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Forest Disturbance Effects on Insect and Bird Communities: Insectivorous Birds in Coast Live Oak Woodlands and Leaf Litter Arthropods in the Sierra Nevada by Kyle Owen Apigian B.A. (Bowdoin College) 1998 A dissertation submitted in partial satisfaction of the requirements for the degree of Doctor of Philosophy in Environmental Science, Policy, and Management in the GRADUATE DIVISION of the UNIVERSITY OF CALIFORNIA, BERKELEY Committee in Charge: Professor Barbara Allen-Diaz, Chair Assistant Professor Scott Stephens Professor Wayne Sousa Spring 2005 The dissertation of Kyle Owen Apigian is approved: Chair Date Date Date University of California, Berkeley Spring 2005 Forest Disturbance Effects on Insect and Bird Communities: Insectivorous Birds in Coast Live Oak Woodlands and Leaf Litter Arthropods in the Sierra Nevada © 2005 by Kyle Owen Apigian TABLE OF CONTENTS Page List of Figures ii List of Tables iii Preface iv Acknowledgements Chapter 1: Foliar arthropod abundance in coast live oak (Quercus agrifolia) 1 woodlands: effects of tree species, seasonality, and “sudden oak death”. Chapter 2: Insectivorous birds change their foraging behavior in oak woodlands affected by Phytophthora ramorum (“sudden oak death”). Chapter 3: Cavity nesting birds in coast live oak (Quercus agrifolia) woodlands impacted by Phytophthora ramorum: use of artificial nest boxes and arthropod delivery to nestlings. Chapter 4: Biodiversity of Coleoptera and other leaf litter arthropods and the importance of habitat structural features in a Sierra Nevada mixed-conifer forest. Chapter 5: Fire and fire surrogate treatment effects on leaf litter arthropods in a western Sierra Nevada mixed-conifer forest. Conclusions References Appendices LIST OF FIGURES Page Chapter 1 Figure 1. Arthropod abundance on Q. agrifolia vs. U. californica. Figure 2. Arthropod abundance on symptomatic vs. asymptomatic oaks. Figure 3. NMS ordination of arthropod assemblage data. Chapter 2 Figure 1. Map of SOD study sites. Figure 2 (a-f). Tree species, maneuver, and substrate use. Figure 3 (a-c). Preference figures for oaks, bays, and “other”. Figure 4 (a-b). Use of three tree categories relative to SOD dieback. Chapter 3 Figure 1. Map of SOD study sites. Chapter 4 Figure 1. Map of Blogett Forest and the compartments sampled. Figure 2. Species accumulation curve for Coleoptera. Figure 3. Rank-abundance plot for Coleoptera. Figure 4. beetle species vs. abundance on a geometric (log2) scale. Figure 5 (a-b). CCA ordination diagrams. Chapter 5 Figure 1. Map of Blogett Forest and the treatment compartments. Figure 2. Rank abundance diagrams of beetle assemblages. Figure 3 (a-b). CCA ordination diagrams. LIST OF FIGURE (cont.) Page Chapter 5 Figure 4. NMS ordination diagram. LIST OF TABLES Page Chapter 1 Table 1. Total numbers of each arthropod taxon collected. Table 2. Diversity indices for each tree species and month. Table 3. Diversity indices for symptomatic and asymptomatic oaks. Chapter 2 Table 1. Vegetation data summary. Table 2. Total foraging observations. Table 3. Plant species used and counts of foraging observations. Table 4. Substrates used and counts of foraging observations. Table 5. Maneuvers used and counts of foraging observations. Chapter 3 Table 1. Vegetation data summary. Table 2. Total numbers of nests and percent occupancy, by species. Table 3. Total number of nests and percent occupancy, by site. Table 4. Nesting data, by species. Table 5. Total number of territories. Table 6. Total number and percent of prey delivered to nestlings. Table 7. Summary of foraging effort and dietary data. Table 8. Foraging effort and dietary data vs. SOD, regressions. Chapter 4 Table 1. Richness measures of beetles at Blodgett Forest. LIST OF TABLES (cont.) Page Chapter 4 Table 2. Summary of habitat variables. Table 3. Multiple regression results. Table 4. Results from Canonical Correspondence Analysis (CCA). Chapter 5 Table 1. Differences between pre- and post-treatment years. Table 2. Results from Canonical Correspondence Analysis (CCA). PREFACE Ecologists increasingly view disturbances as a natural part of the forest landscape. However, anthropogenic disturbances, brought about either by introduced species or forest management, may not mimic natural disturbances. Understanding the multi-trophic and multi-scale effects of anthropogenic disturbances is the first step in mitigating their negative effects. I studied forest disturbance in two different ecosystems in California: oak woodlands in the San Francisco Bay Area and mixed conifer forests in the Sierra Nevadas. The types of disturbance studied in each of these sytems are very different. In the Bay Area, I examine an invasive forest pathogen, while in the Sierras I study fire and forestry practices. However, that these studies can be viewed through a common lens of how habitat disturbance can have many multi-scale and multi-trophic level effects, despite the fact the the ecosystems and fauna studied are very different. The first three chapters of this dissertation focus on insects and insectivorous birds in oak woodlands impacted by “sudden oak death”. Chapter 1 examines how foliar arthropods might respond in these woodlands. I compare the abundance of two guilds of arthropods on coast live oak versus bay trees, and also between symptomatic and asymptomatic oaks. I also look at abundances during two points in the spring that are roughly analogous to early and late nesting season of some songbirds in these woodlands. These findings have implications not only for the ultimate fate of arthropods in these woodlands, if oaks are replaced by bays, but also reveal how certain arthropod groups may be impacted by physiological changes in infected oaks. In Chapter 2, I shift my focus to the predators of these foliar arthropods, two species of insectivorous birds. Through detailed foraging observations of chestnut- backed chickadees and oak titmice, I determine the tree species in oak woodlands from which these birds most prefer feeding, as well as the behaviors they use and the microhabitats from which they procure prey. By comparing foraging behavior in stands that reflect a gradient of SOD decline, I determine how these two species shift their foraging behavior in the face of the loss of a common foraging substrate, the coast live oak. I discuss how foraging behavior may impact the relative ability of these birds to compensate for the loss of oaks in ths ecosystem. The ultimate fate of chickadee and titmice populations in affected oak woodlands depends on whether there are changes in their nesting success. In Chapter 3, I use nest boxes to examine relative use of artificial nest holes and nestling survival. I also use video cameras trained on the boxes to measure foraging effort, or the amount of time spent looking for food, and the composition of the diet delivered to nestlings by adult birds. The results from this chapter, combined with Chapters 1 and 2, reveal that oak decline from SOD may have complex direct and indirect effects on cavity-nesting, insectivorous birds related to changes in prey availability, behavioral responses to oak decline, natural cavity availability, and nestling diet. In Chapters 4 and 5 I shift my focus to an entirely different ecosystem, the mixed- conifer forests of the Sierra Nevadas. The results from both of these chapters come from a portion of the Fire and Fire Surrogate (FFS) study. This study is a nationwide effort to examine the impacts of prescribed burning and fire risk reduction thinning techniques on the forest ecosystem. I studied leaf litter arthropods, with particular emphasis on the Coleoptera, and how they responded to burning, thinning, and combined treatments. Chapter 4 is largely a survey of the biodiversity at Blodgett Forest, where the study took place. It is one of only a very few studies of arthropod biodiversity in the Sierra Nevadas. In this chapter, I also use multiple regression to determine which habitat structural features are important in determining the abundances of various arthropod groups. This acts as a lead-in to Chapter 5, in which I specifically focus on the effects of the treatments on the abundance and diversity of leaf litter arthropod groups, and how changes in habitat features might influence beetle assemblage structure. The two studies described above, the first on SOD in oak woodlands and the second on fire in the Sierras, share in common their focus on forest disturbance as well as on insect assemblages. Beyond this, the studies are quite independent and seek to answer different specific questions. I hope, however, that the results from this work may contribute to answering larger questions involving habitat disturbance, ecosystem resiliency, and multi-trophic level effects of habitat change. ACKNOWLEDGEMENTS First and foremost, I must extend my gratitude to my friend, mentor, and former advisor, the late Dr. Donald Dahlsten. This dissertation could not have been completed without Don’s passion for this work and his support for me during my time at Berkeley. I will miss him greatly and remember him fondly. A great thank you goes to Dr. Barbara Allen-Diaz for her encouragement, advice, and collaboration as I finished my Ph.D. Dr. Scott Stephens and Dr. Wayne Sousa were helpful during many facets of this project, and provided many helpful comments on the manuscript. David Rowney and Dr. Nadir Erbilgin were both very supportive in numerous ways during my time at Berkeley. They also provided excellent statistical advice. I also want to thank Letty Brown for her collaboration on the SOD project. The insect work accompanying the fire and fire surrogate study required the help of dozens of scientists, technicians, and fire fighters. The staff at the Blodgett Forest Research Station, particularly Sheryl Rambeau, were helpful and accommodating during my time there. I want to thank Jason Moghaddas for his excellent and tireless logistical support with the FFS. Several scientists lent their time in helping me identify insects, including Dr. Kip Will, Dr. John Doyen, Dr.