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

Untersuchung über die Quellen der Conquestes de Charlemaine (Dresdener Hs. O81).

"Der Rest dieser Arbeit erscheint in den Romanischen Forschungen; ... Bd. XII Heft 4."Cover title.Halle-Wittenber

O índio na fotografia brasileira: incursões sobre a imagem e o meio The Indian in Brazilian photography: incursions into image and medium

Pretende-se explorar contradições e confluências entre o meio (fotográfico) e a imagem do índio brasileiro sob uma perspectiva histórica da fotografia brasileira. A imagem do índio nessa fotografia manifesta-se em três momentos distintos. Na fase inicial, no lugar do exótico, contraditório ao sentido moderno da fotografia durante o Segundo Império. Na segunda fase, as fronteiras entre o etnográfico e o nacional se diluem, nos primeiros cinquenta anos do século XX, a exemplo da Comissão Rondon/Seção de Estudos do SPI e do fotojornalismo moderno no Brasil da revista O Cruzeiro. No terceiro momento, as manifestações de uma etnopoética das fotografias de Claudia Andujar fazem meio e imagem se fundirem como lugar etnográfico na arte contemporânea.<br>The article explores contradictions and convergences between a medium (photography) and the image of the Brazilian Indian from the perspective of the history of Brazilian photography. During the first of three distinct moments, the image of the Indian was of someone exotic, in contradiction with the modern meaning of photography under the Second Empire. During the second moment, in the first fifty years of the twentieth century, the boundaries between ethnography and Brazil as a nation were blurred, as exemplified by the Rondon Commission/Indian Protection Bureau's Research Section (Serviço de Proteção ao Índio) and Brazil's modern photojournalism, as found in the magazine Cruzeiro. During the third moment, the expressions of an ethno-poetry present in the photographs of Cláudia Andujar can be seen to blend medium and image as an ethnographic space in contemporary art

Linking seed size and number to trait syndromes in trees

International audienceAim Our understanding of the mechanisms that maintain forest diversity under changing climate can benefit from knowledge about traits that are closely linked to fitness. We tested whether the link between traits and seed number and seed size is consistent with two hypotheses, termed the leaf economics spectrum and the plant size syndrome, or whether reproduction represents an independent dimension related to a seed size-seed number trade-off.Location Most of the data come from Europe, North and Central America and East Asia. A minority of the data come from South America, Africa and Australia.Time period 1960-2022.Major taxa studied Trees.Methods We gathered 12 million observations of the number of seeds produced in 784 tree species. We estimated the number of seeds produced by individual trees and scaled it up to the species level. Next, we used principal components analysis and generalized joint attribute modelling (GJAM) to map seed number and size on the tree traits spectrum.Results Incorporating seed size and number into trait analysis while controlling for environment and phylogeny with GJAM exposes relationships in trees that might otherwise remain hidden. Production of the large total biomass of seeds [product of seed number and seed size; hereafter, species seed productivity (SSP)] is associated with high leaf area, low foliar nitrogen, low specific leaf area (SLA) and dense wood. Production of high seed numbers is associated with small seeds produced by nutrient-demanding species with softwood, small leaves and high SLA. Trait covariation is consistent with opposing strategies: one fast-growing, early successional, with high dispersal, and the other slow-growing, stress-tolerant, that recruit in shaded conditions.Main conclusions Earth system models currently assume that reproductive allocation is indifferent among plant functional types. Easily measurable seed size is a strong predictor of the seed number and species seed productivity. The connection of SSP with the functional traits can form the first basis of improved fecundity prediction across global forests

Globally, tree fecundity exceeds productivity gradients

Lack of tree fecundity data across climatic gradients precludes the analysis of how seed supply contributes to global variation in forest regeneration and biotic interactions responsible for biodiversity. A global synthesis of raw seedproduction data shows a 250-fold increase in seed abundance from cold-dry to warm-wet climates, driven primarily by a 100-fold increase in seed production for a given tree size. The modest (threefold) increase in forest productivity across the same climate gradient cannot explain the magnitudes of these trends. The increase in seeds per tree can arise from adaptive evolution driven by intense species interactions or from the direct effects of a warm, moist climate on tree fecundity. Either way, the massive differences in seed supply ramify through food webs potentially explaining a disproportionate role for species interactions in the wet tropics