Analysis of soil texture using terrasar x-band sar

International audienceIn this paper, it is proposed to use TERRASAR-X data for analysis and estimation of soil surface texture. Our study is based on experimental campaigns carried out over a semi-arid area in North Africa. Simultaneously to TERRASAR-X radar acquisitions, ground measurements (texture, soil moisture and roughness) were made on different test fields. A strong correlation is observed between soil texture and a processed signal from two radar images, the first acquired just after a rain event and the second corresponding to dry soil conditions, acquired three weeks later. An empirical relationship is proposed for the retrieval from radar signals of clay content percent. Soil texture mapping is proposed over the study site, which includes bare soils and olive groves

Efficiency of marker-assisted selection in detection of ascochyta blight resistance in Tunisian chickpea breeding lines

Ascochyta blight (AB) resistance reactions were studied in 23 chickpea cultivars, mainly advanced lines and Tunisian varieties from the Tunisian chickpea breeding program, growing both at two locations and under controlled conditions. Two co-dominant markers both associated with AB resistance were also used in this study; the CaETR marker tightly linked to QTLAR1 in combination with the SCAR SCY17590 marker linked to QTLAR2 to explore their usefulness in discriminating between resistant and susceptible chickpea genotypes. These two markers contribute efficiently in the selection of new chickpea varieties with better combinations of alleles to ensure durable resistance to AB. The advanced line V10 presenting the resistance allele for CaETR, but being still heterozygous for the SCAR17590 was characterized as resistant to moderately resistant in field studies and under controlled conditions. This line could be very useful for developing a new variety that is fixed for both resistance alleles and expresses good levels of resistance to AB in different chickpea cropping environments. These markers are very useful in assisting chickpea breeding programs, especially thanks to their robustness, their co-dominance and their utility across different genetic backgrounds

Soil texture estimation over a semiarid area using TerraSAR-X radar data

In this letter, it is proposed to use TerraSAR-X data for analysis and estimation of soil surface texture. Our study is based on experimental campaigns carried out over a semiarid area in North Africa. Simultaneously with TerraSAR-X radar acquisitions, ground measurements (texture, soil moisture, and roughness) were made on different test fields. A strong correlation is observed between soil texture and a processed signal from two radar images, with the first acquired just after a rain event and the second corresponding to dry soil conditions, acquired three weeks later. An empirical relationship is proposed for the retrieval from radar signals of clay content percent. Soil texture mapping is proposed over the study site, which includes bare soils and olive groves

Analysis of Vegetation Behavior in a North African Semi-Arid Region, Using SPOT-VEGETATION NDVI Data

The analysis of vegetation dynamics is essential in semi-arid regions, in particular because of the frequent occurrence of long periods of drought. In this paper, multi-temporal series of the Normalized Difference of Vegetation Index (NDVI), derived from SPOT-VEGETATION satellite data between September 1998 and June 2010, were used to analyze the vegetation dynamics over the semi-arid central region of Tunisia. A study of the persistence of three types of vegetation (pastures, annual agriculture and olive trees) is proposed using fractal analysis, in order to gain insight into the stability/instability of vegetation dynamics. In order to estimate the state of vegetation cover stress, we propose evaluating the properties of an index referred to as the Vegetation Anomaly Index (VAI). A positive VAI indicates high vegetation dynamics, whereas a negative VAI indicates the presence of vegetation stress. The VAI is tested for the above three types of vegetation, during the study period from 1998 to 2010, and is compared with other drought indices. The VAI is found to be strongly correlated with precipitation

Estimation régionale de l'évapotranspiration sur la plaine de Kairouan (Tunisie) à partir de données satellites multi-capteurs

The main objective of this thesis is to understand the functioning of a semi-arid ecosystem by developing methodologies from combined optical and microwave satellite measurements in order to assess evapotranspiration and its seasonal dynamics in a semi-arid region (Kairouan plain). The retrieving of the latter requires a good description of the vegetation dynamics and monitoring the water content in the soil. For this purpose, an analysis of vegetation dynamics is made on the basis of the SPOT VEGETATION time series from 1998 to 2010. To understand the vegetation behavior along frequent periods of drought, fractal analysis is an appropriate tool to study the vegetation persistence. A new statistical index referred to VAI "Anomaly Vegetation Index" describing the state of vegetation water stress is proposed. This quantitative index can be used to describe at a monthly scale the state of vegetation. Several validation approaches are implemented to test the performance of this index that confirms its reliability. In terms of monitoring the soil water content, moisture products derived from ERS and ASCAT / Metop scatterometer are availables. These products are validated in our study using two different approaches. A statistical drought monitoring index is proposed from a long time series of moisture products that covers twenty years (from 1991 to 2010). The index proposed referred to MAI "Moisture Anomaly Index" is based on anomaly analysis of temporal variability of soil water content, estimated from ERS and ASCAT / Metop scatterometers. A comparative analysis with other drought indices, particularly SPI "Standardized Precipitation Index" is made and shows the performance of our index. This information derived from the two time series optical and microwave are then integrated into a simple and operational model FAO-56 (dual crop coefficient approach) for mapping at a daily scale the evapotranspiration at 1km resolution. A validation of this approach is generated by comparing the results with the outputs of a SVAT model: ISBA-A-gs.L'objectif principal de cette thèse est de comprendre le fonctionnement d'un écosystème semi-aride, en développant des méthodologies permettant de combiner des mesures satellites optique et micro-onde et un modèle semi-empirique pour estimer l'évapotranspiration et sa dynamique saisonnière dans une région semi-aride (plaine de Kairouan). L'estimation de cette dernière nécessite une bonne description de la dynamique du couvert végétal et un suivi du stock d'eau dans le sol. Pour se faire, une analyse de la dynamique de la végétation est faite sur la base de la série temporelle SPOT VEGETATION de 1998 à 2010. Pour appréhender le comportement de la végétation face à des fréquentes périodes de sècheresse, une analyse fractale est developpée pour étudier la persistance du couvert végétal. Un nouvel indice statistique VAI " Vegetation Anomaly Index " décrivant l'état du stress hydrique de la végétation a été proposé. Cet indice quantitatif permet de décrire à l'échelle mensuelle l'état de la végétation. Plusieurs approches de validation sont mises en œuvre pour montrer la performance de cet indice. En termes de suivi du stock d'eau dans le sol, l'analyse est basée sur des produits d'humidité (IPF Université de Vienne) des diffusiomètres spatiaux ERS et ASCAT/METOP. Ces produits ont été validés sur notre site d'étude via deux approches différentes. Un indice de sécheresse a été proposé à partir de la longue série de produits d'humidité qui couvre vingt années (de 1991 à 2010). L'indice proposé MAI " Moisture Anomaly Index " est basé sur une analyse des anomalies des variabilités temporelles des stocks d'eau dans le sol, estimées par les satellites ERS et ASCAT/METOP. Une analyse comparative avec d'autres indices de sécheresse, particulièrement le SPI " Standardized Precipitation Index " est faite pour mettre en évidence la performance de cet indice. Ces informations tirées à partir des deux séries temporelles optiques et micro-ondes sont ensuite intégrées dans un modèle simple et opérationnel, le modèle FAO-56 (approche double coefficient culturale) pour la cartographie de l'évapotranspiration réelle journalière. Une validation de cette approche est proposée en confrontant les résultats avec des sorties d'un modèle SVAT : ISBA-A-gs

Soil moisture mapping in a semi-arid region, based on ASAR/Wide Swath satellite data

International audienceIn this paper, an operational algorithm is proposed for the mapping of surface moisture over a site in North Africa. A change detection approach is applied, using 160 Envisat ASAR Wide Swath images acquired over a 7-year period. Parameterization of this algorithm is considered for three classes of vegetation cover density (NDV

Analysis of the Effects of Drought on Vegetation Cover in a Mediterranean Region through the Use of SPOT-VGT and TERRA-MODIS Long Time Series

The analysis of vegetation dynamics and agricultural production is essential in semi-arid regions, in particular as a consequence of the frequent occurrence of periods of drought. In this paper, a multi-temporal series of the Normalized Difference of Vegetation Index (NDVI), derived from SPOT-VEGETATION (between September 1998 and August 2013) and TERRA-MODIS satellite data (between September 2000 and August 2013), was used to analyze the vegetation dynamics over the central region of Tunisia in North Africa, which is characterized by a semi-arid climate. Products derived from these two satellite sensors are generally found to be coherent. Our analysis of land use and NDVI anomalies, based on the Vegetation Anomaly Index (VAI), reveals a strong level of agreement between estimations made with the two satellites, but also some discrepancies related to the spatial resolution of these two products. The vegetation’s behavior is also analyzed during years affected by drought through the use of the Windowed Fourier Transform (WFT). Discussions of the dynamics of annual agricultural areas show that there is a combined effect between climate and farmers’ behavior, leading to an increase in the prevalence of bare soils during dry years

Efficiency of marker-assisted selection in detection of ascochyta blight resistance in Tunisian chickpea breeding lines

Ascochyta blight (AB) resistance reactions were studied in 23 chickpea cultivars, mainly advanced lines and Tunisian varieties from the Tunisian chickpea breeding program, growing both at two locations and under controlled conditions. Two co-dominant markers both associated with AB resistance were also used in this study; the CaETR marker tightly linkedto QTLAR1 in combination with the SCAR SCY17590 marker linked to QTLAR2 to explore their usefulness in discriminating between resistant and susceptible chickpea genotypes. These two markers contribute efficiently in the selection of new chickpea varieties with better combinations of alleles to ensure durable resistance to AB. The advanced line V10 presentingthe resistance allele for CaETR, but being still heterozygous for the SCAR17590 was characterized as resistant to moderately resistant in field studies and under controlled conditions. This line could be very useful for developing a new variety that is fixed for both resistance alleles and expresses good levels of resistance to AB in different chickpea cropping environments. These markers are very useful in assisting chickpea breeding programs, especially thanks to their robustness, their co-dominance and their utility across different genetic backgrounds. © Firenze University Press.This research was funded by MESRT (Ministère de l’Enseignement Supérieur et de la Recherche Scientifique- Tunisie) and Co-funded by the bilateral Spain Tunisian project (AECI: Agencia Española de Cooperación Internacional).Peer Reviewe

Description of the Tournaments Which are Reconstructible from Their k-cycle Partial Digraphs for k∈{3,4}k \in \{3, 4\} k ∈ { 3 , 4 }

International audienceIf T is a tournament on n vertices and k is an integer with , then the k-cycle partial digraph of T, denoted by T(k), is the spanning subdigraph of T for which the arcs are those of the k-cycles of T. In 1989, Thomassen proved that given two irreducible tournaments T and on the same vertex set with at least 6 vertices, if , then . This result allows us to introduce the following notion of reconstruction. A tournament T is reconstructible from its k-cycle partial digraph whenever is isomorphic to T for each tournament such that is isomorphic to T(k). In this paper, we give a complete description of the tournaments which are reconstructible from their k-cycle partial digraphs where . For , our proof is based on the above result of Thomassen. For , we introduce and study the tournaments for which all modules are irreducible. We use properties of the dilatation operator to describe such tournaments, and then we obtain a new modular decomposition of tournaments sometimes finer than that of Gallai

Efficiency of marker-assisted selection in detection of ascochyta blight resistance in Tunisian chickpea breeding lines

Ascochyta blight (AB) resistance reactions were studied in 23 chickpea cultivars, mainly advanced lines and Tunisian varieties from the Tunisian chickpea breeding program, growing both at two locations and under controlled conditions. Two co-dominant markers both associated with AB resistance were also used in this study; the CaETR marker tightly linkedto QTLAR1 in combination with the SCAR SCY17590 marker linked to QTLAR2 to explore their usefulness in discriminating between resistant and susceptible chickpea genotypes. These two markers contribute efficiently in the selection of new chickpea varieties with better combinations of alleles to ensure durable resistance to AB. The advanced line V10 presentingthe resistance allele for CaETR, but being still heterozygous for the SCAR17590 was characterized as resistant to moderately resistant in field studies and under controlled conditions. This line could be very useful for developing a new variety that is fixed for both resistance alleles and expresses good levels of resistance to AB in different chickpea cropping environments. These markers are very useful in assisting chickpea breeding programs, especially thanks to their robustness, their co-dominance and their utility across different genetic backgrounds. © Firenze University Press.This research was funded by MESRT (Ministère de l’Enseignement Supérieur et de la Recherche Scientifique- Tunisie) and Co-funded by the bilateral Spain Tunisian project (AECI: Agencia Española de Cooperación Internacional).Peer Reviewe