Testing Different Topographic Indexes to Predict Wetlands Distribution

AbstractRural landscapes are characterized by great heterogeneity, thus for any policy of landscape protection and management, the delineation of landscape structures is a prerequisite and the demand for such information at the scale of large catchments or basins. Focusing on wetlands, different studies proposed indexes to predict their extension, based on topographic and climatic information, mainly within small order catchments. The topic of this paper is to determine the validity of different indexes for different orders of catchments and to propose an improved index predicting the delineation of wetland for large order catchments.The work is based on a 830 km2 basin where the actual extension of wetlands is partially known on the base of a soil map. We checked the efficiency of different topographic and hydrological indexes as the climato-topographic index and others, by comparing the map of predicted and actual wetlands, for different stream orders. Results have showed that we improved the prediction of wetland delineation for large catchments when we took into account the importance of the flatness of the bottomland. We proposed the ordinated climato-topographic index that reflects this effect in including the local downhill difference in level to the stream, weighted by the drained volume by the stream as an indicator of the stream order. Such index allows environmental stakeholders a better prediction of wetlands at the management scale

Improving the cost-effectiveness of visual devices for the control of Riverine tsetse flies, the major vectors of Human African Trypanosomiasis

Control of the Riverine (Palpalis) group of tsetse flies is normally achieved with stationary artificial devices such as traps or insecticide-treated targets. The efficiency of biconical traps (the standard control device), 161 m black targets and small 25625 cm targets with flanking nets was compared using electrocuting sampling methods. The work was done on Glossina tachinoides and G. palpalis gambiensis (Burkina Faso), G. fuscipes quanzensis (Democratic Republic of Congo), G. f. martinii (Tanzania) and G. f. fuscipes (Kenya). The killing effectiveness (measured as the catch per m2 of cloth) for small targets plus flanking nets is 5.5–15X greater than for 1 m2 targets and 8.6–37.5X greater than for biconical traps. This has important implications for the costs of control of the Riverine group of tsetse vectors of sleeping sickness

Towards an optimal design of target for tsetse control: comparisons of novel targets for the control of palpalis group tsetse in West Africa

Background: Tsetse flies of the Palpalis group are the main vectors of sleeping sickness in Africa. Insecticide impregnated targets are one of the most effective tools for control. However, the cost of these devices still represents a constraint to their wider use. The objective was therefore to improve the cost effectiveness of currently used devices. Methodology/Principal Findings: Experiments were performed on three tsetse species, namely Glossina palpalis gambiensis and G. tachinoides in Burkina Faso and G. p. palpalis in Côte d'Ivoire. The 1×1 m2 black blue black target commonly used in W. Africa was used as the standard, and effects of changes in target size, shape, and the use of netting instead of black cloth were measured. Regarding overall target shape, we observed that horizontal targets (i.e. wider than they were high) killed 1.6-5x more G. p. gambiensis and G. tachinoides than vertical ones (i.e. higher than they were wide) (P<0.001). For the three tsetse species including G. p. palpalis, catches were highly correlated with the size of the target. However, beyond the size of 0.75 m, there was no increase in catches. Replacing the black cloth of the target by netting was the most cost efficient for all three species. Conclusion/Significance: Reducing the size of the current 1*1 m black-blue-black target to horizontal designs of around 50 cm and replacing black cloth by netting will improve cost effectiveness six-fold for both G. p. gambiensis and G. tachinoides. Studying the visual responses of tsetse to different designs of target has allowed us to design more cost-effective devices for the effective control of sleeping sickness and animal trypanosomiasis in Africa

Combining farmers' decision rules and landscape stochastic regularities for landscape modelling

International audienceLandscape spatial organization (LSO) strongly impacts many environmental issues. Modelling agricultural landscapes and describing meaningful landscape patterns are thus regarded as key-issues for designing sustainable landscapes. Agricultural landscapes are mostly designed by farmers. Their decisions dealing with crop choices and crop allocation to land can be generic and result in landscape regularities, which determine LSO. This paper comes within the emerging discipline called "landscape agronomy", aiming at studying the organization of farming practices at the landscape scale. We here aim at articulating the farm and the landscape scales for landscape modelling. To do so, we develop an original approach consisting in the combination of two methods used separately so far: the identification of explicit farmer decision rules through on-farm surveys methods and the identification of landscape stochastic regularities through data-mining. We applied this approach to the Niort plain landscape in France. Results show that generic farmer decision rules dealing with sunflower or maize area and location within landscapes are consistent with spatiotemporal regularities identified at the landscape scale. It results in a segmentation of the landscape, based on both its spatial and temporal organization and partly explained by generic farmer decision rules. This consistency between results points out that the two modelling methods aid one another for land-use modelling at landscape scale and for understanding the driving forces of its spatial organization. Despite some remaining challenges, our study in landscape agronomy accounts for both spatial and temporal dimensions of crop allocation: it allows the drawing of new spatial patterns coherent with land-use dynamics at the landscape scale, which improves the links to the scale of ecological processes and therefore contributes to landscape ecology.L'organisation du paysage influe sur les problèmes environnementaux. Modéliser les paysages pour les décrire à l'aide de formes significatives est une étage clé. Les paysages agricoles sont principalement construits par les agriculteurs dont les décision d'assolement peuvent être génériques et déterminer des régularités dans l'organisation du paysage. Cet article contribue à l'agronomie des paysage qui est une discipline émergente. Nous cherchons à articuler les échelles du paysage et de l'exploitation agricole en développant deux méthodes : l'une consiste à identifier les décisions des agriculteurs par le bais d'enquêtes, l'autre consiste à retrouver des régularités stochastiques dans le paysage par le bais de fouille de données. Nous avons appliqué cette approche au paysage de la plaine de Niort en France. Les résultats montrent que les décisions des agriculteurs en matière de tournesol et maïs sont génériques et ont des effets sur le paysages que des méthodes de fouille de données révèlent et quantifient

Influence de la haie de ceinture de fond de vallée sur le transfert d'eau et de nitrate

RENNES-Agrocampus-CRD (352382323) / SudocSudocFranceF

Les bocages armoricains : repères sur l'évolution des thèmes de recherche depuis les années 1960

Le thème du bocage a été traité depuis fort longtemps, mais dans un nombre limité de disciplines (histoire, géographie...). L'année 1964 est marquée par les premières manifestations d'intérêt pour le bocage armoricain de la part de la recherche agronomique. Une analyse bibliométrique montre à la fois une explosion des publications sur le bocage et un renversement de point de vue depuis la dernière décennie. Après avoir étudié autrefois le rôle des haies sur le fonctionnement du champ, on se penche aujourd'hui sur le fonctionnement de la haie en elle-même, voire sur le rôle du champ sur la haie. L'analyse des recherches montre que celles réalisées dans la première période ont laissé de côté un certain nombre de questions pertinentes, voire de champs disciplinaires, et ont manqué de vision systémique. Les recherches mettent aujourd'hui en avant l'utilité environnementale objective du bocage, mais aussi ses fonctions subjectives paysagères, historiques et patrimoniales

Impact of hedgerows on water and soil resources as illustrated in Brittany - Recent results and outlook

Since environmental issues have come to the fore and an awareness of changes in agricultural landscapes has developed, hedges are generally considered to be key regulating factors for water and soil resources. The aim of this study is to assess recent work done on the effect of hedges on those resources in Brittany, and to discuss prospects for research in this area. The role played by hedges on erosion and runoff is well known. More recent work based on in situ measurements on particular hedges shows that on the one hand hedges play a non-negligible role in respect of carbon storage in soils and furthermore that their impact on evapotranspiration, groundwater recharge and nitrate content can be quantified. In parallel, modelling tools designed for the acquisition of knowledge through research together with more operations-oriented tools intended for managers are being developed so as to generalize the results obtained locally and take on board the interactions between hedges and other factors that control water and soil quality (the physical environment, other landscape elements).Depuis l’émergence des problématiques environnementales et la prise de conscience de l’évolution des paysages agricoles, les haies sont généralement considérées comme des éléments régulateurs clés des ressources en eau et en sol. L’objectif de ce travail est de faire le point sur les travaux menés récemment sur le rôle effectif des haies sur ces ressources en Bretagne et de discuter des perspectives de recherche dans ce domaine. Le rôle des haies sur l’érosion et le ruissellement est bien connu. Des travaux plus récents, basés sur des mesures in situ sur des haies particulières, ont permis d’une part de mettre en évidence le rôle non négligeable des haies sur le stockage de carbone dans les sols, d’autre part de quantifier leur impact sur l’évapotranspiration, la recharge des eaux de nappe et les teneurs en nitrates. Parallèlement, des outils de modélisation destinés à l’acquisition de connaissances par la recherche, et des outils plus opérationnels destinés aux gestionnaires, sont développés pour généraliser les résultats obtenus localement et prendre en compte les interactions des haies avec les autres facteurs de contrôle de la qualité de l’eau et des sols (milieu physique, autres structures paysagères)