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Evolution recente de la foret fran chises : Surface, volume sur pied, productivity

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... Chez les oiseaux des milieux forestiers, la situation est plus complexe. Les espèces des milieux jeunes ont majoritairement des aires et des populations en recul alors que la déprise agricole s'étend mais que les taillis régressent (PIGNARD, 2000). Ces espèces, pour bon nombre migratrices au long cours, sont exposées à des pressions hors de leur aire de nidification (dégradation des habitats sur leur aire d'hivernage) et sont les plus touchées par le réchauffement climatique (BOTH et al., 2010). ...
... Ces espèces, pour bon nombre migratrices au long cours, sont exposées à des pressions hors de leur aire de nidification (dégradation des habitats sur leur aire d'hivernage) et sont les plus touchées par le réchauffement climatique (BOTH et al., 2010). En revanche, face à l'extension de la forêt française au profit des futaies (PIGNARD, 2000), les espèces des forêts mâtures ont une dynamique spatiale et démographique très partagée, pour moitié à l'expansion, pour moitié à la régression. À ces deux tendances majeures -expansion de la forêt française et étalement urbain -s'ajoute une régression des milieux herbacés. ...
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Habitat typology of breeding birds in France. Testing the influence of the typological level on trend assessment. The purpose is to define the habitat of the 268 breeding bird species in France in order to standardize comparisons of ecological data dealing with bird habitats in space (betweenhabitats, between-regions) and in time (long time or short time surveys). After a bibliographical research, experts were contacted on the basis of 60 pictures of habitats used by breeding birds. The major habitat of each species was determined by crossing two approaches, one defined by the vote of experts and the other statistically by pooling together the species sharing the same habitat. The suggested typology is considered at three levels: the domain (5 classes), the landscape (11 classes) and the habitat (18 classes). A synthetic table of distribution of the 268 species in relation to this typology is presented. The typology is tested in relation to trends of distribution and long term abundance of these species in France. The conclusions by habitat are discussed in relation to the considered level of the analysis, the one at level 2 (landscape) and the other at level 3 (habitat). Finally, the conclusions between the typological levels are congruent
... The present proportion of Douglas Fir in the national volume is small (2.2%) but rapidly increasing. It is a major species in reafforestation (Pignard, 2000), which deserves special interest. An additional sample of 123 bigger trees was added, with only merchantable wood (threshold diameter 7 cm) available. ...
Article
In order to improve the estimation of carbon stored in the French forest biomass from National Forest Inventory data, we developed six species-specific equations for estimating the total aboveground volume of trees, including merchantable volume, branches and twigs. Equations use circumference at breast height and total height as independent variables. They were built from even-aged forests of the Landes massif, the northern half and the eastern mountain regions of France. The sample was selected within archives of volume measurements taken in growth and yield permanent plots between 1920 and 1955. It is made up of 4619 trees belonging to seven important species: 1222 Sessile Oak, 1293 Common Beech, 347 Douglas Fir, 309 Norway Spruce, 389 Scots Pine, 297 Maritime Pine and 762 Silver Fir. These trees were felled and measured in 26 different forests (62 stands). Tree form factor was analysed, rather than volume, to remove heteroscedasticity, and height was substituted by a hardiness coefficient to remove diameter–height correlation. The analysis identified species-specific modes of variation of tree form with respect to developmental stage and tree hardiness. Maritime and Scots Pine did not differ statistically, despite large differences between ecological and silvicultural situations of both species. This suggests the possibility to use identical volume equations for species belonging to the same genus. Regional variations of tree form were explored by a cross-validation technique. Prediction biases did not exhibit a clear geographic structure. A 5% overestimation for hardwoods in southern sites is possible, and would deserve further testing. The hypothesis that recent growth changes may have slightly altered tree form is also discussed. Finally, a national-scale application provided Biomass Expansion Factors consistent with former studies and suggested that these volume equations behave well in extrapolation to coppices, uneven-aged or mixed stands.
Article
The purpose is to define the habitat of the 268 breeding bird species in France in order to standardize comparisons of ecological data dealing with bird habitats in space (between- habitats, between-regions) and in time (long time or short time surveys). After a bibliographical research, experts were contacted on the basis of 60 pictures of habitats used by breeding birds. The major habitat of each species was determined by crossing two approaches, one defined by the vote of experts and the other statistically by pooling together the species sharing the same habitat. The suggested typology is considered at three levels: the domain (5 classes), the landscape (11 classes) and the habitat (18 classes). A synthetic table of distribution of the 268 species in relation to this typology is presented. The typology is tested in relation to trends of distribution and long term abundance of these species in France. The conclusions by habitat are discussed in relation to the considered level of the analysis, the one at level 2 (landscape) and the other at level 3 (habitat). Finally, the conclusions between the typological levels are congruent but may differ from one level to the other.
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