Abstract: A model to simulate the ecological processes of tree growth, mortality and recruitment, and the processes of forest management, in the terra firme forests of the eastern Amazon is described. It is implemented within the SYMFOR (http://www.symfor.org) framework. It is based on measurements of all trees that have a diameter greater than 5 cm from experimental plots in the Jari Cellulose and Tapajos National Forest areas over a 16-year period. Ten species groups are used to describe the natural processes affecting tree behaviour. Growth rates are calculated for each species group using the tree diameter and a competition index. Mortality and recruitment are simulated as stochastic processes. Recruitment probability is based on the predicted growth rate of a hypothetical tree. Options exist to vary the human interaction with the forest reflecting forest management decisions, as for other SYMFOR models. Model evaluation compares the performance of the model with data describing forest recovery for 16 years following logging. The model was applied to simulate current forest management practice in the Brazilian Amazon, with 40 m(3) ha(-1) of timber extracted with a cutting cycle of 30 years. Results show that yields are sustained for three harvests following the first logging of primary forest, but that the composition of timber moves towards lightwooded species rather than hardwooded. The predicted size of extracted trees decreases and the number of trees extracted increases with successive harvests, leading to a prediction of increased costs and lower profits for the logging company despite constant yields. The standing volume of all trees just before harvest is reduced by 15% over 150 years, with pioneer species becoming increasingly prevalent in the stand. The model, in the SYMFOR framework, can be used to help understand the differences between alternative forest management strategies in the Brazilian Amazon. Such knowledge is required to improve forest management, regulation and certification, and help to conserve the worlds largest remaining tropical forest. (C) 2003 Elsevier B.V. All rights reserved.

Abstract: The high tree species diversity in tropical forests is difficult to take into account in models. The usual solution consists of defining groups of species and then adjusting a set of parameters for each group. In this study, we address this issue by allowing a species to move from one species group to another, depending on the biological process that is concerned. We developed this approach with a matrix model of forest dynamics, for a tropical rainforest in French Guiana, at Paracou, focusing on the methodological aspects. The forest dynamics is split into three components: recruitment, growth and mortality. We then built five recruitment groups, five growth groups and five mortality groups. One species is characterized by a combination of the three groups, thus yielding in total 5 X 5 X 5 = 125 possibilities, out of which 43 are actually observed. The resulting matrix model provides a better view of the floristic composition of the forest, and does not have more parameters than it would have with five global species groups. However, its predictions are no more precise than those of the matrix model based on five global groups.

Abstract: When ordinating plots of tropical rain forests using stand-level structural attributes such as biomass, basal area and the number of trees in different size classes, two patterns often emerge: a gradient from poorly to highly stocked plots and high positive correlations between biomass, basal area and the number of large trees. These patterns are inherited from the demographics (growth, mortality and recruitment) and size allometry of trees and tend to obscure other patterns, such as site differences among plots, that would be more informative for inferring ecological processes. Using data from 133 rain forest plots at nine sites for which site differences are known, we aimed to filter out these patterns in forest structural attributes to unveil a hidden pattern. Using a null model framework, we generated the anticipated pattern inherited from individual allometric patterns. We then evaluated deviations between the data (observations) and predictions of the null model. Ordination of the deviations revealed site differences that were not evident in the ordination of observations. These sites differences could be related to different histories of large-scale forest disturbance. By filtering out patterns inherited from individuals, our model analysis provides more information on ecological processes

Abstract: This study compares variability in the longitudinal Modulus of Elasticity (MOE) values, measured by three different methods, for eight tropical wood species covering a wide range of densities, a property that has been little described in the literature for some of the species studied. The modulus of elasticity in wood species is one of the main mechanical properties measured to characterize wood materials. However, this property is seldom described for the tropical wood species studied here, and the method used is often variable. The aim is to answer the following questions. In the methods used, what are the main variability factors which influence modulus measurement? Is the modulus different with regard to the solicitation direction (radial or tangential)? Which relationship exists between modulus and density for these species?
The samples were subjected to the four-point bending test, then to the free vibration test and to the forced-vibration test (which allows tests on small samples).The samples were subjected to stress in radial and tangential directions. The modulus values obtained by the different methods were well correlated for most of the species. The relationship between modulus and density was very good at inter-specific level because sampling covered a wide range of densities. But this relationship was not so good for each of the species sampled.
This kind of test was not appropriate for detecting differences in behavior between the two directions of solicitation for these species. The main features of the three methods were summarized, highlighting the advantages of each for the species studied.

Abstract: One third of contemporary tropical forests is designated by national forest services for timber production. Tropical forests are also increasingly affected by anthropogenic disturbances. However, there is still much uncertainty around the capacity of tropical forests to recover their timber volume after logging as well as other disturbances such as fires, large blow-downs and extreme droughts, and thus on the long-term sustainability of logging. We developed an original Bayesian hierarchical model of Volume Dynamics with Differential Equations (VDDE) to infer the dynamic of timber volumes as the result of two ecosystem processes: volume gains from tree growth and volume losses from tree mortality. Both processes are expressed as explicit functions of the forest maturity, i.e. the overall successional stage of the forest that primarily depends on the frequency and severity of the disturbances that the forest has undergone. As a case study, the VDDE model was calibrated with data from Paracou, a long-term disturbance experiment in a neotropical forest where over 56 ha of permanent forest plots were logged with different intensities and censused for 31 years. With this model, we could predict timber recovery at Paracou at the end of a cutting cycle depending on the logging intensity, the rotation cycle length, and the proportion of commercial volume. The VDDE modelling framework developed presents three main advantages: (i) it can be calibrated with large tree inventories which are widely available from national forest inventories or logging concession management plans and are easy to measure, both on the field and with remote sensing; (ii) it depends on only a few input parameters, which can be an advantage in tropical regions where data availability is scarce; (iii) the modelling framework is flexible enough to explicitly include the effect of other types of disturbances (both natural and anthropogenic: e.g. blow-downs, fires and climate change) on the forest maturity, and thus to predict future timber provision in the tropics in a context of global changes. © 2018 Elsevier B.V.