Plantations and biodiversity: A comment on the debate in New Brunswick

Abstract

The importance of biodiversity has become widely recognized but the best methods for conserving forest biodiversity are still being debated. Central to this debate is the influence of plantations and managed stands on local and landscape-scale biodiversity. A recent paper by Erdle and Pollard in The Forestry Chronicle (2002), which concluded that few plantations are strict monocultures in terms of the total number of tree species, could be interpreted as making the case that plantations have relatively minor consequences for biodiversity. We argue that: (1) it is not only the number of species, but also the identities and relative abundances of species that are of ecological importance, and (2) defining biodiversity in terms of tree species alone is of limited applicability. Existing research in New Brunswick on the impact of plantations on biodiversity at the stand scale reveals potentially significant biodiversity losses, at least in certain taxa. The proposal that incorporating more structural elements (e.g., snags, coarse woody debris, vertical structure) and retaining greater tree species diversity to ameliorate negative consequences of plantations remains a hypothesis to be tested in this region. Scientific information gathered in the following areas will allow better decision making: (1) to what degree are older plantations used by native species? (2) are productivity and survivorship of vertebrates in intensively managed stands similar to those in unmanaged forest? (3) are intensively managed stands suitable habitat for non-vertebrates? (4) are there thresholds in the response of some species to landscape-scale habitat loss caused by intensive forest management?Key words: plantations, biodiversity, species composition, landscape scale, stand structures RÉSUMÉ L'importance de la biodiversité est acceptée de façon générale mais les meilleures méthodes de conservation de la biodiversité forestière font encore l'objet d'un débat. Au coeur de celui-ci, on retrouve l'influence des plantations et des peuplements aménagés sur la biodiversité locale et à l'échelle de l'écosystème. Un article récent publié par Erdle et Pollard dans Le Forestry Chronicle en 2002 qui concluait que rares sont les plantations qui constituent des monocultures absolues en terme du nombre total d'espèces d'arbres, pouvait être interprété comme énonçant que les plantations entraînent des conséquences relativement mineures au niveau de la biodiversité. Nous alléguons que (1) ce n'est pas seulement le nombre d'espèces, mais également l'identité et l'abondance relative des espèces qui sont d'importance écologique et, (2) la défini-tion de la biodiversité en terme d'espèces d'arbres seulement est d'une applicabilité restreinte. Les recherches en cours au Nouveau-Brunswick sur les retombées des plantations sur la biodiversité au niveau du peuplement révèlent des pertes de biodiversité potentiellement significatives, du moins pour certains taxons. La proposition cherchant à incorporer plus d'éléments structuraux (par ex., les chicots, l...

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