INVERTEBRATES AS WEBMASTERS IN ECOSYSTEMS This is an edited volume honouring the contributions of Professor D.A. (Dac) Crossley, Jr to the field of ecosystem science. Invertebrates as Webmasters in Ecosystems Edited by D.C. Coleman and P.F. Hendrix Institute of Ecology University of Georgia Athens, USA CABI Publishing CABI Publishing is a division of CAB International CABI Publishing CABI Publishing CAB International 10 E 40th Street, Wallingford Suite 3203 Oxon OX10 8DE New York, NY 10016 UK USA Tel: +44 (0)1491 832111 Tel: +1 212 481 7018 Fax: +44 (0)1491 833508 Fax: +1 212 686 7993 Email: [email protected] Email: [email protected] © CAB International 2000. All rights reserved. No part of this publication may be repro- duced in any form or by any means, electronically, mechanically, by photocopying, recording or otherwise, without the prior permission of the copyright owners. A catalogue record for this book is available from the British Library, London, UK Library of Congress Cataloging-in-Publication Data Invertebrates as webmasters in ecosystems / edited by D.C. Coleman and P.F. Hendrix. p. cm. Includes bibliographical references and index. ISBN 0–85199–394–X (alk. paper) 1. Invertebrates––Ecology. I. Coleman, David C., 1938– . II. Hendrix, Paul F. QL364.4.I58 2000 592.17––dc21 99–41246 CIP ISBN 0 85199 394 X Typeset in 10/12pt Photina by Columns Design Ltd, Reading Printed and bound in the UK by Biddles Ltd, Guildford and King’s Lynn. Contents Contributors vii Preface ix Part I. Webmaster Functions in Ecosystems 1 1 Food Web Functioning and Ecosystem Processes: Problems and Perceptions of Scaling 3 J.M. Anderson 2 Keystone Arthropods as Webmasters in Desert Ecosystems 25 W.G. Whitford 3 Responses of Grassland Soil Invertebrates to Natural and Anthropogenic Disturbances 43 J.M. Blair, T.C. Todd and M.A. Callaham, Jr 4 Effects of Invertebrates in Lotic Ecosystem Processes 73 J.B. Wallace and J.J. Hutchens, Jr Part II. Webmasters in Feedback Interactions and Food Webs 97 5 Insects as Regulators of Ecosystem Development 99 T.D. Schowalter 6 Herbivores, Biochemical Messengers and Plants: Aspects of Intertrophic Transduction 115 M.I. Dyer v vi Contents 7 Soil Invertebrate Controls and Microbial Interactions in Nutrient and Organic Matter Dynamics in Natural and Agroecosystems 141 C.A. Edwards 8 Invertebrates in Detrital Food Webs along Gradients of Productivity 161 J.C. Moore and P.C. de Ruiter Part III. Webmasters and Ecosystem Diversity 185 9 Biodiversity of Oribatid Mites (Acari: Oribatida) in Tree Canopies and Litter 187 V. Behan-Pelletier and D.E. Walter 10 Diversity in the Decomposing Landscape 203 R.A. Hansen 11 The Pervasive Ecological Effects of Invasive Species: Exotic and Native Fire Ants 221 C.R. Carroll and C.A. Hoffman 12 Soil Invertebrate Species Diversity in Natural and Disturbed Environments 233 J. Rusek Part IV. Webmasters in Regional and Global Contexts 253 13 Invertebrates and Nutrient Cycling in Coniferous Forest Ecosystems: Spatial Heterogeneity and Conditionality 255 T.M. Bolger, L.J. Heneghan and P. Neville 14 Impacts of Insects on Human-dominated and Natural Forest Landscapes 271 R.N. Coulson and D.F. Wunneburger 15 Soil Fauna and Controls of Carbon Dynamics: Comparisons of Rangelands and Forests across Latitudinal Gradients 293 T.R. Seastedt 16 Soil Processes and Global Change: Will Invertebrates Make a Difference? 313 P.M. Groffman and C.G. Jones Index 327 Contributors J.M. Anderson, School of Biological Sciences, University of Exeter, Hatherly Laboratories, Prince of Wales Road, Exeter EX4 4PS, UK V. Behan-Pelletier, Biodiversity Program, Research Branch, Agriculture and Agri-Food Canada, K.W. Neatby Building, Ottawa, Canada, K1A 0C6 J.M. Blair, Division of Biology, Kansas State University, 232 Ackert Hall, Manhattan, KS 66506, USA T.M. Bolger, Department of Zoology, University College Dublin, Belfield, Dublin 4, Ireland M.A. Callaham, Jr, Division of Biology, Kansas State University, 201 Bushnell Hall, Manhattan, KS 66506, USA C.R. Carroll, Institute of Ecology, University of Georgia, Ecology Building, Athens, GA 30602–2202, USA D.C. Coleman, Institute of Ecology, University of Georgia, Ecology Annex, Athens, GA 30602–2360, USA R.N. Coulson, Knowledge Engineering Laboratory, Department of Entomology, Texas A&M University, Campus MS 2475, College Station, TX 77843, USA M.I. Dyer, Institute of Ecology, University of Georgia, Ecology Building, Athens, GA 30602–2202, USA C.A. Edwards, Soil Ecology Program, Botany and Zoology Building, The Ohio State University, 1735 Neil Avenue, Columbus, OH 43210, USA P.M. Groffman, Institute of Ecosystem Studies, Box AB, Millbrook, NY 12545, USA R.A. Hansen, Department of Biological Sciences, University of South Carolina, Coker Life Sciences 402, Columbia, SC 29208, USA P.F. Hendrix, Institute of Ecology, University of Georgia, Ecology Building, Athens, GA 30602–2202, USA vii viii Contributors L.J. Heneghan, Environmental Sciences Program, DePaul University, 2320 North Kenmore Avenue, Chicago, IL 60614-3298, USA C.A. Hoffman, Institute of Ecology, University of Georgia, Athens, GA 30602–2202, USA J.J. Hutchens, Jr, Institute of Ecology, University of Georgia, 413 Biological Sciences Building, Athens, GA 30602, USA C.G. Jones, Institute of Ecosystem Studies, New York Botanical Gardens, Cary Arboretum, Millbrook, NY 12545, USA J.C. Moore, Department of Biological Sciences, University of Northern Colorado, Greeley, CO 80639, USA P. Neville, Department of Zoology, University College Dublin, Belfield, Dublin 4, Ireland P.C. de Ruiter, Department of Environmental Studies, University of Utrecht, PO Box 80115, 3508 TC Utrecht, The Netherlands J. Rusek, Institute of Soil Biology, Academy of Sciences of Czech Republic, Nasádkách 7, 370 05 »eské BudÏjovice, Czech Republic T.D. Schowalter, Department of Entomology, Oregon State University, 2046 Cordley Hall, Corvallis, OR 97331–2907, USA T.R. Seastedt, Institute of Arctic and Alpine Research, University of Colorado, Boulder, CO 80309-0450, USA T.C. Todd, Department of Plant Pathology, Kansas State University, Manhattan, KS 66506, USA J.B. Wallace, Professor of Entomology and Ecology, 711 Biological Science Building, University of Georgia, Athens, GA 30602, USA D.E. Walter, Department of Zoology and Entomology, University of Queensland, St Lucia, Queensland 4072, Australia W.G. Whitford, USDA/ARS Jornada Experimental Range, New Mexico State University, PO Box 30003, MSC 3JER, Las Cruces, NM 88003–8003, USA D.F. Wunneburger, College of Architecture, Texas A&M University, College Station, TX 77843, USA Preface The last frontiers on Earth for the study of biocomplexity and ecosystem function are in the depths of the oceans, the canopies of forests and in soils (Haagvar, 1998). Remoteness and inaccessibility contribute to our lack of knowledge of oceanic and high canopy systems, but it is remarkable that life processes in the very underpinnings of our otherwise familiar terrestrial environment remain veiled. Obstacles to studying organisms and biological processes in soil include the opacity of the medium in which they exist and our inability to observe, collect and measure them without altering their charac- teristics (Coleman, 1985; Wall and Moore, 1999). Despite scientific limitations (or perhaps because of them), in all three situations there has been no shortage of innovative methods for studying biology along the frontiers or of creative ideas to explain phenomena observed there. The present state of knowledge from this work, as limited as it may be, clearly is that invertebrates are con- spicuous, ecologically influential components in all of these systems. This fact and the exciting questions that it raises are the bases for this book, which aims to review and assess our current understanding of invertebrates in terrestrial and terrestrially dominated (i.e. lower-order stream) ecosystems. In computing terminology, ‘A webmaster is one who designs, organizes, and maintains a webpage. The webmaster has a global, not a local perspective. No matter what language is used, the webmaster facilitates access to the web’ (Aram Rouhani, personal communication). While not imputing purpose in a human-oriented sense to actions of individual species in ecosystems, we suggest that entire assemblages of invertebrates occupying many hot-spots in soils, such as the rhizosphere and drilosphere, and other portions of both terrestrial and aquatic ecosystems, assume an organizing function and, hence, may be con- sidered as ‘webmasters’. This theme emphasizes the centrality of the activities ix x Preface of invertebrates, which influence ecosystem function far out of proportion to their physical mass in a wide range of ecosystems, particularly at the interfaces between land and air (litter/soil), water and land (sediments), and in tree canopies and root/soil systems. The webmasters concept reflects both direct and indirect influences of organismal activities, for example on nutrient dynamics in entire watersheds, and is thus qualitatively different from the keystone species concept, which relates to impacts of a particular species on other species and communities in a given habitat. The webmasters concept spans scales ranging from microsites to aspects of global climate change. We have invited 17 internationally renowned researchers from five coun- tries to participate in this focused, edited volume. Their papers cover a variety of current topics on invertebrate ecology, including spatial scale and nature of invertebrate controls on ecosystem processes;