Dead Wood in Forest Ecosystems

by

Jürgen Bauhus, Kristin Baber, Jörg Müller

• LAST REVIEWED: 22 February 2018
• LAST MODIFIED: 22 February 2018
• DOI: 10.1093/obo/9780199830060-0196

Introduction

Dead wood occurs in every forested ecosystem. Even if trees are harvested, some of their wood remains on site; for example, in the form of roots and branches. This wood from dead and dying trees plays a key role in ecosystem processes and functioning. Through the removal of wood, this dead-wood resource, in particular that of larger dimension, termed “coarse woody debris” (CWD), has become scarce in most managed forests. The term “debris” indicates that this resource was not valued, neither economically nor ecologically. The recognition that many species were threatened by low levels of this resource initiated a wave of research into the ecology of dead wood beginning in the 1970s to 1980s. It is now estimated that 20–40 percent of organisms in forested ecosystems depend, during some part of their life cycle, on wounded or decaying woody material from living, weakened, or dead trees. In addition to its habitat function, it has been recognized that dead wood plays important roles in carbon, nutrient, and hydrological cycles and is a key structural component influencing ecosystem processes such as erosion. Dead wood is a dynamic resource. Disturbances such as fires or windthrow as well as individual tree death and harvesting supply dead wood, which is subsequently decomposed. The most important species driving the decomposition process are fungi and insects. Together with a number of other species, including vertebrates, they form complex food webs of detritivores, fungivores, predators, scavengers, and parasitoids, including various symbioses. The high variability of dead wood in space and time makes its description challenging. In this article we describe this variability of dead wood, present dynamics of dead wood in unmanaged and managed forests, and characterize the decomposition of dead wood and point to its role in the carbon and nutrient cycles. An overview of the role of dead wood for ecosystem processes and as habitat is followed by a section on the effects of forest management on CWD and strategies to manage for dead wood.

General Overviews

An often-citied classic publication on the ecology of dead wood in temperate forests is the review in Harmon, et al. 1986. A comprehensive introduction to the biodiversity in decaying wood is provided in Stokland, et al. 2012. Speight 1989 provides the key literature on saproxylic species, manly invertebrates, while Rayner and Boddy 1988 is a comprehensive overview of fungal wood decay and how it is influenced by wood properties and the fungi involved. Substantial reviews on the ecology and conservation of saproxylic species with particular reference to the effect of forest management include Siitonen 2001 and Lonsdale, et al. 2008, focusing on wood-decaying fungi, and Grove 2002, on saproxylic insects. Maser, et al. 1979 represents an early yet comprehensive attempt to develop some guidelines for the management of dead and downed wood on the basis of the recognized ecological functions. With respect to the increasing demand for information about dead-wood quality and quantity, especially in the context of forest management and nature conservation, Ståhl, et al. 2001 offers a valuable overview of coarse woody debris (CWD) monitoring methods.

• Grove, Simon J. 2002. Saproxylic insect ecology and the sustainable management of forests. Annual Review of Ecology and Systematics 33:1–23.

  DOI: 10.1146/annurev.ecolsys.33.010802.150507

  A literature review on saproxylic insect ecology and conservation as influenced by management in different forest ecosystems. Relating shared ecological traits of saproxylic insects to forest management practices, the author offers considerations and suggestions for the future of saproxylic insects in managed forests worldwide.

• Harmon, Mark E., Jerry F. Franklin, Fred J. Swanson, et al. 1986. Ecology of coarse woody debris in temperate ecosystems. Advances in Ecological Research 15:133–302.

  DOI: 10.1016/S0065-2504(08)60121-X

  This seminal paper provided the first broad review of dead-wood ecology and placed the topic firmly in the context of forest ecology. Most of the topics covered in this review are still in the focus of dead wood–related research in the early 21st century.

• Lonsdale, David, Marco Pautasso, and Ottmar Holdenrieder. 2008. Wood-decaying fungi in the forest: Conservation needs and management options. European Journal of Forest Research 127.1: 1–22.

  DOI: 10.1007/s10342-007-0182-6

  The review primarily focuses on wood-decaying fungi in boreal and temperate forests. It points to the factors that determine the diversity of wood-decaying fungi, and provides suggestions on how this diversity may be protected in managed forests.

• Maser, Chris, Ralph G. Anderson, Kermit Cromack Jr., Jerry T. Williams, and Robert E. Martin. 1979. Dead and down woody material. In Wildlife habitats in managed forests: The Blue Mountains of Oregon and Washington. Edited by Jack Ward Thomas, 78–95. USDA Agriculture Handbook 553. Washington, DC: US Department of Agriculture, Forest Service.

  The chapter provides a comprehensive overview of the then-known important ecological functions of dead wood and provides suggestions how this resource may be managed.

• Rayner, Alan D. M., and Lynne Boddy. 1988. Fungal decomposition of wood: Its biology and ecology. Hoboken, NJ: John Wiley.

  One of the main books on wood-decaying fungi that comprises an in-depth examination of the wood decay process while taking into account the fungal biology and ecology and the complex interactions among wood resources, organisms, and the environment.

• Siitonen, Juha. 2001. Forest management, coarse woody debris and saproxylic organisms: Fennoscandian boreal forests as an example. In Special issue: Ecology of woody debris in boreal forests. Edited by Bengt Gunnar Jonsson and Nicholas Kruys. Ecological Bulletins 49:11–41.

  The Fennoscandian boreal forests are used as an example to present the influence of forest management on the quantity and quality of CWD and its effect on the diversity of saproxylic organisms. While pointing to the importance of the resource-species interactions, the authors provide important theoretical and practical issues for conservation, management, and research of CWD and the species dependent on dead-wood habitats. Available online by subscription.

• Speight, Martin C. D. 1989. Saproxylic invertebrates and their conservation. Nature and Environment 42. Strasbourg, France: Council of Europe.

  This book provides an established definition of saproxylic invertebrates, which has been developed and refined more recently. On the basis of the sensitivity of many saproxylic species to forest disturbances and management regimes, it describes criteria for selection of saproxylics to be employed as bioindicators of forest quality. In addition, the book contains a valuable list of many saproxylic invertebrate species found in the United Kingdom that meet these criteria.

• Ståhl, Göran, Anna Ringvall, and Jonas Fridman. 2001. Assessment of coarse woody debris: A methodological overview. In Special issue: Ecology of woody debris in boreal forests. Edited by Bengt Gunnar Jonsson and Nicholas Kruys. Ecological Bulletins 49:57–70.

  This offers an overview of different standards as well as methods to estimate the amount of CWD, with a description of methodological principles, in addition to aspects of theoretical efficiency and practical application. Available online by subscription.

• Stokland, Jogeir N., Juha Siitonen, and Bengt Gunnar Jonsson. 2012. Biodiversity in dead wood. Ecology, Biodiversity and Conservation. New York: Cambridge Univ. Press.

  DOI: 10.1017/CBO9781139025843

  A highly recommended book with a comprehensive introduction to biodiversity in decaying wood, also synthesizing natural history and conservation needs of wood-inhabiting organisms.