Chapter 2 Old-Growth Forest Definitions: a Pragmatic View Christian Wirth, Christian Messier, Yves Bergeron, Dorothea Frank, and Anja Fankhanel Introduction: Many of us possess an archetype of old-growth forest appearance. We expect majestic trees, small pockets of regenerating trees thriving to reach the sun, heaps of dead wood covered with mosses | Chapter 2 Old-Growth Forest Definitions a Pragmatic View Christian Wirth Christian Messier Yves Bergeron Dorothea Frank and Anja Fankhanel Introduction Many of us possess an archetype of old-growth forest appearance. We expect majestic trees small pockets of regenerating trees thriving to reach the sun heaps of dead wood covered with mosses snags spangled with cavities and bracket fungi and rare wildlife. However thinking twice we may realise that this archetype 1 is not a scientific definition but merely a picture and 2 is not generic but rather describes the late stage of succession in the temperate forest biome where the great majority of ecologists live and work. In boreal forests trees rarely reach majestic dimensions and yet may attain great ages. In some pine forests trees become very old but gap phase regeneration is impeded by recurring surface fires. In tropical forests trees grow tall but dead wood does not pile up because of high decomposition rates. These examples illustrate that there are many ways for a forest to grow old and that it is probably a futile task to aim at providing a concise scientific definition of old-growth forest that encompasses the full spectrum of successional and structural options. This chapter consists of four sections. Section reviews existing attempts to define old-growth forest and discusses their merits and problems. Subsequent sections are devoted to the more applied aspects of old-growth forest definitions and their implications. Specifically Sect. presents a literature analysis conducted to understand how the term old-growth is actually used in the literature as well as how often and why it is replaced by competing terms. Section explores how disturbance regimes and successional dynamics interact in determining the occurrence of old-growth across the globe and the topic of old-growth forest conservation is briefly covered in Sect. . The chapter concludes by discussing the usefulness of definitions in
