Individual vulnerability factors of Silver fir (Abies alba Mill.) to parasitism by two contrasting biotic agents: mistletoe (Viscum album L. ssp. abietis) and bark beetles (Coleoptera: Curculionidae: Scolytinae) during a decline process

Marion Durand-Gillmann (1) , Maxime Cailleret (1) , Thomas Boivin (1) , Louis-Michel Nageleisen (2) , Hendrik Davi (1)

1 URFM - Ecologie des Forêts Méditerranéennes
2 Ministère de l’alimentation, de l’agriculture, de la pêche, de la ruralité et de l’aménagement du territoire DGAL/SDQPV, Département de la Santé des Forêts Antenne Spécialisée,

• Context In recent decades, there have been increasing reports of forest decline, especially in Mediterranean forest ecosystems. Decline in tree vitality is usually due to complex interactions between abiotic factors and biotic agents that attack weakened trees. • Aims and methods Estimating dendrometrical characteristics [basal area increment (BAI), age at DBH from tree ring counting, social status, height, and diameter], tree health status, and a competition index, we investigated the individual vulnerability of a French declining silver fir forest to both mistletoe (Viscum album L. ssp. abietis) and bark beetles (Pityophthorus pityographus Ratz., Pityokteines vorontzovi Jac., and Pityokteines spinidens Reitt.). • Results BAI was negatively correlated with both mistletoe infection (via mistletoe biomass) and bark beetle attack (number of insects per square meter), but there was evidence of divergence in tree choice between two groups of parasites. Mistletoe preferentially infected isolated and dominant trees that showed higher past growth rates than non-infected ones. Conversely, bark beetles mainly attacked defoliated and preferably declining trees with diameter (DBH) lower than 44.5 cm and slower past growth. • Conclusion While successive severe drought periods are thought to greatly weaken southern silver fir populations, mistletoe and bark beetles may contribute actively to their decline processes as inciting and contributing factors, respectively.

Mots clés: Viscum album L.; Bark beetles; Growth

Mots clés: Fir plantations; Parasitism

Domaines: Sciences du Vivant [q-bio]

Marion Durand-Gillmann, Maxime Cailleret, Thomas Boivin, Louis-Michel Nageleisen, Hendrik Davi. Individual vulnerability factors of Silver fir (Abies alba Mill.) to parasitism by two contrasting biotic agents: mistletoe (Viscum album L. ssp. abietis) and bark beetles (Coleoptera: Curculionidae: Scolytinae) during a decline process. Annals of Forest Science, 2014, 71 (6), pp.659-673. ⟨10.1007/s13595-012-0251-y⟩. ⟨hal-01102700⟩