Ripoche A.,Montpellier SupAgro |
Celette F.,ISARA Lyon |
Cinna J.-P.,French National Institute for Agricultural Research |
Gary C.,Montpellier SupAgro
European Journal of Agronomy | Year: 2010
Designing intercrop management plans (IMP) to meet objectives related to both crop production and environmental impacts is a challenge for farmers. A multiple criteria decision analysis is thus needed to evaluate and rate various cropping systems in different soil and climate conditions. Different intercrop management plans in vineyards were analysed in this study so as to classify them in relation to their ability to fulfil a particular set of objectives and to deal with climatic variability. The method included five steps. A set of intercrop management plans was defined by combining the type of grass, the covered soil surface ratio, and the intercropping duration. Four evaluation criteria were chosen: grapevine vegetative development, yield, product quality and runoff. Corresponding indicators were identified and the range of values that would be desirable or not were defined. A water balance model designed for row crops was run to simulate the behaviour of the grapevine-intercrop-soil system under different management plans and at various soil depths. The model was used to calculate, for each management plan and soil depth, the four indicators and evaluate the overall agreement and discordance with various weights assigned to the four criteria. A frequency analysis on 30 years of weather data was carried out to estimate the robustness of the most satisfactory intercrop management plans. The most satisfactory intercrop management plans differed according to the priority given to managing production or reducing environmental impacts and depended on the soil depth. This confirms the conclusions drawn on the basis of various experiments assessing a limited range of intercropping policies. Overall, giving priority to the environmental criterion was favourable for cropping systems with a long intercrop period regardless of the soil type. Few management plans were suitable for all years. The observed yearly rainfall varied from 330 to 1200 mm during the 1975-2003 period, which generated marked variations in the water balance of the grapevine-intercrop-soil system. The lack of robustness of the explored intercrop management plans could be a consequence of the poor description of the management plans due to the limited combinations of technical options considered. Strategic or tactical adjustments could be introduced by farmers. We assume that more robust intercrop management plans could be developed by introducing such rules in a decision model combined with the present biophysical model. © 2009 Elsevier B.V. All rights reserved.
Pobel D.,ISARA Lyon |
Robin J.,ISARA Lyon |
Humbert J.-F.,French National Institute for Agricultural Research
Water Research | Year: 2011
Sampling cyanobacteria in freshwater ecosystems is a crucial aspect of monitoring programs in both basic and applied research. Despite this, few papers have dealt with this aspect, and a high proportion of cyanobacteria monitoring programs are still based on monthly or twice-monthly water sampling, usually performed at a single location. In this study, we conducted high frequency spatial and temporal water sampling in a small eutrophic shallow lake that experiences cyanobacterial blooms every year. We demonstrate that the spatial and temporal aspects of the sampling strategy had a considerable impact on the findings of cyanobacteria monitoring in this lake. In particular, two peaks of Aphanizomenon flos-aquae cell abundances were usually not picked up by the various temporal sampling strategies tested. In contrast, sampling once a month was sufficient to provide a good overall estimation of the population dynamics of Microcystis aeruginosa. The spatial frequency of sampling was also important, and the choice in the location of the sampling points around the lake was very important if only two or three sampling points were used. When four or five sampling points were used, this reduced the impact of the choice of the location of the sampling points, and allowed to obtain fairly similar results than when six sampling points were used. These findings demonstrate the importance of the sampling strategy in cyanobacteria monitoring, and the fact that it is impossible to propose a single universal sampling strategy that is appropriate for all freshwater ecosystems and also for all cyanobacteria. © 2010 Elsevier Ltd.
Stokes A.,French National Institute for Agricultural Research |
Mine F.-X.,ISARA Lyon |
Mao Z.,French National Institute for Agricultural Research |
Brancheriau L.,CIRAD - Agricultural Research for Development
Journal of Vegetation Science | Year: 2012
Question: Many woody plants persist in a temporal 'persistence' niche, through resprouting after disturbance events. Will multi-stemming (as a consequence of resprouting or life form) and biomechanical traits enable certain species to survive disturbance and occupy a persistence niche? Location: A 1200-m long avalanche corridor in the French Alps, with disturbance events ca. every 2 yr. Methods: We measured tree/shrub size and multi-stemming in transects along and around the avalanche corridor. The mechanical traits, wood density, modulus of elasticity (E d), bending strength (σ) and stiffness (EI), along stems of several subalpine tree/shrub species were measured to test for differences in flexibility and strength. Results: The multi-stemmed pioneer shrubs Alnus viridis, Salix appendiculata and to a lesser extent, Corylus avellana, were more abundant where disturbance was most severe. Multi-stemming broadleaf species, in particular Fagus sylvatica, had more tapered, shorter and more numerous stems in severely disturbed zones. Single-stemmed conifers were usually found furthest from the avalanche track. A. viridis, codominant at the centre of the track, had the lowest E d, σ and EI. In A. viridis, Alnus incana, F. sylvatica and Betula pendula, E d was lower at the stem base and increased with height up the stem. Alnus viridis and C. avellana stems were most flexible (low EI), whereas single-stem tree forms, Picea abies and B. pendula, were stiffest. Corylus avellana had the highest σ and lowest wood mechanical construction cost (ρ) per unit function (E d), whereas P. abies had highest construction cost. Conclusions: High flexibility of A. viridis, and to a lesser extent C. avellana and the multi-stemmed form of F. sylvatica, allows individuals to bend during snow loading, before an avalanche; therefore, stem damage and uprooting during an avalanche are minimized. Increased stem basal flexibility in these species will also facilitate bending during snow loading. More rigid distal sections will confer extra mechanical advantage to stems that need to grow quickly upwards, dominate and maintain their position in the canopy during the growing season. © 2011 International Association for Vegetation Science.
Dufour A.,Isara Lyon |
Dedieu B.,French National Institute for Agricultural Research
Cahiers Agricultures | Year: 2010
Society puts pressure on working time as does the rationalisation movement in dairy farms. Farmers need to de- and re-construct their relationships to time, work and organisation. This paper analyses the diversity of dairy farmers' conceptions of work based on 30 interviews conducted in the Segala Region, SW France, a natural area of small and medium-sized family dairy units. Farmers describe diversified conceptions which combine the standardisation of livestock farming norms at various levels, clearly influenced by industrial production, as well as societal norms based on a well-controlled working time management and the breeders' passion for their work and their animals. Three conceptions are highlighted: "creative and impassionate," whose principal characteristic is a continuous learning process, "mastered and efficient" and a "difficult" approach which differs from the other two in that it reflects work as an inflicted activity. The organisational modes which are related to these approaches are described in this paper: technical models, equipment, labour division. This variety of conceptions leads us to examine the role and working methods of experts and advisors as changes are under way.
Amosse C.,ISARA Lyon |
Jeuffroy M.-H.,French National Institute for Agricultural Research |
Jeuffroy M.-H.,Agro ParisTech |
David C.,ISARA Lyon
Field Crops Research | Year: 2013
Wheat yields and grain protein content are lower and more variable in organic conditions than in conventional agriculture, mainly due to nitrogen (N) deficiency and weed competition. The undersowing of legume cover crops in growing winter wheat, also known as relay intercropping, is assumed to be a proficient way of enriching the soil-crop system with N and improving weed control. However, competition for resources may impair wheat performance. Relay intercropping in springtime in growing winter wheat is expected to limit competition for resources from the legume. The aim of our study was to analyze wheat performance and resource competition in relay intercropping systems with legume cover crops under various environmental conditions.Eight field experiments were conducted on organic grain-oriented farms located in southeast France. Black medic (Medicago lupulina), alfalfa (Medicago sativa), red clover (Trifolium pratense) and white clover (Trifolium repens), undersown at wheat tillering stage, were compared with a sole crop of winter wheat (Triticum aestivum cv. Lona). The aerial biomass of wheat and legumes and total N content of wheat were determined at both the flowering stage and harvest time of the wheat. The main trophic resources (water, N and light) were monitored at similar stages. Wheat grain yield and grain protein content were also measured. Sites were classified according to wheat sole crop performance at harvest to evaluate the effect of relay intercropping in the various conditions tested.In all but one of the thirty-two treatments, wheat grain yield was not significantly disturbed by relay intercropping whatever the aerial development of legumes. Abundant aerial development of legumes after flowering (>20% of the aerial biomass of wheat at harvest) was associated with a mean significant decrease in wheat grain protein content of 8.5% of the control treatment value, this occurring in one third of the situations. These ratios of aerial biomasses of legumes compared to wheat were also associated with reductions in soil moisture and wheat N uptake. The effect on the availability of trophic resources for wheat may have led to a decrease in grain protein content without having any effect on grain yield. Sites which registered a low performance for wheat sole crops were less negatively impacted by the presence and aerial development of legumes.The performance of the four legume species and the mechanisms of induced disturbance of resource availability are then discussed. Finally, we try to define ranges of legumes' development and resource availability in which wheat performance was maintained or limited. © 2013 Elsevier B.V.
Amosse C.,ISARA Lyon |
Jeuffroy M.-H.,French National Institute for Agricultural Research |
Jeuffroy M.-H.,Agro ParisTech |
Celette F.,ISARA Lyon |
David C.,ISARA Lyon
European Journal of Agronomy | Year: 2013
In organic grain production, weeds are one of the major limiting factors along with crop nitrogen deficiency. Relay intercropping of forage legume cover crops in an established winter cereal crop might be a viable option but is still not well documented, especially under organic conditions.Four species of forage legumes (. Medicago lupulina, Medicago sativa, Trifolium pratense and Trifolium repens) were undersown in six organic wheat fields. The density and aerial dry matter of wheat, relay-intercropped legumes and weeds were monitored during wheat-legume relay intercropping and after wheat harvest until late autumn, before the ploughing of cover crops.Our results showed a large diversity of aerial growth of weeds depending on soil, climate and wheat development. The dynamics of the legume cover crops were highly different between species and cropping periods (during relay intercropping and after wheat harvest). For instance, T. repens was two times less developed than the other species during relay intercropping while obtaining the highest aerial dry matter in late autumn. During the relay intercropping period, forage legume cover crops were only efficient in controlling weed density in comparison with wheat sole crop. The control of the aerial dry matter of weeds at the end of the relay intercropping period was better explained considering both legumes and wheat biomasses instead of legumes alone. In late autumn, 24 weeks after wheat harvest, weed biomass was largely reduced by the cover crops. Weed density and biomass reductions were correlated with cover crop biomass at wheat harvest and in late autumn. The presence of a cover crop also exhibited another positive effect by decreasing the density of spring-germinating annual weeds during the relay intercropping period. © 2013 Elsevier B.V.
Arthaud F.,University Claude Bernard Lyon 1 |
Vallod D.,University Claude Bernard Lyon 1 |
Robin J.,University Claude Bernard Lyon 1 |
Wezel A.,ISARA Lyon |
Bornette G.,University Claude Bernard Lyon 1
Journal of Vegetation Science | Year: 2013
Questions: The highest species richness is usually expected at an intermediate stage of development since the last major disturbance event, but some studies have shown that ecosystem productivity and dispersal may modify this pattern, suggesting the need for further studies on the effects of productivity and dispersal on the dynamics of species richness through succession. In this study, we analysed aquatic plant species richness in relation to (1) succession stage, measured as numbers of years since the last disturbance that affected the ecosystems; (2) lake productivity, measured as the chlorophyll a concentration; and (3) connectivity to similar nearby ecosystems, a proxy for the potential input of diaspores. Location: Shallow lakes of the Dombes region, France. Methods: Every 5-7 yr these shallow lakes are emptied and left to dry out for 1 yr. These drought disturbances lead to complete destruction of the submerged aquatic plant communities. Sixty lakes arranged along a gradient of productivity were selected. The probability of diaspore input was considered to increase from upstream to downstream, as lakes are organized in hydrologically connected networks via ditches, through which the downstream lakes receive water from the upstream lakes. For each lake, the aquatic plant species richness (from systematic summer vegetation sampling), time since the last disturbance (last summer drying), productivity (estimated as chlorophyll a concentration) and probability of diaspore input (assessed from position in the network) were recorded. Results: The aquatic plant species richness decreased with the time since the last disturbance for all of the lakes, but there was a significant interaction with the chlorophyll a concentration and position of the lake in the network. At the lowest ecosystem productivities, the relationship between successional stage and species richness was hump-shaped, whereas the species richness decreased with increasing time since the last disturbance when productivity increased. The lake's position in the network did not influence species richness during the first 2 yr after disturbance, but from year 3 and thereafter, lakes connected to high numbers of upstream lakes consistently exhibited decreased richness, contradicting the expected trend of increasing species richness with increasing diaspore inputs. Conclusions: This study indicates that both ecosystem productivity and connectivity strongly affected the relationship between aquatic plant species richness and succession, and that these factors should be taken into account in further developments of the intermediate disturbance hypothesis. In this study, we analysed the effect of the lake productivity and the lake connectivity on the relationship between aquatic plant species richness and the succession stage. These factors affected the dynamics of species richness through succession and they should be taken into account in further developments of the intermediate disturbance hypothesis. © 2012 International Association for Vegetation Science.
Arthaud F.,CNRS Ecology of Natural and Anthropized Hydrosystems Laboratory |
Mousset M.,CNRS Ecology of Natural and Anthropized Hydrosystems Laboratory |
Vallod D.,CNRS Ecology of Natural and Anthropized Hydrosystems Laboratory |
Robin J.,CNRS Ecology of Natural and Anthropized Hydrosystems Laboratory |
And 2 more authors.
Freshwater Biology | Year: 2012
The way light stress controls the recruitment of aquatic plants (phanerogams and charophytes) is a key process controlling plant biodiversity, although still poorly understood. Our aim was to investigate how light stress induced by phytoplankton, that is, independent from the aquatic plants themselves, determines the recruitment and establishment of plant species from the propagule bank. The hypotheses were that an increase in light stress (i) decreases abundance and species richness both of established aquatic plants and of propagules in the bank and (ii) decreases the recruitment success of plants from this bank. These hypotheses were tested in 25 shallow lakes representing a light stress gradient, by sampling propagule banks before the recruitment phase and when the lakes are devoid of actively growing plants (i.e. at the end of winter), established vegetation at the beginning of the summer and phytoplankton biomass (chlorophyll a) during the recruitment and establishment phase. The phytoplankton biomass was negatively correlated with the richness and abundance of established vegetation but was not correlated with the propagule bank (neither species richness nor propagule abundance). The similarity between the propagule bank and established vegetation decreased significantly with increasing phytoplankton biomass. The contrast in species composition between the vegetation and the propagule bank at the highest light stress suggests poor recruitment from the propagule bank but prompts questions about its origin. It could result from dispersal of propagules from neighbouring systems. Propagules could also originate from a persistent propagule bank formerly produced in the lake, suggesting strong year-to-year variation in light stress and, as a consequence, in recruitment and reproductive success of plants. © 2012 Blackwell Publishing Ltd.
Mundler P.,ISARA Lyon |
Rumpus L.,ISARA Lyon
Food Policy | Year: 2012
The possible contribution of local sales chains to the reduction of energy consumption has been hotly debated in recent years. Some authors establish a link between the reduction of distances traveled by food and lower energy consumption due to transportation, while others hold that local supply chains have a poor energy performance. This article engages this debate by comparing the rates of energy consumption attributable to different modes of distribution of fruits and vegetables in a region of France.By studying actors' actual practices, we show that the establishment of local food systems leads to organizational efforts at the local level or in the form of geographically centralized networks which allow energy expenditures linked to distribution to be minimized. The studied chains' performances are variable, from 13.5 to 44.8. GOE/€ (Gram of Oil Equivalent per euro) of product, bringing them close to long chains in the best examples. Comparison with other research underscores the diversity of methods which are put in place. They also show that energy performance remains very dependent on where the study was conducted. Ultimately this study invites us to better analyze the ways in which actors collaborate to optimize energy expenditures relative to the distribution of food products in local sales chains. © 2012 Elsevier Ltd.
Vallod D.,ISARA Lyon |
Sarrazin B.,ISARA Lyon
Hydrological Sciences Journal | Year: 2010
This study reports the monitoring of the water quality during filling and draining periods of a 24 ha pond built with a bypass ditch, and managed extensively for carp production. The total volume of water was determined by using a digital elevation model based on topographic data. Total suspended solids and main nutrients have been measured. An adapted hydrobiological score was calculated in the downstream. The results show that outlet opening and fish harvesting are critical steps for the export but concern only 5% of the total effluent volume. The effluent exported 8.5 t of total suspended solids and was rich in P and organic matter. The sedimentation in the ditch could explain that the receiving stream was not so affected by this organic discharge. Better practices of managing and harvesting could improve the quality of the effluent and limit its potential impact. © 2010 IAHS Press.