Limits to reproduction and seed size-number trade-offs that shape forest dominance and future recovery

International audienceThe relationships that control seed production in trees are fundamental to understanding the evolution of forest species and their capacity to recover from increasing losses to drought, fire, and harvest. A synthesis of fecundity data from 714 species worldwide allowed us to examine hypotheses that are central to quantifying reproduction, a foundation for assessing fitness in forest trees. Four major findings emerged. First, seed production is not constrained by a strict trade-off between seed size and numbers. Instead, seed numbers vary over ten orders of magnitude, with species that invest in large seeds producing more seeds than expected from the 1:1 trade-off. Second, gymnosperms have lower seed production than angiosperms, potentially due to their extra investments in protective woody cones. Third, nutrient-demanding species, indicated by high foliar phosphorus concentrations, have low seed production. Finally, sensitivity of individual species to soil fertility varies widely, limiting the response of community seed production to fertility gradients. In combination, these findings can inform models of forest response that need to incorporate reproductive potential

Limits to reproduction and seed size-number tradeoffs that shape forest dominance and future recovery

The relationships that control seed production in trees are fundamental to understanding the evolution of forest species and their capacity to recover from increasing losses to drought, fire, and harvest. A synthesis of fecundity data from 714 species worldwide allowed us to examine hypotheses that are central to quantifying reproduction, a foundation for assessing fitness in forest trees. Four major findings emerged. First, seed production is not constrained by a strict trade-off between seed size and numbers. Instead, seed numbers vary over ten orders of magnitude, with species that invest in large seeds producing more seeds than expected from the 1:1 trade-off. Second, gymnosperms have lower seed production than angiosperms, potentially due to their extra investments in protective woody cones. Third, nutrient-demanding species, indicated by high foliar phosphorus concentrations, have low seed production. Finally, sensitivity of individual species to soil fertility varies widely, limiting the response of community seed production to fertility gradients. In combination, these findings can inform models of forest response that need to incorporate reproductive potential

Analyse de la faible colonisation des cônes de pin cembro (Pinus cembra L.) par les insectes

National audienc

Analyse de la faible colonisation des cônes de pin cembro (Pinus cembra L.) par les insectes

National audienc

Larch- and pine-feeding host races of the larch bud moth ( Zeiraphera diniana) have cyclic and synchronous population fluctuations.

International audiencePopulation cycles of many forest-defoliating insects often show synchronous fluctuations at both intra-specific (spatial synchrony) and inter-specific levels. However, population dynamics of different host-associated biotypes of the same species, such as those of the larch budmoth (LBM), Zeiraphera diniana (Lepidoptera: Tortricidae), have never been compared. This species causes extensive defoliation of larch forests every 8 to 9 years in the Alps, but it consists of two genetically-differentiated host races, the first one developing on European larch, Larix decidua, and the other one developing on Swiss stone pine, Pinus cembra. The dynamics of Zeiraphera populations have been extensively studied on..

Intraspecific Variation in Floral Color and Odor in Orchids

International audienc

Efficiency of spraying mountain pine cones with oleoresin of Swiss stone pine cones to prevent insect attack

31 ref.International audienceThe difference in cone colonization by specialized insects that had been observed between Swiss stone pine (Pinus cembra L.) and mountain pine (P. uncinata Ram.) prompted us to test whether volatiles and oleoresin of Swiss stone pine cones may serve as a barrier for insect attack. The volatiles emitted by cones of both pine species were sampled using headspace techniques in the French Alps. The cone volatiles of both species essentially consisted of seven similar monoterpenes, but the terpene profiles markedly differed between species. α-Pinene (67% of the total), β-pinene, and limonene + β-phellandrene were dominant in the cone volatiles of Swiss stone pine, while the cone emissions of mountain pine showed no dominant terpenoid. The cone oleoresin of P. cembra significantly differed from cone volatiles by a lower level of α-pinene and higher levels of β-pinene and limonene + β-phellandrene. Field sprays of mountain pine cones with oleoresin extracts of Swiss stone pine cones significantly reduced the overall damage of specialized cone insects. None of the cones sprayed with oleoresin were attacked, whereas 11% and 31% of the unsprayed control cones were damaged by insects. Specific cone damage due to a cone weevil, Pissodes validirostris Gyll. (Coleoptera: Curculionidae), and a cone pyralid, Dioryctria mutatella Fuchs (Lepidoptera: Pyralidae), were significantly decreased in one year. The volatile profile of the sprayed cones differed markedly from that of unsprayed mountain pine cones, especially in the higher level of myrcene. However, the volatile profile of the sprayed cones also differed from that of the oleoresin extract used for spraying. The role of monoterpenes in protecting the sprayed cones from insect attack is discussed

Cone and foliage volatiles emitted by Pinus Cembra and some related conifer species

3 tables 1 graph.International audienc