Static winching tests were carried out in order to determine the mechanical resistance of Maritime pine to overturning. The tested stands were selected according to podzolic soil conditions: "wet Lande", characterised by a shallow ground water table and a hard pan horizon, and "dry Lande", with a deeper ground water table and a hard pan absent or broken up. As this soil horizon limits the vertical growth of tree roots, anchorage resistance was investigated with regards to the presence or absence of a hard pan underneath each tree. To determine if mechanical behaviour differed within a stand, trees from inside the stand and edge trees at the border exposed to prevailing winds were also tested. The critical turning moment (TM crit,total ) at the base of the stem was positively related to the variable (H × DBH 2 ) (H, total tree height; DBH, tree diameter). Linear regression analyses between TM crit,total and (H × DBH 2 ) showed that the presence of a hard pan had no significant effect on anchorage resistance in uprooted trees. Stem failure occurred for 82% of trees on dry Lande when (H × DBH 2 ) < 1 m 3 . Moreover, stem failure type on dry Lande indicated that trees were better anchored. On soil with a hard pan, edge trees were found to be 20% more resistant to overturning than inner trees. Edge trees differed from inner trees in that the soil-root plate was two times larger and also possessed a larger surface area on the windward side.

L . A u g u s t o a , M . R . B a k k e r b , C . M o r e l a , C . M e r e d i e u c , P . T r i c h e t d , V . B a d e a u e,f , D . A r r o u a y s g , C . P l a s s a r d h , D . L . A c h a t b , SummarySoil scientists are receiving increasing numbers of requests for expert advice on soil over large areas, but at a high resolution. We tested the use of the soil data contained in sources of information that are not directly accessible (referred to as 'grey' data) to accomplish this task. We collected grey data about a pine forest, which is currently the subject of drastic, and questionable, changes in management, including a rapid rate of biomass removal. These grey data (from 266 sites) were compared with soil data obtained directly from our field sampling (83 sites). Our comparisons showed that the two sources of data were consistent when the variables concerned had been sampled and analysed by using methods shared by the soil scientists such as particle-size distribution. Conversely, significant discrepancies appeared for variables for which different methods existed, such as for CEC. For the latter, using corrective equations gave contrasting results, depending on the soil variable. The final database was used to characterize the soils of the study region. Results showed that soils of the study region (mainly sandy podzols and arenosols) were acidic and particularly oligotrophic. Several important properties (CEC, phosphorus cycling, pH, bulk density) were related to the organic fraction or carbon (C) content of soils. For instance, CEC values were linearly and exclusively dependent on C content. The most oligotrophic sites of the study region were clearly not suitable for the new intensive management of the forest in the long term. For the other sites, the question remains open because some specific data are still needed before drawing conclusions. We conclude that as a complement to conventional soil studies, the grey literature is a useful source of data and information to characterize soils at a regional scale.

Lem assif landais est le premier massif forestier deFrancep ars asurface,saproduction totale et son homogénéité.Ilaétél ep remier massif mesuré parl 'IFN dès 1961'IFN dès -1962.Aujourd'huiq uatre inventaires sont publiés pourl aG ironde,le quatrième est réalisé dans les Landes mais sapublication est retardée parl a tempêtededécembre 1999.Les inventaires ont permis deconstater une augmentation del aproduction au cours des trois dernières décennies.Dans le même temps,le massif asubiden ombreuses évolutions : -abandon du gemmage et del asylviculture associée, -g énéralisation d'unm odedes ylviculture intensive:laligniculture, -i ntroduction dem atériel génétiqueamélioré.Lem assif subit également des ravages périodiques :incendies,gels, tempêtes.Les inventaires del 'IFN permettent,d ans une certaine mesure,d er etrouver ces événementsdans les caractéristiques des peuplements( structure des classes d'âge, volume surp ied).Cet article se propose dechiffrer,àpartir des données del 'IFN, l'incidencedel 'évolution des pratiques sylvicoles surl aproduction et larécoltep assées et futures du massif.

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The dam-break connected flood hydrograph properties primarily depend on the breach geometry and the time for the breach to fully develop. Therefore, the prediction of dam's breach geometry is essential in dam-break studies. To understand the impact of breach parameters on flood peak hydrograph, five of the most common breach prediction methods are implemented in the presented study to estimate the flood hydrographs using 2dimensional HEC-RAS model. The Ürkmez Dam is chosen as the case study due to the presence of a residential settlement located right at the dam downstream where undesirably any breach of the dam body can have inevitable and dramatical risks on downstream populations and properties. Various levels for reservoir storage are investigated in each method. To assess the impact of each breach parameter on the resulting flood hydrographs, sensitivity analysis is carried out. The peak discharge rates and the times to peak for each analyzed scenario are investigated and discussed. Results reveal that Froehlich approach is the most reasonable method for estimating dam-breach parameters as far as exemplified in the Ürkmez Dam case. Furthermore, sensitivity analysis points out that the parameter of the breach side slope has no major influence on the time to peak while having an insignificant impact on the peak discharge. Besides, the study exhibits that both the peak discharge and the time to peak characteristics are highly sensitive to breach time formation parameter. In the light of these targeted findings, the study is aimed to contribute to other relevant research in designating the set of key parameters in experimental or modeling efforts in a way to limit the uncertainty that substantially originates from personal judgment.