Ecological Studies

Ecological Studies Analysis and Synthesis Volume 224 Series editors Martyn M. Caldwell Logan, UT, USA Sandra Díaz Cordoba, Argentina Gerhard Heldmaier Marburg, Germany Robert B. Jackson Durham, NC, USA Otto L. Lange Würzburg, Germany Delphis F. Levia Newark, DE, USA Harold A. Mooney Stanford, CA, USA Ernst-Detlef Schulze Jena, Germany Ulrich Sommer Kiel, Germany Ecological Studies is Springer’s premier book series treating all aspects of ecology. These volumes, either authored or edited collections, appear several times each year. They are intended to analyze and synthesize our understanding of natural and managed ecosystems and their constituent organisms and resources at differ- ent scales from the biosphere to communities, populations, individual organisms and molecular interactions. Many volumes constitute case studies illustrating and synthesizing ecological principles for an intended audience of scientists, students, environmental managers and policy experts. Recent volumes address biodiversity, global change, landscape ecology, air pollution, ecosystem analysis, microbial ecology, ecophysiology and molecular ecology. More information about this series at http://www.springer.com/series/86 Thomas R. Horton Editor Mycorrhizal Networks 123 Editor Thomas R. Horton Department of Environmental and Forest Biology State University of New York – College of Environmental Science and Forestry Syracuse, NY USA ISSN 0070-8356 ISSN 2196-971X (electronic) Ecological Studies ISBN 978-94-017-7394-2 ISBN 978-94-017-7395-9 (eBook) DOI 10.1007/978-94-017-7395-9 Library of Congress Control Number: 2015951398 Springer Dordrecht Heidelberg New York London © Springer Science+Business Media Dordrecht 2015 This work is subject to copyright. All rights are reserved by the Publisher, whether the whole or part of the material is concerned, specifically the rights of translation, reprinting, reuse of illustrations, recitation, broadcasting, reproduction on microfilms or in any other physical way, and transmission or information storage and retrieval, electronic adaptation, computer software, or by similar or dissimilar methodology now known or hereafter developed. The use of general descriptive names, registered names, trademarks, service marks, etc. in this publication does not imply, even in the absence of a specific statement, that such names are exempt from the relevant protective laws and regulations and therefore free for general use. The publisher, the authors and the editors are safe to assume that the advice and information in this book are believed to be true and accurate at the date of publication. Neither the publisher nor the authors or the editors give a warranty, express or implied, with respect to the material contained herein or for any errors or omissions that may have been made. Printed on acid-free paper Springer Science+Business Media B.V. Dordrecht is part of Springer Science+Business Media (www.springer.com) I dedicate this book to Michael Booth. Michael was an incredible scientist whose Ph.D. on mycorrhizal networks took us to a new level with respect to field experiments on mycorrhizal networks. I was fortunate enough to be on his committee and see that his energy and intellect combined to give him an edge that few have at that stage. He agreed to contribute to this book and was working on the chapter with Jason Hoeksema when we lost him. His influence on the field was large and he was just getting started. Foreword In 1842, Carlo Vittadini, Professor of Medicine at the University of Milan and eminent mycological taxonomist, described the husk of tree feeder rootlets enclosing mature sporocarps of the mycorrhizal hypogeous genus Elaphomyces. He pointed out that the rootlets were mantled by hyphae growing out of such sporocarps, yet showed no sign of disease. He bravely stated “extra omne dubium,” beyond all doubt, that the rootlets were nourished by the Elaphomyces hyphae. Bravely, because at that time fungi were universally regarded either as causing disease or rotting organic matter. Buried in his monograph of Elaphomyces, that startling assertion was overlooked by mycorrhiza researchers for more than a century, and Vittadini did not pursue the topic again. Nonetheless, it was the first hypothesis later proven true that led to the real meaning of mycorrhizae and the translocating function of the mycorrhizal fungi. The ensuing 45 years witnessed considerable discussion about the fungal col- onization of rootlets of achlorophyllous plants such as Monotropa spp. and its connection with tree roots. The nature of that connection was debated, but no firm conclusions reached: Is the fungus a parasite on the achlorophyllous plant, or is the plant “humicolous,” obtaining its nutrients directly from soil organic matter via the fungi? Feeder rootlets of ectomycorrhizal trees were noted to be among those of the achlorophyllous plants, but the sharing of those fungi was mentioned in passing or not at all. The Russian botanist F. Kamienski speculated in 1882 that Monotropa might be nourished by overstory trees through shared hyphae, or perhaps the fungus was humicolous. His rather convoluted discussion leaves the reader in doubt exactly what he hypothesized. Then, the German plant pathologist A.B. Frank publishes his epic paper in 1885, in which he accurately describes with clarity the morphology of ectomycorrhizae, coins the term “mycorrhiza” for them, and correctly interprets their mutualistic symbiotic nature. Given the confusion about the phenomenon at the time, Frank’s paper was an amazing tour de force. But, the puzzle of achlorophyllous plants remained. vii viii Foreword In the early half of the twentieth century, a rather desultory interest in mycorrhizae continued, albeit a few important contributions appeared, such as that on the role of mycorrhizae in mineral nutrition of plants by the American A.B. Hatch in 1937. After World War II, Prof. Elias Melin and his students at the University of Uppsala, Sweden, became the first mycorrhiza researchers to enlist isotopes in study of translocation via mycorrhizal hyphae of elements and com- pounds from external sources to mycorrhizal seedlings and vice versa. Melin’s group performed the epochal experiments that confirmed Frank’s hypotheses of some 65 years earlier, thus laying the methodological foundation for study of common mycorrhizal networks (CMN). Eric Björkman, also Swedish, reported his results from experiments with 14C-labelled glucose and 32P-labelled phosphate injected into pine and spruce trees under which grew achlorophyllous Monotropa plants 1–2 m from the tree trunks. In 5 days, actively growing Monotropae had concentrated the isotopes, which did not appear in other nearby Ericaceae. This would seem to be the 1st experimental demonstration of CMN in Nature. Little attention was then paid to CMN until the 1980s, when Roger Finlay and David Read of the University of Sheffield experimentally demonstrated movement of 14C and 32P to tree seedlings linked through CMN. From then to the present, research on the role of CMN in plant nutrition in laboratory and field has blos- somed. As shown in the chapters of this book, CMN can have immense nutritional, ecological, agricultural, and forestry consequences undreamed of 40 or even 20 years ago. New terms have entered the lexicon of mycorrhiza research, e.g., CMN, infochemicals, and network theory. So, readers, feast your eyes and minds on the pages that follow. Jim Trappe Department of Forest Ecosystems and Society Oregon State University U.S. Forest Service Pacific Northwest Research Station Forestry Sciences Laboratory Preface The overwhelming majority of the world’s plant species are associated with mycorrhizal fungi in nature. As the term mycorrhiza implies, the association involves fungal hyphae interacting in the roots of a plant. Importantly, the hyphae do not penetrate the cell membranes of the root cells, although they may penetrate the cell wall. Further, the plant does not reject the fungus as a parasite or pathogen. The hyphae extend away from the roots into the soil where they take up nutrients and transport them through the mycelium and to colonized roots. Multiple hyphae connect plant hosts into what has become known as a mycorrhizal network. Mycorrhizal networks are below ground and cryptic. As such, plant and ecosystem ecologists in the past had to largely “black-box” the role of mycorrhizal networks in plant community and ecosystem dynamics. Björkman was the first to report field evidence of a mycorrhizal network in his work on the nutritional mode of the mycoheterotrophic plant Monotropa hypopitys (Björkman 1960). Newman (1988) provided a thorough review of the structure and function of mycorrhizal networks. Since Newman’s initial review there has been an impressive amount of work on the topic using advanced methods such as isotopic labeling and PCR-based identifi- cation methodologies and additional reviews have followed (Simard and Durall 2004; Selosse et al. 2006; Horton and Van der Heijden 2008; Peay et al. 2008; Van Der Heijden and Horton 2009; Bahram et al. 2014). The textbook explanation for the benefit to plants of associating with mycorrhizal fungi is that fungi provide plants with a physical extension of the root system. Importantly, the fungi also produce unique enzymes that give plants access to pools of nutrients with limited availability to the plants alone (e.g., organic nitrogen, phosphorus). However, an individual mycorrhizal plant colonized by a single fungus individual is too simple. The mycorrhizal condition is much more complex and interesting. For example, an ectomycorrhizal tree may support tens of fungus species on its roots and multiple genotypes of each (Bahram et al. 2011). And each genetic entity (genet) may be isolated into multiple independent ramets. Further, this does not address the increasingly recognized role of mycorrhizal fungi in forming intra- and inter-specific plant connections, the mycorrhizal networks. ix x Preface It has become clear that most mycorrhizal fungi colonize and provide nutrients to multiple plant species. This has important implications for plant competition for soil nutrients, seedling establishment, plant succession, and plant community and ecosystem dynamics.

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