Florian Fort

Pour ceux qui veulent en savoir plus sur mes recherches passée et les projets qui me motivent vous regarder ma soutenance pour l’obtention de l’habilitation à diriger les recherches.

Germain Montazeaud, Cyrille Violle, Pierre Roumet, Aline Rocher, Martin Ecarnot, Frédéric Compan, Guillaume Maillet, Florian Fort, Hélène Fréville

Journal of Applied Ecology

https://doi.org/10.1111/1365-2664.13735

Abstract

1. Ecological theories suggest that higher plant genetic diversity can increase productivity in natural ecosystems. So far, varietal mixtures, that is, the cultivation of different genotypes within a field, have shown contrasting results, notably for grain yield where both positive and negative mixing effects have been reported. Such discrepancy between ecological theories and agronomical applications calls for a better understanding of plant–plant interactions in crops.
2. Using durum wheat Triticum turgidum ssp. durum as a model species, we investigated the effect of functional trait composition on productivity and grain quality of varietal mixtures by growing 179 highly diverse genotypes in pure stands and 197 two-way mixtures in field conditions. We quantified the agronomic performance of the mixtures relative to their components grown in pure stands on two variables related to productivity, vegetative biomass yield and grain yield, and one variable related to grain quality, grain protein content. We then analysed the relationship between the relative performance of the mixtures and their functional composition that we characterized with trait means and trait differences on 19 above- and below-ground traits.
3. We found that biomass and grain yield increased by 4% overall in mixtures relative to single varieties, but that mixing effects were non-significant for grain protein content. The combined effects of trait means and trait differences explained 12%, 17% and 22% of the variability of relative grain yield, biomass yield and grain protein content, respectively, with different traits affecting productivity and grain quality. Clustering varieties into functional groups allowed us to identify the most beneficial associations for multifaceted agronomic performance.
4. Synthesis and applications. Functional traits explained a significant part of the relative agronomic performance of mixtures compared to monocultures (12%–22%, depending on the yield component). They can thus serve as a basis to identify groups of varieties whose combinations are expected to generate positive mixing effects, especially for productivity, and without compromising grain quality. Selection could then target convergence between groups for some traits and divergence between groups for other traits using empirically derived relationships between functional traits and agronomic performance as a guideline.

Plant ecological indicator values as predictors of fine‐root trait variations

Farming plant cooperation in crops

Germain Montazeaud , François Rousset , Florian Fort , Cyrille Violle , Hélène Fréville† and Sylvain Gandon†

Published:22 January 2020

https://doi.org/10.1098/rspb.2019.1290

Selection of the fittest can promote individual competitiveness but often results in the erosion of group performance. Recently, several authors revisited this idea in crop production and proposed new practices based on selection for cooperative phenotypes, i.e. phenotypes that increase crop yield through decreased competitiveness. These recommendations, however, remain difficult to evaluate without a formal description of crop evolutionary dynamics under different selection strategies. Here, we develop a theoretical framework to investigate the evolution of cooperation-related traits in crops, using plant height as a case study. Our model is tailored to realistic agricultural practices and shows that combining high plant density, high relatedness and selection among groups favours the evolution of shorter plants that maximize grain yield. Our model allows us to revisit past and current breeding practices in light of kin selection theory, and yields practical recommendations to increase cooperation among crops and promote sustainable agriculture

Root and shoot competition lead to contrasting competitive outcomes under water stress: A systematic review and meta-analysis.

Foxx, Alicia J.; Fort, Florian
PLoS ONE . 12/11/2019, Vol. 14 Issue 12, p1-17. 17p.

Abstract:
Background: Competition is a critical process that shapes plant communities and interacts with environmental constraints. There are surprising knowledge gaps related to mechanisms that belie competitive processes, though important to natural communities and agricultural systems: the contribution of different plant parts on competitive outcomes and the effect of environmental constraints on these outcomes. Objective: Studies that partition competition into root-only and shoot-only interactions assess whether plant parts impose different competitive intensities using physical partitions and serve as an important way to fill knowledge gaps. Given predicted drought escalation due to climate change, we focused a systematic review–including a meta-analysis on the effects of water supply and competitive outcomes. Methods: We searched ISI Web of Science for peer-reviewed studies and found 2042 results. From which eleven suitable studies, five of which had extractable information of 80 effect sizes on 10 species to test these effects. We used a meta-analysis to compare the log response ratios (lnRR) on biomass for responses to competition between roots, shoots, and full plants at two water levels. Results: Water availability treatment and competition treatment (root-only, shoot-only, and full plant competition) significantly interacted to affect plant growth responses (p < 0.0001). Root-only and full plant competition are more intense in low water availability (-1.2 and -0.9 mean lnRR, respectively) conditions than shoot-only competition (-0.2 mean lnRR). However, shoot-only competition in high water availability was the most intense (— 0.78 mean lnRR) compared to root-only and full competition (-0.5 and 0.61 mean lnRR, respectively) showing the opposite pattern to low water availability. These results also show that the intensity of full competition is similar to root-only competition and that low water availability intensifies root competition while weakening shoot competition. Conclusions: The outcome that competition is most intense between roots at low water availability emphasizes the importance of root competition and these patterns of competition may shift in a changing climate, creating further urgency for further studies to fil knowledge gaps addressing issues of drought on plant interactions and communities.

Allocation, morphology, physiology, architecture: the multiple facets of plant above and belowground responses to resource stress.

Grégoire T. Freschet, Cyrille Violle, Malo Y. Bourget^, Michael Scherer-Lorenzen, Florian Fort

https://doi.org/10.1111/nph.15225

Crop mixtures: does niche complementarity hold for belowground resources? An experimental test using rice genotypic pairs

Montazeaud G., Violle C., Fréville H., Luquet D., Ahmadi N., Courtois B., Bouhaba I., Fort F.

Agathe Roucou, Cyrille Violle, Florian Fort, Pierre Roumet, Martin Ecarnot, Denis Vile

1. Human selection, changes in environmental conditions and management practices drove the phenotypic trajectory of crops during domestication. The characterization of the crop domestication syndrome lies mostly on reproductive characters. However, biophysical and ecophysiological constraints during vegetative growth are also at play and can strongly impact crop phenotypes. It has been argued that a broadened examination of crop phenotypes through a functional trait‐based lens should improve our understanding of the domestication syndrome.
2. We used a collection of 39 genotypes representative of key steps during tetraploid wheat domestication and grew them in a common garden experiment. We quantified the vegetative phenotype of each genotype through the measurements of 13 functional traits related to root, leaf and whole‐plant dimensions.
3. In modern cultivars, compared to ancestral forms, leaf longevity was shorter, while net photosynthetic rate, leaf production rate and nitrogen content were higher. Modern cultivars had a shallower root system and exhibited a larger proportion of fine roots, preferring to invest biomass above‐rather than below‐ground. We found ancestral forms to be integrated phenotypes characterized by coordination between above‐ and below‐ground functioning. Conversely, in modern forms, human selection appeared to have broken this coordination and to have generated a new type of network of trait covariations.
4. Synthesis and applications. The examination of leaf, root and whole‐plant traits of wheat accessions indicated a strong shift in plant functional strategies over the course of domestication. Elite genotypes tended to better optimize resource‐use acquisition strategies than ancestral ones. The characterization of the crop phenotype based on vegetative traits thus suggests a much more complete domestication syndrome. Our findings highlight the benefits of using a functional trait‐based characterization of crop phenotypes to document the extent of domestication syndrome and to further advance the agroecological management of cereals.
   

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Grégoire T. Freschet, Oscar J. Valverde‐Barrantes, Caroline M. Tucker, Joseph M. Craine, M. Luke McCormack, Cyrille Violle, Florian Fort, Christopher B. Blackwood, Katherine R. Urban‐Mead, Colleen M. Iversen, Anne Bonis, Louise H. Comas, Johannes H. C. Cornelissen, Ming Dong, Dali Guo, Sarah E. Hobbie, Robert J. Holdaway, Steven W. Kembel, Naoki Makita, Vladimir G. Onipchenko, Catherine Picon‐Cochard, Peter B. Reich, Enrique G. de la Riva, Stuart W. Smith, Nadejda A. Soudzilovskaia, Mark G. Tjoelker, David A. Wardle, Catherine Roumet

1. Ecosystem functioning relies heavily on below‐ground processes, which are largely regulated by plant fine‐roots and their functional traits. However, our knowledge of fine‐root trait distribution relies to date on local‐ and regional‐scale studies with limited numbers of species, growth forms and environmental variation.
2. We compiled a world‐wide fine‐root trait dataset, featuring 1115 species from contrasting climatic areas, phylogeny and growth forms to test a series of hypotheses pertaining to the influence of plant functional types, soil and climate variables, and the degree of manipulation of plant growing conditions on species fine‐root trait variation. Most particularly, we tested the competing hypotheses that fine‐root traits typical of faster return on investment would be most strongly associated with conditions of limiting versus favourable soil resource availability. We accounted for both data source and species phylogenetic relatedness.
3. We demonstrate that: (i) Climate conditions promoting soil fertility relate negatively to fine‐root traits favouring fast soil resource acquisition, with a particularly strong positive effect of temperature on fine‐root diameter and negative effect on specific root length (SRL), and a negative effect of rainfall on root nitrogen concentration; (ii) Soil bulk density strongly influences species fine‐root morphology, by favouring thicker, denser fine‐roots; (iii) Fine‐roots from herbaceous species are on average finer and have higher SRL than those of woody species, and N₂‐fixing capacity positively relates to root nitrogen; and (iv) Plants growing in pots have higher SRL than those grown in the field.
4. Synthesis. This study reveals both the large variation in fine‐root traits encountered globally and the relevance of several key plant functional types and soil and climate variables for explaining a substantial part of this variation. Climate, particularly temperature, and plant functional types were the two strongest predictors of fine‐root trait variation. High trait variation occurred at local scales, suggesting that wide‐ranging below‐ground resource economics strategies are viable within most climatic areas and soil conditions.
   

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