Intra and inter-annual climatic conditions have stronger effect than grazing intensity on root growth of permanent grasslands

Understanding how direct and indirect changes in climatic conditions, management, and species composition affect root production and root traits is of prime importance for grassland C sequestration service delivery. We studied during two years the dynamics of root mass production with ingrowth-cores and annual above- and below-ground biomass (ANPP, BNPP) of upland fertile grasslands subjected for 10 years to a gradient of herbage utilization by grazing. We observed strong seasonal root production across treatments in both a wet and a dry year but response to grazing intensity was hardly observed within growing seasons. In abandonment, spring and autumn peaks of root growth were delayed by about one month compared to cattle treatments, possibly due to later canopy green-up and lower soil temperature. BNPP was slightly lower in abandonment compared to cattle treatments only during the dry year, whereas this effect on ANPP was observed the wet year. In response to drought, the root-to-shoot biomass ratio declined in the abandonment but not in the cattle treatment, underlining higher resistance to drought of grazed grassland communities. Rotational grazing pressure and climatic conditions variability had very limited effects on root growth seasonality although drought had stronger effects on BNPP than on ANPP

Landscape effects on water vole (Arvicola terrestris sherman) outbreak dynamics in the Massif Central

In order to identify the habitat types that favour water vole outbreaks, it is important to characterise the links that exist between landscape composition, land use, and outbreak risk Using data obtained during water vole population monitoring efforts carried out in the Puy-de-Dome and Cantal departments from 1985 to 2001, 3 major classes of vole population dynamics were identified and characterised. They are the following: 0 zones of low outbreak risk, which are dominated by fields of arable crops or mosaics of grasslands and croplands (ratio of land under permanent grass to usable agricultural area of <0.75); ii) zones of intermediate outbreak risk (characterised by localised outbreaks), which are dominated by permanent grasslands associated with large forested areas; and iii) zones that experience frequent and severe outbreaks, which are almost entirely dominated by permanent grasslands located within open landscapes. These results match those found in Franche-Comte

Simulations spatialisées des pullulations de campagnols terrestres : Etude de l'influence des structures paysagères

For more than 30 years we have been periodically observing multiannual outbreaks of grassland rodents, Arvicola terrestris Sherman, in Auvergne (France). This phenomenon is more and more frequent and heavy despite chemical treatment. That’s why we study the relationships between water voles and their predators within landscape and farming practices. In order to test different situations of landscape organization, we develop a simulator which will enable us to quantify the evolution of predator and vole populations. This simulator uses a spatial model based on cellular automata. Instead of the classical approach of population dynamics, we have chosen cellular automata. This technique enables us to perform spatial simulations. Simple rules apply on wide number of elements. These local and individual interactions determine complex behaviors of the system at the global level. Nowadays, high computer speeds enable this kind of approach. Maps of land use, maps of vole densities and number of various predators are the input variables of the model. Several parameters enable us to tune constitutive rules of our model (movement and reproduction of voles, hunt territory and predation, evolution of predator density, …). Outputs: for each iteration, the simulator creates maps of vole densities and calculates the number of each species. One iteration represents one year. The first results which are obtained on a real territory (municipalities of Ceyssat and Olby in the department of Puy-de-Dôme) are encouraging. We hope that our simulator (when it will be tuned and validated) will enable us to carry out a wide number of “virtual” experiments that are unfeasible in the “real” world

Effets de la hauteur et de l’espèce végétale sur la valeur nutritive de l’herbe en hiver

National audienceThe necessity of reconciling control of production costs, improvement of food autonomy and work efficiency on livestock farms generates new questions today. An answer to this issue seems to be a better valuation of grass by increasing the share of grazing in the ration. The implementation of this practice re qui - res the knowledge of grassland evolution along winter in terms of quality and quantity. To answer this issue, two forage collections have been established in two sites with different soil and climatic conditions in France. Two levels of stockpiling were studied on five grass covers ( Lolium perenne, Dactylis glomerata, Festuca ru - bra, F. arundinacea, permanent grassland). Biomass and nutritional values were studied over winters of 2010/2011 and 2011/2012. An effect of grass species and height at the beginning of winter can be observed on dry-matter yield and pepsin-cellulase dry-matter digestibility. L. perenne and F. rubra maintain good nutri- tional values along winter but the accumulation is limited as compared to D. glomerata . A good compromise is obtained with F. arundinacea . Stockpiling with a younger grass allows to maintain correct nutritional values at the end of winter.La nécessité de concilier maîtrise des coûts de production, amélioration de l’autonomie alimentai- re et efficacité du travail sur des exploitations d’élevage génère aujourd’hui de nouveaux questionnements. Une réponse à cette problématique semble être une meilleure valorisation de l’herbe en augmentant la part du pâturage dans la ration. La mise en œuvre de cette pratique et son insertion dans un système de pro- duction nécessite de connaitre l’évolution de la prairie au cours de l’hiver, en valeur et en quantité. Pour y répondre, deux collections fourragères ont été mises en place dans des contextes climatiques différents en France. Deux niveaux de stock d’herbe en début d’hiver ont été étudiés sur cinq types de couverts végétaux (ray grass, dactyle, fétuque élevée, fétuque rouge, prairie permanente). L’évolution de la biomasse et des valeurs nutritives a été étudiée sur deux hivers : 2010/2011 et 2011/2012. Des effets « espèce » et « hau- teur » ont pu être observés sur la digestibilité à la pepsine cellulase. Lolium perenne et Festuca rubra main- tiennent de bonnes valeurs nutritives tout au long des hivers mais l’accumulation de biomasse reste limitée contrairement au dactyle. Festuca arundinacea semble être une espèce qui offre un bon compromis entre valeur nutritive et accumulation. Des stocks sur pied avec une herbe plus jeune ont permis de garder des valeurs nutritives correctes à la fin de l’hiver

Predicting annual grassland from community-level mean traits : how does a rapid method based on botanical survey perform ?

International audienc

How does pasture size alter plant–herbivore interactions among grazing cattle?

International audienceGrassland management impacts ecosystem functioning and is critical for livestock production and biodiversity conservation. Decreasing the stocking rate usually benefits biodiversity but also decreases production per unit area. Here, we assessed the combined effects of cattle herd and pasture size on sward structure, diet quality and daily grazing time while maintaining a constant stocking rate. The experiment was conducted over four successive years in two blocks of a species-rich upland grassland that was continuously grazed for 5 months between May and October. Each block consisted of one 3-ha pasture that was grazed by a group of three heifers, one 9-ha pasture grazed by nine heifers, and one 27-ha pasture grazed by 27 heifers. The grazed patches were discriminated using a mathematical model that for each point gave a probability of being grazed based on sward height and spatial dependence. Heifers created fewer patches and had less control over sward height in the smallest (3-ha) plots, while no difference was found between the 9- and 27-ha plots. The small heifer groups also had the shortest daily grazing time. These observations point out a risk that animal impacts on sward structure could be partly missed in grazing experiments conducted with very small groups. Estimated diet quality was unaffected by pasture size. Patch stability was frequent between two successive years but we observed a decrease in interannual patch stability as time intervals increase. Such observations are useful for calibrating spatial interaction models combining foraging behaviour and vegetation dynamics rules and enhance their predictive ability

Simplifications de l’affouragement pour les troupeaux allaitants : évaluation des pratiques et de leurs conséquences zootechniques

Les simplifications des pratiques d’alimentation et d’affouragement telles que les modifications des modes et de rythmes de distribution des aliments, peuvent influer sur les performances zootechniques des ruminants. La distribution de l’alimentation hivernale par remorque mélangeuse qui broie partiellement les brins longs conduit à des niveaux d’ingestion d’autant plus accrues que les fourrages utilisés sont grossiers. La distribution séparée d’aliments concentrés de différentes natures à des agneaux à l’engrais ne modifie que peu les quantités et les proportions moyennes ingérées en comparaison à un mélange, et n’affecte pas les croissances. Mais la distribution à des bovins d’ensilage une fois tous les deux jours ou trois fois par semaine, et l’alternance de la distribution des composants de la ration sur la semaine, sont des pratiques qui conduisent à une moindre utilisation nutritive des aliments de la ration. La gestion de la composition des groupes qui reçoivent cette alimentation simplifiée peut renforcer ou atténuer ces effets. L’utilisation de ces techniques est possible mais limitée à des animaux modérément productifs. Ils peuvent mobiliser la plasticité du comportement d’ingestion, des processus digestifs et métaboliques pour s’adapter à des rythmes de distribution d’alimentation très variés sans modifier les lois de réponses aux apports alimentaires. Cette capacité d’adaptation est une caractéristique forte des ruminants sur lequel l’éleveur peut s’appuyer pour aménager son travail selon ses contraintes personnelles. La modification des pratiques se raisonne donc toujours au regard des capacités d’adaptation des animaux, lesquelles doivent être mieux quantifiées par les travaux de recherches à venirSimplification of feeding practices such as changes in patterns and rythmes of feeding do influence ruminant performance. Distribution of winter feed using a mixer wagon that partially grinds long strands of fiber leads to higher intake levels especially for coarser fodder. The separate distribution of different types of concentrate to fattening lambs only slightly modifies the quantities and average proportions in gested as compared to mixtures and does not affect growth. But distribution of silage to fattening cattle once, two or three times a week, or alternating diet components during the week lead to a lower nutritional value of the diet’s constituents. Managing the composition of the groups receiving this simplified feed may reinforce or attenuate these effects. The use of these techniques is possible, when limiting them to animals with a low or medium level of production. Thus the animals can mobilize the plasticity of feed-intake behaviour and of the digestive and metabolic processes to adapt themselves to various changes in diet distribution without upsetting the known laws of generic responses. This capacity to adaptation is an important trait of ruminants that breeders can use when organising his/her work according to personal constraints. Modification of practices should always keep in mind the capacity of adaptation of the animals, which in the future, must be better understood through researc

Parcelis, un outil de gestion des données dans le cadre de l’expérimentation système Bota Pépi

National audienc

Parcelis, un outil de gestion des données dans le cadre de l’expérimentation système Bota Pépi

National audienc

De nouveaux outils de diagnostic pour mieux comprendre et mieux utiliser la diversité des prairies

absen