University of Alberta Spider Comrnunities in Boreal Mixed-Wood Forests of Alberta: Succession, Species Interactions and Habitat
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University of Alberta Spider comrnunities in boreal mixed-wood forests of Alberta: succession, species interactions and habitat utilization Christopher Martin Buddle @ A thesis submitted to the Faculty of Graduate Studies and Research in partial fulfllrnent of the requirements for the degree of Doctor of Philosophy in Environmental Biology and Ecology Department of Biological Sciences Edmonton, Alberta Spring 200 1 National Library Bibliothèque nationale 1*1 of Canada du Canada Acquisitions and Acquisitions et Bibliographie Services services bibliographiques 395 Weltington Street 395, rue Wellington Ottawa ON KIAON4 Oltawa ON KI A ON4 Canada Canada The author has granted a non- L'auteur a accordé une licence non exclusive licence allowing the exclusive pemiettant à la National Lïbrary of Canada to Bibliothèque nationale du Canada de reproduce, loan, distribute or sell reproduire, prêter, distribuer ou copies of this thesis in microform, vendre des copies de cette thèse sous paper or electronic formats. la forme de microfiche/fllm, de reproduction sur papier ou sur format électronique. The author retains ownership of the L'auteur conserve la propriété du copyright in this thesis. Neither the droit d'auteur qui protège cette thése. thesis nor substantial extracts fiom it Ni la thèse ni des extraits substantieIs may be printed or otherwise de celle-ci ne doivent être imprimés reproduced without the author's ou autrement reproduits sans son permission. autorisation. 1 dedicate this thesis to my wzye, Rebecca Stone, for her love and stpporr, my son Evnn for showirtg me joy, and my parents for teaching me the wlzre of r vilderness Abstract Spiders (Araneae) are important and ubiquitous predators in terrestrial ecosystems, and they are an ideal taxon for assessing the impact of forest harvesting on the biota of boreal forests. I investigated how spider succession differs following wildfire and clear-cutting in a chronosequence study of aspen- dominated stands in north-central Alberta, Canada. Such cornparisons support insights into how harvesting may alter natural succession in fire-driven ecosystems. Results showed that spiders recovered rapidly fiom both disturbances, and by 30 years after disturbance, there was a faunal recovery and general convergence to ward pre-disturbance community structure. There were, however, some important differences between the two disturbances in that wildfire stands harboured a more diverse spider fauna and certain species appeared dependent on some of the conditions associated with wildfire. Wolf spiders (Lycosidae) were dominant in most of the study sites in the chronosequence study. Expenments in a rnixed-wood forest in central Alberta revealed that two species, Pardosa moesta Banks and P. mackenziana (Keyserling), had nearly identical biennid life-cycles, and young stages of these species have the potential to interact in the leaf-litter. A competition experiment, however, showed that exploitative competition did not govern populations of P. moesta and P. mackenziana, and suggested that mortaiity factors such as intraguild predation and cannibalism play important roles in their survival. Knowledge from the cornpetition and life-history experirnents served to explain patterns in the occurrence of Pardosa species throughout north-central Alberta The chronosequence study also suggested that fallen logs, or downed woody material (DWM), was an important habitat for spiders. This \vas tested by trapping spiders directly on the surface of fallen logs and by rnanipulating the volume of DWM on the forest floor and tracking changes in spider assemblages. Results showed that a diverse spider fauna uses the surface of DWM, and that some species are dependent on the habitat complexity of fallen logs. Manipulating the volume of DWM on the forest floor, however, had few short-tenn effects on spider assemblages, except that diversity tended to increase when DWM was augmented on the forest floor. Acknowledgments I must first thank my family, here and in Ontario and British Columbia, for their confidence in me and for their constant support. Second, thanks to my supervisors John Spence and David Langor for continual guidance and insight. John Spence aiso supported rny attendance to numerous conferences which greatly aided my development as a scientist, Thariks also to my cornmittee members Anne Naeth, Robert Holmberg, and Mark Dale. 1 am greatly indebted to Don Buckle for assistance with spider taxonomy; without his ski11 and tutelage this work would not have been possible. Robb Bennett, Charles Dondale, and Robin Leech also provided taxonomie help. Outstanding field and Zaboratory assistance was provided by Alice Graham, Karen Cryer, Eric Nijenhuis, Jim Harnmond, Greg Pohl? and Daryl Williams. Thanks also to Dave Shorthouse, Tim Work: Jeff Battigelli, Ian Robertson, Lusi Korinus, Brent Karner, Josh Jacobs, Dustin Hartley, countless "bug pickers", and my other fiends and lab-mates who helped make my research productive, stimulating, and enjoyable. Malcolm "Mac'' McIntyre always kept George Lake running smoothly, and Ed Donald kindly kept the goats fiom eating pitfall traps. P. Lee, S. Crites, and colleagues at the Alberta Research Council kindly provided CWD estirnates and assisted in project initiation and site selection for Chapter 2. Financial assistance was provided by the Naturd Science and Engineering Research Coüncil of Canada (NSERC) in the form of a research gant to J. Spence and a post-graduate scholarship to CMB, the Manning Diversified Forest Products Research Trust Fund, the SustainabIe Forest Management Network (National Centres for Excellence), Challenge Grants in Biodiversity Program (Dept. of Biotogical Sciences, University of Alberta and the Alberta Conservation Association), Natural Resources Canada (Northem Forestry Centre), Province of Alberta Scholarships and Fellowships, and a University of Aiberta Dissertation Award. Trans-Alta Utilities kindly provided telephone poles for experiments. Table of Contents 1. Introduction.. .......................................................... Background and rationale........ .. ............................. Spiders: a mode1 study taxon .................................... Structure of thesis................................................. Re ferences......................................................... 2 .Succession of boreal forest spider assemblages following wildfire and harvesting.................................................. Introduction ......................................................... Materials and Methods ............................................ Study area .................................................. Sarnpling.................................................... Anaiyses ..................................................... Results................................................................ Abundance and diversity.................................. Environmental variables ................................... Succession and comrnunity patterns ..................... Species associated with stand conditions following wildfire .......................................... Discussion ............................................................ Abundance and diversity................................... Succession and community patterns ...................... Species associated with stand conditions following wildfire ........................................... References ............................................................ 3 . The recovery of boreal forest spider assemblages following wildfire and harvesting...................... ., .. .... ...................... Introduction.......................................................... Methods ............................................................... Results and Discussion ............................................. References ............................................................ 4 .Life history of Pardosa moesta and P. mackenzktna (Araneae, Lycosidae) in central Alberta ............. .........O..................... Introduction .......................................................... Methods ............................................................... Study sitc and species descriptions ...................... Density estimates........................................... Fecundity .................................................... Life cycle .................................................... Adult population dynamics ............ ,. ........ Juvenile growth and development. ............. Spring cohorts ..................................... Results ................................................................ Density estimates ........................................... Fecundity .................................................... Life cycle .................................................... Adult population dynamics...................... Juvenile growth and development .............. Spring cohorts ..................................... Discussion ............................................................ Density ........................................................ Fecundity ..................................................... Life cycle ..................................................... References ............................................................ 5. Interactions among young stages of the wolf spiders Pardosa moesta and P. mackenziana ................ ...........................O. Introduction .........................................................