Estimating taxonomic diversity and functional types of perennial forage grasses in mountain meadows: potentialities of Pléiades imagery

Estimating taxonomic diversity and functional types of perennial forage grasses in mountain meadows: potentialities of Pléiades imagery

Discriminating small wooded elements in rural landscape from aerial photography: a hybrid pixel/object-based analysis approach

While small, fragmented wooded elements do not represent a large surface area in agricultural landscape, their role in the sustainability of ecological processes is recognized widely. Unfortunately, landscape ecology studies suffer from the lack of methods for automatic detection of these elements. We propose a hybrid approach using both aerial photographs and ancillary data of coarser resolution to automatically discriminate small wooded elements. First, a spectral and textural analysis is performed to identify all the planted-tree areas in the digital photograph. Secondly, an object-orientated spatial analysis using the two data sources and including a multi-resolution segmentation is applied to distinguish between large and small woods, copses, hedgerows and scattered trees. The results show the usefulness of the hybrid approach and the prospects for future ecological applications

Non-renormalization for planar Wess-Zumino model

Using a non-perturbative functional method, where the quantum fluctuations are gradually set up,it is shown that the interaction of a N=1 Wess-Zumino model in 2+1 dimensions does not get renormalized. This result is valid in the framework of the gradient expansion and aims at compensating the lack of non-renormalization theorems

Detecting clear-cuts and decreases in forest vitality using MODIS NDVI time series

This paper examines the potential of MODIS-NDVI time series for detecting clear-cuts in a coniferous forest stand in the south of France. The proposed approach forms part of a survey monitoring the status of forest health and evaluating the forest decline phenomena observed over the last few decades. One of the prerequisites for this survey was that a rapid and easily reproducible method had to be developed that differentiates between forest clear-cuts and changes in forest health induced by environmental factors such as summer droughts. The proposed approach is based on analysis of the breakpoints detected within NDVI time series, using the "Break for Additive Seasonal and Trend" (BFAST) algorithm. To overcome difficulties detecting small areas on the study site, we chose a probabilistic approach based on the use of a conditional inference tree. For model calibration, clear-cut reference data were produced at MODIS resolution (250 m). According to the magnitude of the detected breakpoints, probability classes for the presence of clear-cuts were defined, from greater than 90% to less than 3% probability of a clear-cut. One of the advantages of the probabilistic model is that it allows end users to choose an acceptable level of uncertainty depending on the application. In addition, the use of BFAST allows events to be dated, thus making it possible to perform a retrospective analysis of decreases in forest vitality in the study area

Les éleveurs et l'estive : pour une approche compréhensive des pratiques pastorales

International audienceCattle farmers and mountain summer pastures: a comprehensive approach to pastoral practices. In the Ariège department (French Pyrénées), the restructuring of mountain cattle farming and of pastoralism has brought about profound changes in the relations cattle farmers entertain with the high mountain pastureland. Gaining insight into the endogenous meaning of the practices of cattle breeders traditionally using these summer pastures allows the highlighting of the emergence and confrontation of two technical and symbolic bodies of references on the mountain. While the summer pastures remain the organizing and identitary principle for the mountain farmers who are the traditional "users" of the high mountain area, other "non-local" farmers from lower lying areas who practise short distance transhumance view these pastures as one among other economic opportunities. Strong attachment to customary rights, the sole guarantee for people's and animals' legitimacy to use the "high mountain", enables these high mountain farmers, even though a minority, to keep control over the management methods of grazing resources.Dans les Pyrénées ariégeoises, la restructuration de l'élevage de montagne et du pastoralisme est à l'origine d'une profonde modification des relations que les éleveurs entretiennent avec les territoires d'altitude. La compréhension du sens endogène des pratiques des éleveurs transhumants permet de mettre au jour l'émergence et la confrontation de deux référentiels techniques et symboliques sur la montagne. Alors que l'estive reste le principe organisateur et identitaire des éleveurs "usagers" de haute montagne, elle tend à être envisagée comme une opportunité économique parmi d'autres par les éleveurs "étrangers" pratiquant une transhumance de proximité. L'attachement aux droits d'usage, seuls garants de la légitimité des hommes et des bêtes sur la "montagne", permet alors aux premiers, même minoritaires, de garder le contrôle des modalités de gestion de la ressource pastorale

Biodiversité et services rendus à l’agriculture. Principaux enseignements de différents dispositifs de recherche récents et actuels en Midi-Pyrénées

Dans le canton d’Aurignac, des chercheurs de l’Institut national de la recherche agronomique et de l’Institut national polytechnique de Toulouse travaillent depuis une trentaine d’années sur l’agriculture, les paysages et la biodiversité. Les paysages agricoles étudiés sont caractérisés par une agriculture de polyculture élevage et la présence de petits bois. Ces paysages agri-forestiers constituent un site d’étude à long terme qui est reconnu au niveau national et européen