Diagnosing Nitrogen, Phosphorous and Potassium Status of Natural Grassland in the Presence of Legumes

In most temperate areas, sustainable management of grassland ecosystems has to deal with evaluation and management of N, P and K resources. For this purpose, appropriate diagnostic systems are needed in order to manage fertilisation accordingly. The nutrient index method based on nutrient concentrations in plant tissues relative to the degree of growth has been developed; it relies on critical curves which serve for diagnostic: for N, the critical curve gives the optimum N concentration for different levels of biomass accumulation in swards, for P and K optimum concentrations are a linear function of sward N concentration (Duru & Thélier-Huché, 1997). However limitations in the use of P nutrient index (PNI) were reported when the herbage contained a large proportion of white clover (Jouany et al., 2004). Our objectives were to verify whether similar behaviour were observed with other legumes and for K and N nutrition indices (KNI, NNI) as well

How to Simplify Tools for Natural Grassland Characterisation Based on Biological Measures Without Losing Too Much Information?

In marginal areas, such as the Pyrenees, natural grasslands are the only available resource for livestock feeding. Despite this, there is a lack of simple and efficient tools for advisers to aid the management of the complex vegetation of these grasslands. Therefore, we tested an approach derived from functional ecology, to construct such tools: using biological traits to inform on the agronomic characteristics and the way farmers’ practices act on them (Ansquer et al., 2004). Nevertheless, the required protocol of measurement is still time-consuming and difficult. In this paper, we test different ways of simplifying this protocol by reducing the number of species measured and not considering specific abundances

A Herbage Growth Model for Different Types of Natural Grassland

The aim of this work was to extend existing growth models established for pure stands to a wide range of grassland communities. For this purpose we built a simple growth model, including sub-models for radiation interception and use. Parameters for the effect of nutrient rates (N, P) and defoliation regimes were based on a plant trait database. Senescence and reproductive processes were particularly considered because of their importance in late spring growth. The model makes it possible to simulate the daily biomass production as a function of both environmental factors and the functional type of the dominant species in the community

Variation of LDMC and SLA Relationship Between Growth Forms in Natural Grasslands

In agro-ecological studies, there is a growing interest in measuring both leaf dry matter content (LDMC) and specific leaf area (SLA). This interest lies on the fact that leaf traits are linked to gradients of environmental factors and ecosystem functions. Working with three contrasting wild species, Garnier et al. (2001) proposed a model linking these two traits. The model shows a relatively simple non linear and negative correlation between LDMC and SLA. Nevertheless, none of the species used to build the model were grasses (GRA) or forb rosettes (ROS = i.e. dicotyledonous with large entire leaves and absence of stem at the vegetative stage); the species which make the largest contribution to the standing biomass of most natural grasslands. Furthermore, due to the divergent range of LDMC (and not SLA) values between these growth forms, Cruz et al. (2002) proposed that grass records alone could be used as an indicator of fertility gradients. The aim of this paper was to analyse discrepancies in the LDMC - SLA correlation with respect to model predictions in order to consider them in any development of LDMC-based tools for the management of natural vegetation

Managing the Reproductive Development of Grasses by Grazing Practices

Grazing natural grassland communities is necessary for both productive (feeding herbivores) and environmental (maintenance of open landscapes) objectives. Management guidelines should take into account the functional diversity of plant species between and within grassland communities. The management of the heading stage of grasses by grazing is an important tool to maintain acceptable forage quality and to avoid the seeding of low-valued species. The heading stage should be managed even in extensive systems and this needs a good knowledge of the phenological development of dominant species. In this work we illustrate the approach through the study of the development of four contrasting grasses and analysing the consequences for grazing management. This work concerned only diversity of the plant components of the grassland ecosystem

Are Leaf Traits Stable Enough to Rank Native Grasses in Contrasting Growth Conditions?

The growing interest in classifying species in response groups relating to variations in environmental factors has triggered the search for functional traits that express differences in ecological behaviour among plant species (Lavorel & Garnier, 2002). Specific leaf area (SLA) and leaf dry matter content (LDMC) reflect a fundamental trade-off in plant functioning between a fast growth rate (high SLA, low LDMC species) and nutrient conservation (low SLA, high LDMC species). This study aimed to analyse the stability of ranking native grasses by SLA and LDMC values under different plant growing conditions

Activité alimentaire des brebis sur les pâturages naturels des Pyrénées pendant la période hivernale

International audienc

Functional ecology for evaluating and predicting the aptitude of permanent grassland to provide services

International audienceApplying the principles of functional ecology helps better predict the services which can be provided by permanent grassland. Farming practices and environmental characteristics influence the functional composition of grassland. Functional plant types have a generic effect on forage services which can be assessed. 13 types of grassland composed of distinct functional types were defined based on 1,283 sample grassland fields located on 8 sites. This approach was validated by checking 8 Ellenberg indicator values (used to evaluate environmental characteristics and farming practices) against climatic data and descriptive data for farming practices. The interest of a functional approach is discussed as a means of understanding the structure of plant communities, estimating the effect of changes in climatic conditions and farming practices, and predicting input services and services not included in farm income

A plant-functional-type approach tailored for stakeholders involved in field studies to predict forage services and plant biodiversity provided by grasslands

International audienceThe plant-trait-based method is powerful for assessing ecosystem services provided by species-rich grasslands, but its use presents difficulties for stakeholders involved in field studies. Therefore, we examined whether a simplified plant-functional-type method could overcome such difficulties. A total of 1287 grasslands, spread over eight regions, were characterized according to their environmental and management factors, eight indicator (including Ellenberg) values and abundance of five previously defined grass functional types (GFTs) differing in growth strategies (fast-slow, early-late). Four related plant-community-composition descriptors indicating forage services (forage production, digestibility, distribution of herbage biomass throughout the growing season and management flexibility) responded to environmental and management factors that are correlated to indicator values. Based on GFTs, cluster analysis defined vegetation types (VTs). Their relationships to environmental and management factors (or proxies of them), forage services and species richness were subsequently analysed. Of the thirteen VTs, four consisted mainly of GFTs with a dominant fast-growth strategy and three with a slow-growth strategy. These clusters were clearly related to two stress axes (temperature and nutrients). The other six VTs consisted of a mixture of both strategies and corresponded to intermediate levels of stress and disturbance. Although simplified, the method distinguished VTs that responded consistently to environmental and management factors and provides accurate indicators of forage services