Enhancing Wet Praire Restoration Following the Removal of Frangula

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ENHANCING WET PRAIRIE RESTORATION FOLLOWING THE REMOVAL OF FRANGULA ALNUS (GLOSSY BUCKTHORN)

Jacob A. Meier

A Thesis

Submitted to the Graduate College of Bowling Green State University in partial fulfillment of the requirements for the degree of

MASTER OF SCIENCE

August 2013

Committee:

Dr. Helen J. Michaels, Advisor

Dr. Karen Root

Jacob Meier

Helen Michaels, Advisor

Invasive species, notably Frangula alnus (Glossy Buckthorn), have dominated many former wet prairie habitats that currently cover less than 1% of their original extent.

Restoration of wet prairie often involves removal of large monoculture buckthorn stands followed by the application of herbicide and natural regrowth from the seed bank.

Remnant seed banks are important for the ability to preserve communities during unsuitable conditions. The goal of this study was to determine if the existing seed bank at upper and lower soil depths contains the appropriate native seeds for restoration, and to examine the effect of hydrologic conditions on seed bank emergence. Fifty-two georeferenced, randomly selected 10 x 10 m plots were established across three sites at different stages of restoration: an established restored wet prairie, an area that had been cleared of buckthorn and sprayed the previous summer, and a pre-restoration buckthorn monoculture. Soil samples from 0-10 and 10-20 cm depths were collected from each plot, then divided and randomly distributed between simulated wetlands with saturated or flooded conditions. Soil samples were also sifted following the experiment to check for any remaining buckthorn seeds. 41 species emerged and were identified. Similarities in abundance, richness, WPI and FQAI showed that sites were similar and represented quality wet prairie communities for future restoration efforts. Greater native richness and diversity in upper soil layers showed that invasion had not occurred long enough to alter seed bank composition. Low numbers of invasive species indicates restoring hydrologic iv conditions and prolonged flooding may be a plausible management technique for wet prairie habitats. v ACKNOWLEDGEMENTS

There are many people I would like to thank that have been influential in the completion of this project. Most importantly, I thank my advisor, Helen Michaels, for her guidance and patience every step of the way. Frank Schemenauer deserves a special thanks as an instrumental part of the design, setup, and life of plants during the greenhouse portion of this project. I would also like to give special thanks my field assistants Paige Arnold and Lindsay Blair for their willingness to help without complaint.

My committee members Dr. Karen Root and Dr. Enrique Gomezdelcampo provided advice from the beginning of the project. Dr. Tim Schetter, Karen Menard, and Dennis

Franklin of Metroparks of the Toledo Area, as well as Ryan Schroeder of Ohio DNR

Division of Natural Areas and Preserves, deserve many thanks for graciously granting access to awesome field sites. Dr. Rick Gardner and Dr. Tim Walters provided help with plant identification. My family has provided encouragement and given me the opportunity to pursue my academic goals. Finally, I would like to thank the rest of the

Michaels Lab (Mike Plenzler, Ryan Walsh, Jennifer Shimola, Jacob Sublett, and Alyssa

Dietz) for support and companionship. vi

TABLE OF CONTENTS

Page

INTRODUCTION ...... 1

MATERIALS AND METHODS ...... 9

Study System ...... 9

Study Sites ...... 11

Seed Bank Experiment ...... 13

Statistical Analysis ...... 15

RESULTS ...... 18

DISCUSSION ...... 21

Management Implications ...... 26

TABLES ...... 28

FIGURES ...... 35

REFERENCES ...... 44 vii

LIST OF TABLES

Table Page

1 Total species list including native/invasive status and presence/absence ...... 28

2 List of importance values for each species at each site including coefficient of

conservatism used for FQAI calculations ...... 30

3 Distribution of elevations at each site ...... 32

4 Least Square Means ANOVA of Total Abundance, Native Abundance, Native Richness,

Diversity, WPI, and FQAI ...... 33

5 Non-parametric comparisons among sites of Invasive Abundance and Richness .... 34

6 Least Square Means ANOVA of F. alnus distribution ...... 34 viii

LIST OF FIGURES

Figure Page

1 Map of site locations showing boundary of historic and current wet prairies ...... 35

2 Diagram of ponded bench setup ...... 36

3 Difference in elevation among sites ...... 36

4 Difference in total abundance between soil core depths ...... 37

5 Difference in native abundance between soil core depths ...... 37

6 Difference in native richness between soil core depths ...... 38

7 Difference in native richness between water treatments ...... 38

8 Difference in native richness among sites ...... 39

9 Difference in native richness between soil core depths among sites ...... 39

10 Differences in Shannon-Wiener diversity among sites ...... 40

11 Differences in Shannon-Wiener diversity between water treatments ...... 40

12 Differences in Shannon-Wiener diversity between soil core depths ...... 41

13 Differences in Shannon-Wiener diversity between soil core depths among sites ... 41

14 Differences in WPI values among sites ...... 42

15 Differences in FQAI values between soil core depths ...... 42

16 Differences in number of mean buckthorn seeds among sites ...... 43

17 Differences in number of mean buckthorn seeds between soil core depths ...... 43 1

INTRODUCTION

It has been estimated that 50,000 foreign species have been introduced into the United

States resulting, in approximately $120 billion in annual damages and losses (Pimentel et al. 2005). The ecology of invasion has been extensively studied in the last fifty years, addressing a variety of questions from invasive species impacts and native community response, to control and management (Lowry et al. 2012). To best understand invasive species ecology, a distinction of terms must be made. For this paper, “natives” are any species believed to exist since at least the last glacial period based on historical and ecological data, including early botanist accounts and the ability to grow in natural or semi-natural habitats (Pysek et al. 2004). Invasive species will be considered as species that have been introduced from their native range or exhibit local dominance within their native range due to changes in environmental conditions, and which continue to alter ecological processes (Richardson et al. 2000; Mitchel et al. 2006; Rout and Callaway

2012). It is important to note that some native species can become invasive after biotic or abiotic conditions within an ecosystem have changed. A recent review found that invasive plants exhibit trait values in areas of physiology (photosynthetic rate, transpiration, nitrogen use efficiency), leaf-area allocation, shoot allocation, growth rate, size, and fitness (numbers of flowers per plant, seeds per plant, seedling establishment, and mortality) that were significantly higher than their non-invasive counterparts (Van

Kleunen et al. 2010).

Invasive species have many negative effects on natural ecosystems. Invasive plants can affect a natural community by directly altering ecosystem functioning

(Weidenhammer and Callaway 2010), hybridizing with native species, and out competing 2 native species (Pysek and Richardson 2010), causing losses in biodiversity. Others found that although predicting impacts of invasive plants is context dependent, consistent impacts on community function include: reduced survival of resident biota; reduced community productivity; changes in fire regime; changes in animal activity; and changes in mineral and nutrient content in plant tissues (Pysek et al. 2012). Invasive plant species can reduce species diversity, disrupt mutualistic networks for pollination and dispersal, and alter seed bank composition (Gioria and Osborne 2010; Montera-Castaño and Vilà

2012; Pysek et al. 2012).

Non-forested wetlands have been the focus of many restoration efforts because their degradation is often the result of human development (Zedler et al. 2012). The amount of wetland habitat has been reduced by half globally (Mitsch et al. 2007), including roughly half of the area within the prairie pothole region of North America

(Dahl 1990; Gleason et al. 2011), and up to 90% loss in the glaciated interior Plains of the Midwest (Dahl 1990; Hopple and Craft 2013). It is estimated over $70 billion has been spent on wetland restoration during the last 20 years (Moreno-Mateos et al. 2012).

Restoration studies throughout the Midwest focusing on wet prairies, sedge meadows, and similar coastal wetlands with fluctuating water levels have found that invasions cause significant loss in ecosystem functions (Herr-Turoff and Zedler 2005; Frieswyk and

Zedler 2006; Moreno-Mateos et al. 2012).

Restoring wet prairie plant communities is particularly important because they help maintain ecosystem functions such as: stable base flows in local streams, provide erosion control, nutrient cycling, and water purification and recharge (Keough et al.

1999; Forbes et al. 2012). Conversion of wet and upland prairies into agricultural lands 3 has lowered the water table, can lead to flooding when basins are filled with crops or pasture, and increase nutrient discharge in many American watersheds (Bartzen et al.

2010). Wet prairies also provided important habitats for many rare animal species including the eastern fox snake (Elaphe gloydi) and the blue spotted salamander

(Ambystoma lateralea) (Albert and Kost 1988).

Wet prairies can be identified by community composition, soil types, and hydroperiod regimes. Kushlan (1990) effectively summarized the range of hydroperiods typical of freshwater marshes and wet prairies as short hydroperiod areas, flooded less than 6 months per year. Seasonal flooding in wet prairies and frequent fires in dry periods combine to restrict the expansion of woody vegetation and succession (Hayes

1964). Because they are seasonally flooded, most wet prairie and freshwater marsh species are tolerant of anaerobic soil conditions for varying periods of soil saturation and/or inundation.

Sometimes referred to as sedge meadows, wet prairies were originally very diverse ecosystems. One study estimated one-quarter square meter could support 4.5 species in 1974, but only 2.0 in 2001 (Zedler et al. 2001). Communities typical of wet prairies are often dominated by graminoids (Deberry and Perry 2000) of the Poaceae,

Cyperaceae and Juncaceae families, including the Carex and Juncus genera, respectively.

Forb, tree and shrub species common to Midwest wet prairies are also adapted to wet conditions and can include Asclepias incarnata, Iris versicolor, Cornus sericea, Quercus palustris, and Populus deltoides (Keddy and Reznicek 1986; Brewer and Vankat 2004).

Many wet prairie, sedge meadow, and other wetland restorations have resulted in non- 4 native monocultures, but native species can be restored under the correct conditions

(Zedler 2005).

Historically, seed banks have been considered important potential seed sources for the restoration of invaded plant communities (Bakker & Berendse 1999). Seed banks have the ability to bridge periods of unsuitable habitat and preserve genetic diversity

(Bossuyt and Honnay 2008). At the community level, the seed bank also co-determines the direction of secondary succession following disturbance (Pakeman & Small 2005).

The use of the seed bank however, cannot always guarantee the desired community will emerge during restoration efforts (Bakker et al. 2005; Nabity & Hoagland 2006). In one wetland restoration, removing woody species and restoring hydrology resulted in only half of the emerging species resembling the desired wetland community while wood resprouts persisted (De Steven et al. 2006). Recurring disturbance cycles and continued degradation selects for species that produce large numbers of long-lived seeds (Bossuyt and Honnay 2008; Klimkowska et al. 2010), which include many invasive species, such as Frangula. alnus (glossy buckthorn) and Lythrum salicaria (purple loosestrife) (Boers et al. 2006). Factors including the length of invasion, unfavorable environmental conditions, and repeated disturbance events can prevent revegetation from the seed bank alone (Hölzel 2005; Bossuyt and Honnay 2008; Hall and Zedler 2010; Wand et al. 2012).

Despite the risks associated with relying on a natural seed bank, many experimental restorations have had success (Dalrymple et al. 2003; Plassmann et al.

2009; Marchante et al. 2011), but the resulting community is often dependent on the types of species present in the seed bank, existing vegetation, micro-topography, and land management (Weng et al. 2013). Forest communities often have lower seed densities 5 compared to marsh communities, which often have high seed densities but low diversity and evenness (Bossuyt and Honnay 2008). Upper soil layers are often more diverse but dominated by non-native and invading species, while lower soil layers often have fewer exotic or weedy species (Hausman et al. 2007; Stroh 2012). Species diversity may also be affected in wetlands with fluctuating water levels; wet prairie communities may be reduced during lower than normal water levels due to competitive advantages to other species in dry conditions (Frieswyk and Zelder 2010). These are important considerations to take into account if the restoration of a wet prairie habitat is going to be successful.

Specific species traits and environmental conditions are important for the community that emerges from the seed bank. Many wetland species in the Cyperaceae family have seed coats adapted for waterlogged and oxygen-poor conditions and have an average viability of over fifteen years (Schütz 2000; Leck and Schütz 2005). This characteristic may make restoration of the sedge community more likely in sites with variable water levels. Time following management events can also contribute to the composition of restored plant communities. Species richness of sedge-meadow and emergent perennials was found to continue to accumulate 12 years after management

(Galatowitsch 2006). Providing the appropriate conditions, which benefit natives and restrict invasive species, is important for preventing long-term reinvasion (Iannone and

Galatowitsch 2008).

As reviewed by Inderjit (2005), disturbance and resource fluctuation are the two most important ecological factors making a habitat prone to invasion. The most likely disturbance leading to invasion in the wet prairie habitats can be linked to the alteration 6 of hydrological conditions by agricultural and urban development. In other areas affected by urban development, natural hydrologic regimes typically have lowered water tables and reduced groundwater recharge when compared to previous, more natural conditions

(Brinson 1993; Kercher and Zedler 2004). Understanding the hydrology is important for wet prairie restoration as it may be considered the most important factor influencing wetland species (Mitsch and Gosselink 2000; Zedler 2000; Kercher and Zedler 2004;

Raulings et al. 2010).

The development of species composition following disturbance can be related to changes in ecologic processes (Klimkowska et al. 2010). The effect of water regime on wetland plants is species specific (Raulings et al. 2010), and loss of vernal flooding regimes can allow the recruitment of flood intolerant species (Hall and Zedler 2010).

Following disturbances such as changes in flooding regimes, generalist species often replace specialist species (Klimkowska et al. 2010), and few wet prairie communities are capable of forming persistent seed banks capable of withstanding long-term disturbance

(Bekker et al. 1998). Woody shrubs and non-natives can increase stress from disturbance following establishment by reducing water levels through increased uptake and evapotranspiration (Brooks 2004), as well as change ecological function through natural succession by filling the canopy and preventing germination of gap dependent seeds

(Hölzel 2005). Other invasives such as Rhamnus cathartica (common buckthorn) have been shown to alter soil carbon, nitrogen, pH, and moisture (Heneghan et al. 2006).

Frangula alnus Mill. (glossy buckthorn), a close relative of R. cathartica, is a common invader in many forested wetlands, prairies, and wet prairies throughout the

Northeastern United States and Eastern Canada (Converse 1984; Fagan and Peart 2004; 7

Houlahan and Findlay 2004; Fiedler and Landis 2012). Soils that are wet but not inundated have been found to be advantageous for F. alnus seedling establishment (Peach and Zedler 2006), and F. alnus has also been found to displace native plant species once it is established (Sinclair and Catling 1999). By replacing native species in wetland and wet prairie communities, F. alnus may be reducing native input to the seed bank, preventing native seedling germination and emergence, and altering soil moisture properties. Invasive species such as buckthorn can also alter hydrologic conditions.

Invasive woody species in the Great Plains have higher rates of evapotranspiration

(Cavaleri and Sack 2010; Huddle et al. 2011), which removes greater amounts of groundwater. A recent study has also documented that the water table remains depressed in Oak Openings sites invaded by buckthorn compared to restored sites where buckthorn has been removed (Gomezdelcampo personal communication).

Because the depth of water able to be tolerated by seedlings ranges widely between individual species (Fraser and Karnezis 2005), and changes in water levels may shift community compositions between native and invasive species. Growth of Rhamnus cathartica, can be limited by water inundation (Godwin 1943, Gourley 1985), while many of the other non-natives found in invaded wet prairie systems have a wetland indicator status that falls into the facultative upland category, and may also be intolerant of elevated water levels. Plants in this upland category are defined as usually occurring in non-wetlands (estimated probability 67%-99%), but are occasionally found in wetlands

(estimated probability 1%-33%) (USDA 2012). Restoring hydrologic conditions may therefore be essential for restoring wet prairie communities. 8

The objectives of this study are to evaluate the quality of the seed bank in former wet prairies that have been selected for wet prairie restoration, and test the potential effect of improved hydrologic conditions on areas projected for wet prairie restoration. I hypothesize the existing seed bank at two sites being prepared for wet prairie restoration, have not been negatively affected by invasive species. Therefore, native abundance, richness, and diversity will not differ between the restoration sites and a remnant wet prairie. Because hydrologic conditions are an important aspect of wet prairie restoration, elevated water levels should lead to greater native richness and diversity consistent with a previous wetland restoration (Zedler 2005). Furthermore, while greater numbers of total species may be found in upper soil layers, native richness and diversity are predicted to be greater in lower soil core depths (Hausman et al. 2007). 9

MATERIALS AND METHODS

Study System

The Oak Openings Region of Northwest Ohio contains small areas of remnant wet prairie habitats within a unique mosaic of diverse habitat types spread across approximately 476 km2. Habitat types common to the region include oak savanna, wet prairie, oak woodland, oak barren, and floodplain forest (Brewer and Vankat 2004).

Considered a regional biodiversity hotspot, the area boasts over 100 state endangered or threatened species (ODNR 2013), and one federally endangered species, the Karner blue butterfly (Schetter and Root 2011). Wet prairies once covered approximately 128 km2, one third of the Oak Openings region, but currently only cover 1% of that original area

(Brewer & Vankat 2004; Schetter and Root 2011).

Within the Oak Openings, wet prairies occur on poorly drained clay soils covered by sand deposits. These prairies are seasonally flooded from late fall to late spring with standing water levels that often reach up to one meter (Moseley 1928; Mayfield 1969;

Torbick 2004). The sandy soils of the Oak Openings are a result of ancient Lake Warren that once covered the area of current Lake Erie (Moseley 1928, Abella et al. 2001). As the glacial lake receded, oak and other woodland communities colonized rolling dunes, while wet prairies filled the interdunal depressions (Sears 1926; Abella et al. 2001). The vegetation characterizing these areas is sedge dominated, generally treeless, and occurs on the sand flats and interdunal swales (Brewer and Vankat 2004; Schetter and Root

2011). Seasonal flooding and frequent fires occurring during summer dry periods that were believed to help prevent the encroachment of exotic and woody species have been 10 reduced due to anthropogenic influence (Tryon and Easterly 1975; Brewer and Vankat

2004).

Frangula alnus (glossy buckthorn) is common throughout the northeastern United

States, and has been recorded through the northern plains states and as far west as Idaho

(USDA 2013). A common invader in Oak Openings wet prairies, F. alnus was first reported in Ohio by Shaffner in the Revised Catalog of Ohio Vascular Plants (1932), and estimated to have been introduced sometime during the 1920s (Howell & Blackwell

1977). Herbarium samples from Bowling Green State University indicate glossy buckthorn was first documented in Northwest Ohio in 1932, recorded in the Oak

Openings Region by Hawkins in 1969 and Irwin Prairie by Tryon in 1970. Fruit production was observed to range between 430 and 1800 fruits per individual in one year, with either two or three seeds per fruit (Medan 1994; Hampe and Bairlein 2000). Remote sensing techniques found a combination of R. cathartica and F. alnus to cover 945 ha

(0.43% of all land cover) within the Oak Openings Region (Becker et al. 2012). Due to the length of F. alnus invasion and its prolific seed production, the success of wet prairie restoration in the Oak Openings is unknown. While these two factors are expected to generate an extensive and persistent F. alnus seed bank, hydrochory can remove F. alnus seeds from suitable growing places in its native range, reducing accumulation in the seed bank directly surrounding fruiting trees (Hampe 2004).

Environmental changes in the Oak Opening’s wet prairies create challenges for local managers. Conversion of land for agriculture and urban expansion following

European settlement has lowered the water table resulting in a change of environmental conditions (Shade and Valkenberg 1975; Lawrence et al. 2003), which may have 11 facilitated the spread of F. alnus. The success of F. alnus can also be attributed to its ability to tolerate a wide range of soil types and conditions. F. alnus prefers wetter soils that are not fully flooded and closer to the water table, and can also withstand high levels of water during the winter (Tansley 1968; Medan 1994; Frappier et al. 2003; Frappier et al. 2004; Webster et al. 2006). It is also capable of establishing in drier or nutrient poor soils (Godwin 1943; Converse 1984; Medan 1994).

Study Sites

Three study site locations were chosen within the Oak Openings Region (Figure

1). Two sites, the Bumpus property and the Dorr and Irwin property, (owned and managed by the Metroparks of the Toledo Area), had been heavily invaded by Frangula alnus and were being prepared for restoration by Metroparks staff. At the time samples were taken, each site had reached a different level of restoration management. The

Bumpus property remained heavily invaded by F. alnus and had not yet received any management efforts. However, at the Dorr and Irwin site during the year before samples were collected, a large skid-steer tractor had cut down all woody foliage other than large oaks. Resprouting and newly emergent F. alnus seedlings were treated with Garlon 4 herbicides via backpack sprayers following this cutting event. As a result, the Bumpus site was considered a pre restoration site and Dorr and Irwin was an early restoration site for comparison during analysis.

The third site, Irwin Prairie, is owned and maintained by the Ohio Department of

Natural Resources and served as a reference site for this study. The Irwin Prairie State

Nature Preserve is a 226 acre preserve with a remnant wet prairie at its core (ODNR

2013), surrounded by adjacent wooded areas (Tyron and Easterly 1975). Many of the 12 adjacent wooded areas have also been invaded by F. alnus and received treatments similar to those at Metropark properties. The core wet prairie however, has not been invaded by F. alnus and did not undergo any management treatments during the course of this study.

All three sites are located within a land use matrix of private and public lands including parks, urban development, agriculture and industry. Secor Metropark, a large woodlot, and many agricultural fields are located within 1 km of the study sites, while wet prairie previously restored by the Nature Conservancy is more than 2 km away from

Bumpus, the southernmost site. This fragmented matrix of surrounding habitats can influence seed input in the existing seed bank as well as future seed rain (Auffret and

Cousins 2011; Farnsworth et al. 2012). The soils at all three sites are listed as Granby

Loamy Fine Sand (USDA 2012), which are described as outwash plains with a slope of less than 2%, very poorly drained, with frequent ponding.

Removal of F. alnus in preparation for wet prairie restoration within the Oak

Openings follows a general approach successfully employed previously by The Nature

Conservancy at Kitty Todd Nature Preserve (Tu et al. 2001). First, buckthorn is removed with a large mulcher mounted on the front of a skid driven tractor, producing coarse woody debris that is left on site. Following buckthorn removal areas are sprayed with the foliar herbicides. The timing of herbicide application following F. alnus cutting and removal depends on factors such as size of restoration site, equipment, accessibility with respect to frozen ground and flooding, and workforce availability. After sites have been cut and sprayed with herbicide, site restoration relies entirely on the seed bank and seed rain for native repopulation. Herbicides are then applied to emergent seedlings and 13 resprouts using backpack sprayers 3-5 growing seasons following the initial removal event (D. Franklin, personal communication).

Seed Bank Experiment

To evaluate the seed bank within the restoration sites, soil was collected from sample plots chosen within each of the three sites in July of 2011. To select these plots, property boundary shapefiles were obtained from Toledo Metroparks for all three sites and examined using ESRI ArcGIS 9.3 software. The Repeating Shapes extension from

Jenness Enterprises (Jenness 2010, Arizona, USA) was used to overlay 10 m x 10 m square grids over each property area. Thirty plots were randomly selected from each site for sampling and located in the field using a Trimble Geo XH GPS unit. Elevation for each plot was also determined using the Trimble GPS using the geoid 09 model to maximize accuracy.

At the center of the plot, a premeasured frame was used to define a 4 m x 4 m plot, with five points within each plot. A compass was used to ensure plots were oriented

North to South. Two soil cores were taken from each of the five sample points within each plot, one core from the surface to a depth of 10 cm and the second from a depth of

10 cm to 20 cm. Cores from the same depth within a plot were homogenized resulting in two soil samples per plot. Soil samples were stored at approximately 4 oC in the absence of light, to prevent germination, until the emergence trial began in October 2011.

Soil samples were transferred to the Bowling Green State University greenhouse, and distributed among experimental treatments for emergence from October 19-21, 2011.

The seed emergence technique (Gross 1990) was used to obtain the most complete listing of species present. Samples were initially sifted using a 4 mm mesh, large enough for 14 buckthorn seeds to pass through, and divided evenly between four experimental pans producing a soil layer approximately 2 cm deep. Each aluminum pan measured approximately 17 cm x 11 cm, and contained a layer of sterilized sand 2 cm deep to provide additional elevation for proper submergence depths. Each pan was randomly distributed within one of four experimental greenhouse benches. Pans containing only sterile sand and potting soil were also randomly distributed throughout each bench to control for any airborne seed contaminants within the greenhouse.

Simulated wetlands were created in each bench using a ponded bench setup

(Adams and Steigerwalt 2008). Ponded benches were created using waterproof pond liner and maintained water levels by carefully measured overflow drains custom fit to each greenhouse bench, which received a constant flow of carbon-filtered water (Figure

2). Two benches received high water level treatments with water maintained at 2 cm above the soil surface, and two received low water treatments with water maintained at 2 cm below the soil surface. Water level conditions were chosen based on Fraser and

Karnezis (2005), which evaluated water tolerance of wetland plants, and water levels found in our field sites in spring of 2011. To reduce mineral crust accumulation, top watering was administered once a week with distilled water to simulate precipitation events.

Air temperatures throughout the study were maintained between 12-32 OC (55-90

OF). Supplemental illumination was provided by an evenly distributed combination of

1000-watt metal halide and high pressure sodium bulbs on a twelve hour photoperiod from October 21, 2011 to January 9, 2012 to simulate the spring growing season. The photoperiod was then set to fourteen hours for the remainder of the study. Water 15 manipulations were discontinued on June 6, 2012. The drawdown conditions were continued with weekly top watering until September 10, 2012 to allow any remaining viable species to emerge that would naturally germinate during summer drawdown conditions. The emergence period exceeded a natural single growing season, but was extended to allow the emergence of new species and to attempt to identify all possible species from the seed bank.

Pans were checked approximately every other day for seedling germination and emergence. After emergence, individuals were maintained until they produced the appropriate reproductive structures needed for identification. Vouchers of each species were prepared and deposited in the Bowling Green State University Herbarium. At the conclusion of the study existing vegetation was counted, removed, and soils were sifted for any remaining buckthorn seeds that had not germinated. Individuals were identified to species using published taxonomic keys (Crowe and Hellquist 2000a,b; Rabeler 2007), and compared to existing specimens from the BGSU herbarium.

Statistical Analysis

Data from individual pans were pooled by site, depth, water treatment and replicate for analysis. To determine the quality of each seed bank, analyses of Wetland

Prevalence Index (WPI), Floristic Quality Assessment Index (FQAI), Shannon-Weiner diversity index, and species richness was calculated for each pooled unit. The WPI was calculated according to weighted averages of wetland indicator ranks (Wentworth et al.

1988, Moser et al. 2007). Wetland indicator values based on the National Wetland Plant

Database (USDA 2013) were used to rank species based on the following scale: obligate wetland = 1, facultative wetland = 2, facultative = 3, facultative upland = 4, upland = 5 16

(Moser et al. 2007). The FQAI uses weighted averages based on coefficients of conservatism assigned to individual species by a group of professional botanists familiar with a geographical region (Andreas et al. 2004). The Shannon-Wiener index of diversity accounts for both numbers of species and evenness, assigning higher diversity values when the numbers of each species present are similar (Andreas et al. 2004).

Each species was assigned to a life history group (annual or perennial) and given an importance value, a measure of relative dominance, based on the sum of the relative density and relative frequency per site (Kent and Coker 1992). The number of seedlings was converted to density (seeds per m2) and calculated by dividing by 0.187, based on the area of the experimental pans (Poiani and Johnson 1989). All dependent variables were tested for normality using the Shapiro-Wilk W test for goodness of fit and transformed as needed. Because elevation, importance values, invasive richness, and invasive abundance were never normally distributed they were analyzed for differences among sites using a Kruskal-Wallace non-parametric ANOVA.

Other dependent variables (abundance, native abundance, native richness, diversity, WPI, FQAI) were initially analyzed as a Standard Least Squares ANOVA with site, water treatment (high or low), soil core depth (0-10 cm or 10-20 cm), and all pairwise interactions as independent variables. AIC and p values were used to select the best model for each variable. Significant main and interaction effects (p < 0.05) were examined with a Student’s t test or Tukey HSD depending on the number of levels.

Due to the small number of emerged buckthorn seedlings, all pans were sifted following the drawdown and final counting of seedlings to determine numbers of buckthorn seeds present. The total number of buckthorn present was estimated by 17 totaling the number of emergent seedlings and seeds recovered from sifting. The total number of buckthorn present was log transformed and analyzed using a Standard Least

Squares ANOVA Model. AIC and p values were used to determine the best model. All statistical tests were analyzed using JMP 9.0.2 (SAS Institute, California, USA). 18

RESULTS

A total of forty-three different taxa emerged from the seed bank experiment, but two different taxa remain unknown due to lack of reproductive features for identification.

Of the identified species, Thirty-three were species native to Ohio, including the state endangered Lipocarpha micrantha (Vahl) G. Tucker (Cyperaceae). Nine others were identified as invasive species (Table 1). The dominant families (by number of taxa present) for all three sites were Cyperaceae (7), and Asteraceae (6). The most abundant family was Juncaceae (56% of the total number of emerged individuals), while

Cyperaceae only accounted for 7% of the total number of emergent individuals.

A total of 20 species was found at all three sites (Table 1), while 4 species were found exclusively at Bumpus (BP), 7 species were found exclusively at Dorr-Irwin

(hereafter abbreviated D-I), and 2 species were found exclusively at Irwin Prairie (IP).

Of the 7 species found exclusively at Dorr-Irwin, 6 were listed as invasive species.

Importance values, which take into account density and abundance of individual species, were not different between sites, but the Juncaceae family dominated importance values at all three sites (Table 2). Two species, Hypericum majus and Proserpinaca palustris, had much higher importance values at the Irwin Prairie reference site than the other two restoration sites.

Mean elevation differed among sites where Bumpus was found to be lower than

Dorr-Irwin (Χ2 = 11.05, p = 0.004, Figure 3). Mean elevation did not explain any variation in abundance, diversity, or life form types (annuals and perennials) (data not shown). The range in elevation however, appeared to vary more at Bumpus than the other two sites (Table 3). 19

Total and native abundance were influenced only by soil depth (p < 0.0001, and p

< 0.001 respectively, Table 4), where almost half as many seedlings emerged from 0-10 cm soil core depths compared to 10-20 soil core depths (Figures 4 and 5). Like total abundance and native abundance, native richness differed between soil depths (p =

<0.0001), as well as water treatments (p = 0.012), site (p = 0.019) and by soil depths among sites (p = .039, Table 4). Native richness was lower in the 10-20 cm soil depths

(Figure 6), and the high water treatment (Figure 7). Native richness was also higher at

Bumpus compared to Irwin Prairie, but similar to Dorr-Irwin (Figure 8). The interaction effects showed native richness was lower in the deeper soil core depths at Irwin Prairie compared to any other soil depths at any of the sites (Figure 9). Invasive richness and abundance differed by site (p = .0005 and p = .0004 respectively, Table 5). Both were found to be higher at the Dorr-Irwin site.

Shannon-Wiener Diversity was significantly affected by site, water treatment and soil core depth (Table 4). Diversity was higher at the Dorr-Irwin site (p = 0.0004, Figure

10), and lower in high water treatments (p < 0.0001, Figure 11) and deeper soil depths (p

= .047, Figure 12). The interaction effect between site and depth was not significant, but showed an interesting trend with diversity increasing in lower soil levels at D-I while decreasing at the other two sites (Figure 13).

Analyses of Wetland Prevalence Index (WPI) and Floristic Quality Assessment

Index (FQAI) were used to further evaluate wetland characteristics and quality of emerged communities. Sites differed slightly in wetland quality (p = 0.022) as indicated by WPI values (Table 4). The mean WPI value was higher at D-I (Figure 14), but was only 1.83, which would still be considered a wetland community. While the WPI showed 20 that all three sites represented wetland communities, analysis of FQAI indicated that

FQAI was influenced only by soil depth (p = 0.015, Table 4), and was found to be lower in soil cores from 10-20 cm (Figure 15).

Low numbers of emerged buckthorn and other exotics were found during the experiment. Five F.alnus seedlings emerged from low water treatments and four from high water treatments, while no buckthorn emerged from the reference site. Soil sifting following the conclusion of the experiment did yield a moderate number of buckthorn seeds. Buckthorn was present in 14 of 27 sample plots at the Bumpus property (pre- restoration), 16 of 25 at Dorr and Irwin (early-restoration), and only 5 of 26 plots at Irwin

Prairie (reference site). The total number of F. alnus seeds differed between sites (p =

0.019) and soil depths (p = 0.0004, Table 6). Fewer seeds were found at the reference site than either restoration site (Figure 16), and in low soil depths (Figure 17). 21

DISCUSSION

The considerable loss of wet prairie habitat in the Oak Openings region has created a need for large-scale restoration efforts at sites that once supported wet prairie.

Because current restoration practices utilize the existing seed bank as the only source for seedling recruitment, it is important to characterize the seed bank in these areas.

Identification of species can help define the resulting community and ecological function in a given area (Hausman et al. 2007). Disturbances that lower the water table can have drastic effects on species traits in aboveground vegetation as well as the seed bank.

Klimkowska et al. (2010) found plants with strong resprouting abilities increased with degradation, and that the increase of species with strong regeneration traits at the cost of species with persistence related traits has negative consequences for restoration.

Comparisons of importance values and overall abundance showed that Juncaceae was the dominant family emerging from the seed bank in this experiment. While this family is common in wet prairie habitats (Keddy and Reznicek 1986; T Schetter personal interview, 2010), I expected that members of the family Cyperaceae, most notably Carex lasiocarpa, a dominant sedge in observations of aboveground vegetation at the reference site, would also be major contributors to the community composition at restoration sites.

The reduced Carex abundance however, is not completely unexpected due to specific germination requirements for many members of the genus (van der Valk et al. 1999).

Hall and Zedler (2010) found that prolonged periods of flooding may prevent Carex emergence, which also prefers periods of continuous drawdown over a fluctuating hydroperiod. 22

The analysis showed that plant communities were similar between sites according to abundance, native richness, WPI, and FQAI values. These patterns follow the expected results and indicate the seed bank at the two restoration sites is capable of wet prairie restoration. While the WPI values were slightly higher at Dorr-Irwin, they all represented wetland communities. However, the higher WPI value at this site may indicate the presence of more generalist species, which have been found to replace specialist species during succession following a disturbance (Klimkowska 2010).

Seed bank diversity indices also suggest that restorations may produce different communities in these sites. For example the Dorr-Irwin site seed bank had a higher diversity index value than Bumpus and Irwin Prairie. However, while diversity increased in lower soil cores at Dorr-Irwin, the other two sites decreased in diversity with core depth. This pattern in diversity at Dorr-Irwin may be due to differences in the composition of species at this site. Differences in composition are most likely due to an increased number of invasive species at Dorr-Irwin, which is supported by increases in both invasive abundance and richness, and the number of invasive species specific to this site.

The greater total abundance and diversity found in upper soil core depths of our study was consistent with previous studies (Bakker et al. 2005; Hausman et al. 2007).

These studies however, also found native richness to be lower in deeper soil core depths, which was not consistent with our results. Reduced native richness in lower soil core depths can be explained by a number of possibilities. First, greater diversity of upper soil core samples could reflect recent seed rain from nearby source populations. However, seed rain from nearby source populations is not likely because few wet prairie remnant 23 source populations exist in the area. While it is possible that other non-wetland native species could be influencing native diversity in upper soil layers, WPI values for natives remained low. Irwin Prairie, the greatest potential wet prairie seed source, also showed similar patterns in a loss in native richness in deeper soil core depths compared to the restoration sites.

It is also possible that the seed bank reflects the community existing before the current non-natives colonized these sites, and that the invasion has not been long enough to alter the seed bank composition. It has been shown that the length of invasion can limit restoration success in urban wetlands (Hall and Zedler 2010), while costal dune areas subject to more recent Acacia longifolia invasions more closely resemble uninvaded areas (Marchante et al. 2011). The Oak Openings wet prairies may therefore have not reached the long-invaded stage described in these studies and be more resilient for reestablishment from the seed bank.

Finally, a natural loss in seed viability and reduced emergence due to prolonged flooding can also explain reductions in native richness in deeper soil core layers. The reduced overall abundance in deeper soil layers seen in our studies suggests that seed viability in the seed bank at these sites is also declining over time due to natural processes. (Bekker et al. 1998) showed that while wetland seed viability can be dependent on species and available nutrients, they tend to decrease over time. Prolonged flooding may also contribute to fewer numbers of some natives such as Carex as suggested by Hall and Zedler (2010). Hölzel and Otte (2004) also found that dominant species in wet meadows may form persistent seed banks that only emerge during optimal soil conditions. 24

High numbers of buckthorn individuals in aboveground vegetation would be expected to generate high numbers of buckthorn seeds in the seed bank. However, only nine individuals emerged from pans in the experiment. Additional F. alnus in the seed bank was confirmed by sifting each soil sample at the end of the study. Our results showed a significant decreasing trend in the number of total buckthorn present from pre- restoration to early restoration and reference sites. One possible explanation for this small number of seeds is that they do not maintain long term viability in the seed bank, as is common with other woody species (Middleton 2003). It is also possible that most seeds are emerging shortly after being introduced to the soil, similar to observations by

Hampe (2004), or lack extended viability, and therefore do not form a long-term seed bank (Gleason and Cronquist 1963; Converse 1984). Germination and emergence may also be directly inhibited by extended periods of water inundation, as was found with

Rhamnus cathartica (Gourley 1985).

The small number of emerged invasive individuals, 29 seedlings compared to over 2000 native seedlings, leads to two possible conclusions. First the number of invasive seeds in the seed bank may have been low. This is unlikely because all three sites exist near unmanaged forests and agricultural areas where invasive species are the greatest seed sources. Secondly, experimental conditions may have had a strong negative effect on invasive germination and emergence. While not as heavily impacted, native species also saw a reduction in seedling emergence in higher water treatments. Our results indicate that both high and low water treatments reduced seedling abundance and may represent similar field conditions representative of very wet years. In the absence of a completely dry treatment (due to lack of sufficient greenhouse space), which may have 25 allowed non-hydrophyte natives and invasives in the seed bank to emerge in greater numbers, these results cannot conclusively demonstrate that few invasives were present in the seed bank. However, this is unlikely due to the presence of these taxa in observations of aboveground vegetation and recovery of unviable buckthorn seeds found at the end of the experiment.

The length of flooding may also have limited both native and invasive seedling emergence. Prolonged flooding may have been high enough to prevent necessary oxygen and temperature requirements to break dormancy. This may explain the high importance values of Hypericum majus and Proserpinaca palustris, which both prefer long periods of inundated conditions (Keddy and Reznicek 1986). The drawdown period at the end of the experiment was intended to simulate a drawdown following the extended water inundation to create drier conditions that are favorable to species with a wider range of germination requirements. The lack of emergence following the drawdown suggests that invasive seeds are either not present in the seed bank, or the period of inundation was long enough to render seeds no longer viable or remain dormant. To completely test these alternative explanations, a follow up experiment should be conducted with a greater number of water levels. The lack of emergence of some species due to experimental conditions is consistent with slightly lower values of seed bank native richness and FQAI scores at our Irwin Prairie reference site compared to FQAI values from a recent study of above ground vegetation at that site (Schetter 2012). This study found that native richness at Irwin Prairie ranged between 19 and 38 taxa, and FQAI varied between 22.9 and 28.3, while in our seed bank samples, richness ranged from 11 to 16 with FQAI only estimated at 12 to 16. Despite the experimental limitations, I believe these results show 26 that appropriate hydrologic conditions are an essential tool to facilitate regeneration of wet prairie communities following invasive removal.

Management Implications

Like any ecosystem restoration, that of wet prairie communities is a dynamic process comprised of multiple steps. Within the Oak Openings Region, removal of invasives, especially F. alnus can be a daunting task. Fortunately for land managers, our results indicate the F. alnus invasion has not yet formed a persistent seed bank that will compromise regeneration of native wet prairie communities.

This study also suggests that a detailed understanding of hydrology (including depth of inundation, length of inundation, and effects of invasive species on hydrology) will be an important key to the success of wet prairie restoration. Knowledge of the effect of these variables on community composition may improve restoration planning and may require specific management approaches. Our results indicate that length of inundation can affect emergence and dictate community composition. Although current research in the area suggests removal of buckthorn can elevate water table levels

(Gomezdelcampo, personal communication), it may be essential to identify areas where seasonal water levels are already high, or where hydrologic conditions of the proper depth, constancy, and duration can be achieved once invasives are removed.

It is also important to identify areas where wet prairie habitat is less likely to occur because hydrologic conditions cannot be met. Microtopography varies greatly throughout the region, as can be seen in elevation at the Bumpus site, and management practices should be altered to better suit the communities most likely to occur in those areas. Continued management such as removal of invasives and application of herbicides 27 is also important. Our study suggests that invasive species do not have a significant presence in the seed bank and natives will establish if invasive emergence is prevented, providing habitat resiliency and preventing future invasions (Iannone and Galatowitsch

2008). 28

TABLES

Table 1: List of species identified and which sites they were found. Native/Invasive indicates how species were classified for analysis.

Family Species Native/Invasive Bumpus Dorr- Irwin Prairie Irwin Asteraceae Cirsium arvense Invasive X Asteraceae Cirsium muticum Native X Asteraceae Conyza canadensis Invasive X Asteraceae Eupatorium perfoliatum Native X X X Asteraceae Solidago canadensis Native X X X Asteraceae Solidago rugosa Native X X X Clusiaceae Hypericum majus Native X X X Cornaceae Cornus racemosa Native X X X Crassulaceae Penthorum sedoides Native X X X Cyperaceae Carex bebbii Native X Cyperaceae Carex cristatella Native X X X Cyperaceae Carex granularis Native X X X Cyperaceae Cyperus esculatus Invasive X Cyperaceae Cyperus odoratus Native X X Cyperaceae Lipocarpha micrantha Native X Cyperaceae Scirpus pendulus Native X X X Haloragaceae Proserpinaca palustris Native X X X Juncaceae Juncus acuminatus Native X X X Juncaceae Juncus dudleyi Native X X X Juncaceae Juncus marginatus Native X X X Lamiaceae Lycopus americanus Native X X Lamiaceae Mentha x gracilis Invasive X X X Linderniaceae Lindernia dubia var. anagallidea Native X X X Lythraceae Lythrum alatum Native X X X Lythraceae Rotala ramosior Native X X Onagraceae Epilobium ciliatum Native X Onagraceae Ludwigia palustris Native X X X Onagraceae Ludwigia polycarpa Native X X Phrymaceae Mimulus ringens Native X X X Plantaginaceae Plantago major Invasive X Plantaginaceae Veronica peregrina Native X X X Plantaginaceae Veronica scutellata Native X Poaceae Dichanthelium implicatum Native X X X Poaceae Digitaria ischaemum Invasive X X Poaceae Phragmites australis Invasive X Poaceae Poa annua Invasive X Polygonaceae Polygonum amphibium Native X 29

Ranunculaceae Ranunculus seratus Native X Rhamnaceae Frangula alnus Invasive X X Rubiaceae Galium tinctorium Native X X Verbenaceae Verbena hastata Native X 30

Table 2: Importance Values of each species at each site. C of C indicates coefficient of Conservation values used for FQAI calculation (Andreas et al 2004).

Dorr- Family Species C of C Bumpus Irwin Irwin Prairie Asteraceae Cirsium arvense 0 0.7 0.0 0.0 Asteraceae Cirsium muticum 8 0.7 0.0 0.0 Asteraceae Conyza canadensis 0 0.0 1.4 0.0 Asteraceae Eupatorium perfoliatum 3 5.0 3.7 2.2 Asteraceae Solidago canadensis 1 2.2 2.7 0.7 Asteraceae Solidago rugosa 2 13.3 11.2 8.6 Clusiaceae Hypericum majus 6 6.5 1.7 22.0 Cornaceae Cornus racemosa 1 1.4 3.7 1.6 Crassulaceae Penthorum sedoides 2 0.2 1.4 0.7 Cyperaceae Carex bebbii 7 0.0 5.6 0.0 Cyperaceae Carex cristatella 3 12.9 15.4 14.5 Cyperaceae Carex granularis 3 4.4 5.1 3.9 Cyperaceae Cyperus esculatus 0 0.0 0.7 0.0 Cyperaceae Cyperus odoratus 4 1.1 0.7 0.0 Cyperaceae Lipocarpha micrantha 8 0.0 0.0 0.9 Cyperaceae Scirpus pendulus 2 5.1 5.2 5.6 Haloragaceae Proserpinaca palustris 7 5.0 3.7 10.2 Juncaceae Juncus acuminatus 4 33.7 35.7 42.5 Juncaceae Juncus dudleyi 3 51.6 35.6 41.0 Juncaceae Juncus marginatus 4 2.2 1.4 2.3 Lamiaceae Lycopus americanus 3 0.1 0.0 0.7 Lamiaceae Mentha x gracilis 0 2.2 3.7 0.7 Linderniaceae Lindernia dubia var. anagallidea 2 1.4 6.8 7.4 Lythraceae Lythrum alatum 6 13.9 15.9 14.4 Lythraceae Rotala ramosior 6 0.7 0.0 0.9 Onagraceae Epilobium ciliatum 3 0.0 0.0 1.4 Onagraceae Ludwigia palustris 3 6.3 3.7 2.9 Onagraceae Ludwigia polycarpa 5 0.0 0.7 2.2 Phrymaceae Mimulus ringens 4 0.8 3.1 2.0 Plantaginaceae Plantago major 0 0.0 1.4 0.0 Plantaginaceae Veronica peregrina 1 1.1 3.4 1.6 Plantaginaceae Veronica scutellata 6 7.3 0.0 0.0 Poaceae Dichanthelium implicatum 3 15.3 17.9 8.6 Poaceae Digitaria ischaemum 0 0.0 3.3 0.7 Poaceae Phragmites australis 0 0.0 1.4 0.0 Poaceae Poa annua 0 0.0 0.7 0.0 Polygonaceae Polygonum amphibium 4 0.9 0.0 0.0 Ranunculaceae Ranunculus seratus 1 0.1 0.0 0.0 31

Rhamnaceae Frangula alnus 0 3.0 1.0 0.0 Rubiaceae Galium tinctorium 4 0.7 1.6 0.0 Verbenaceae Verbena hastata 4 0.0 0.7 0.0 32

Table 3: Distribution of elevation in feet among all three sites. Bumpus Dorr-Irwin Irwin Prairie Minimum 663.15 668.1 668.5 Maximum 681.7 673.5 671.6 Mean 669.1 670.8 669.7 Std. Dev. 4.46 1.29 0.79 Std. Err. 1.19 0.28 0.17 33

Table 4: Results of best model Least Square Means ANOVA for dependent variables. Non-significant values are marked by ns.

Dependent Variable Source df F P AICc R2 Abundance Whole Model 1 45.76 <0.0001 215.11 0.68 Depth 1 45.76 <0.0001

Native Abundance Whole Model 1 44.81 <0.0001 214.9 0.67 Depth 1 44.81 <0.0001

Native Richness Whole Model 6 8.87 0.0002 105.59 0.76 Depth 1 27.36 <0.0001 Water 1 7.93 0.012 Treatment Site 2 5.02 0.019 Depth x Site 2 3.94 0.039

Shannon-Weiner Whole Model 6 12.51 <0.0001 -14.3 0.82 Depth 1 4.55 0.048 Water 1 41.29 <0.0001 Treatment Site 2 12.91 0.0004 Site x Depth 2 1.69 ns

WPI Whole Model 2 4.61 0.022 -37.8 0.31 Site 2 4.61 0.022

FQAI Whole Model 4 8.48 0.035 102.56 0.41 Depth 1 8.96 0.0075 Water 1 2.2 ns Treatment Site 2 0.9 ns 34

Table 5: Results of Kruskal-Wallis test for differences in invasive abundance and richness among sites.

Dependent Variable Chi Square DF Prob>ChiSquare Invasive Abundance 15.68 2 0.0004 Invasive Richness 15.2 2 0.0005

Table 6: Results of Least Square Means ANOVA of total F. alnus seeds.

F. alnus seeds Source DF F P AICc R2 Whole Model 4 7.42 0.0012 213.4 0.64 Depth 1 41.8 0.0190 Water Treatment 1 ns Site 2 0.0004 Depth x Water Treatment ns Site x Water Treatment ns Site x Depth ns 35

FIGURES

Figure 1: Dark shaded polygons show areas where wet prairie exists or is believed to exist based on historic aerial photos and field observations from local land managers in 2010. Black outlines designate the boundaries of historical wet prairies according to Brewer and Vankat 2004. Background color gradient indicates LIDAR data where darker shades indicate lower elevations. Source: Metroparks of the Toledo Area, Ohio Geographically Referenced Information Program. 36

Figure 2: Diagram of ponded bench setup showing low water treatment.

671.5 671 670.5 670 669.5 669 668.5 668 Elevation (Feet) 667.5 667 666.5 666 Bumpus Dorr-Irwin Irwin Prairie Figure 3: Mean elevation at Dorr-Irwin was higher than the mean elevation at Bumpus property (p = 0.004). Bars sharing same letters are not significantly different. 37

140 A

120

100 B 80

40 Mean Total Abunance 20

0 0-10 cm 10-20 cm Figure 4: Total abundance (LS means) was lower in 10-20 cm soil depths (p < 0.0001). Bars sharing same letters are not significantly different.

140

120

100

Native Abundance 40

0 0-10 cm 10-20 cm Figure 5: Native abundance (LS means) was lower in deeper soil core depths (p < 0.0001). Bars sharing same letters are not significantly different. 38

A 18 16 B 14 12 10 8 6 Native Richness 4 2 0 0-10 cm 10-20 cm Figure 6: Native richness (LS means) was lower in 10-20 cm soil depths (p < 0.0001). Bars sharing same letters are not significantly different.

A 18 B 16 14 12 10 8 6 Native Richness 4 2 0 Low High Figure 7: Native richness (LS means) was lower in high water treatments (p = 0.012). Bars sharing same letters are not significantly different. 39

18 A AB 16 B 14 12 10 8

Native Richnss 6 4 2 0 BP D_I IP Figure 8: Native richness (LS means) was lower at Irwin Prairie than Bumpus (p = 0.019). Bars sharing same letters are not significantly different.

20 A A A 18 A A 16

14 B 12 10 0-10 cm 8 10-20 cm

Native Richness 6 4 2 0 Bumpus Dorr-Irwin Irwin Figure 9: Native richness was lower in deeper soil depths at Irwin Prairie than any other soil depths at any site (p = .039). Bars sharing same letters are not significantly different. 40

B 2.5 A A 2

1.5

0.5 Shannon-Wiener Diversity

0 Bumpus Dorr-Irwin Irwin Prairie Figure 10: Shannon-Wiener diversity (LS means) was higher at Dorr-Irwin (p = 0.0004). Bars sharing same letters are not significantly different.

A 2.5 B

1.5

0.5 Shannon-Wiener Diversity

0 Low High Figure 11: Shannon-Wiener diversity (LS means) was higher in low water treatments (P <0.0001). Bars sharing same letters are not significantly different. 41

A 2.2

2.15 B 2.1

2.05

1.95

Shannon-Wiener Diversity 1.9

1.85 0-10 cm 10-20 cm Figure 12: Shannon-Wiener diversity (LS means) was higher in lower soil core depths (p = 0.048). Bars sharing same letters are not significantly different.

2.5

1.5 0-10 cm

1 10-20 cm

Shannon-Wiener Diversity 0.5

0 Bumpus Dorr-Irwin Irwin Figure 13: Shannon-Wiener diversity (LS means) was higher in lower soil depths at Dorr- Irwin but not the other two sites. Differences were not significant. 42

1.9 B 1.85 1.8 A

1.75 A 1.7 1.65 WPI 1.6 1.55 1.5 1.45 1.4 Bumpus Dorr-Irwin Irwin Prairie Figure 14: WPI values (LS means) were higher at Dorr-Irwin (p = 0.022). Bars sharing same letters are not significantly different.

A 16 15.5 15 B 14.5 14

FQAI 13.5 13 12.5 12 11.5 0-10 cm 10-20 cm Figure 15: FQAI values (LS means) were lower in 10-20 cm soil depths (p = 0.075). Bars sharing same letters are not significantly different. 43

A 1.2 A

0.8

0.6 B 0.4 Mean Buckthorn Seeds 0.2

0 Bumpus Dorr-Irwin Irwin Prairie Figure 16: The number of buckthorn seeds (LS means) per sample plot was lower at Irwin Prairie than the other two sites (p = 0.019). Bars sharing same letters are not significantly different.

A 1 0.9 0.8 0.7 B 0.6 0.5 0.4 0.3

Mean Buckthorn Seeds 0.2 0.1 0 0-10 10-20 Figure 17: Total F. alnus seeds (LS means) per sample plot was higher in upper soil layers. Data has been log transformed. Bars sharing same letters are not significantly different. 44

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