Improvement of Native Perennial Forage Plants for Sustainability of Mediterranean Farming Systems

The amount of water available to agriculture in the Mediterranean is declining because of increasing population pressure and greater incidence of drought. Therefore, the efficiency of the use of water for agricultural production must be maximized and, in this context, perennial forage species have a number of advantages in comparison to the predominantly-used annuals. They can utilize water throughout the whole year besides being able to halt rangeland degradation, restore soil fertility and enhance forage production, thereby contributing to greater sustainability of rain-fed agricultural systems in the southern European Union and North Africa. Despite these advantages, the small size of individual national markets has so far worked against the development of a viable forage industry based on perennials. By adopting a multi-national approach and targeting the key breeding objectives of superior drought-resistance and water-use efficiency (WUE), an European Commission-funded project aims to produce commercially cultivars of a number of species of broad regional interest and adaptation

Designing Resilient and Sustainable Grasslands for a Drier Future: Adaptive Strategies, Functional Traits and Biotic Interactions

In many regions of the world, such as Southern Europe and most Mediterranean areas, the frequency and magnitude of droughts and heat waves are expected to increase under global warming and will challenge the sustainability of both native and sown grasslands. To analyze the adaptive strategies of species, genotypes and cultivars, we aim both: (1) to understand the composition and functioning of natural grasslands; and (2) to propose ideotypes of cultivars and optimal composition for mixtures of species/genotypes under water deficit and high temperatures. This review presents a conceptual framework to analyze adaptive responses of perennial herbaceous species, starting from resistance to moderate drought with growth maintenance (dehydration avoidance and tolerance of lamina) to growth cessation and survival of plants under severe stress (dehydration avoidance and tolerance of meristems). The most discriminating functional traits vary according to these contrasting strategies because of a trade-off between resistance to moderate moisture deficit and survival of intense drought. Consequently it is crucial to measure the traits of interest in the right organs and as a function of soil water use, in order to avoid misleading interpretations of plant responses. Furthermore, collaboration between ecologists, eco-physiologists, and agronomists is required to study the combination of plant strategies in natural grasslands as only this will provide the necessary rules for species and cultivars or ecotypes assemblage. This ‘agro-ecological’ approach aims to identify and enhance functional complementarity and limit competition within the multi-specific or multi-genotypic material associated in mixtures since using plant biodiversity should contribute to improving grassland resistance and resilience

Measuring Summer Dormancy of Perennial Grasses in Contrasting Environments

The summer dormancy trait has been shown to confer enhanced levels of survival to temperate perennial forage species over long periods of intense summer drought (Volaire and Norton 2006) and is therefore valuable in plant improvement. Normally found in species endemic to drier Mediterranean climates it is recommended that the trait be measured in the field under typical Mediterranean hot, dry summer conditions (Norton et al. 2008). However, this trait has potential utility in regions with summers that can receive substantial rainfall, but still experience extended periods of intense moisture deficit. Therefore, it is important to determine whether summer dormancy expression can be reliably measured in environments cooler and moister than those considered typically Mediterranean. This paper compares the measurement of summer dormancy across a range of three commercially important temperate perennial grass species when undertaken in typical Mediterranean summer conditions and in a cooler and wetter summer environment

The Potential for Summer-Dormant Perennial Grasses in Mediterranean and Semi-Arid Pastures

In rain-fed Mediterranean and semi-arid areas, herbage production of perennial grasses depends on their ability to grow efficiently during the rainy seasons and to persist over the dry summer. A key survival strategy in these harsh conditions is summer dormancy (Volaire, 2002). Within the species Dactylis glomerata L., two cultivars (cvs.), contrasting in this trait, were compared in order to analyse their suitability in terms of yield and survival in these environments

La diversité fonctionnelle racinaire peut-elle favoriser la résilience des mélanges de graminées méditerranéennes sous sécheresses sévères ?

The sustainability of grasslands is threatened under climate change especially in Mediterranean areas. As biodiversity is increasingly recognized to enhance and stabilize processes within plant communities, we aimed to test whether the associations of forage species with contrasting belowground functional strategies improve soil water use and resilience of biomass productivity under increasing summer aridity. Monocultures and bi- or tri-specific mixtures of perennial grasses were compared in a 3-years field experiment under either an average or an extreme summer drought scenario in southern France. From the measured root traits, both the functional identity (mean traits of associated species) and the functional diversity (trait differences) were calculated for each mixture. Overyielding and resilience were assessed from seasonal aboveground biomass (AGB). Total Transpirable Soil Water (TTSW) was derived from monthly soil water content monitoring. Across all treatments and drought scenari, AGB productivity and resilience were highly correlated with TTSW and root depth. The functional identity of mixtures better explained overyielding and resilience responses than the functional diversity. These results provide sound agro-ecological rules to design suitable associations of species for drought-prone areas.La durabilité des prairies est menacée sous changement climatique surtout en zones méditerranéennes. Comme une biodiversité élevée est reconnue pour stabiliser les communautés végétales, cette étude a testé si des mélanges d’espèces fourragères avec des stratégies fonctionnelles racinaires contrastées pouvaient améliorer les prélèvements hydriques et la résilience des couverts sous sécheresses sévères. Des monocultures et des mélanges bi ou tri-spécifiques de graminées pérennes ont été comparés dans un essai au champ sous sécheresse estivale moyenne et extrême dans le sud de la France.Les traits racinaires ont permis de calculer l’identité fonctionnelle (traits moyens des espèces associées) et la diversité fonctionnelle (différence de traits) pour chaque mélange. Overyielding et résilience ont été estimés par des mesures de biomasses aériennes (AGB). La fraction de l’eau du sol transpirable par les plantes (TTSW) a été mesurée. Pour tous les traitements et niveaux de sécheresse, AGB et résilience sont très corrélés à TTSW et profondeur racinaire. L’identité fonctionnelle racinaire permet de mieux expliquer les réponses d’overyielding et de résilience que la diversité fonctionnelle. Ces résultats ont des implications pour la conception de mélanges fourragers adaptés aux zones sèches

CLIMAGIE: A French INRA Project to Adapt the Grasslands to Climate Change

Climate change in France, central and southern Europe is expected to provoke more frequent and more intense summer water deficits, with increased amplitude in temperatures, exposing the same perennial crops to frosts as well as to heat waves and severe droughts. The impacts on sown monospecific grasslands have been assessed using crop models (Durand et al. 2010) but with less accuracy in extreme situations. Since less work has been done on intra-specific genetic variability there is urgent need to investigate both ranges of climate conditions and genetic variability (Poirier et al. 2012). Phenology and plant productivity responses to water, temperature and nitrogen (N) in particular need to be re-assessed over the full range of temperatures projected in the future

Contribution a la caracterisation des horizons de surface pour les sols des formations herbacees de Corse

National audienc

Caractères morpho-physiologiques associés à la survie à la sécheresse dans des prairies herbacées pérennes bispécifiques

International audiencePerennial grasslands provide numerous environmental benefits but their response to severe drought and therefore their sustainability in arid and Mediterranean areas have been little studied. Our work aimed to investigate the morpho-physiological traits associated with drought survival for bi-specific mixtures of perennial forage plants, and to test whether growth potential in spring was correlated with the capacity to survive subsequent summer droughts. Five cultivars (two of tall fescue, two of cocksfoot and one of Lucerne) were grown in monoculture and mixtures. Standard leaf functional traits and aerial biomass were assessed under non-limiting water supply in spring. In summer, under continuous severe drought, leaf water status, foliage senescence and plant survival were measured. Senescence of aerial tissues at the end of spring, associated with endogenous summer dormancy were the variables best correlated with drought survival. Specific leaf area under spring irrigation was also correlated with drought survival. These traits associated with dehydration tolerance strategies in pots should be completed with root traits contributing to dehydration delay in the fieldLes enherbements pérennes ont des fonctions environnementales reconnues mais leur réponse à des sécheresses sévères et donc leur durabilité pluri-annuelle dans les zones à climat semi-aride et méditerranéen ont été peu étudiées. Notre objectif était d'étudier les caractères morpho-physiologiques associés à la survie à une sécheresse sévère dans des mélanges bi-spécifiques de plantes fourragères pérennes et de tester si le potentiel de croissance printanier était corrélé à la capacité ultérieure de survie à la sécheresse. Cinq cultivars (deux de fétuque élevée, deux de dactyle et un de luzerne) ont été étudiés en monocultures et en mélanges. Les caractères fonctionnels foliaires standards et la biomasse aérienne ont été mesurés en conditions hydriques non limitantes au printemps. En été, sous sécheresse sévère, la teneur en eau des tissus, la sénescence foliaire et les taux de survie ont été évalués. Le taux de sénescence des tissus aériens en fin de printemps, associé au niveau de dormance estivale endogène ainsi que la surface foliaire spécifique ont été les variables les plus corrélées à la survie au stress hydrique. Ces caractères associés à des stratégies de tolérance à la déshydratation en pots doivent être complétés par l'analyse des caractères racinaires contribuant aux prélèvements hydriques différentiels au cham