“There would doubtless be a just feeling of pride and satisfaction in the heart of a naturalist who could say that he had made himself thoroughly acquainted with all the species of a particular group of animals, had learned their most secret habits, and mastered their several relations to the objects, animate and inanimate, which surrounded them. But perhaps a still keener pleasure is enjoyed by one who carries about with him some problem of the kind but partially solved, and who, holding in his hand the clue which shall guide him onwards, sees in each new place that he visits fresh opportunities of discovery.” J. Traherne Moggridge Harvesting Ants and Trap-door Spiders, page 180 Saville, Edwards and Co., London 1874 University of Alberta Composition and structure of spider assemblages in layers of the mixedwood boreal forest after variable retention harvest by Jaime H. Pinzón A thesis submitted to the Faculty of Graduate Studies and Research in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Wildlife Ecology and Management Department of Renewable Resources ©Jaime H. Pinzón Fall 2011 Edmonton, Alberta Permission is hereby granted to the University of Alberta Libraries to reproduce single copies of this thesis and to lend or sell such copies for private, scholarly or scientific research purposes only. Where the thesis is converted to, or otherwise made available in digital form, the University of Alberta will advise potential users of the thesis of these terms. The author reserves all other publication and other rights in association with the copyright in the thesis and, except as herein before provided, neither the thesis nor any substantial portion thereof may be printed or otherwise reproduced in any material form whatsoever without the author's prior written permission. To my wife for her unconditional love, support and understanding To the memory of my father, who was always there for me, constantly encouraging me to follow my heart Abstract Natural disturbances are important drivers of ecosystem change in the boreal forest and new approaches to sustainable forest management draw on natural disturbance patterns as a template for harvesting. The main premise for such approach is that species have evolved and adapted to stand-replacing natural disturbances and thus are more likely to be maintained on landscapes managed to preserve spatial patterns of natural disturbance. I used spiders – one of the most important, diverse and ubiquitous groups of terrestrial predatory invertebrates – as a model for assessing the impacts of variable retention harvesting practices on biodiversity in the mixedwood boreal forest. Spiders were collected from the Ecosystem Management Emulating Natural Disturbance (EMEND) project landbase over a period of five years from different harvest treatments and forest-types. Results for 249 species in 18 families are included in this study. Changes in composition of spider assemblages clearly followed the disturbance gradient from clear-cut to uncut treatments and these changes were linked to habitat and forest structure. Ground-dwelling assemblages were mostly affected by harvesting, whereas canopy assemblages were less influenced when stand connectivity remained. Low tree retention (i.e., 10-20%, which is the range currently applied by the forestry industry) showed some ability to mitigate adverse effects of clear-cutting; yet, higher retention levels are needed to maintain forest specialist species, especially in late successional seres (e.g., conifer dominated). A “life-boating” effect of aggregated retention was evident, and was more effective when applied in combination with dispersed retention. The application of different harvesting practices alone is unlikely to entirely emulate the effects and processes caused by major disturbances on the landscape. Thus, keeping in mind that fire is an important component in the boreal forest, this type of disturbance cannot be excluded from management if the goal is to preserve a natural range of biodiversity. In conclusion, to sustain rich and diverse spider assemblages, management of the boreal mixedwood should aim towards maintaining landscape heterogeneity. Consequently, no single practice is effective to emulate natural post-disturbance patterns and to adapt harvesting to effectively imitate the processes of a disturbance driven system, a combination of prescriptions is recommended. Acknowledgements When one embarks in such adventure, generally this is not accomplished alone. There are always people that stand besides you during the journey and many others that come and go, providing you with help and support from short periods of time to extended ones. Someone once told me that one’s life is like a tree; the roots, what supports your whole life, represent your parents and, in a broader way, your family, right from the very beginning, since you are just a seedling. Branches are moments in life and leaves represent all the people you meet along the way. Some leaves stay, some may fall to the ground, some may be carried away by the wind; yet all of them, in one way or another, nurture you and play an important role in your life. I feel I’m a lucky one, I mean, a lucky tree. I have been very fortunate to have had besides me so many good people during these few last years since I arrived to Canada (and not to mention all those others before). It is just overwhelming to think how to write this without missing someone, and if I do, is absolutely unintentional; so just in case, thank you all for making this possible. Claudia, my love, thanks for being who you are, for being always on my side and supporting me when needed. Dad, mom, may your souls rest happily knowing that all your sacrifices were worth it. Eto and Olo, thanks for teaching me the value of life. Cabito and Tona, your support and words have been and always will be a treasure. Moni, thanks for opening your home and your heart for me, from the very beginning. Adrianas (yes the two of you) and Eli, there will always be a special place for you. Leito, compadre, you know it, thanks. Cata, I feel lucky to have met you, thanks for always being there. Guillaume, your time, the endless hours and all your advice are priceless, I’m fortunate to have you as a good friend. Vale and Jose, thanks for your friendship. You all know, in good and bad times, all are like family. John Spence, more than a supervisor I consider you as a good friend. Thanks for believing in me, for your insight and guidance and for your constant support, there will never be enough words to express my gratitude. Dave Langor thanks for your advice, support, time and effort you put in my project. Special thanks to my committee members, Ellen Macdonald and Felix Sperling, you were an example and an inspiration, and to all in the examining committee, David Wise, Heather Proctor, Anne Oxbrough and Andreas Haman. Fangliang He, I really appreciate your constant feedback. Numerous people provided assistance in the field and in the laboratory, with analyses, with spider identification and way beyond. Emily thanks for overcoming your fear to spiders and being such an excellent field assistant and friend. Erin, even though it was for a brief period of time, I will always be grateful for your help. In no particular order, Stephane, Josh, Colin, Chris, Tyler, Matti, Matthew, Charlene, Suzie, Evan, Esther, Seung-Il, Dustin, Stu, Phil, Sonja, Ana, Amy, Kim, you are all a crazy bunch, thanks for your patience and stimulating discussions, my life in the lab wouldn’t be as easy, fun and enjoyable if you were not around. Anne, I wish you had come to the lab earlier; I really appreciate our spider talks. A big thanks goes to EMEND core crews for all the assistance and help during fieldwork, especially Jason and Charlene, your help at EMEND was invaluable. Don Buckle and Dave Shorthouse, thanks for your time and aid in identifying some of my spiders. And of course, thanks to all those that provided financial support, without it, this would have been not possible. Colfuturo scholarships from Colombia provided the means to come to Canada and start my studies at UofA; the Department of Renewable Resources, through countless teaching assistantships and aids; the Killam Trusts through the Killam Memorial Scholarship; the Alberta Conservation Association Grants in Biodiversity; the Alberta Sustainable Research Development (SRD); the Forest Resource Improvement Association of Alberta (FRIAA) through DMI (Daishowa-Marubeni International Ltd.) and CANFOR (Canadian Forest Products); the Manning Forestry Research Fund; the Sustainable Forest Management Network; and the Natural Sciences and Engineering Research Council of Canada (NSERC) from a research grant to J. Spence Table of Contents Page 1 INTRODUCTION...................................................................................... 1 1.1 Background and Rationale..................................................................................... 1 1.2 Testing the Emulation of Natural Disturbances Model......................................... 3 1.3 Spiders as a Study Model…................................................................................... 8 1.4 Thesis Structure..................................................................................................... 15 1.4.1 Overall Objectives...................................................................................... 15 1.4.2 Thesis Chapters.........................................................................................