Abstract: Experimental results are presented with single nail joints of gonfolo rose which were loaded at different grain angles and compared to results obtained by Eurocode V. A wide range of embedding strength tests was conducted. The embedding behaviour across the grain was also investigated with a specific test apparatus. The results were analysed and modelled in terms of strength. Initial loading and unloading stiffness of the timber have been taken into account. The embedment strength of the nails varied according to the angle between the direction of loading and that to the grain. This work is part of a larger research project to establish a computer program for the prediction of stiffness and limit strengths of all timber-to-timber and timber-to-steel joints.

Abstract: Tropical tree floras are highly diverse and many genera and species share similar anatomical patterns, making the identification of tropical wood charcoal very difficult. Appropriate tools to characterize charcoal anatomy are thus needed to facilitate and improve identification in such species-rich areas. This paper presents the first computer-aided identification key designed for charcoals from French Guiana, based on the wood anatomy of 507 species belonging to 274 genera and 71 families, which covers respectively 28%, 67% and 86% of the tree species, genera and families currently listed in this part of Amazonia. Species of the same genus are recorded together except those described under a synonym genus in Détienne et al. (1982) that were kept separately. As a result, the key contains 289 'items' and mostly aims to identify charcoals at the genus level. It records 26 anatomical features leading to 112 feature states, almost all of which are illustrated by SEM photographs of charcoal. The descriptions were mostly taken from Détienne et al.'s guidebook on tropical woods of French Guiana (1982) and follow the IAWA list of microscopic features for hardwood identification (Wheeler et al. 1989). Some adjustments were made to a few features and those that are unrelated to charcoal identification were excluded. The whole tool, named CharKey, contains the key itself and the associated database including photographs. It can be downloaded on Figshare at https://figshare.com/s/d7d40060b53d2ad60389 (doi: 10.6084/m9.figshare.6396005). CharKey is accessible using the free software Xper 2 , specifically conceived for taxonomic description and computer aided-identification.

Abstract: Key message: Pterocarpus officinalisis able to (1) improve its acclimation capacity if soil salinity increases slowly and (2) benefit from afreshwater episode.
Abstract: One likely effect of global change is an increase of the amplitude of salt variations in the soil of brackish coastal wetland forests. In the Antilles, such forests are dominated by the species Pterocarpus officinalis. The study aimed to determine the effect of 3 salinity levels (freshwater, moderate, and hypersalinity—i.e., 0, 10, and 30 ‰, respectively) and 3 patterns of salinity variation (fast or slow salinity increase, fluctuating salinity) on the growth and ecophysiology of P. officinalis seedlings. P. officinalis proved tolerant to 10 ‰ salinity, even if at this salt concentration the water constraint altered the plant’s water status and reduced stomatal conductance. No impact of the pattern of salinity variation was observed at 10 ‰. Seedlings were strongly affected by hypersalinity, but were able to acclimatize efficiently and to improve their performances (higher survival, total biomass, and photosynthesis) when salinity increased slowly. Young P. officinalis were also able to take advantage of a freshwater episode on the longer term, certainly through leaf desalination associated with enhanced photosynthesis and water use efficiency. Higher soil salinity and more intense dry seasons in the context of climate change could affect the stand-level regeneration potential of P. officinalis seedlings. © 2014, Springer-Verlag Berlin Heidelberg.

Abstract: We characterised the among species variability in leaf gas exchange and morphological traits under controlled conditions of seedlings of 22 tropical rainforest canopy species to understand the origin of the variability in leaf carbon isotope discrimination (Delta) among species with different growth and dynamic characteristics (successional gradient). Our results first suggest that these species pursue a consistent strategy in terms of. throughout their ontogeny (juveniles grown here versus canopy adult trees from the natural forest). Second, leaf Delta was negatively correlated with WUE and N, and positively correlated with g(s), but among species differences in Delta were mainly explained by differences in WUE. Finally, species belonging to different successional groups display distinct leaf functional and morphological traits. We confirmed that fast growing early successional species maximise carbon assimilation with high stomatal conductance. In contrast, fast and slow growing late successional species are both characterised by low carbon assimilation values, but by distinct stomatal conductance and leaf morphological features. Along the successional gradient, these differences result in much lower Delta for the intermediate species (i.e. fast growing late successional) as compared to the two other groups.

Abstract: Key message: We review the recent findings on the influence of drought on tree mortality, growth or ecosystem functioning in tropical rainforests. Drought plays a major role in shaping tropical rainforests and the response mechanisms are highly diverse and complex. The numerous gaps identified here require the international scientific community to combine efforts in order to conduct comprehensive studies in tropical rainforests on the three continents. These results are essential to simulate the future of these ecosystems under diverse climate scenarios and to predict the future of the global earth carbon balance. Context: Tropical rainforest ecosystems are characterized by high annual rainfall. Nevertheless, rainfall regularly fluctuates during the year and seasonal soil droughts do occur. Over the past decades, a number of extreme droughts have hit tropical rainforests, not only in Amazonia but also in Asia and Africa. The influence of drought events on tree mortality and growth or on ecosystem functioning (carbon and water fluxes) in tropical rainforest ecosystems has been studied intensively, but the response mechanisms are complex. Aims: Herein, we review the recent findings related to the response of tropical forest ecosystems to seasonal and extreme droughts and the current knowledge about the future of these ecosystems. Results: This review emphasizes the progress made over recent years and the importance of the studies conducted under extreme drought conditions or in through-fall exclusion experiments in understanding the response of these ecosystems. It also points to the great diversity and complexity of the response of tropical rainforest ecosystems to drought. Conclusion: The numerous gaps identified here require the international scientific community to combine efforts in order to conduct comprehensive studies in tropical forest regions. These results are essential to simulate the future of these ecosystems under diverse climate scenarios and to predict the future of the global earth carbon balance. © 2015, INRA and Springer-Verlag France.