|
Résumé :
|
Forest ecosystems shelter a major part of terrestrial biological diversity, and over the past decades, conservation of biodiversity has become a key element in national forest policies and planning. Plantation forests are cultivated forest ecosystems established primarily for wood biomass production but also for soil and water conservation or wind protection. During the past decade, the global forest plantation area has increased by an estimated 32 million ha while the area of natural forests has declined by 126 million ha. Biodiversity is an issue of increasing relevance to the development and management of plantation forests and their long-term sustainabifity. Plantations can and do play a vital role in forest conservation by providing a substitute for wood from unsustainable harvesting of natural forests. In many parts of the world plantations also play a key role in restoring local ecosystem services and by reducing runoff and erosion on previously degraded sites. Despite these positive attributes, planta- tion forests are widely viewed in a negative light in relation to biological diversity conservation, especially when intensive monocultures of exotic species are involved. While a plantation stand will, in general, support fewer native species than a native forest at the same site, plantations are increasingly replacing other human-modified ecosystems (e.g., degraded pasture) and often support a greater diversity of native species, particularly in understorey communities. As such, plantations can play an important role in conserving or even restoring native biodiversity in production landscapes. As weil as providing habitat in their own right, plantations play particularly important roles in buffering native forest remnants and in enhancing connectivity between areas of native ecosystems. In doing so, these plantation forests may help foster the overall sustainability of agriculture and other land uses across these landscapes. However, to sustain health and productivity of planted forests, managers need to preserve genetic diversity through adapted breeding strategies and controlled deployment of improved genetic material, and enhance interspecific diversity using a greater variety of planted species (exotic and native) and alternative forest management regimes and practices, such as the extension of rotation lengths in some stands, and adoption of a variety of harvesting approaches.
|
