Evidence of a community-level root acquisition-conservation trade-off

Gramond

Photography H. Bessière

Grassland root functional parameters vary according to a community-level resource acquisition-conservation trade-off

Florian Fort, Pablo Cruz, Eric Lecloux, Leandro Bittencourt de Oliveira, Ciprian Stroia, Jean-Pierre Theau, Claire Jouany

Summary

This study has for objective to test how do soil depth gradient and fertility changes influence communities’ below-ground parameters on a long-term experiment set on a French temperate grassland.

Our results support the hypothesis that fertile communities are dominated by acquisitive species and highlight the fact that soil depth has a strong effect on functional parameters.

Accepted for publication in Journal of Vegetation Science

 

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A tool to quantify review activity!

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Un peu d’enseignement!

Un peu d’enseignement!

Voici la présentation d’un nouveau module d’enseignement mêlant, écologie, sociologie et génétique pour la conception de nouveaux types de variétés : « Designing new crops for the future » proposé par Dominique This, Isabel Martin-Grande et moi même à Montpellier SupAgro.

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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

Summary

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

A new article investigating the relations between Ellenberg indicators and functional traits values

Hierarchical traits distances explain grassland Fabaceae species’ ecological niches distances

Florian Fort1, 3*, Claire Jouany2, 3 and Pablo Cruz2, 3
1 Montpellier SupAgro, France
2 INRA, France
3 Université de Toulouse, France

Abstract

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.

Root functional trait drive Fabaceae stresses tolerance.

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

Abstract

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 is coming!

psp5-2014PSP5 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

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Intraspecific functional trait variation and performance of Populous tremuloides

Intraspecific functional trait variation and performance of Populous tremuloides

A commentary on « Intraspecific variation in root and leaf traits and leaf-root trait linkages in eight aspen demes (Populus tremula and P. tremuloides » by Hajek, P., Hertel, D., and Leushner C. (2013) Front. Plant Sci. doi: 10.3389/fpls.2013.00415

New article accepted!!!

Hierarchy of root functional trait values and plasticity drive early-stage competition for water and phosphorus among grasses

Florian Fort*, Pablo Cruz, Claire Jouany

Functional Ecology

Summary

1. The link between species’ functional traits and competitive abilities has been described as a major factor structuring plant communities. However, two diverging hypotheses have been proposed to explain this process: competition-trait similarity and competition-trait hierarchy.

2. We performed a greenhouse experiment to determine whether grasses’ root foraging strategies, from acquisitive or conservative functional groups, are linked to plant competitive ability and to test which hypothesis better explains interactions during the early stage of grass establishment under contrasting growth conditions.

3. Two grass species of each functional group were grown with and without a neighbour under two levels of water and phosphorus supplies. Three functional traits related to plant competitive ability were measured on all plants grown without neighbours: specific root length (SRL), root phosphorus use efficiency and root length density. Aboveground biomass was measured on plants grown with and without neighbours to evaluate the intensity of plant interaction.

4. We demonstrated that for the three traits the intensity of interaction is driven mainly by hierarchical trait distance, i.e. trait distance between target and neighbour, and not by trait similarity. Growth conditions strongly affected the significance of the relation between hierarchical distances and competition intensity. For the SRL hierarchical distance, this effect may be due to the most competitive species (with high SRL) being strongly impacted by water shortage, which modified the competitive hierarchy. Trait plasticity in response to stresses also appeared an important factor influencing the competitive ability of species, i.e. species with the most plastic SRL in response to P stress were also the most competitive under P stress.

5. A strong hierarchy exists among grasses’ competitive abilities in non-limiting growth conditions that is linked to their root functional traits and investment in the root system. Consequently, our results support the trait-hierarchy hypothesis in its ability to describe competitive interaction among grasses during early stages of establishment.

6. Our study provides evidence that root functional hierarchical trait distance and plasticity explain how grasses interact with their neighbours. This distance enables species to be ranked according to their competitive ability; however, this ranking may be influenced by the growth conditions and traits considered.

Keywords: specific root length, root phosphorus use efficiency, root length density, plant competition, trait similarity, trait hierarchy

Lay summary

Thesis defence « Grassland species root functional strategies to face abiotic and biotic stresses »

Abstract
In order to optimise grassland ecosystem services we need to improve our understanding of root system functioning. As a result, we decided to characterise strategies of species coming from grassland’ Fabaceae and Poaceae families, by root functional traits measurement.
The main result of this work is the establishment of several axes of root strategies differentiation. The main axis is the trade-off between resources capture and conservation
strategies. Species with capture strategies appear to be adapted to non-water stressful habitat and are barely impacted by phosphorus shortage; they also happen to be strong competitors.
On the opposite, species with conservation strategies are adapted to water stressful continental climates, but are strongly impacted by phosphorus shortage and happen to be weak competitors. The kind of relation between above-ground and below-ground strategies also appears to be a marker of the plants adaptation to stress.
We showed that the root system study is a good way to predict grassland species comportment to face abiotic and biotic constraints. The present work widens interesting perspectives for the sowing of mixed grassland species better adapted to their environments.