Bird assemblages in a mixed woodland–farmland landscape: The conservation value of silviculture-dependant open areas in plantation forest

Abstract

Although considered by some as a less “ecologically suitable” forestry model than “near-natural” stand management, even-aged plantation forest management, with regeneration procedure involving clearcutting, creates temporary habitat for many early-successional birds. The present study addresses the question of the conservation value for birds of clearcutting-related open areas in European temperate forest, in the context of a mixed woodland–farmland landscape. The point count technique was used to census the breeding birds on 300 sampling plots, distributed in the eight main habitat types of the Ardenne region (southern Belgium), including agricultural land, edge habitats, closed forest habitats and open areas in forest. Most of these open areas in forest derive from clearcutting practices, rapidly planted with young Norway Spruce ( Picea abies). We quantified the conservation value of a given habitat type by using a “conservation value index”, integrating the frequency of occurrence of each species in the considered habitat and their conservation status in Europe or in southern Belgium. Both conservation value index and species richness were higher for edge habitats and open areas in forest, compared to forest interior and agricultural land. Detrended Correspondence Analysis of the plot species lists showed that bird assemblages from open area in forest are not intermediate between forest and agricultural open land, as opposed to external edge habitats. Hence, open areas in forest do not contain bird assemblages composed of forest species mixed with colonizing agricultural species but rather shelter specific bird assemblages. An Indicator Species analysis further emphasized this specificity and identified seven species, which, in the Ardenne context, form a group of species specific to open areas in forest. Due to major changes of land use in the Ardenne during the 20th century, which leads to a tremendous decrease of moor, heath and fallow land areas, clearcut openings in the plantation forest progressively gained high conservation value at the regional scale. Further studies about habitat requirement of the conservation interest species inhabiting these open areas is needed, including a better understanding of how early-successional species react to forest planning. If plantation forestry evolves to an uneven-aged and more permanently closed forest, then other options, including semi-natural habitat restoration, are urgently required to save early-successional bird communities.