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Edge-effects on tree regeneration in the Colombian Andes

by Arango-Caro, Sandra, PhD

Abstract (Summary)
ABSTRACT Some of the most pervasive effects of contemporary human impact on the persistence of species are the effects of habitat fragmentation. In fragmented landscapes the abrupt contrast between forest edge and the surrounding matrix (pastures) generates differences in abiotic and biotic conditions, and plant-animal interactions at edges relative to forest interior (edge-effects). Consequently, edgeeffects may degrade remaining habitats by altering the structure and function of ecosystems. In this investigation I used a community-level approach to examine edge-related patterns of forest structure and tree species composition and their link to abiotic and biotic factors, during a wet and a dry season in five edge sites. I used a species-level approach to test mechanistic hypotheses of tree regeneration processes. I experimentally examined if the abiotic environment and/or seed predation and seedling herbivory exhibit edge-mediated effects on regeneration processes in five species of trees in two edge sites. I empirically examined if light and conspecific seedling density act as edge-mediated effects on insect seedling herbivory in eight species of trees in four edge sites. This study was conducted in Andean forest, a largely unexplored ecosystem, which is one of the most threatened and richest ecosystems worldwide. Forest structure and tree composition were affected by abiotic edge-effects. Such responses likely result from edge-mediated effects of the abiotic environment on tree regeneration. Seed predation and seedling herbivory, although major sources of plant mortality, were no edge-mediated effects of tree regeneration. Seed predators and herbivores appear to be generalists, and light conditions were apparently too subtle to generate differences in chemical defenses of plants. Results were not consistent due to species-specific and site-specific responses likely reducing the power to observe if general principles of edge-effects exist. General patterns may emerge as species ecology and commonalities and differences among sites are taken into account.
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Bibliographical Information:

Advisor:Bette Loiselle

School:University of Missouri-Saint Louis

School Location:USA - Missouri

Source Type:Doctoral Dissertation

Keywords:Andes, trees, forest regeneration, edge-effects

ISBN:

Date of Publication:08/11/2002

Document Text (Pages 1-10)

ABSTRACT

Some of the most pervasive effects of contemporary human impact on the persistence of
species are the effects of habitat fragmentation. In fragmented landscapes the abrupt contrast between
forest edge and the surrounding matrix (pastures) generates differences in abiotic and biotic conditions,
and plant-animal interactions at edges relative to forest interior (edge-effects). Consequently, edgeeffects
may degrade remaining habitats by altering the structure and function of ecosystems.
In this investigation I used a community-level approach to examine edge-related patterns of
forest structure and tree species composition and their link to abiotic and biotic factors, during a wet
and a dry season in five edge sites. I used a species-level approach to test mechanistic hypotheses of
tree regeneration processes. I experimentally examined if the abiotic environment and/or seed
predation and seedling herbivory exhibit edge-mediated effects on regeneration processes in five
species of trees in two edge sites. I empirically examined if light and conspecific seedling density act
as edge-mediated effects on insect seedling herbivory in eight species of trees in four edge sites. This
study was conducted in Andean forest, a largely unexplored ecosystem, which is one of the most
threatened and richest ecosystems worldwide.
Forest structure and tree composition were affected by abiotic edge-effects. Such responses
likely result from edge-mediated effects of the abiotic environment on tree regeneration. Seed
predation and seedling herbivory, although major sources of plant mortality, were no edge-mediated
effects of tree regeneration. Seed predators and herbivores appear to be generalists, and light
conditions were apparently too subtle to generate differences in chemical defenses of plants. Results
were not consistent due to species-specific and site-specific responses likely reducing the power to
observe if general principles of edge-effects exist. General patterns may emerge as species ecology and
commonalities and differences among sites are taken into account.


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EDGE-EFFECTS ON TREE REGENERATION IN THE COLOMBIAN ANDES

by Sandra Arango-Caro

A Thesis Submitted to the Graduate School,
University of Missouri-St. Louis, USA,

In Partial Fulfillment of the Requirements
for the Degree of Doctor of Philosophy in Biology.

August 2002

ADVISORY COMMITTEE DATE

__________________________________
Elizabeth Kellogg, Ph. D. (chair)
___________

__________________________________
Bette Loiselle, Ph. D. (advisor)
___________

__________________________________
James Campbell, Ph. D.
___________

__________________________________
Charlotte Taylor, Ph. D.
___________

__________________________________
Elizabeth Braker, Ph. D.
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AKNOWLEDGEMENTS

I appreciate the support and guidance of my advisor Bette Loiselle. Her
experience and knowledge in ecology and conservation issues have profoundly
influenced this document and my goals for future research. The members of my
committee: Elizabeth Kellogg, James Campbell, Charlotte Taylor, and Elizabeth Braker
provided invaluable comments during different stages of this study. Victoria Sork, Carla
Restrepo, Svata Louda, Evan Notman, John Lill, Robert Marquis, Robert Ricklefs
reviewed early drafts, significantly improving the content of this document. John Blake,
Juan Fernández, and especially William Connett spent hours discussing the experimental
design and statistical methods with me. Members of the laboratories of Bette Loiselle,
John Blake and Robert Marquis contributed with enriching discussions and draft reviews.
William Laurance, Julieta Benítez-Malvido, Carolina Murcia, Eric Veneklas, Josiane Le
Corff and Carla Restrepo provided inspiring suggestions for the project proposal. My
friends and colleagues John Lill, Evan Notman, Jorge Pérez-Eman, Ana Cristina
Villegas, Antonio Guillén, Alex Scheuerlein, Juan Fernández, and especially Luis Miguel
Renjifo, accompanied me in different stages of my studies, while providing invaluable
insights on the design and analysis of this research. Eric Wiener and Damond Kyllo
provided advice for the analysis of the hemispherical photos. Susanne Renner, Rebecca
Forkner, Henk van der Werff provided information on the chemical composition of some
of the study species. Sarah Heyman, Ellen McCallie, James Francis and Derek Hildreth
kindly reviewed the documents for content and English editing.
In the field this project would have been impossible to be successful without the
invaluable support of William Vargas who identified and provided information of the

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regeneration ecology of the tree species. Juan Pablo Velásquez, Carlos Andrés Pérez,
Beatriz Arias, Rogelio Gutiérrez, René and Horacio Zapata, Herney Zuluaga, and others
worked many hours in the construction of cages, sowing, transplanting, uprooting plants,
gathering data and working for hours inputting data. Private property owners allowed me
to conduct my research on their lands, always interested and willing to help.
Several institutions provided logistical support and funding. Fundación Herencia
Verde facilitated letters of presentation and allowed me to use their office and shadehouse.
I am especially thankful to Julio Andrés Ospina, Lorenza Gálvez, Gloria Torres,
and Pedro Burgos who were always willing to collaborate in what I needed. The
Corporación Regional del Quindío facilitated the data for air temperature and rainfall.
Financial support was provided by Colciencias (Instituto Colombiano para el Desarrollo
de la Ciencia y la Tecnología – Francisco José de Caldas), Fundación para la Promoción
de la Investigación y la Tecnología from Banco de la República, Fondo José Celestino
Mutis- FEN, International Center for Tropical Ecology at the University of Missouri-St.
Louis, American Association of University Women (AAUW), MacArthur Foundation,
Federated Garden Clubs of Missouri, Inc.
The biology department and the graduate school at the University of Missouri -
St. Louis, the directors of the graduate studies, as well as Dianne Dei Santi, Maryann
Hempen, Bernardette Dalton, and Raouf Haddad helped me unconditionally during the
development of my studies.
Finally, and very especially, I want to thank my mother, my husband, and in
general my family and friends for their continuous support and motivation to conduct my
graduate studies.

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I dedicate this dissertation to my mother,
the greatest motivator of my education.

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TABLE OF CONTENTS

List of Tables ………………………………………………………………………. ix
List of Figures………………………………………………………………………. xi
List of Appendices …………………………………………………………………. xv
General Introduction ……………………………………………………………… 1
Chapter 1. Abiotic and biotic edge-effects on forest structure and tree species
composition in Andean remnant forests
Abstract……………………………………………………………………… 22
Introduction …………………………………………………………………. 24
Methods…………………………………………………………………….... 28
Study site and edges…………………………………………………. 28
Abiotic environment ………………………………………………… 31
Forest structure and species composition …………………………… 32
Data analysis …………………………………………………………. 33
Results ……………………………………………………………………….. 39
Abiotic edge-effects ……………………………………………….…. 39
Forest structue and edge-effects …………………………………….. 40
Species composition in different life stages and edge-effects …….…. 41
Abiotic vs. biotic edge-effects………………………..………………. 45
Discussion …………………………………………………………………… 46
Abiotic edge-effects …………………………………………………. 46
Edge-related patterns of forest structure…………………………..…. 49

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Edge-related patterns of tree species composition………………….. 50
Abiotic vs. biotic edge-effects on species composition…………….. 51
Conclusion…………………………………………………………………… 53
Literature cited ………………………………………………………………. 55
Tables………………………………………………………………………… 63
Figures………………………………………………………………………... 68
Appendix……………………………………………………………………... 82
Chapter 2. Edge-mediated effects on tree regeneration in Andean forest fragments:
Abiotic or herbivory effects ?
Abstract…………………………………………………………………….... 90
Introduction …………………………………………………………………. 92
Methods……………………………………………………………………… 96
Study site and edges…………………………………………………. 96
Study species ……………………………………………………..… 99
General experimental design………………………………………… 99
Seed survival and germination experiment ……………………….... 102
Seed survival of small-seeded species experiment ……………….... 103
Seedling establishment experiment ………………………………... 104
Data analysis ……………………………………………………….. 107
Results …………………………………………………………………….... 110
Abiotic edge-effects ………………………………………………....110
Seed survival……………………………………………………....... 111
Sources of seed mortality.........................…………………………... 112

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Seed germination ………………………………………………….... 113
Seedling survival ………………………………………………….... 114
Seedling growth ………………………………….......…………….. 115
Leaf production. ………………………………….......…………….. 116
Insect seedling herbivory …………………………………………….117
Discussion …………………………………………………………………... 117
Edge-effects and the abiotic environment ………………………….. 117
Edge-mediated effects on the abiotic environment, seed predation,
and seedling herbivory on tree regeneration.................…………..…. 118
Conclusion………………………………………………………………….... 122
Literature cited …………………………………………………………….... 124
Tables………………………………………………………………………....132
Figures……………………………………………………………………….. 140
Chapter 3. Edge-mediated effects on tree seedling herbivory in Andean remnant
forests
Abstract…………………………………………………………………….. 156
Introduction ………………………………………………………………... 158
Methods…………………………………………………………………….. 162
Study site and edges………………………………………………… 162
Experimental design and study species ……………………………. 165
Data analysis ………………………………………………………. 169
Results …………………………………………………………………..… 171

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General herbivory patterns……………………………………...…. 171
Light and edge-mediated effects on seedling herbivory...…………. 171
Conspecific seedling density and edge-mediated effects on seedling
herbivory............................................................................................ 172
Discussion …………………………………………………………………. 173
Light and edge-mediated effects on seedling herbivory...…………. 173
Conspecific seedling density and edge-mediated effects on seedling
herbivory............................................................................................ 176
General patterns……………………………………………………. 179
Conclusion…………………………………………………………………. 181
Literature cited …………………………………………………………….. 183
Tables…………………………………………………………………….... 192
Figures…………………………………………………………………...… 197
Appendix………………………………………………………………...… 209
General Conclusion ……………………………………………………………... 213

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