which
contains decomposed organic material called humus and where most of the biological activity
occurs. With a highly organic composition and high rates of decomposition in the underground
plant biomass, mollisols have been found to be the most productive in the world and later,
resulting to be the most economically important (Etherington 1975). Of the nutrients collected in
the A horizon, calcium is the most dominant due to the heavy precipitation that easily percolates
through the porous layers (Eyre 1963). The prairies receive high seasonal precipitation every
year at about 75-100 cm with periods of low humidity and drought in the months of July and
August. Winds carry the moisture content to these areas from the Gulf of Mexico; otherwise the
Midwest would suffer from longer drought periods (Taft et al. 2009).
With tallgrass prairie being one of the most productive grasslands in North America due
to various variables unique to its landscape, the availability of nutrients in these particular soils
are exceptionally high compared to soils of other environments. Nitrogen content is generally
higher since there is a presence of natural fires, which promote forb growth and pull nitrogen
from the air into the soil.
11
Virgin and Restored Prairies
Grasslands found today that have never been plowed or heavily grazed are called virgin
prairie. These bits of land are fragments of original prairie, however fairly degraded due to the
human, animal, non-native plant impacts. Now, virgin prairie remnants are under ten acres each
(Sivicek et al. 2011). There are a variety of reasons for the existence of these original landscapes.
An area is considered restored prairie when the land has been reseeded after plowing.
Efforts have increased to preserve this land as the importance of the prairie landscape is
recognized. Several of these prairies are surrounded by urbanization, which heavily degrades the
land and can counteract any restoration work being done if not continuously monitored.
A study by J.D. Jastrow was conducted looking at the soil aggregates between virgin and
restored prairies. Plant species, soil type (especially parent material and vulnerability to
weathering), type and amount of organic matter, clay content, microorganism species, etc are all
variables that affect the soil aggregation formation, stability and degradation. Soil aggregation is
the binding of soil particles into stable aggregates of various sizes that help determine the
porosity a soil type would have. The porosity indicates the ability for soil to store plant-available
water, transmit air and water, and promote root growth. The prairie soils are ideal for aggregate
formation and stabilization due to the net of grass roots, making them some of the most
agriculturally productive in the world (Jastrow 1987).
Restoration Efforts
Restoration projects have greatly increased over the last couple decades as humans are
becoming more aware of prairie importance. The goal of restoration is to establish native species
communities on the remaining remnants of prairie. With the proper care, these native species can
become a part of the successional process and affect the interactions and relationships of all the
plant species for long-term future success (Baer et al. 2003). Virgin, or remnant, prairies are
especially important to preserve and provide regular managed care in order to salvage any roots
from high quality plant species. There are records of some animal species that have been
extirpated from majority of their original homes, but found in salvaged virgin prairie (Sachdeva
et al. 2003).
12
Besides the prescribed burns as mentioned before, native seed addition is another
common management approach for restoring degraded prairie remnants to become a better
quality. It shifts the relationship between native species and exotic species richness in favor of
increasing the native diversity. It has been studied and recorded multiple times that native
species richness is positively correlated to exotic species richness. In some cases with varying
degrees of exotic species richness, seed addition has increased native richness up to fifty percent,
without changing the exotic richness. However, if there is a high percentage of exotic species,
then the native seeds will have a larger chance of not succeeding. Therefore, the native richness
does not change (Sudling et al. 2006).
Purpose of Study
To better understand the prairie environment, research objectives are: 1) to compare the
soil quality within a restored prairie based on plant species diversity, 2) compare virgin prairie to
restored prairie based on soil composition and testing certain properties. Considering present
management techniques, the soil of the virgin prairie is expected to have similar soil properties to
the restored prairie, in terms of moisture limitations and nutrient availability stimulated by fire.
Methodology
Site Description
Soils were sampled from two locations in the Chicago suburbs of northeastern Illinois.
They are both examples of mesic tallgrass prairie. The first is James Woodworth Prairie Preserve
(JWP), also known as Peacock Prairie, and located on the edge of Niles, Illinois in Cook County.
The other is Air Station Prairie (ASP) found in Glenview, Illinois.
James Woodworth Prairie covers a total of five acres of virgin prairie remnant that is now
surrounded by urban development (Nyberg 2011). This land is considered virgin since it was
never plowed or heavily grazed. In 1843, George Peacock was granted a land patent from the
government that gave him ownership of this prairie plus a considerably larger area surrounding
it. The Long family owned some of the land as well. From 1843 to 1953, both families were
among the many settlers to shift the vast grasslands from prairie to farms and residences.
However, there was a small ten acres land, specifically owned by the Peacock family, preserved
13
within this area during the duration of ownership. Reasons for its preservation are unknown, but
there have been records of families preserving this natural environment for pure enjoyment and
aesthetics. When a developer purchased these ten acres in 1953, four acres were converted into
residential development and some more land turned into commercial development as well. In
1966, preservation efforts began and have succeeded. The land is now owned by the University
of Illinois at Chicago and named after Chicago Mayor James Woodworth of 1849 (Sachdeva
2003). The five acres left are known as virgin prairie since it has maintained its species diversity
and characteristics of prairies from pre-settlement years, despite the various abuses over the
years. Management efforts strongly emphasize maintaining the native species even though some
exotics have been introduced. Over a hundred plant species have been recorded that can only be
found in the black soils of Illinois prairie (Nyberg 2011).
Figure 2: Aerial map of James Woodworth Prairie with the general upward direction
assumed north.
Air Station Prairie is a 32 acre plot that has been restored since the closing of the Naval
Air Station Glenview (NAS Glenview). From 1923 to 1995, the Navy used the area as a security
zone for an adjacent air strip (Folk 2009). After the naval base closed, the Glenview Park District
worked with volunteers from the North Branch Restoration Project (NBRP) to restore the natural
habitat and plant communities at the site. They fought to preserve and show the importance in
saving the existing plant species. In order to obtain proper permits to manage the area, a census
was taken in 1997 to tally the number of native species based on their quality (Fuller Interview
14
Aug 2011). Quality was determined on a scale from one to ten based on sensitivity to disturbance
with ten being the most conservative. Since the Navy maintained the land with consistent
mowing, they inadvertently saved the prairie plants and their roots, so the census was able to
produce roughly fourteen acres of salvageable land. With over fifty percent of the plant species
being native, it was defined as tallgrass prairie (Flakne Interview Aug 2011). Kent and Jerry
Fuller, volunteers of the NBRP, had a particular interest in this area and fought to formally
preserve the area. They obtained an Environmental Impact Statement, where a variety of
endangered species present in the area were listed in order to back up the rights of preservation
(Fuller Interview Aug 2011). In 2005, the interpretive center with the highest possible rating for
a green building was constructed and the prairie gained recognition as Air Station Prairie (ASP).
Now, it has become a popular place for visitors and school groups, further raising awareness of
the native landscape (Darr Interview Aug 2011).
Figure 3: Aerial map of Air Station
Prairie with the sampling sites
labeled. The yellow indicates the path
and the blue dots indicate the areas
sampled with “L” marking the low
quality prairie and “H” marking the
high quality prairie. The general
upward direction is assumed north as
well.
Various tall grass species are present at both sites with big bluestem (Andropogon
gerardii), little bluestem (Andropogon scoparius), indiangrass (Sorghastrum nutans), and
switchgrass (Panicum virgatum) as the dominant species. Also, numerous forb species are added
15
to the prairies’ vegetation list with black-eyed susan (Rudbeckia hirta), goldenrod (Solidago
spp.), oxeye daisy (Chrysanthemum leucanthemum), and rosenweeds (Silphium spp.).
Soil Sampling
Soils from JWP were taken on a July morning in 1995 during which the Niles area was
experiencing record high temperatures. Soils from ASP were taken the morning of October 15,
2011 and the Glenview area had experienced heavy rainfall days before collection. At JWP, five
randomly chosen samples were taken, while avoiding small topographic depressions and
mounds. Flat topography is ideal in order to obtain an accurate soil sample with the proper
layers. Plant roots were also avoided by sampling between plants in order to retrieve the
optimum amount of soil (McKinley 2001). At ASP, four samples were taken, two in high quality
regions within the prairie and two in low quality. Quality was based on species diversity with a
ratio of native to non-native species. Using small corers with a 2.2 cm diameter, soil was
extracted and collected to fill a small, sterile Ziploc bag about three-fourths full. The corers
penetrated the ground to obtain soil from a depth of 5-7 centimeters.
Soil Analysis
Three soil types, based on the USGS soil analysis, were found at the James Woodworth
Prairie and five soil types at the Air Station Prairie, all of which generally consisted of silty clay
loams. The soil texture of each soil type was classified using the textural triangle with USDA
approved soil classes.
16
Figure 4: Aerial map of James Woodworth Prairie obtained from a USGS Soil Survey,
indicating the two soil types located within the area of interest. 320A soil type is a silt loam on 0
to 2 percent slope. 805B soil type is very shallow entisol clay that is most prone to erosion.
17
Figure 5: Aerial map of Air Station Prairie obtained from a USGS Soil Survey, indicating
the five soil types located within the area of interest. 152A and 232A soil types are silty clay
loams. 189A and 697A are silt loams. 805B is very shallow entisol clay that is most prone to
erosion.
Soil Tests
To obtain soil texture, a sieving process was used in order to determine particle-size
distribution, which would indicate the content of sand, silt, and clay within each soil sample. In
sieving or physical separation, the soil particles passed through a series of sieves with given
mesh sizes that decrease. The sieves determined the soil composition of each soil type and
distributed as such:
1st sieve (#5 mesh) = gravel
2nd sieve (#10 mesh) = fine gravel
18
3rd sieve (#25 mesh) = sand
4th sieve (#50 mesh) = silt
bottom pan = clay
Particles were separated based on whether they could pass through the mesh openings and thus
give them each a size class. Before they were added to the sieve, each dry soil sample was
crushed using a mortar and pistil in order to get individual soil particles. Then, the sample was
poured into a container with screen sieves that were arranged from largest size on top to
proportionally smaller. Once the sample was within the container, the top was closed in order to
shake the container for the particles to reach the bottom container. The container was shaken
back-and-forth for a minute. Then, the soil particles found in each sieve were recorded based on
weight in grams.
Bulk density and porosity were also calculated to help determine organic content. The
soil samples were weighed and then left open in their Ziploc bags to air dry. After a week, the
samples were reweighed and recorded. Then, they were put into an oven at 105°C for 24 hours,
reweighed after being oven-dried, and recorded. The bulk density was determined by calculating
(oven dried soil weight (g)/volume of soil (cm^3)) = bulk density (g/cm^3). The porosity was
calculated as (bulk density/2.65)*100% = porosity.
Soil moisture was determined through a series of weighing and drying. To obtain the
water holding capacity of each soil type, the sample of each were put into small aluminum tins
and saturated with distilled water until all of the sample was moist. Next, after weighing the
saturated samples, they were put into an oven at 105°C for 24 hours. The next day, soils were
weighed again. To get the water holding capacity percentage by weight, calculate (weight of
water/weight of dry soil)*100%= %WHC by weight.
The LaMotte soil test kit was used to determine the pH levels of each soil sample as well
as the levels of the nitrogen, phosphorus, and potassium elements. For the pH test, the test tube
labeled 0755 was filled to line 4 with the pH Indicator labeled 5701 and then three scoops of soil
sample were poured in using a 0.5g spoon that is provided. The sample was mixed for one
minute and set aside to settle for ten minutes. Finally, the color reaction was recorded using the
pH Color Chart (1353) by matching the color to the specific pH that the soil had. This test was
performed for all soil samples. Similarly, the same sized test tube was used for the phosphorus
19
test. Phosphorus Extracting Solution (5704) was filled up to line 6 and then three measures of
soil sample were added using the 0.5g spoon. After mixing the contents of the test tube for one
minute, the soil was set aside to settle until a clear liquid separates from the soil. Then, a pipet
(0364) was used to transfer the clear liquid into a second clean test tube, making sure that the tip
did not agitate the soil layer and that the second tube was filled up to line 3. Next, six drops of
the Phosphorus Indicator Reagent (5705) was added to the soil extract in the second tube and
then mixed before adding one Phosphorus Test Tablet (5706). After the tube was capped and
mixed until the tablet dissolved, the blue color developed and indicated the level of phosphorus
within the soil based on the Phosphorus Color Chart (1372). This process was repeated for each
soil sample. As for the nitrogen test, a test tube of 0755 was filled to line 7 with Nitrogen
Extracting solution (5702) and then two measures of soil was added using a 0.5g spoon. Then,
the test tube was capped and mixed for one minute followed by setting aside to settle. Once the
clear liquid separated from the soil, the liquid was removed with a pipet and added to a second
test tube of the same size. Next, two measures of the Nitrogen Indicator Powder (5703) was
added to the liquid using a 0.25g spoon. After test tube was capped and mixed, then the pink
color was assessed based on the Nitrogen Color Chart (1371) to determine to the nitrogen level
within the soil. This process was done for every soil type. Lastly, the potassium test was
performed on each of the soil types. A test tube (0755) was filled to line 7 with Potassium
Extracting Solution (5707) and then four measures of the soil sample were added using the 0.5g
spoon. After the test tube was capped and mixed for one minute, then the cap was removed and
the soil was allowed to settle. Next, a clean pipet was used to transfer the clear liquid that
extracted from the soil and add it to a second test tube without agitating the soil. The second tube
was filled up to line 5, so those soils that did not produce enough clear liquid had the first steps
repeated again. The Potassium Indicator tablet (5708) was added to the soil extract next and then
capped and mixed until the tablet dissolved. Once a purplish color appeared, the Potassium Test
solution (5709) was added two drops at a time and then mixed. The drops were stopped when the
color changed from purplish to blue. The color change determined the amount of potassium
found in the soil based on the Potassium End Point Color Chart (1352).
Statistical Analysis
The results were analyzed using t-tests conducted through Microsoft Excel. Statistical
significance was accepted if p-value was < 0.05.
20
Results
The soils were labeled based on where they were sampled with Air Station Prairie as ASP
and James Woodworth Prairie as JWP. ASP specifically had four samples labeled L1 and L2 for
low quality prairie soils and H1 and H2 for high quality prairie soils. The quality was determined
by species diversity and presence of more native species than nonnative species.
Figure 6: Texture of Each Soil Type found in ASP and JWP
90.00
80.00
Soil Class (%)
70.00
60.00
50.00
% Sand
40.00
% Silt
30.00
% Clay
20.00
10.00
0.00
L1
L2
H1
H2
JWP
Soil Type
a)
Soil Texture
The contents of soil were divided into percentages of sand, silt, and clay. Statistically, the
p-values calculated show no significance among the soil classes since they are each > 0.05.
Comparing low and high quality soils within the ASP prairie, sand percentage has a p-value of
0.589, silt percentage has 0.293, and clay percentage has 0.706. Comparing ASP soils to JWP
soils, sand percentage has a p-value of 0.494, silt percentage has 0.081, and clay percentage has
0.625.
The soil class of silt is shown to be the closest in significant than sand and clay, making it
most likely the best indicator of texture. The high quality soils show higher percentages of silt
with 13.33% for H1 and 66.67% for H2. Even though there was not significance, sand is
primarily shown as the dominant soil class with exceedingly high percentages of 83.33% for L1
and 66.67% for L2 in the low quality soil samples.
21
Figure 7: Porosity of Each Soil Type Found in ASP
80.000
70.000
Porosity (%)
60.000
50.000
40.000
30.000
20.000
10.000
0.000
L1
L2
H1
H2
Soil Type
b)
Soil Porosity
The p-value for low and high quality is 0.305 and is not significant. The low quality soils
show slightly higher percentages in porosity than high quality. The highest percentage is clearly
L2 with 65.5% and the lowest is H1 with 38.5%.
Figure 8: Water Holding Capacity of Each Soil Type Found in ASP
90.000
80.000
Percentage (%)
70.000
60.000
50.000
40.000
30.000
20.000
10.000
0.000
L1
L2
H1
H2
Soil Type
22
c)
Soil Water Holding Capacity
The p-value for low and high quality soil is 0.089, which is not significant. In general, the
low quality soils have higher capacities at 73.79% for L1 and 76.29% for L2.
Figure 9: Predicted pH Levels of Each Soil Type Found in ASP and JWP
7.1
7.0
pH
6.9
6.8
6.7
6.6
6.5
6.4
ASP - L1
ASP - L2
ASP - H1
ASP - H2
JWP
Soil Type
d)
pH
The levels of pH in the soil for low and high quality soils have a p-value of 0.712. For
comparing ASP and JWP soils, the p-value is 0.231. Both p-values are insignificant. Generally,
the pH levels were fairly neutral in the 6 and 7 range.
23
Figure 10: Predicted Nutrients of Each Soil Type Found in ASP and JWP
6
Nutrient Level (scale)
5
4
Phosphorus Test
3
Nitrogen Test
2
Potassium Test
1
0
L1
L2
H1
H2
JWP
Soil Type
e)
Nutrients
Of all nutrients present in soil, phosphorus, nitrogen, and potassium were tested.
Comparing the high and low quality soils in ASP, phosphorus has a p-value of 0.7, nitrogen has
0.3, and potassium has 0.396. With ASP soils and JWP soils, phosphorus has a p-value of 1,
nitrogen has 0.148, and potassium has 0.396. None of these p-values show significance. In
general, nitrogen had the smallest content in every soil type with phosphorus and potassium
more available.
Discussion
The purpose of this study was to compare the soil properties and quality in virgin (JWP)
to restored (ASP) tallgrass prairies in order to assess how these factors can impact restoration
efforts. Texture, porosity, water holding capacity, pH, and nutrients were each of the tests run as
the soil properties in this study.
Based on the textural triangle with USDA approved soil classes, the soil texture of each
soil type was classified. L1 is loamy sand, L2 is a sandy clay loam, H1 is loamy sand, H2 is a
clay loam, and JWP soils are sandy loams (Figure 6). The p-values were not significant.
However, texture differences could be based on other variables. With texture controlling the
24
water movement in soil, texture influences nutrient availability and can be a factor in the erosion
potential of the soil.
Porosity is the amount of pore space within the soil calculated from a known bulk density
and a standard particle density. The amount of organic matter influences the porosity. The results
were not statistically significant and did not seem to show a distinctive pattern. If the litter layer
is taken into account however, then it explains why L2 would have the highest porosity
percentage since it had the highest amount of litter by far of the four sites. With more litter, the
higher amount of organics is present since the decomposition process occurs. L1, with 52.92%
porosity (Figure 7), is unexpected though since the site of sampling was a part of the burned
region just a couple months before. The burning would have greatly decreased the litter layer and
then the organic content should not be as high.
The water holding capacity is the amount of water that soil can withstand between the
field capacity (soil water capacity between particle spaces) and wilting point (water is removed
due to drought and cannot keep plant upright). There is no apparent reason for the low quality
soils having the highest percentages since the textures of L1 and H1 are the same and L2 and H2
are fairly similar.
The data for pH shows a p-value fairly close to having significance (Figure 9). There is a
confidence level in the 90th percentile, which means the low quality pH levels correlate to the
high quality pH levels.
Of the phosphorus, potassium, and nitrogen tests, the closest p-value being statistically
significant is the relationship between nitrogen levels in ASP and JWP prairies at 0.148, meaning
there is a ninety percent confidence level that both nitrogen levels occurred for a reason.
None of the data was shown to be significant; however, several factors were not included
in the data that could alter the results of the soil and its composition. Some can be controlled and
others cannot. The controlled variables are scheduling the sample dates and times and methods
used to collect and analyze data. In this study, the schedules were a bit off since they were taken
during different seasons with JWP soils from the summer and ASP soils from the fall. However,
the location of both sites are very similar, which should provide similar results.
25
The amount of litter layer has an impact on the soil due to the decomposition activity,
which would increase the nutrient levels and porosity with the high organic content. At the ASP,
only one-third of the prairie is burned every spring due to the management team. Therefore,
some of the soils sampled did not experience the prairie burn from this year. Those soils of
unburned land have more litter content than the burned areas. In a study partitioning nitrogen
over growing seasons, Dell et al. (2005) found only 55% of the nitrogen applied recovered from
an unburned prairie, whereas 85% was recovered from burned prairie. This data shows that
nitrogen is more abundant after a burn with an assumption that it is due to the increased
decomposition rates. If a part of the prairie does not get burned in the annual prescribed burn,
then the litter layer will build up, leaving little to no sun and oxygen reaching the soil to begin
the decomposition rate (Dell et al. 2005).
Plant species diversity and soil microbial communities were not taken into account as
well. Plant species diversity can make a tremendous impact based on whether the plants near the
sampling were native, non-native, or even invasive. Invasive plants tend to degrade the
environment, which means poor quality in soil composition. Also, diverse communities should
be better at resisting invasive species (Ortega et al. 2005). According to a study based on the
possibility of linking plant diversity to microbial communities, Zak et al. (2003) states that there
are reasons to believe that plant diversity could affect microbial communities and their functions.
Resources for the communities come from organic compounds in detritus in the form of cellular
energy. Since plant species have different biochemical compositions, they create different forms
of detritus that could or could not be useful to the communities present (Zak et al. 2003).
Urbanized surroundings are similar at both study sites, being in the same Chicago
suburban region. Both have records of the previously agricultural influences as well. JWP was
surrounded by agriculture and ASP was a part of farmland until the 1930s when JWP shrank due
to urbanization and ASP was converted into the naval base. Preservation for both prairies began
in 1970s for JWP and 1990s for ASP. It is important to understand the history and surroundings
of the sites due to the risk of erosion and degradation. The more urbanized around the prairie, the
more edge effect will take place and erode the outer limits.
26
Future Recommendations
With more time and resources, more samples could have been collected from various
other virgin and restored prairies in the Chicago suburbs region of Illinois. These samples would
have created more data to work with to create more accurate averages, which would be closer to
the true soil type. Also, if sampling had been conducted at the same time, fewer variables would
have differed and the range of variation would have been smaller. Sampling in the same season
is highly important and must not be overlooked. Whether the samples are taking during the
growing season or frost season, it must be the same for all samples because it could alter the
results greatly. Along with the seasons, the scheduled burns at the prairies need to be recorded
and schedule sampling around them in order to understand the ecological processes underground
at the time when the soil was taken. The soil composition, before and after a burn, should be
composed differently. A better assessment on plant species diversity would have been helpful as
well as the presence of invasive species could detrimentally affect the results.
Overall, more tests and samples would have created better research for the study in order
to obtain more accurate results and possibly gained statistically significant data. The soil
properties tested, however, could have been proper analyses to assess the quality of each soil
type. Recording the various outside factors that influence the soil properties would be pertinent
to the study and ideal for a complete analysis.
27
Acknowledgements
I would like to sincerely thank my academic advisor and professor Dr. Tracy Gartner for
her guidance and assistance in the completion of this thesis. She did a wonderful job answering
my questions and pushing me to work to my potential. To Dr. Matthew Zorn, I am grateful for
the support and additional guidance towards my work. I also appreciate all of the knowledge and
skills that I learned from the professors in the Environmental Science and Geography
departments at Carthage College. I cannot express the gratitude I have toward each one in
helping me obtain a degree in both majors. Specifically, I would like to thank Dr. Joy Mast,
whose classes helped me decide the route I would like to take in the future towards a career. To
my friends and family, I appreciate all of the help and support in maintaining my sanity through
the countless hours spent in the library. To my fellow classmates that became my friends over
the years, I thank for the support and willingness to answer my questions and to keep me
motivated. Lastly, my thesis on the prairie landscape would not be anywhere without the help of
my summer work at Air Station Prairie. I sincerely thank Katy Darr for her encouragement and
great enthusiasm in teaching me all of the plant species and understanding of the prairie. Also to
Kent Fuller and Robyn Flakne, I thank for the time spent in gaining even more knowledge on the
prairie environment as well as history of my specific study sites.
28
References
Albertson, F.W. 1937. Ecology of Mixed Prairie in Western Central Kansas. Ecological
Monographs 7(4): 481-547.
Ammann, R. L. and D. W. Nyberg. 2005. Vegetation Height and Quality of Original and
Reconstructed Tallgrass Prairies. Am. Midl. Nat. 154: 55-66.
Apfelbaum, S. I. and A. S. Rouffa. 1983. James Woodworth Prairie Preserve: A case history of
the ecological monitoring programs. p. 27- 30 in Proceeding of the 8th North American
Prairie Conference. Western Michigan University, Kalamazoo, Michigan.
Baer, S.G., J.M. Blair, S.L. Collins, and A.K. Knapp. 2003. Soil Resources Regulate Productivity
and Diversity in Newly Established Tallgrass Prairie. Ecology 84(3): 724-735.
Betz, Robert F. and Herbert F. Lamp. 1989. Species Composition of Old Settler Silt-Loam
Prairies. Proc. 11th N.A. Prairie Conference: 33-39.
Corbett, Erica and R.C. Anderson. 2006. Landscape analysis of Illinois and Wisconsin remnant
prairies. Journal of the Torrey Botanical Society 133(2): 267-279.
Cunningham, M.A. and D.H. Johnson. 2006. Proximate and Landscape Factors Influence
Grassland Bird Distributions. Ecological Applications 16(3): 1062-1075.
Damhoureyeh, S.A. and D.C. Hartnett. 1997. Effects of Bison and Cattle on Growth,
Reproduction, and Abundances of Five Tallgrass Prairie Forbs. American Journal of
Botany 84(12): 1719-1728.
Darr, Katy. (August 30, 2011). Personal Interview.
Dell, C.J., Williams, M.A., and C.W. Rice. 2005. Partitioning of Nitrogen over Five Growing
Seasons in Tallgrass Prairie. Ecology 86(5): 1280-1287.
Etherington, J.R. Environment and Plant Ecology. John Wiley and Sons, Ltd, 1975.
Eyre, S.R. Vegetation and Soils. Chicago: Aldine Publishing Company, 1963.
Flakne, Robyn. (August 30, 2011). Personal Interview.
Folk, Stephanie. 2009. Air Station Prairie. Chicago Wilderness Magazine:
http://www.chicagowildernessmag.org/issues/summer2009/itw_airstation_prairie.html
Fuller, Jerry and Kent Fuller. (August 30, 2011). Personal Interview.
29
Gerrity, Sean. Grassland Birds. American Prairie Foundation. 2011.
http://www.americanprairie.org/projectprogress/science-and-wildlife/grassland-birds/
Gibson, David J. 1988. Regeneration and Fluctuation of Tallgrass Prairie Vegetation in
Response to Burning Frequency. Bulletin of the Torrey Botanical Club 115(1): 1-12.
Henderson, F. Robert. 2003. Guidelines for Increasing Wildlife On Farms and Ranches.
Colorado State University Cooperative Extension: 14A-16A.
Hobbs, R.J. and L.F. Huenneke. 1992. Disturbance, Diversity, and Invasion: Implications for
Conservation. Conservation Biology 6(3): 324-337.
Howe, Henry F. 1994. Managing Species Diversity in Tallgrass Prairie: Assumptions and
Implications. Conservation Biology 8(3): 691-704.
Jastrow, J.D. 1987. Changes in Soil Aggregation Associated with Tallgrass Prairie Restoration.
American Journal of Botany 74(11): 1656-1664.
Knapp, Alan K. 1985. Effect of Fire and Drought on the Ecophysiology of Andropogon gerardii
and Panicum virgatum in a Tallgrass Prairie. Ecology 66(4): 1309-1320.
Mason, Jim. Flora and Fauna of the Great Plains. Great Plains Nature Center, 2011.
McKinley, Vicky L. 2001. Microbial Biomass and Activity in Soils From Virgin Prairies
Compared with Prairie Restoration, Forest and Agricultural Sites in Illinois. Proc. 17th
N.A. Prairie Conference: 107-117.
Nyberg, Dennis.2011. James Woodworth Prairie née Peacock Prairie: An Illinois Prairie
Remnant. University of Illinois at Chicago. http://www.uic.edu/depts/bios/prairie/
Ortega, Y.K. and D.E. Pearson. 2005. Weak vs. Strong Invaders of Natural Plant Communities:
Assessing Invasibility and Impact. Ecological Applications 15(2): 651-661.
Risser, P.G. and W.J. Parton. 1982. Ecosystem Analysis of the Tallgrass Prairie: Nitrogen Cycle.
Ecological Society of America 63(5): 1342-1351.
Robertson, Ken. The Tallgrass Prairie in Illinois: What is a Prairie? Illinois National History
Survey, 2008.
30
Sachdeva, Anna and Dennis Nyberg. 2003. Neighbors Save an Ancient Prairie. Chicago
Wilderness Magazine:
http://www.chicagowildernessmag.org/issues/summer2003/neighborssaveprairie.html
Sivicek, Valerie A. and J.B. Taft. Jan 2011. Functional Group Density as an index for assessing
habitat quality in tallgrass prairie. 1251-1258.
Smith, E.F. and C.E. Owensby. 1970. Effects of Fire on True Prairie Grasslands.
http://spuds.agron.ksu.edu/Burntgp.pdf
Suding, Katharine Nash and Katherine L. Gross. 2006. Modifying Native and Exotic Species
Richness Correlations: The Influence of Fire and Seed Addition. Ecological Applications
16(4): 1319-1326.
Taft, John B., R.C. Anderson, and L.R. Iverson. Vegetation Ecology and Change in Terrestrial
Ecosystems. Illinois Natural History Survey (4): 35-47.
Towne, G.E., Hartnett, D.C., and R.C. Cochran. 2005. Vegetation Trends in Tallgrass Prairie
from Bison and Cattle Grazing. Ecological Applications 15(5): 1550-1559.
Towne, E. Gene and A.K. Knapp. 1996. Biomass and Density Responses in Tallgrass Prairie
Legumes to Annual Fire and Topographic Position. American Journal of Botany 83(2):
175-179.
Vinton, Mary A. and I.C. Burke. 1995. Interactions Between Individual Plant Species and Soil
Nutrient Status in Shortgrass Steppe. Ecological Applications 76(4): 1116-1133.
Wilson, S.D. and J.M. Shay. 1990. Competition, Fire, and Nutrients in a Mixed-Grass Prairie.
Ecology 71(5): 1959-1967.
Wisiol, K., Apfelbaum, S. I. and A. S. Rouffa. 1991. How is Woodworth Prairie changing in
time and space? New ways to analyze and map patterns. p. 133-141 in Proceedings of the
10th Northern Illinois Prairie Workshop. Northern Illinois University, DeKalb, Illinois.
Woodwar, Susan. The North American Prairies. Radford University, 1996.
Zak, D.R., Holmes, W.E., White, D.C., Peacock, A.D., and D. Tilman. 2003. Plant Diversity,
Soil Microbial Communities, and Ecosystem Function: Are There Any Links? Ecology
84(8): 2042-2050.
31