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I explore the relationship between leaf and root functional traits syndromes and their consequences on the plants ability to face interaction with other plants and abiotic stress mainly water and phosphorus.
I’m particularly interested in the functioning of the grassland and crops communities and on how fertility and climate change impact communities performances in interaction with their functional structure.
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New paper write in collaboration with an excellent young agronomist, Miss Tribouillois, accepted by PlosOne
A functional characterisation of a wide range of cover crop species: growth and nitrogen acquisition rates, leaf traits and ecological strategies.
Hélène Tribouillois1, Florian Fort1, Pablo Cruz1, Raphaël Charles2, Olivier Flores3, Eric Garnier4 and Eric Justes*1
1 INRA, UMR AGIR, 24 Chemin de Borde Rouge – Auzeville, CS 52627, 31326 Castanet-Tolosan Cedex, France; 2 Agroscope, Institute of Plant Production Sciences, 50 Route de Duillier, CP 1012, CH-1260 Nyon 1, Suisse; 3 Université de la Réunion/CIRAD, UMR—Peuplements Végétaux et Bioagresseurs en Milieu Tropical, 97410 Saint Pierre, France; 4Centre d’Ecologie Fonctionnelle et Evolutive (UMR 5175), CNRS – Université de Montpellier – Université Paul-Valéry Montpellier – EPHE, 1919, route de Mende, 34293 Montpellier Cedex 5, France
Cover crops can produce ecosystem services during the fallow period, as reducing nitrate leaching and producing green manure. Crop growth rate (CGR) and crop nitrogen acquisition rate (CNR) can be used as two indicators of the ability of cover crops to produce these services in agrosystems.
We used leaf functional traits to characterise the growth strategies of 36 cover crops as an approach to assess their ability to grow and acquire N rapidly. We measured specific leaf area (SLA), leaf dry matter content (LDMC), leaf nitrogen content (LNC) and leaf area (LA) and we evaluated their relevance to characterise CGR and CNR. Cover crop species were positioned along the Leaf Economics Spectrum (LES), the SLA-LDMC plane, and the CSR triangle of plant strategies.
LA was positively correlated with CGR and CNR, while LDMC was negatively correlated with CNR. All cover crops could be classified as resource-acquisitive species from their relative position on the LES and the SLA-LDMC plane. Most cover crops were located along the Competition/Ruderality axis in the CSR triangle. In particular, Brassicaceae species were classified as very competitive, which was consistent with their high CGR and CNR. Leaf functional traits, especially LA and LDMC, allowed to differentiate some cover crops strategies related to their ability to grow and acquire N. LDMC was lower and LNC was higher in cover crop than in wild species, pointing to an efficient acquisitive syndrome in the former, corresponding to the high resource availability found in agrosystems. Combining several leaf traits explained approximately half of the CGR and CNR variances, which might be considered insufficient to precisely characterise and rank cover crop species for agronomic purposes. We hypothesised that may be the consequence of domestication process, which has reduced the range of plant strategies and modified the leaf trait syndrome in cultivated species.
Keywords: catch crop; domesticated species; green manure; functional traits; nitrogen; resource-use strategy
Fabaceae species play a key role in ecosystem functioning through their capacity to fix atmospheric nitrogen via their symbiosis with Rhizobium bacteria. To increase benefits of using Fabaceae in agricultural systems, it is necessary to find ways to evaluate species or genotypes having potential adaptations to sub-optimal growth conditions.
We evaluated the relevance of phylogenetic distance, absolute trait distance and hierarchical trait distance for comparing the adaptation of 13 grassland Fabaceae species to different habitats, i.e. ecological niches. We measured a wide range of functional traits (root traits, leaf traits and whole plant traits) in these species. Species phylogenetic and ecological distances were assessed from a species-level phylogenetic tree and species’ ecological indicator values, respectively.
We demonstrated that differences in ecological niches between grassland Fabaceae species were related more to their hierarchical trait distances than to their phylogenetic distances. We showed that grassland Fabaceae functional traits tend to converge among species with the same ecological requirements. Species with acquisitive root strategies (thin roots, shallow root systems) are competitive species adapted to non-stressful meadows, while conservative ones (coarse roots, deep root systems) are able to tolerate stressful continental climates. In contrast, acquisitive species appeared to be able to tolerate low soil-P availability, while conservative ones need high P availability.
Finally we highlight that traits converge along the ecological gradient, providing the assumption that species with similar root-trait values are better able to coexist, regardless of their phylogenetic distance.
Fort F., Cruz P., Catrice O., Stroia C., Delbrut A., Luzarreta M., Jouany C. Root functional trait syndromes and plasticity drive the ability of grassland Fabaceae to tolerate water and phosphorus shortage. Environmental and Experimental Botany
Water, N and P shortages are three major factors that limit plant development worldwide. Understanding which plant strategies allow them to cope with these stresses may encourage the selection of species or genotypes better able to make the most of non-optimal growth conditions in grassland agrosystems.
To test which strategies allowed species to be more efficient under P and water shortages, we grew 13 Fabaceae species under four growth conditions in a greenhouse experiment that resulted from crossing two levels of both P and water availability.
Ten root functional traits were measured under the four growth conditions, including cross-sectional area occupied by aerenchyma, mycorrhizal rate, root hair length, and specific root length (SRL). We determined relations between species’ root trait values and their plasticity and response to P and/or water stress in terms of total biomass production and stress intensity.
Results showed that mycorrhizal rates were negatively related to biomass production in the four growth conditions. Long root hairs and high aerenchyma production were respectively associated with high biomass production in growth conditions without and with P stress, respectively. Species with acquisitive strategies (high SRL) were less impacted by P and water stress than those with conservative ones (low SRL). Additionally, increased SRL and root hair length decreased the impact of P stress on species’ performances.
Results showed that grassland Fabaceae display a wide range of root functional strategies (i.e. root functional trait attributes and plasticity), which explain their performances under P and/or water shortage.
Keywords: Drought, Fabaceae, GLM, PCA, Phosphorus, Root functional trait
PSP5 will be a multidisciplinary event, gathering plant nutritionists (plant physiology, genetics and systems biology), agronomists, ecologists, biogeochemists and soil scientists from worldwide, fostering scientific exchanges across discipline boundaries, in order to face the challenge of phosphorus limitations in many agroecosystems and terrestrial ecosystems.
PSP5 will be immediately followed by the 4th Sustainable Phosphorus Summit to be held in Montpellier from 1st to 3rd September 2014, where global concerns about Phosphorus sustainability will be discussed. You will thus have the opportunity to attend both events and be part of this unique P week.
Philippe Hinsinger, UMR Eco&Sols, Montpellier SupAgro-CIRAD-INRA-IRD