Interactions of insect herbivory and multiple abiotic stress agents on two wetland tree species in

235 Pages·2017·1.48 MB·English

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LSU Doctoral Dissertations Graduate School
2004
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Rebecca Faye Souther-Effler
Louisiana State University and Agricultural and Mechanical College
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Souther-Effler, Rebecca Faye, "Interactions of insect herbivory and multiple abiotic stress agents on two
wetland tree species in southeast Louisiana swamps" (2004). LSU Doctoral Dissertations. 50.
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INTERACTIONS OF INSECT HERBIVORY AND MULTIPLE ABIOTIC STRESS
AGENTS ON TWO WETLAND TREE SPECIES
IN SOUTHEAST LOUISIANA SWAMPS

A Dissertation

Submitted to the Graduate Faculty of the
Louisiana State University and
Agricultural and Mechanical College
in partial fulfillment of the
requirements for the degree of
Doctor of Philosophy

in

The Department of Entomology

by
Rebecca Faye Souther-Effler
B.S. Southeastern Louisiana University, 1998
M.S. Southeastern Louisiana University, 2000
August 2004
In memory of my dear friend

Carrie Lynn Yoder

and all of the other
beautiful, strong, independent women that were
wrongly taken.

ii
ACKNOWLEDGEMENTS

Taking on such a massive project was no easy task. Without the help of so may
people, research of this depth could not have happened. Foremost, I would like to
thank Dr. Richard A. Goyer for providing me with this opportunity to receive my PhD and
taking me as his graduate student. He has always been eager to help me through the
toughest challenges during my time at LSU, such as logistics, physical labor, writing,
and public speaking to name only a few. I honestly believe that he will retire in
September 2004 and I will be his last student, and I feel honored. I would also like to
thank Carolyn Goyer for advice on word usage and punctuation for my dissertation (and
baking cookies, brownies, and the like for us through the years). My husband, Donald
“Ray” Effler, has given me the utmost support and encouragement and has provided me
with the strength necessary to complete this lifetime achievement. I can only imagine
how difficult obtaining this degree would have been without him.
I would like to thank my committee members, Dr. Seth J. Johnson, Dorothy P.
Prowell, and especially Dr. Michael J. Stout for the thought and assistance they lent me
was needed to complete my experiments and their comments on my dissertation
including my outside committee member Dr. Gordon Holcomb. Jerry Lenhard has
helped the greatest in field work, graphics and imaging, and in every aspect of this
project, as well as providing interesting and enjoyable music to the lab as well. My
mother, Peggy McClain, has been a great help, despite her devotion to her own
Master’s degree program in landscape architecture here at LSU. Labmates and student
workers that have made this work accomplishable were Ankit Modi, Wood Johnson, Jay
iii
Curole, Tessa Bauman, Will Shepherd, Brandi, Dee Glass, Brendan Watson, and Anil
Surathu.
Also, I would like to thank Dr. Gary P. Shaffer and the Southeastern Louisiana
University Wetland Research Lab in Hammond, LA for initiating my interest in the Lake
Maurepas Basin as well as for the encouragement they gave me to pursue my PhD.
They were the spark that kindled the flame.
I would like to thank Forest Service - Region-8 Forest Health for providing
funding to accomplish this research and LSU Ag Chemistry for conducting nutrient
analyses. I would also like to thank William Salzer for providing greenhouse space and
assistance for three years of experiments. Field sites were available through landowner
Glen Martin (The Waterfront Properties, Maurepas, LA) and the Manchac Wildlife
Management Area. Also, I would like to thank Jackie “Jacko” Robinson for sharing his
excellent knowledge of waterways in the Lake Maurepas Basin. I would like to thank
the staff at Black Lake Club for looking out for the field crew.

iv
TABLE OF CONTENTS
Acknowledgments........................................................................................................iii

Abstract.......................................................................................................................vii

Chapter 1 Overview..................................................................................................1
1.1 Importance of Forested Wetlands ...........................................................1
1.2 Wetland Restoration Issues in Coastal Louisiana ...................................2
1.3 Lake Maurepas Basin..............................................................................3
1.4 Defoliation in the Swamp.........................................................................5
1.5 Cypress and Tupelo Responses to Abiotic Stressors..............................7
1.6 Plant-Insect Interactions to Stressors....................................................10
1.7 Study Sites in the Lake Maurepas Basin...............................................13
1.8 Objectives..............................................................................................15

Chapter 2 Baldcypress and Water Tupelo Sapling Responses to Defoliation and
Multiple Abiotic Environmental Stressors...............................................16
2.1 Introduction............................................................................................16
2.2 Methods.................................................................................................18
2.3 Statistical Analyses................................................................................24
2.4 Results...................................................................................................29
2.5 Discussion.............................................................................................69

Chapter 3 Forest Tent Caterpillar and Baldcypress Leafroller Responses to Plant
Stress and Phytochemical Parameters..................................................74
3.1 Introduction............................................................................................74
3.2 Methods.................................................................................................79
3.3 Statistical Analyses................................................................................87
3.4 Results...................................................................................................90
3.5 Discussion...........................................................................................116

Chapter 4 Baldcypress and Tupelo Productivity Responses to Insect Herbivory and
Nutrient Augmentation in Lake Maurepas Swamps.............................122
4.1 Introduction..........................................................................................122
4.2 Methods...............................................................................................126
4.3 Statistical Analyses..............................................................................128
4.4 Results.................................................................................................129
4.5 Discussion............................................................................................144

Chapter 5 Foliar Nutrient Cycling Patterns of Fertilized Baldcypress and Tupelo
Trees in Lake Maurepas Swamps .......................................................146
5.1 Introduction..........................................................................................146
5.2 Methods...............................................................................................152
5.3 Statistical Analyses..............................................................................154
5.4 Results.................................................................................................158
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5.5 Discussion..............................................................................................182

Chapter 6 Summary of Tree and Insect Responses to Wetland Environmental
Stressors................................................................................................184
6.1 Baldcypress and Tupelo Responses......................................................184
6.2 Forest Tent Caterpillar and Baldcypress Leafroller Responses..............188
6.3 Swamp Ecosystem Processes ...............................................................190

Literature Cited..........................................................................................................193

Appendix A: Baldcypress Moth Oviposition Experiment............................................208

Appendix B: Preliminary Studies...............................................................................212

Appendix C: Raw Data and Source Tables of Greenhouse Experiments..................213

Vita............................................................................................................................226
vi
ABSTRACT

Abstract: Forested wetlands in Louisiana are hydrologically isolated from the
Mississippi River, impounded by manmade structures, impacted by saltwater intrusion,
and are sinking, resulting in more frequent flooding for longer periods. Additionally,
defoliation of the two dominant trees, baldcypress (Taxodium distichum L. Rich) and
water tupelo (Nyssa aquatica L.), occur frequently during spring. In Louisiana, the
baldcypress leafroller, BCLR, (Archips goyerana Kruse) and the forest tent caterpillar,
FTC, (Malacosoma disstria Hubner) defoliate up to 120,000ha of baldcypress-tupelo
swamps. Restoration plans call for reintroducing Mississippi River water (diversions) to
increase sediment elevation, promote natural regeneration, and enhance primary and
secondary productivity. In this study, insect-tree-health relationships were evaluated in
field and in multifactor, greenhouse and larval rearing experiments incorporating these
environmental stressors and nutrient enhancements under simulated diversion
conditions.
It was ascertained from three field sites of varying tree density/health in Lake
Maurepas swamps that nutrient augmentation (similar to N and P loading rates
expected from 8000cfs diversion) increased stem growth of both tree species (more for
cypress than tupelo) at moderately degraded sites. Nutrient augmentation also
increased nitrogen in foliage, insect frass (insect feces), spring-clipped leaves, and
abscised litterfall at all sites for both tree species. Nitrogen content of canopy foliage
and litterfall was positively correlated with site health. These findings support the
hypotheses that the swamps in Lake Maurepas are nutrient limited, and the existing
trees can utilize, benefit, and act as nutrient sinks for nutrient-laden river water
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accompanying diversions. Positive insect responses to nitrogen found in lab rearing
assays and field studies that defoliators are receiving nitrogen augmentation, and insect
field populations might increase, particularly the FTC.
The greenhouse study demonstrated that the combination of nutrient deprivation
and flooding lead to the “poor” sapling growth, which was similar to the growth in the
salt-stressed (3ppt) saplings. Encouragingly, when fresh water and nutrients were
supplied to saplings after prolonged stresses of defoliation, flooding, and salt stress,
growth was restored. Taken collectively, these studies demonstrated that river
diversions are viable management tools for improving health and productivity of
declining forested wetlands.
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CHAPTER 1
OVERVIEW

1.1 Importance of Forested Wetlands
Forested wetlands are an important component of the southern United States
coastal ecosystems. Cypress-tupelo swamps represent a distinct and important portion
of these forested wetland systems and generally found along rivers and streams of the
Atlantic Coastal Plain from Delaware to Florida, along the Gulf Coast Plain to
southeastern Texas, and up the Mississippi River to southern Illinois (U.S. Division of
Timber Management Research 1965). The southcentral United States contains an
estimated 650,000 hectares of this type (Rosson et al 1988). Swamps play a critical
role in the biogeochemical cycles, serve as nutrient and sediment sinks that enhance
water quality, and support fresh water and saltwater commercial fisheries through
transport of organic debris to many aquatic food webs (Taylor et al 1990, Mitsch and
Gosselink 1993, Walbridge 1995). They provide cover for resident and transient
species of fish and wildlife, surface water and/or moist soil important for wading birds
and waterfowl, and serve as dispersion and migration corridors (Brinson 1981).
Baldcypress (Taxodium distichum (L.) Rich.) is one of the most commercially and
ecologically valuable tree species of these southeastern floodplain forests (Brown and
Montz 1986). Heartwood from old growth cypress swamps (and to a lesser extent
second growth cypress) is extremely durable. Ecologically, cypress also is the keystone
species for many game species and formerly or presently threatened and endangered
species such as the bald eagle (Haliaeetus leucophalus (L.)), Louisiana black bear
1