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Projet Corylus : influences de la composition et de la structure des masses forestières sur la biodiversité. Rapport final de la Convention GIP Ecofor-MEEDM n°0000192

Abstract : Context and objectives - French landscapes are marked by a continuous increase in forest cover for the last two hundred years (from 15 to 30% of the surface area of France). For some biota, such as plant species, very few studies dealt with the impact of spatial structure of woodlands on biodiversity patterns. This project planned to analyze such relationships between plant and bird species diversity and spatial structure of woodlands. In order to be able to separate between local (soil, climate, stand type) and landscape effects, and to get enough statistical replicates of different landscape configurations, we worked with the National Forest Inventory (NFI) data gathered over all Northern France for plants, and with the entire French STOC network for birds. Landscape indices were measured or calculated from aerial photo-interpretation and existing national forest maps. Questions - (1) Do forest plant species display specific patterns of presence according to the distance to the external forest edge? What is the maximum range of this "edge effect"? (2) How did forest spatial organization changed since the beginning of the XIXth century? (3) What is the influence of the structure and composition of the surrounding forest habitats on the local flora? What are the respective proportions of plant composition variation explained by local factors versus landscape features? Does the magnitude of landscape effects vary according to the scale of measurement? (4) Have hedgerows connecting woodland patches a beneficial role on forest bird species, because they would act as corridors and counteract the detrimental effects of forest fragmentation? Results - (1) More than 100 plant species, among the most common species in French forests, showed a significant positive or negative response to edge distance. The depth of edge influence often extended over 1200 m. The depth of edge influence is not only due to abiotic effects (light, humidity, soil nutrient richness) but could also be linked to movement of the forest edges during the past. Forest species migration could not track the change in the position of forest edges. (2) Forest area in Lorraine increased from 29.6% in 1830 to 34.9% in 2000, i.e. a 18% increase over 170 years. This increase rate was much lower than the national average previously estimated from ancient inventories. The proportion of ancient woodlands varied a lot according to land owner: 90% in state forests, 88% in communal forests and 49% only in private forests. The proportion of recent forests connected to ancient woodlands was high (87%). This confirms that the increase in forest cover mainly resulted in a centrifuge movement of edges towards the exterior of woodland patches. (3) The part of variation in vegetation composition explained by landscape variables was 4 to 5 times less than by the part explained by local factors (soil, climate and stand type). Vegetation responded to three main landscape gradients: the first one was the distance to the external forest edge, the second was the proportion of cuttings and young stands (
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https://hal.inrae.fr/hal-02593353
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Submitted on : Friday, May 15, 2020 - 5:11:27 PM
Last modification on : Thursday, November 18, 2021 - 4:06:05 AM

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  • HAL Id : hal-02593353, version 1
  • IRSTEA : PUB00029007

Citation

J.L. Dupouey, Laurent Bergès, J.G. Boureau, C. Cluzeau, M. Duprez, et al.. Projet Corylus : influences de la composition et de la structure des masses forestières sur la biodiversité. Rapport final de la Convention GIP Ecofor-MEEDM n°0000192. [Rapport de recherche] irstea. 2010, pp.160. ⟨hal-02593353⟩

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