WIREGRASS and OTHER HERBACEOUS SPECIES' RESPONSE to HERBICIDE and FIRE TREATMENTS by ALLYSON S. READ (Under the Direction of S

WIREGRASS AND OTHER HERBACEOUS SPECIES’ RESPONSE TO HERBICIDE

AND FIRE TREATMENTS

ALLYSON S. READ

(Under the Direction of SARA H. SCHWEITZER)

ABSTRACT

The longleaf pine (Pinus palustris) ecosystem was once dominant within the Atlantic Coastal

Plain of the southeastern United States, but it is now reduced to a fraction of its original area.

Today, there is a resurgence of interest in the restoration of the longleaf pine-wiregrass (Aristida

stricta Michx. and A. beyrichiana Trin. & Rupr.) ecosystem. My objective was to examine the

effects of the herbicides, hexazinone (Velpar L) and imazapyr (Chopper), with and without fire,

on the regeneration of wiregrass and associated herbaceous plant species typical of the

understory of longleaf pine savannas. I hypothesized that treatments would differ in their effect

on groundcover vegetation, that the combination of fire and herbicide would better control

competition from hardwood species and promote regeneration of wiregrass and associated

herbaceous vegetation. Longleaf pine seedling survival and Quercus species frequency of

occurrence was greater in hexazinone treatments. Species diversity did not differ among

treatments in October 2006.

INDEX WORDS: longleaf pine, Pinus palustris, wiregrass, Aristida stricta, A. beyrichiana,

hexazinone, imazapyr, sandhill.

WIREGRASS AND OTHER HERBACEOUS SPECIES’ RESPONSE TO HERBICIDE AND

FIRE TREATMENTS

ALLYSON S. READ

B.A., The University of Georgia, 1981

A Thesis Submitted to the Graduate Faculty of The University of Georgia in Partial Fulfillment

of the Requirements for the Degree

MASTER OF SCIENCE

ATHENS, GEORGIA

2007

Allyson S. Read

WIREGRASS AND OTHER HERBACEOUS SP ECIES’ RESPONSE TO HERBICIDE AND

FIRE TREATMENTS

ALLYSON S. READ

Major Professor: Sara H. Schweitzer

Committee: Karl V. Miller Ronald L. Hendrick

Electronic Version Approved:

Maureen Grasso Dean of the Graduate School The University of Georgia August 2007

ACKNOWLEDGMENTS

It has been such a pleasure and reward to work with Dr. Sara Schweitzer on this project.

She was always there with a bright smile and great advice. I am grateful to the Georgia

Department of Natural Resources, Wildlife Resources Division and the BASF Corporation for funding for this research. This project has been difficult at times, sampling in the hottest place in

Georgia in the heat of the summer, but rewarding in the many people I met along the way and all of the wildlife encounters while out in the woods. Nathan Klaus, Haven Barnhill, Alan Isler, and

I. B. Parnell and other personnel of the GA DNR, WRD were very helpful with the many questions I had about details and history of Yuchi WMA, and plant species ranking. I am grateful to Don Wardlaw with BASF for outreach support. The East Central Region DNR area managers and supervisor did a wonderful job burning the plots on a dry, windy day in the sandhills. Mike Murphy was invaluable as a research professional helping me with everything from sampling to grants, and organizing all the tedious paper work that needed to be done before we left and when we returned from trips to the field site. I also want to acknowledge the gracious help of the technicians for their positive attitudes and excellent help while assisting in the field:

Jason Keenan, Daniel Van Dijk, Jamie Manangan, Mandy McElroy, Lora Loke, Danny

Gammon, and Beth Wright of the Warnell School of Forestry and Natural Resources, University of Georgia. My committee members, Karl Miller and Ron Hendrick, were very helpful with advice when things didn’t always go right and in the writing of this paper. And last, but not least, I want to thank my family for supporting me in accomplishing my goal of becoming a wildlife biologist. v

TABLE OF CONTENTS

Page

ACKNOWLEDGMENTS ...... iv

LIST OF TABLES...... vii

LIST OF FIGURES ...... viii

CHAPTER

1 Introduction...... 1

References ...... 5

2 Experimental restoration of wiregrass communities...... 9

Introduction ...... 10

Study Area...... 11

Methods and materials...... 12

Results ...... 14

Discussion ...... 17

Acknowledgments ...... 20

References ...... 21

3 Conclusion ...... 34

References ...... 36

APPENDICES ...... 37

A. List of plant species and their ranking as developed with N. A. Klaus, L. Kruse, and

M. Moffett of the Georgia Department of Natural Resources, Wildlife Resources

Division, estimated seasonally relative to six treatments at Yuchi WMA, Burke

County, Georgia, USA. 2 = characteristic of a healthy sandhill community; 1 =

can be found on sandhills as well as other areas; 0 = neutral or disturbance prone

species that should not be problematic and diminish as soon as climax species

take hold; -1 = generally offsite or exotic, may be problematic; -2 = offsite and an

indication that fire has been suppressed or other imbalance, may be problematic to

recovery of sandhill ecosystem...... 37

B. Total plant species abundance by rank relative to six treatments at Yuchi WMA,

Burke County, Georgia, USA, from October 2005 through October 2006...... 41

vii

LIST OF TABLES

Page

Table 1: Horizontal cover (Braun-Blanquet cover scale) of woody plant species, bare ground,

and forb species measured within 1-m2 square frames at Yuchi WMA, Burke County,

Georgia, USA, from October 2005 through October 2006...... 26

Table 2: Plant height (dm) measured with a Robel pole at Yuchi WMA, Burke County, Georgia,

USA, from October 2005 through October 2006...... 27

Table 3: Vertical cover (%) of vegetation measured within the 0-0.5-m, 0.5-1.0-m, 1.0-1.5-m,

and 1.5-2.0-m increments of a 2.5-m vegetation profile board at Yuchi WMA, Burke

County, Georgia, USA, from October 2005 through October 2006...... 28

Table 4: Plant species diversity (H’ = Shannon-Wiener index) estimated seasonally relative to six

treatments at Yuchi WMA, Burke County, Georgia, USA...... 30

Table 5: Plant species ranking developed with the Georgia Department of Natural Resources,

Wildlife Resources Division, estimated seasonally relative to six treatments at Yuchi

WMA, Burke County, Georgia, USA. 2 = characteristic of a healthy sandhill

community; 1 = can be found on sandhills as well as other areas; 0 = neutral or

disturbance prone species that should not be problematic and diminish as soon as

climax species take hold; -1 = generally offsite or exotic, may be problematic; -2 =

offsite and an indication that fire has been suppressed or other imbalance, may be

problematic to recovery of sandhill ecosystem...... 31

Table 6: Plant species evenness estimated seasonally relative to six treatments at Yuchi WMA,

Burke County, Georgia, USA...... 32 viii

LIST OF FIGURES

Page

Figure 1: Timeline showing dates of treatment applications and data collection at Yuchi WMA,

Burke County, Georgia, USA, October 2005 through October 2006...... 33

CHAPTER 1

INTRODUCTION AND LITERATURE REVIEW

The longleaf pine (Pinus palustris) ecosystem was once dominant within the Atlantic

Coastal Plain of the southeastern United States, but it is now reduced to a fraction of its original area. In the early 1900s, longleaf pine was valued for naval stores and timber (Frost 1993).

Later, destructive logging, intensive agricultural practices (e.g. cotton farming), and fire exclusion led to further loss of old growth pine forests (Clewell 1989; Noss 1989; Frost 1993;

Landers et al. 1995). Today, there is a resurgence of interest in the restoration of the longleaf pine-wiregrass (Aristida stricta Michx. and A. beyrichiana Trin. & Rupr.) ecosystem. Longleaf pine is valued as timber for utility poles, its resistance to pine beetles and fusiform rust, its long life and potential as a carbon sink, and the aesthetic quality of the forest (Longleaf Alliance

2007). Federally sponsored programs like the Conservation Reserve Program’s (CRP) Longleaf

Pine Initiative, promote reforestation of longleaf pine by private landowners with annual payments and cost-share assistance (USDA, Farm Service Agency 2006).

Longleaf pine originally covered 28 - 37 million hectares from Virginia to Texas, but, today, <3% of the area remains (Frost 1993). Wiregrass, a perennial bunchgrass native to the southeastern U.S., is a keystone component of the longleaf pine ecosystem (Boyer 1990). The current longleaf pine-wiregrass ecosystem extends from southeastern North Carolina into

Georgia, Florida, and westward to Alabama, and Mississippi (Parrott 1967; Clewell 1989;

Duever 1989; Hardin and White 1989; Outcalt et al. 1999). The open, savannah-like ecosystem is considered one of the most diverse, yet, endangered ecosystems in the world (Noss 1989; Peet and Allard 1993; Landers et al. 1995). 2

A remarkable number of unique plant and animal species are associated with the longleaf

pine-wiregrass ecosystem (Hardin and White 1989). Plant species counts of more than 40 per m2

are very large compared with other temperate ecosystems (Peet and Allard 1993; Kirkman et al.

2001). Thirty-six mammal species are characteristic of the longleaf pine-wiregrass ecosystem

and characteristic bird species include 86 residents, breeders, and transients (Engstrom 1993).

Many of these species are federally and/or state listed as threatened, endangered, or species of

special concern. Twenty-seven plant species of the longleaf pine-wiregrass ecosystem are

considered threatened or endangered (Van Lear 2005). Fourteen percent of the mammals and

5% of the birds are threatened, endangered, or species of concern (Engstrom 1993; Engstrom et al. 2001). Interest in longleaf pine and the associated biodiversity has encouraged development

of management protocols for the establishment and maintenance of the longleaf pine-wiregrass

ecosystem.

Wiregrass grows in habitats ranging from sandhills dominated by longleaf pine and

turkey oaks (Quercus laevis Walt.), to slash pine (Pinus elliottii Engelm.) flatwoods, and seasonally wet bog-like areas (Clewell 1989; Hardin and White 1989). It is found primarily in deep infertile sandy loam soils, deficient in nitrogen and phosphorus (Parrot 1967; Clewell

1989). Percolation of rainwater is rapid in these soils, leaving a landscape prone to frequent ground fires.

These frequent ground fires were a natural occurrence in the longleaf pine-wiregrass ecosystem reducing competition between longleaf pine and hardwood species. Wiregrass provided a continuous fuel source for carrying low-intensity fires with its long, thin, and involuted leaves. Arching from a clump, they catch the fallen longleaf pine needles creating ready tinder (Clewell 1989). Frequent, low-intensity fire temporarily enhances soil fertility and 3

availability of nitrogen for the herbaceous plant community growing in nutrient-poor sandy soils

(Christensen 1993). Ground litter and herbaceous plant cover is reduced by fire, enabling seeds of the longleaf pine to contact soil directly, germinate, and establish seedlings. Frequent, low- intensity fires also reduce hardwood competition. Without fire, hardwood species develop into a

thick understory, suppressing the growth of longleaf pine and wiregrass and limiting plant

diversity by decreasing sunlight and increasing ground litter (Peet and Allard 1993). When fire

finally occurs, the result is an intense burn with greater nutrient fluxes that may favor hardwood

species (Christensen 1993).

Wiregrass is dependent on fire because it will only enter a reproductive state when

burned during the growing season (Parrott 1967). However, use of prescribed fire during the

growing season increases the risk of spot fires and property damage. Public concern about air

quality, smoke management, and property damage from escaped fires is affecting the timing and

use of fire as a management tool in pine stands (Johnson and Hale 2000).

Land managers commonly burn during the cooler and wetter winter months to reduce the

possibility of fires escaping the burn area and potential liability. Flowering and seed production

is not as successful for wiregrass exposed to dormant-season burns (Parrott 1967; Brockway and

Lewis 1997), but frequent dormant-season burns reduce competition from hardwood species,

allowing vegetative recruitment from existing stocks of naturally occurring wiregrass (Brockway

and Lewis 1997).

Wiregrass is also intolerant of soil disturbance (Clewell 1989; Outcalt 1992). Wiregrass

regenerates by expanding outward in a doughnut shape, eventually splitting into several smaller

plants. Severe disturbance of the roots causes the clone or bunch to die (Clewell 1989); thus 4

mechanical treatments should not be used in restoration of areas with naturally occurring

wiregrass.

With the future use of prescribed burning at risk and the intolerance of wiregrass to soil

disturbance, the use of herbicides has been investigated as an alternative tool to restore longleaf

pine-wiregrass communities (Wilkins et al. 1993; Boyd et al. 1995; Brockway et al. 1998;

Brockway and Outcalt 2000). Herbicide use is common within pine plantations across the South

and can be effective in obtaining some of the ecological effects of fire, but used in combination

with fire they may be more effective in getting the desired response (Wigley et al. 2000).

In this study, we examined two herbicides as surrogates for fire in young longleaf

plantations to restore wiregrass and the associated herbaceous groundcover species. We tested hexazinone (Velpar-L) because its efficacy is greater on sandy soils (positively correlated with percent sand; Minogue et al. 1988), and wiregrass is resistant to hexazinone (Duever 1989).

Other studies conducted in sandhill regions of the southeastern U.S. found that hexazinone

releases wiregrass by preventing competition from hardwood species (Wilkins et al. 1993;

Brockway et al. 1998). Hexazinone also enhances the effects of fire by reducing survival of

hardwood species and releasing herbaceous species that serve as fine fuels (Brockway and

Outcalt 2000). Vegetation usually shows the symptoms from hexazinone treatment within 2 – 6

weeks depending on plant species, humidity, and amount of precipitation (du Pont de Nemours

and Company 2005).

We also examined imazapyr (Chopper) because it is commonly used to prepare sites for

re-planting with pine seedlings. Chopper is a special formulation of imazapyr that can be mixed

with oil, oil and water emulsions, or water carriers. For example, methylated seed oil can be

added to enhance uptake of imazapyr by plants with waxy leaves (Lauer 2006). Most studies of 5

Chopper combine it in a tank mix with other herbicides (Lauer 2006) or use it as site preparation

for pine plantations (Schuler 2004). Plants treated with imazapyr will stop growing soon after

application, but symptoms may not appear for several weeks (or months in woody species). In

our study, Chopper was applied alone.

The objective of this study was to examine the effects of herbicides, hexazinone (Velpar

L) and imazapyr (Chopper), with and without fire, on the regeneration of wiregrass and

associated herbaceous plant species. I hypothesized that treatments would differ in their effect

on groundcover vegetation. To test this hypothesis, I measured vegetation for percentage

horizontal cover, height, percentage vertical cover, and diversity over a 1-year period post-

treatment. Plant species were identified and ranked by significance on a scale developed with

the Georgia Department of Natural Resources, Wildlife Resources Division. The goal of this

study was to provide a restoration management protocol that could be used by state agencies,

land managers, and landowners. Chapter 3 presents a synopsis of the project results and offers recommendations for further research and protocol objectives.

References

Boyd, R. S., J. D. Freeman, J. H. Miller, and M. B. Edwards. 1995. Forest herbicide influences

on floristic diversity seven years after broadcast pine release treatments in central

Georgia, USA. New Forests 10:17-37.

Boyer, W. D. 1990. Longleaf Pine. Silvics of North America. Vol. 1: Conifers. USDA For.

Ser. Handbook 654 [online]. Available from

http://www.na.fs.fed.us/spfo/pubs/silvics_manual/table_of_contents.htm [accessed 5

July 2007]. 6

Brockway, D. G., and C. E. Lewis. 1997. Long-term effects of dormant-season prescribed fire

on plant community diversity, structure and productivity in a longleaf pine wiregrass

ecosystem. Forest Ecology and Management 96:167-183.

Brockway, D. G., and K. W. Outcalt. 2000. Restoring longleaf pine wiregrass ecosystems:

Hexazinone application enhances effects of prescribed fire. Forest Ecology and

Management 137:121-138.

Brockway, D. G., K. W. Outcalt, and R. N. Wilkins. 1998. Restoring longleaf pine wiregrass

ecosystems: plant cover, diversity and biomass following low-rate hexazinone

application on Florida sandhills. Forest Ecology and Management 103:159-175.

Christensen, N. L. 1993. The effects of fire on nutrient cycles in longleaf pine ecosystems.

Proceedings of the Tall Timbers Fire Ecology Conference 18:205-214.

Clewell, A. F. 1989. Natural history of wiregrass (Aristida stricta Michx., Gramineae).

Natural Areas Journal 9:223-233.

Duever, L. C. 1989. Research priorities for the preservation, management, and restoration of

wiregrass ecosystems. Natural Areas Journal 9:214-218.

Engstrom, R. T. 1993. Characteristic mammals and birds of longleaf pine forests. Proceedings

of the Tall Timbers Fire Ecology Conference 18:127-138.

Engstrom, R. T., L. K. Kirkman, and R. J. Mitchell. 2001. Natural history: longleaf pine-

wiregrass ecosystem. Georgia Wildlife Natural Georgia Series 8:5-18.

Frost, C. C. 1993. Four centuries of changing landscape patterns in the longleaf pine ecosystem.

Proceedings of the Tall Timbers Fire Ecology Conference 18:17-43.

Hardin, E. D., and D. L. White. 1989. Rare vascular plant taxa associated with wiregrass

(Aristida stricta) in the southeastern United States. Natural Areas Journal 9:234-245. 7

Johnson, A.S., and Hale, P. E. 2000. The Historical Foundations of Prescribed Burning for

Wildlife: a Southeastern Perspective. USDA For. Ser. NE Res. St. Gen Rep. NE-288.

Kirkman, L. K., R. J. Mitchell, R. C. Helton, and M. B. Drew. 2001. Productivity and species

richness across an environmental gradient in a fire-dependent ecosystem. American

Journal of Botany 88:2119-2128.

Landers, J. L., D. H. Van Lear, and W. D. Boyer. 1995. The longleaf pine forests of the

Southeast: Requiem or Renaissance. Journal of Forestry 93:39-44.

Lauer, D. K., and H. E. Quicke. 2006. Timing of Chopper herbicide site preparation on bedded

sites. Southern Journal of Applied Forestry 30:92-101.

Longleaf Alliance. 2007. Why longleaf [online]? Available from

http://www.longleafalliance.org/landowners/whylongleaf.htm. [accessed 15 July

2007].

Minogue, P. J., B. R. Zutter, and D. H. Gjerstad. 1988. Soil factors and efficacy of hexazinone

formulations of loblolly pine (Pinus taeda) release. Weed Science 36:399-405.

Noss, R. F. 1989. Longleaf pine and wiregrass: keystone components of an endangered

ecosystem. Natural Areas Journal 9:211-213.

Outcalt, K. W. 1992. Factors affecting wiregrass (Aristida stricta Michx.) cover on uncut and

site prepared sandhills areas in Central Florida. Ecological Engineering 1:245-251.

Outcalt, K. W., M. E. Williams, and O. Onokpise. 1999. Restoring Aristida stricta to Pinus

palustris ecosystems on the Atlantic Coastal Plain, U.S.A. Restoration Ecology 7:262-

270.

Parrott, R. T. 1967. A study of wiregrass (Aristida stricta Michx.) with particular reference to

fire. M.S. Thesis, Duke University, Durham, N.C. 8

Peet, R. K., and D. J. Allard. 1993. Longleaf pine-dominated vegetation of the southern Atlantic

and eastern Gulf Coast region, USA. Proceedings of the Tall Timbers Fire Ecology

Conference 18:45–81.

Schuler, J. L., and D. J. Robison. 2004. Assessing the use of Chopper herbicide for establishing

hardwood plantations on a cutover site. Southern Journal of Applied Forestry 28:163-

170.

U. S. Department of Agriculture, Farm Service Agency. 2006. Conservation Reserve Program

Longleaf Pine Initiative [online]. Available from

http://www.fsa.usda.gov/Internet/FSA_File/crplongleaf06.pdf. [accessed 5 June 2007].

Van Lear, D. H., W. D. Carroll, P. R. Kapeluck, R. Johnson. 2005. History and restoration of

the longleaf pine-grassland ecosystem: implications for species at risk. Forest Ecology

and Management 211:150-165.

Wigley, T. B., K. V. Miller, D. S. deCalesta, and M. W. Thomas. 2000. Herbicides as an

alternative to prescribed burning for achieving wildlife management objectives. USDA

For. Ser. NE Res. St. Gen Rep. NE-288.

Wilkins, R. N., G. T. Tanner, R. Mulholland and D. G. Neary. 1993. Use of hexazinone for

understory restoration of a successionally-advanced xeric sandhill in Florida. Ecological

Engineering 2:31-48.

CHAPTER 2

WIREGRASS AND OTHER HERBACEOUS SPECIES’ RESPONSE TO HERBICIDE AND

FIRE TREATMENTS

Read, A. S., and S. H. Schweitzer. To be submitted to the Canadian Journal of Forest Research. 10

Introduction

Wiregrass (Aristida stricta Michx. and A. beyrichiana Trin. & Rupr.) is a perennial

bunch grass native to the southeastern United States and an important component of the longleaf

pine (Pinus palustris) ecosystem of the Atlantic Coastal Plain (Gilliam and Platt 1999). It is

considered a keystone species of this ecosystem and extends from southeastern North Carolina

into Georgia, Florida, and westward to Alabama, and Mississippi (Parrott 1967; Clewell 1989;

Duever 1989; Hardin and White 1989; Outcalt et al. 1999). The longleaf pine-wiregrass

ecosystem is one of the most floristically diverse ecosystems in the world (Peet and Allard

1993). Longleaf pine once dominated the Atlantic Coastal Plain from Virginia to Texas, yet

today it occupies less than 3% of the original area. Estimates of its original extent vary, but current data suggest that it covered approximately 28 - 37 million hectares. The amount of loss of this ecosystem makes it one of the most endangered ecosystems in the world (Noss 1989; Peet and Allard 1993; Landers et al. 1995).

The longleaf pine-wiregrass ecosystem is fire-maintained (Clewell 1989; Noss 1989).

Frequent, low-intensity fire mineralizes the organic components of soil, enhances seed-soil contact, and reduces competition between herbaceous and hardwood species. Natural stands of

longleaf pine depend on grasses as fine fuel that carries fire. The proliferation of wiregrass is

dependent on fire because wiregrass only enters a reproductive state when burned during the

growing season (Parrott 1967).

Land managers in this region recognize the need for fire and commonly burn during

winter when it is cooler and more humid to minimize risk and potential liability. Cool-season

burns reduce survival and growth of hardwood species, and enhance vegetative proliferation of wiregrass clumps. However, due to concern about air quality, smoke management, and property 11

damage from escaped fires, use of prescribed fire is declining. For example, outdoor burning was identified in 2007 by the Georgia Environmental Protection Division (EPD) as a significant

source of ozone and was restricted in 54 counties.

Enhancing communities of wiregrass and other herbaceous species cannot rely on

removal of competing hardwoods by tractors and various implements because wiregrass is

intolerant of soil disturbance (Clewell 1989; Outcalt 1992). In fact, destructive logging practices

and intensive agriculture are primary factors affecting wiregrass communities (Clewell 1989).

Managers of pine plantations across the South commonly use herbicides. Herbicide use

has been investigated as an alternative tool to restore longleaf pine-wiregrass communities

(Wilkins et al. 1993; Boyd et al. 1995; Brockway et al. 1998; Brockway and Outcalt 2000).

Herbicides control hardwood species and do not disturb the soil. Also, herbicides may enhance

the effects of prescribed burns (Brockway and Outcalt 2000; Wigley et al. 2000).

In this study, our objective was to examine the effects of two herbicides, hexazinone

(Velpar-L; E. I. du Pont de Nemours and Company, Wilmington, DE) and imazapyr (Chopper;

BASF Corporation, Research Triangle Park, N.C.), with and without fire, on the regeneration of

wiregrass and associated herbaceous plant species. We expected that treatments would differ in

their effect on groundcover vegetation, that the combination of fire and herbicide would better

control competition from hardwood species and promote regeneration of wiregrass and

associated herbaceous groundcover vegetation. Many of the native plant species associated with

this ecosystem are fire-dependent.

Study Area

Our study area was Yuchi Wildlife Management Area (WMA), a 3,157-ha WMA owned

and managed by the Georgia Department of Natural Resources (GA DNR). Yuchi WMA is 12

located in the sandhills ecological region of eastern Georgia, USA, abutting the Savannah River,

o o 35.4 km from Waynesboro (33 6.122` N, 82 1.041` W). Sandhills are characterized by low-

nutrient soils comprised primarily of deep, droughty sand (U.S. Environmental Protection

Agency 2007). Dominant plants typical of this community include longleaf pine, wiregrass, and turkey oak (Quercus laevis) (Sorrie 2006). Thirty-year mean monthly air temperatures range from a high of 33.2 C in July, to a low of 0.6 C in January. Average mean monthly precipitation

is 9.7 cm, with peak rainfall months in March (11.7 cm) and August (11.7 cm). Drought

conditions were prevalent during June – October 2006 with precipitation falling to 0.18 cm in

July, 0.67 cm in September, and 0.75 cm in October (Southeast Regional Climate Center 2007).

Prior to the 1960s, the WMA was a longleaf pine-wiregrass ecosystem with areas cleared

for grazing, pastures, and small agricultural plots. Small tracts of land (approximately 80 ha)

remained in longleaf and shortleaf pine with scrub oaks interspersed (V. van Sant personal

communication, 2007). Fire was excluded from these tracts. In the late 1960s, the Kimberly-

Clark Corporation bought the land for its timber resources. The trees were clearcut, followed by

mechanical site preparation for re-planting. A root rake was used to pile the logging debris into

windrows, and then windrows were burned. Loblolly and slash pine was machine planted. The

GA DNR acquired the land in 1988.

We selected three study sites located on upper slopes or ridges of xeric sandhill scrub

terrain. Naturally occurring remnant stands of wiregrass and associated species, such as bear

grass (Nolina georgiana), bluecurls (Trichostema dichotomum), gopher apple (Licania

michauxii), and many species of legumes (Fabaceae), were located throughout the WMA.

Materials and Methods

We selected three study sites within Yuchi WMA, each clearcut between October 2003 and February 2004, then hand-planted with container-grown longleaf pine seedlings, at a rate of

1600 trees/ha in November 2004. We delineated each site into 18 0.25-ha plots to which we

randomly-assigned treatments. Each of six treatments was replicated three times within each

site. A 3-m buffer created by plowed fire lines or undisturbed vegetation, separated plots.

Treatments were applications of hexazinone herbicide with and without fire, imazapyr herbicide with and without fire, fire only, and a control (no treatment). In June 2005, hexazinone (Velpar-

L) was applied by broadcast spray from a tank on an all-terrain vehicle (ATV) at 7 L/ha mixed with 233.7 L/ha of water. Imazapyr (Chopper) was broadcast-sprayed from a tractor in

September 2005, at 3.5 L/ha mixed with 374 L/ha. A backing fire was applied in February 2006.

Data were collected during October 2005 (fall), before application of the fire treatment, and

June (spring), August (summer), and October 2006 (fall). In each plot, we estimated the horizontal cover (%) of plant species (grasses, forbs, woody species, bare ground, and debris or plant litter) within 1-m2 square frames, and placed estimates into categories of the Braun-

Blanquet cover scale: 0 – no cover; 1 - <5%; 2 - 5-25%; 3 - 25-50%; 4 - 50-75%; and 5 - >75%

(Bonham 1989). We used a Robel pole to measure vertical height (Robel et al. 1970). A

vegetation profile board was used to estimate percentage of vertical cover in 0.5-m increments,

up to 2.5 m (Nudds 1977). We used a point-step method to estimate frequency of occurrence of

plant species (Owensby 1973). Plant species, bare ground, litter, woody debris, or rocks were

recorded at 25 points distributed evenly along four straight-line transects traversing each plot (n

= 100 points per plot). Diversity of plant communities was quantified with the Shannon-Wiener

Index (H'): 14

n H' = -∑ Pi ln Pi i=1

where Pi was the number of species detected in plot i, divided by total number of species

detected in study area and n = 54 plots. Species richness (S) was a count of the number of

species detected from all plots (i = 1,…,54). Evenness was: E = H/ln(S) (Odum 1971). Plants

were identified to genus and species (Radford et al. 1968; Porcher 1995; Miller and Miller 1999)

and taxonomy reported followed U.S. Department of Agriculture Plants Database 2007. Plant

species detected during the point-step method were ranked by significance on a scale developed

with N. A. Klaus, L. Kruse, and M. Moffett of the GA DNR: 2 = characteristic of a healthy

sandhill community; 1 = can be found on sandhills as well as other areas; 0 = neutral or

disturbance prone species that should not be problematic and diminish as soon as climax species

take hold; -1 = generally offsite or exotic, may be problematic; -2 = offsite and an indication that fire has been suppressed or other imbalance, may be problematic to recovery of sandhill ecosystem (Appendix A).

We used a nested design and analysis of variance (ANOVA) to detect differences in

response variables among treatments, with significance set at P < 0.05. If differences were

detected, we used Tukey’s honestly significant difference multiple comparison test (Dowdy et al.

2004) to identify them. We used SAS 9.1 (SAS Institute Inc. 2004) for all statistical analyses.

Percentage data from vertical cover estimates were arcsin-transformed before analyses (Dowdy

et al. 2004). We used a repeated measures analysis on each measurement to examine trends

across time (Scheiner and Gurevitch 2001). 15

Results

During October 2005, the horizontal cover of woody species was greater in imazapyr-

only treatments than that in the hexazinone-only treatment (P = 0.04; Table 1). During October

2006, horizontal cover of woody species in hexazinone treatments was less (P = 0.04) than fire- only and control treatments.

There was more bareground (P = 0.02) in the imazapyr-with-fire treatment than the imazapyr-only and control treatments during June 2006 (Table 1).

Horizontal of forbs during August 2006 was greater (P = 0.006) in imazapyr-with-fire and imazapyr-only treatments than in hexazinone-only treatment (Table 1).

During June 2006, plant height was greater (P = 0.02) in the control treatment than imazapyr-only treatment. Plant height was similar among all treatments in October 2005, and

August and October 2006 (Table 2).

The vertical cover in October 2005 was greater at the 0 – 0.5-m increment in imazapry- only and control treatments than in hexazinone-only. In June 2006, vertical cover in the 0 – 0.5- m increment was greater (P = 0.002) in fire-only and control treatments than in imazapyr-with fire and imazapyr-only treatments (Table 3).

In the 0.5 – 1.0-m increment during June 2006, percentage vertical cover was greater (P <

0.0001) in the control treatment, than in the imazapyr-with-fire, imazapyr-only, hexazinone- with-fire, and hexazinone-only treatments. Percentage vertical cover was greater in fire-only and hexazinone-only treatments than in imazapyr-with-fire and imazapyr-only treatments. By

August 2006, percentage of vertical cover was greater (P = 0.04) in the control treatments than in the imazapyr-only treatment. Vertical cover for October 2006 at the 0.5 – 1.0-m increment did not differ among treatments (Table 3). 16

In the 1.0 – 1.5-m increment, in June 2006, the percentage of vertical cover was lower (P

# 0.001) in imazapyr-with-fire, imazapyr-only, and hexazinone-with-fire treatments than in fire-

only and control treatments. In August 2006, the percentage of vertical cover was greater (P =

0.01) in control treatments than in imazapyr-with-fire and imazapyr-only treatments (Table 3).

In the 1.5 – 2.0-m interval, the percentage of vertical cover was greater (P = 0.01) in

control treatment than in the imazapyr-with-fire in June 2006 (Table 3).

During October 2005, plant diversity was greater (P = 0.026) in the control than in the

hexazinone-only treatment. By June 2006, plant species diversity was lower (P = 0.0001) in the

imazapyr-only treatment than in fire-only, control, hexazinone-with-fire, and hexazinone-only

treatments. Plant species diversity estimates did not differ among treatments during August 2006

and October 2006 (Table 4).

During October 2005, June 2006, and August 2006 plant species rankings were not

different among treatments. In October 2006, the plant species mean ranks from hexazinone-

with-fire and hexazinone-only treatments were greater (P = 0.002) than those from imazapyr-

with-fire, and imazapyr-only treatments. Plant species characteristic of the sandhill community

were more numerous in hexazinone-with-fire and hexazinone-only treatments. Plant species

rankings in the imazapyr treatments were similar to those from the fire-only treatment (Table 5).

Species richness (N0) was similar among all treatments throughout the study. However,

in October 2005, evenness was greater (P = 0.01) in imazapyr-only and control treatments than in hexazinone-only treatments. In June 2006, evenness was greater (P = 0.001) in fire-only and control treatments than imazapyr-with-fire and imazapyr-only treatments (Table 6).

Because fire was applied in February 2006, the repeated measures analyses separated the

without-fire treatments from the with-fire treatments. Imazapyr-only, control, and hexazinone- 17

only treatments were analyzed and compared October 2005 through October 2006. Imazapyr-

with-fire, fire-only, and hexazinone-with-fire were analyzed and compared June 2006 through

October 2006. The without-fire results indicated season had a significant effect on horizontal

cover of grass, forb, and bare ground (P = 0.006, 0.007, 0.005, respectively). Treatment and

season had significant effects (P = 0.05, 0.02, respectively) on plant height. Season had a

significant effect on the vertical cover of the plant species within 0 – 0.5-m and 1.5 – 2.0-m (P =

0.04, 0.005, respectively) increments. Within the 0.5 – 1.0-m and 1.0 – 1.5-m increments, the

between-subjects effect was significant (P = 0.02, 0.003, respectively). There was no significant

time-by-treatment interaction in the analysis of vertical cover. There were significant seasonal

(P = 0.01) and time-by-treatment (P = 0.001) interactions in the analysis of plant species

diversity.

Analyses of with-fire treatments detected that season had a significant effect on

horizontal cover of grass (P = 0.03) and bare ground (P = 0.004), and on plant height (P =

0.001). Vertical cover in the 0 – 0.5-m increment was affected by season (P = 0.012) and had a

significant time-by-treatment interaction (P = 0.02). Within the 0.5 – 1.0-m and 1.0 – 1.5-m increments, treatment (P = 0.002, 0.02, respectively) and season (P = 0.004, 0.02, respectively)

had significant effects. Season significantly affected plant species diversity (P = 0.01).

Discussion

In our study, we examined the effects of hexazinone (Velpar-L) and imazapyr (Chopper),

with and without fire, on wiregrass and associated herbaceous groundcover vegetation.

Hexazinone was applied in June 2005, imazapyr was applied in September 2005, and prescribed

fire was applied in February 2006 (Figure 1). The October 2005 results suggest that symptoms

from the imazapyr herbicide application had not had time to appear on the vegetation. By June 18

2006, however, results indicate that imazapyr had affected the vegetation. In August 2006,

horizontal cover of forb species was greatest in imazapyr-with fire and imazapyr-only

treatments. We identified legumes like butterfly pea (Centrosema virginianum), trailing lespedeza (Lespedeza procumbens), and partridge pea (Chamaecrista fasciculata), along with forbs like Baptisia spp., blue curls (Trichostema dichotomum), Liatris spp., and rustweed

(Polyprenum procumbens) in the imazapyr-with-fire and imazapyr-only treatments. Our results support other research that found imazapyr increased percent cover of forb species, with and without fire (Welch et al. 2004).

Horizontal cover of grass species did not differ among treatments throughout the study.

However, wiregrass was present in each treatment for each season. After application of fire in

February 2006, the frequency of occurrence of wiregrass was lower in imazapyr-with-fire, fire- only, and hexazinone-with-fire than in the without-fire treatments for June, August, and October

2006. Wiregrass is usually released by herbicide-with-fire treatments, but we detected decreased

frequency of occurrence of wiregrass in these treatments. Fire was applied less than one year

before these sampling dates and the initial decline of wiregrass after a cool winter burn could explain these results. The combination of herbicide-with-fire has been found to enhance the effects of fire and could also explain the lower frequency of occurrence of wiregrass in the herbicide-with-fire treatments. Wiregrass may take up to five years to show a significant increase after herbicide treatment (Brockway and Outcalt 2000). Andropogon species were also less frequent in the with-fire treatments until October 2006, when the frequency of Andropogon species in the with-fire treatments was equal to or greater than that in the without-fire treatments.

Graminoid species show a decrease in percent horizontal cover the first year post-treatment, and 19

then recover rapidly during ensuing growing seasons (Brockway et al.1998; Brockway and

Outcalt 2000; Wilkins et al. 1993).

In August and October 2006, longleaf pine seedling frequency of occurrence in the hexazinone-with-fire and hexazinone-only treatments was three times that in the imazapyr-with-

fire and imazapyr-only treatments. The longleaf seedlings were planted at a high rate of 1600

trees/ha. Longleaf pine seedlings are sensitive to competition and also self-competing (Boyer

2007). This dense rate of planting may have caused some mortality, but it does not explain the

difference in numbers between the hexazinone and imazapyr treatments. The emulsifying agent

in Chopper may have damaged the 1-year-old longleaf pine seedlings because it was broadcast-

sprayed from an ATV (BASF Corp. 2004). Spot-application of imazapyr would offer control of

application to avoid damage to the longleaf seedlings while providing control of hardwood

species. Exposure to the herbicide by wiregrass and other herbaceous species would be

minimized reducing risk of damage and increasing species diversity and richness (Brockway and

Outcalt 2000).

Quercus species frequency of occurrence was greater in the hexazinone treatments, with

and without fire, than in the imazapyr treatments, with and without fire in October 2006.

Hexazinone was applied on 2 June 2005. This date is somewhat late for application of Velpar-L

herbicide. For best results, application should occur before hardwood buds have broken and

before foliage has hardened (du Pont de Nemours and Company 2005). However, Rubus species

frequency of occurrence was three to five times greater in imazapyr-with-fire and imazapyr-only

treatment applications than in the hexazinone-with-fire and hexazinone-only treatments during

all seasons. In June 2006, evenness was greater in fire-only and control treatments than in

imazapyr-with-fire and imazapyr-only treatments. Imazapyr, with and without fire, releases 20

Rubus species and decreases plant species diversity (Welch et al. 2004). An abundance of Rubus species would compete with wiregrass, longleaf pine seedlings, and other plant species in these plots decreasing species evenness. In imazapyr-with-fire, diversity increased over time, but not necessarily the species desired in the sandhill community. The plant ranking analysis detected that hexazinone-with-fire and hexazinone-only had more species characteristic of the sandhill community in October 2006 than either imazapyr-with-fire or imazapyr-only treatments.

We rejected our hypothesis that treatments would differ in their effect on wiregrass and associated herbaceous groundcover vegetation, that the combination of fire and herbicide would better control competition from hardwood species and promote regeneration of wiregrass and associated herbaceous groundcover vegetation. Due to time constraints, pre-treatment sampling was not possible for this study, but it would have made it possible to verify increases or decreases in horizontal cover, plant height, vegetation cover and species diversity the first year post-treatment. For example, the similarity in plant height, vegetative cover, and plant species diversity among all treatments in October 2006 could be an effect of drought conditions during

June through October 2006. It is possible that these drought conditions affected vegetation recovery time and a pre-treatment sampling would help to verify the results. Also, the timing of the treatment applications makes it difficult to compare the results of the herbicide treatments, with and without fire. The last sampling data were collected 15 months after the hexazinone application, one year after the imazapyr application and, eight months after the prescribed burn

(Figure 1). Based on the length of other, similar studies, and recommendations for future studies, data collection should continue for two to five years post-treatment (Boyd et al. 1995;

Brockway et al. 1998; Brockway and Outcalt 2000; Miller and Miller 2004; Lautenschlager and

Sullivan 2004). Further data collection is needed to fully understand the effects of hexazinone 21 and imazapyr, with and without fire, on the response of wiregrass and other herbaceous plant species.

Acknowledgments

The Georgia Department of Natural Resources (GA DNR), Wildlife Resources Division; and the BASF Corporation provided funding for this research. Much in-kind support was provided by the Warnell School of Forestry and Natural Resources. We thank N. A. Klaus, I. B.

Parnell, and L. A. Isler with GA DNR for project design and field assistance; D. C. Wardlaw with BASF Corporation for outreach support; L. Kruse and M. Moffett with GA DNR for plant species ranking development; and M. Murphy, J. Keenan, J. D. Van Dijk, J. S. Manangan, M. L.

McElroy, L. A. Loke, D. Gammon, and E. Wright of the Warnell School of Forestry and Natural

Resources, University of Georgia, for assistance in the field.

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Table 1. Horizontal cover (Braun-Blanquet cover scale) of woody plant species, bare ground, and forb species measured within 1-m2 square frames at Yuchi WMA, Burke County, Georgia, USA, from October 2005 through October 2006.

October 2005 June 2006 August 2006 October 2006 Treatment Mean1 s.d.2 Mean s.d. Mean s.d. Mean s.d. Woody species Imazapyr-with-fire3 1.26 0.61 1.52 0.32 1.22 0.56 Imazapyr-only 1.86 A 0.14 1.37 0.06 1.15 0.61 1.59 0.57 Fire-only 2.37 0.46 1.74 0.36 1.63 0.23 Control 1.83 AB 0.23 2.15 0.52 2.07 0.39 1.63 0.39 Hexazinone-with-fire 1.67 0.19 0.96 0.51 0.56 0.62

Hexazinone-only 1.16 B 0.40 1.67 0.88 1.67 0.40 0.78 0.11 Bare ground Imazapyr-with-fire 3.96A 0.23 2.78 0.19 2.11 0.68 Imazapyr-only 1.17 0.32 1.48B 0.57 2.04 1.12 1.67 0.22 Fire-only 2.56AB 0.48 2.52 0.94 1.63 0.39 Control 1.30 0.58 1.56B 0.40 1.67 0.88 1.74 0.71 Hexazinone-with-fire 2.81AB 1.33 2.93 0.61 1.89 0.40

Hexazinone-only 1.66 0.71 2.59AB 1.00 1.67 0.22 1.85 0.78 Forb species Imazapyr-with-fire 0.48 0.06 0.70 A 0.17 0.67 0.22 Imazapyr-only 1.22 0.50 0.19 0.06 0.67 A 0.11 0.59 0.42

Fire-only 0.56 0.11 0.59 AB 0.28 0.63 0.13 Control 1.24 0.55 0.44 0.44 0.22 AB 0.11 0.37 0.23 Hexazinone-with-fire 0.3 0.13 0.52 AB 0.23 0.7 0.65

Hexazinone-only 0.57 0.75 0.26 0.36 0.11 B 0 0.59 0.46 1Means within seasons followed by the same or no letter were not different (P > 0.05; Tukey’s honestly significant difference multiple comparison test). 2 s.d. = standard deviation. 3The fire (prescribed burn) treatment was applied during February 2006. 27

Table 2. Plant height (dm) measured with a Robel pole at Yuchi WMA, Burke County, Georgia, USA, from October 2005 through October 2006.

October 2005 June 2006 August 2006 October 2006

Treatment Mean1 s.d.2 Mean s.d. Mean s.d. Mean s.d.

Imazapyr-with-fire3 0.97 AB 0.77 2.70 AB 1.63 5.63 1.35 Imazapyr-only 5.80 1.67 0.88 B 0.21 2.14 B 1.28 4.93 1.02 Fire-only 4.06 AB 1.74 3.75 AB 0.66 6.32 0.26 Control 6.47 1.58 4.72 A 2.54 5.28 A 0.92 5.94 0.84 Hexazinone-with-fire 1.90 AB 0.74 3.33 AB 0.60 5.60 1.16 Hexazinone-only 3.96 0.34 2.85 AB 0.80 3.28 AB 0.99 5.55 0.52

1At P < 0.05, means followed by the same or no letter did not differ among treatments within each season (Tukey’s honestly significant difference multiple comparison test). 2 s.d. = standard deviation. 3The fire (prescribed burn) treatment was applied during February 2006.

Table 3. Vertical cover (%) of vegetation measured within the 0-0.5-m, 0.5-1.0-m, 1.0-1.5-m, and 1.5-2.0-m increments of a 2.5-m vegetation profile board at Yuchi WMA, Burke County, Georgia, USA, from October 2005 through October 2006.

October 2005 June 2006 August 2006 October 2006

Treatment Mean1 s.d.2 Mean s.d. Mean s.d. Mean s.d. 0 - 0.5-m Imazapyr-with-fire3 33 B 6 45 9 74 29 Imazapyr-only 70 A 15 31 B 9 42 15 67 17 Fire-only 70 A 16 56 11 72 8 Control 80 A 13 64 A 7 55 8 66 16 Hexazinone-with-fire 43 AB 6 51 0.3 81 18

Hexazinone-only 61 B 7 52 AB 12 47 9 69 9 0.5 - 1.0-m Imazapyr-with-fire 3 D 5 20 AB 8 36 8 Imazapyr-only 40 15 9 D 4 15 B 12 31 9 Fire-only 38 AB 6 32 AB 6 40 7 Control 49 14 46A 4 40 A 5 36 12 Hexazinone-with-fire 19CD 6 22 AB 7 39 3

Hexazinone-only 33 7 29 BC 10 27 AB 10 32 7

Table 3. Continued.

October 2005 June 2006 August 2006 October 2006

Treatment Mean1 s.d.2 Mean s.d. Mean s.d. Mean s.d.

1.0 - 1.5-m Imazapyr-with-fire3 0 C 0 7 B 8 14 3 Imazapyr-only 25 12 2 C 3 2 B 3 11 5 Fire-only 25 A 6 18 AB 6 26 8 Control 29 16 35 A 6 28 A 7 28 12 Hexazinone-with-fire 9 BC 8 9 AB 10 16 3

Hexazinone-only 19 5 23 AB 3 18 AB 8 11 9

1.5 - 2.0-m Imazapyr-with-fire 0 B 0 5 8 4 4 Imazapyr-only 35 19 4 AB 7 2 3 2 2 Fire-only 17 AB 6 7 12 11 3 Control 38 29 22 A 8 16 14 21 8 Hexazinone-with-fire 8 AB 8 12 7 9 1

Hexazinone-only 21 10 16 AB 8 9 8 11 5

1At P < 0.05, means followed by the same or no letters did not differ among treatments within each season (Tukey’s honestly significant difference multiple comparison test). 2 s.d. = standard deviation. 3The fire (prescribed burn) treatment was applied during February 2006.

Table 4. Plant species diversity (H’ = Shannon-Wiener index) estimated seasonally relative to six treatments at Yuchi WMA, Burke County, Georgia, USA.

October 2005 June 2006 August 2006 October 2006 Treatment Mean1 s.d.2 Mean s.d. Mean s.d. Mean s.d.

Imazapyr-with-fire3 1.75 BC 0.09 2.22 0.24 2.39 0.19 Imazapyr-only 2.40 AB 0.20 1.62 C 0.09 2.06 0.11 2.20 0.16 Fire-only 2.37 A 0.10 2.52 0.24 2.59 0.25 Control 2.52 A 0.39 2.44 A 0.30 2.56 0.25 2.46 0.23 Hexazinone-with-fire 2.11 AB 0.14 2.22 0.25 2.39 0.31 Hexazinone-only 1.78 B 0.23 2.05 AB 0.04 2.18 0.24 2.33 0.11

Table 5. Plant species ranking developed with the Georgia Department of Natural Resources, Wildlife Resources Division, estimated seasonally relative to six treatments at Yuchi WMA, Burke County, Georgia, USA. 2 = characteristic of a healthy sandhill community; 1 = can be found on sandhills as well as other areas; 0 = neutral or disturbance prone species that should not be problematic and diminish as soon as climax species take hold; -1 = generally offsite or exotic, may be problematic; -2 = offsite and an indication that fire has been suppressed or other imbalance, may be problematic to recovery of sandhill ecosystem.

October 2005 June 2006 August 2006 October 2006 Treatment Mean1 s.d.2 Mean s.d. Mean s.d. Mean s.d.

Imazapyr-with-fire3 0.26 0.18 0.48 0.28 0.52 BC 0.16 Imazapyr-only 0.43 0.33 0.22 0.30 0.33 0.26 0.42 C 0.14 Fire-only 0.24 0.22 0.46 0.11 0.76 ABC 0.13 Control 0.42 0.29 0.43 0.15 0.67 0.09 0.84 AB 0.16 Hexazinone-with-fire 0.26 0.07 0.49 0.06 0.97 A 0.11 Hexazinone-only 0.97 0.52 0.45 0.14 0.69 0.11 0.93 A 0.15

Table 6. Plant species evenness estimated seasonally relative to six treatments at Yuchi WMA, Burke County, Georgia, USA.

October 2005 June 2006 August 2006 October 2006 Treatment Mean1 s.d.2 Mean s.d. Mean s.d. Mean s.d.

Imazapyr-with-fire3 0.57 B 0.04 0.70 0.01 0.75 0.01 Imazapyr-only 0.71 A 0.04 0.55 B 0.05 0.66 0.05 0.68 0.02 Fire-only 0.72 A 0.05 0.75 0.03 0.76 0.04 Control 0.74 A 0.05 0.73 A 0.05 0.77 0.07 0.74 0.03 Hexazinone-with-fire 0.65 AB 0.05 0.67 0.07 0.74 0.04 Hexazinone-only 0.57 B 0.05 0.63 AB 0.03 0.68 0.06 0.72 0.01

Time line

Chopper Summer 2006 application Fire sampling Fall 2005 Velpar-L application Spring 2006 Fall 2006 sampling application sampling sampling

June 2005 October 2005 June 2006 October 2006 September 2005 February 2006 August 2006

Figure 1. Timeline showing dates of treatment applications and data collection at Yuchi WMA, Burke County, Georgia, USA, October 2005 through October 2006. 34

CHAPTER 3

CONCLUSION

The primary objective of this project was to examine the effects of two herbicides,

hexazinone (Velpar-L) and imazapyr (Chopper), with and without fire, on the regeneration of

wiregrass and the associated herbaceous groundcover plant community. We expected that

treatments would differ in their effect on groundcover vegetation. Also, we expected that the

combination of herbicide with fire would better control competition from hardwood species and

promote regeneration of wiregrass and associated vegetation. Much of the associated herbaceous

vegetation of this ecosystem is fire-dependent like wiregrass. Herbicides can obtain some of the

ecological effects of fire, but they cannot clear litter and debris that are important for the

regeneration of longleaf pine.

Three sites were selected at Yuchi WMA in the sandhills ecological region of Georgia.

The sites were divided into 18 0.25-ha plots and vegetation was measured for percent horizontal

cover, height, structure, and diversity over a 1-year period from October 2005 to October 2006.

Plant species were identified and ranked by significance on a scale developed with the Georgia

Department of Natural Resources, Wildlife Resources Division. Hexazinone was applied to

randomly selected plots in June 2005, imazapyr was applied to randomly selected plots in

September 2005, and in February 2006, and a backing fire was applied.

Data were analyzed using a nested ANOVA design to test our objectives. A repeated

measures ANOVA was used to evaluate time and treatment effects and interactions (Scheiner

and Gurevitch 2001). Based on the results we reject the hypothesis that plant treatments would

differ in their effect on groundcover vegetation. 35

We concluded that data collection and analyses conducted over a period of 2 – 5 years

post-treatment are needed to understand the effects of the herbicides, hexazinone (Velpar-L) and

imazapyr (Chopper), on the vegetation of this xeric sandhill scrub ecosystem (Lautenschlager

and Sullivan 2004; Miller and Miller 2004). At the time of the last data collection, it had only

been 8 months since the application of fire to selected plots. Wiregrass and other native groundcover species recover quickly after fire, but it may take up to 5 years for these species to respond to herbicide treatment (Brockway and Outcalt 2000). This ecosystem is fire dependent and the use of fire, with and without herbicide, is needed to maintain the biodiversity (Parrot

1967; Clewell 1989; Peet and Allard 1993; Landers 1995). Fire should be applied every two or three years to promote wiregrass reproduction and regeneration of fire-adapted herbaceous species. Fire in combination with herbicide may give us the desired response from the native vegetation.

Some species, like Rubus, are released by the herbicide imazapyr. A tank mix of herbicides in combination with fire may be necessary to control the growth and competition from

Rubus species and maintain a diverse ecosystem. Spot-application of imazapyr, instead of applying a broadcast spray, would selectively control hardwood species and avoid damage to year-old longleaf pine seedlings, wiregrass, and herbaceous species. The effects of hexazinone and imazapyr on plant species growth and response may have been affected by the drought conditions during 2006. Further long-term research on herbaceous plant species response to hexazinone, imazapyr, and fire is needed.

Our goal was to develop a land management protocol for state agencies, land managers, and landowners for the establishment and maintenance of the longleaf pine-wiregrass ecosystem.

To achieve this goal, more investigation is needed to fully understand the effects of hexazinone 36

(Velpar-L) and imazapyr (Chopper), with and without fire, on the response of wiregrass and

other herbaceous plant species.

References

Brockway, D. G., and K. W. Outcalt. 2000. Restoring longleaf pine wiregrass ecosystems:

Hexazinone application enhances effects of prescribed fire. Forest Ecology and

Management 137:121-138.

Clewell, A. F. 1989. Natural history of wiregrass (Aristida stricta Michx., Gramineae). Natural

Areas Journal 9:223-233.

Landers, J. L., D. H. Van Lear, and W. D. Boyer. 1995. The longleaf pine forests of the

Southeast: Requiem or Renaissance. Journal of Forestry 93:39-44.

Lautenschlager, R. A. and T. P. Sullivan. 2004. Improving research into effects of forest

herbicide use on biota in northern ecosystems. Wildlife Society Bulletin 32:1061-1069.

Miller, K. V., and J. H. Miller. 2004. Forestry herbicide influences on biodiversity and wildlife

habitat in southern forests. Wildlife Society Bulletin 32:1049-1060.

Parrott, R. T. 1967. A study of wiregrass (Aristida stricta Michx.) with particular reference to

fire. Master's Thesis, Duke University, Durham, N.C.

Peet, R. K., and D. J. Allard, 1993. Longleaf pine-dominated vegetation of the southern Atlantic

and eastern Gulf Coast region, USA. Proceedings of the Tall Timbers Fire Ecology

Conference 18:45–81.

Scheiner and Gurevitch. 2001. Design and analysis of ecological experiments. Oxford

University Press, Oxford, NY.

APPENDIX A. List of plant species and their ranking as developed with N. A. Klaus, L. Kruse, and M. Moffett of the Georgia Department of Natural Resources, Wildlife Resources Division, estimated seasonally relative to six treatments at Yuchi WMA, Burke County, Georgia, USA. 2 = characteristic of a healthy sandhill community; 1 = can be found on sandhills as well as other areas; 0 = neutral or disturbance prone species that should not be problematic and diminish as soon as climax species take hold; -1 = generally offsite or exotic, may be problematic; -2 = offsite and an indication that fire has been suppressed or other imbalance, may be problematic to recovery of sandhill ecosystem (Radford et al. 1968; Porcher 1995; Miller and Miller 1999).

FAMILY SCIENTIFIC NAME RANK Agavaceae Yucca filamentosa L. 2 Amaranthaceae Froelichia floridana (Nutt.) Moq. 1 Anacardiaceae Toxicodendron radicans (L.) Kuntze -1 Toxicodendron pubescens P. Mill. 1 Rhus copallina L. -1 Apocynaceae Amsonia ciliata Walt. 2 Apocynum cannabinum L. 0 Aquifoliaceae Ilex vomitoria Ait. 0 Aspleniaceae Asplenium platyneuron (L.) B.S.P. 0 Asteraceae Aster L. 1 Bidens bipinnata L. 1 Liatris elegans (Walt.) Michx. 2 Eupatorium rotundifolium L. 1 Heterotheca subaxillaris (Lam.) Britt. & Rusby 0 Rudbeckia hirta L. 1 Coreopsis major Walt. 1 Pseudognaphalium obtusifolium (L.) Hilliard & Burtt -1 Eupatorium capillifolium (Lam.) Small -1 Elephantophus tomentosus L. 0 Erechtites hieracifolia (L.) Raf. Ex DC. 0 Solidago L. 1 Vernonia acaulis (Walt.) Gleason 0 Liatris spicata (L.) Willd. var. resinosa (Nutt.) Gaiser 2 Liatris pilosa (Ait.) Willd. var. pilosa 2 Ambrosia artemisiifolia L. 0 Silphium compositum Michx. 2 Helianthus L. 1 Cirsium repandum Michx. 1 Eupatorium compositifolium Walt. 0 Bignoniaceae Campsis radicans (L.) Seem. ex. Bureau 0 Buddlejaceae Polyprenum procumbens L. 1 38

Appendix A. Continued.

FAMILY SCIENTIFIC NAME RANK Cactaceae Opuntia humifusa (Raf.) Raf. 2 Caprifoliaceae Lonicera japonica Thunb. -2 Chrysobalanaceae Licania michauxii Prance 2 Cladoniaceae Cladonia evansii (Abbayes) Hale & Culb. 1 Clusiaceae Hypericum gentianoides (L.) B.S.P. 0 Hypericum hypericoides (L.) Crantz 1 Commelinaceae Commelina erecta L. 1 Callisa rosea (Vent.) D.R. Hunt 1 Convolvulaceae Stylisma patens (Desr.) Myint ssp. patens 2 Cupressaceae Juniperus virginiana L. -1 Cyperaceae Cyperus retrorsus Chapman 1 Scleria triglomerata Michx. 0 Dennstaedtiaceae Pteridium aquilinum (L.) Kuhn 0 Ebenaceae Diospyros virginiana L. -1 Ericaceae Vaccinium stamineum L. 1 Gaylussacia dumosa (Andr.) Torr. & Gray 2 Vaccinium arboreum Marsh. 1 Lyonia mariana (L.) D. Don -1 Euphorbiaceae Euphorbia ipecacuanhae L. 1 Croton glandulosus var. septentrionalis Muell.-Arg. -1 Euphorbia corollata L. 1 Stillingia sylvatica L. 2 Cnidoscolus urens (L.) Arthur var. stimulosus (Michx.) Govaerts 1 Acalypha gracilens Gray 0 Fabaceae Centrosema virginianum (L.) Benth. 1 Rhynchosia reniformis DC. 2 Tephrosia virginiana (L.) Pers. 2 Baptisia perfoliata (L.) R. Br. Ex Ait. f. 2 Lespedeza hirta (L.) Hornem. 2 Desmodium strictum (Pursh) DC. 2 Galactia volubilis (L.) Britt. 2 Chamaecrista fasciculata (Michx.) Greene 1 Baptisia cinerea (Raf.) Fern. & Schub. 2 Mimosa quadrivalvis L. 1 Lespedeza cuneata (Dum.-Cours.) G.Don -2 Desmodium laevigatum (Nutt.) DC. 1 39

Appendix A. Continued.

FAMILY SCIENTIFIC NAME RANK Rhynchosia tomentosa (L.) Hook. & Arn. 1 Lespedeza procumbens Michx. 1 Strophostyles umbellata (Muhl. ex. Willd.) Britt. 1 Fagaceae Quercus marilandica 1 Quercus incana Bartr. 2 Quercus pumila Walt. 2 Quercus laevis Walt. 2 Hamamelidaceae Liquidambar styraciflua L. -2 Iridaceae Iris verna L. 1 Juglandaceae Carya alba (L.) Nutt. Ex Ell. -1 Lamiaceae Trichostema dichotomum L. 1 Lauraceae Sassafras albidum (Nutt.) Nees -1 Liliaceae Nolina georgiana Michx. 2 Loganiaceae Gelsemium sempervirens (L.) Ait. f. 0 Lythraceae Lagerstroemia indica L. -1 Myricaceae Morella cerifera (L.) Small 0 Passifloraceae Passiflora incarnata L. 0 Pinaceae Pinus taeda L. 1 Pinus palustris P. Mill. 2 Poaceae Andropogon virginicus L. 1 Setaria parviflora (Poir.) Kerguelen 1 Sorghum halepense (L.) Pers. -2 Eragrostis hirsuta (Michx.) Nees 1 Dichanthelium acuminatum (Sw.) Gould & C.A. Clark 1 Piptochaetium avenaceum (L.) Parodi 2 Dichanthelium aciculare (Desv. ex Poir.) Gould & C.A. Clark 1 Panicum L. 1 Paspalum floridanum Michx. 1 Aristida purpurascens Poir. 2 Saccharum alopecuroides (L.) Nutt. 2 Cenchrus echinatus L. 0 Andropogon ternarius Michx. 1 Dichanthelium commutatum (J.A. Schultes) Gould 1 Aristida stricta Michx. 2 Polygonaceae Rumex L. -1 Rosaceae Rubus L. -1 40

Appendix A. Continued.

FAMILY SCIENTIFIC NAME RANK Malus angustifolia (Ait.) Michx. 0 Crataegus flava Ait. 1 Prunus L. 1 Rubiaceae Galium aparine L. 0 Diodia teres Walt. 1 Richardia scabra L. 1 Scrophulariaceae Aureolaria pectinata (Nutt.) Pennell 2 Pedicularis canadensis L. 0 Smilacaceae Smilax L. -1 Verbenaceae Callicarpa americana L. 0 Vitaceae Parthenocissus quinquefolia (L.) Planch. 0 Vitis rotundifolia Michx. 0

APPENDIX B. Total plant species abundance by rank relative to six treatments at Yuchi WMA, Burke County, Georgia, USA, from October 2005 through October 2006.

October 2005 Rank Treatment -2-1012 Total

Imazapyr-only 2 231 264 375 387 1259 Control 1 237 288 410 396 1332 Hexazinone-only 0 112 298 160 422 992 Total 3 580 850 945 1205 3583 June 2006 Imazapyr-with-fire 0 122 17 95 47 281 Imazapyr-only 0 133 15 68 61 278 Fire-only 0 169 66 161 71 469 Control 1 133 119 169 97 519 Hexazinone-with-fire 3 98 95 150 25 371 Hexazinone-only 0 65 139 136 50 390 Total 4 720 451 779 351 2308 August 2006 Imazapyr-with-fire 0 136 19 237 62 454 Imazapyr-only 0 171 40 155 79 445 Fire-only 0 136 87 194 90 507 Control 0 100 117 199 129 545 Hexazinone-with-fire 0 78 102 177 53 410 Hexazinone-only 0 46 127 168 83 424 Total 0 667 492 1130 496 2785 October 2006 Imazapyr-with-fire 0 187 18 245 116 566 Imazapyr-only 0 183 43 185 109 520 Fire-only 1 109 65 253 153 581 Control 0 70 121 225 162 578 Hexazinone-with-fire 0 70 92 164 215 541 Hexazinone-only 0 44 158 136 200 538 Total 1 663 497 1208 955 3324