20-"Différences de provenance et d'espèces dans la résilience des jeunes arbres au givre et au broutement des ongulés accentuent les problèmes de régénérat° dans les forêts de montagne" : A.D. Kupferschmid (Swiss federal institute for forest,snow...)

COLLOQUE « HABITATS FORESTIERS ET FORÊTS HABITÉES » COMMENT USAGES, GESTIONS ET PRATIQUES SOCIALES INTERAGISSENT AVEC LA FAUNE SAUVAGE EN FORÊT ?"

Ce colloque international, qui s'est tenu au sein du Domaine national de Chambord (26 et 27 mars 2019), s'inscrit dans le cadre du projet de recherche COSTAUD (Contribution des OnguléS au foncTionnement de l’écosystème et AUx services rendus à ChamborD, financé par la Région Centre-Val de Loire et porté par l'Irstea, 2016-2019).

Toutes les informations sur le colloque : https://living-forests.sciencesconf.org/

Le colloque "Habitats forestiers et forêts habitées" a abordé la forêt, part de l'imaginaire et des paysages, comme lieu d’interactions entre l’homme et la faune sauvage.

Il a été l'occasion de réfléchir à l’empreinte passée de nos activités, aux déterminants actuels et leurs enjeux, ainsi qu’aux perspectives d’évolution des forêts et des habitats qui les composent.

Pour y parvenir ont été privilégiées les approches pluridisciplinaires tenant compte de l’écologie de la faune sauvage et des forêts, de leurs représentations sociales et de la fréquentation touristique associée à ces patrimoines naturel et culturel.

Session "Conséquences des modes de gestion des habitats forestiers sur la faune sauvage"

"Provenience and species specific differences in sapling resilience to frost and ungulate browsing enhance regeneration problems in mountain forests" : A.D. Kupferschmid (Swiss Federal Institute for Forest, Snow and Landscape Research WSL)

Résumé de l'intervention :

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Local climate and ungulate browsing are two major factors that affect tree regeneration and genetic adaptation in Central European forests. Owing to climate change and increasing ungulate numbers, the abiotic and biotic environments of trees are changing, making it necessary to investigate the separate and joint effects of provenance origin (and climate) and ungulate herbivory. The aim of this study was to analyse the influence of intraspecific genetic variation on the sensitivity and resilience of tree species to stress due to frost and simulated winter browsing.

In an genecological experiment, we investigated quantitative genetic variation within and among provenances of Abies alba, Picea abies, and Fagus sylvatica. Each species was represented by 72 - 90 autochthonous provenances, covering the species' ecological range in Switzerland. In spring 2015, the ca. 4000 saplings per species were clipped with three intensities (heavy, light and no clipping) to simulate winter browsing by roe and red deer. Growth reactions were assessed one and two growing seasons after treatment, and provenance differences were related to environmental variables of seed sources.

For Abies, frost damage and clipping resulted in reduced height growth in the first year after the stress and reduced height for at least two (clipping) to four (frost) vegetation seasons. Sapling biomass and diameter increment decreased after heavy clipping. For Picea and Fagus, the effect of this single simulated browsing event disappeared over time for the growth traits. Reduced growth only persisted for Picea saplings after frost damage. However, sapling quality decreased after clipping for all three species.

The ‘reaction type' after browsing seems to be species specific but independent of seed origin. In contrast, the time lag between simulated browsing and formation of a clear new leader shoot increased for Abies with lower temperatures at the seed source. Differences in sapling resilience to stress enhanced the existing differences among provenances. Lowland provenances with warmer climates grew faster, and in Picea also qualitatively better, and recovered faster (Abies) or more efficiently (Picea) to leader shoot loss. Thus, there is no clear evidence of a tradeoff between adaptation to climate change and resilience to stress.