Plant functional traits are the features (morphological, physiological, phenological) that represent ecological strategies and determine how plants respond to environmental factors, affect other trophic levels and influence ecosystem properties. Variation in plant functional traits, and trait syndromes, has proven useful for tackling many important ecological questions at a range of scales, giving rise to a demand for standardised ways to measure ecologically meaningful plant traits. This line of research has been among the most fruitful avenues for understanding ecological and evolutionary patterns and processes. It also has the potential both to build a predictive set of local, regional and global relationships between plants and environment and to quantify a wide range of natural and human-driven processes, including changes in biodiversity, the impacts of species invasions, alterations in biogeochemical processes and vegetation–atmosphere interactions. The importance of these topics dictates the urgent need for more and better data, and increases the value of standardised protocols for quantifying trait variation of different species, in particular for traits with power to predict plant- and ecosystem-level processes, and for traits that can be measured relatively easily. Updated and expanded from the widely used previous version, this handbook retains the focus on clearly presented, widely applicable, step-by-step recipes, with a minimum of text on theory, and not only includes updated methods for the traits previously covered, but also introduces many new protocols for further traits. This new handbook has a better balance between whole-plant traits, leaf traits, root and stem traits and regenerative traits, and puts particular emphasis on traits important for predicting species’ effects on key ecosystem properties. We hope this new handbook becomes a standard companion in local and global efforts to learn about the responses and impacts of different plant species with respect to environmental changes in the present, past and future.

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New handbook for standardised measurement of plant functional traits worldwide

Wood performs several essential functions in plants, including mechanically supporting aboveground tissue, storing water and other resources, and transporting sap. Woody tissues are likely to face physiological, structural and defensive trade-offs. How a plant optimizes among these competing functions can have major ecological implications, which have been under-appreciated by ecologists compared to the focus they have given to leaf function. To draw together our current understanding of wood function, we identify and collate data on the major wood functional traits, including the largest wood density database to date (8412 taxa), mechanical strength measures and anatomical features, as well as clade-specific features such as secondary chemistry. We then show how wood traits are related to one another, highlighting functional trade-offs, and to ecological and demographic plant features (growth form, growth rate, latitude, ecological setting). We suggest that, similar to the manifold that tree species leaf traits cluster around the 'leaf economics spectrum', a similar 'wood economics spectrum' may be defined. We then discuss the biogeography, evolution and biogeochemistry of the spectrum, and conclude by pointing out the major gaps in our current knowledge of wood functional traits.

Towards a worldwide wood economics spectrum

Terrestrial carbon stock mapping is important for the successful implementation of climate change mitigation policies. Its accuracy depends on the availability of reliable allometric models to infer oven-dry aboveground biomass of trees from census data. The degree of uncertainty associated with previously published pantropical aboveground biomass allometries is large. We analyzed a global database of directly harvested trees at 58 sites, spanning a wide range of climatic conditions and vegetation types (4004 trees ≥ 5 cm trunk diameter). When trunk diameter, total tree height, and wood specific gravity were included in the aboveground biomass model as covariates, a single model was found to hold across tropical vegetation types, with no detectable effect of region or environmental factors. The mean percent bias and variance of this model was only slightly higher than that of locally fitted models. Wood specific gravity was an important predictor of aboveground biomass, especially when including a much broader range of vegetation types than previous studies. The generic tree diameter-height relationship depended linearly on a bioclimatic stress variable E, which compounds indices of temperature variability, precipitation variability, and drought intensity. For cases in which total tree height is unavailable for aboveground biomass estimation, a pantropical model incorporating wood density, trunk diameter, and the variable E outperformed previously published models without height. However, to minimize bias, the development of locally derived diameter-height relationships is advised whenever possible. Both new allometric models should contribute to improve the accuracy of biomass assessment protocols in tropical vegetation types, and to advancing our understanding of architectural and evolutionary constraints on woody plant development.

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Improved allometric models to estimate the aboveground biomass of tropical trees

Reducing carbon emissions from deforestation and degradation in developing countries is of central importance in efforts to combat climate change. Key scientific challenges must be addressed to prevent any policy roadblocks. Foremost among the challenges is quantifying nations' carbon emissions from deforestation and forest degradation, which requires information on forest clearing and carbon storage. Here we review a range of methods available to estimate national-level forest carbon stocks in developing countries. While there are no practical methods to directly measure all forest carbon stocks across a country, both ground-based and remote-sensing measurements of forest attributes can be converted into estimates of national carbon stocks using allometric relationships. Here we synthesize, map and update prominent forest biomass carbon databases to create the first complete set of national-level forest carbon stock estimates. These forest carbon estimates expand on the default values recommended by the Intergovernmental Panel on Climate Change's National Greenhouse Gas Inventory Guidelines and provide a range of globally consistent estimates.

https://iopscience.iop.org/article/10.1088/1748-9326/2/4/045023/pdf

Monitoring and estimating tropical forest carbon stocks: making REDD a reality

Deforestation contributes 6–17% of anthropogenic carbon dioxide emissions. However, much uncertainty in the calculation of deforestation emissions stems from the inadequacy of forest carbon-density and deforestation data. Now an analysis provides the most-detailed estimate so far of the carbon density of vegetation and the associated carbon dioxide emissions from deforestation for ecosystems across the tropics.

Estimated carbon dioxide emissions from tropical deforestation improved by carbon-density maps

Tropical forests hold large stores of carbon, yet uncertainty remains regarding their quantitative contri- bution to the global carbon cycle. One approach to quantifying carbon biomass stores consists in inferring changes from long-term forest inventory plots. Regres- sion models are used to convert inventory data into an estimate of aboveground biomass (AGB). We provide a critical reassessment of the quality and the robustness of these models across tropical forest types, using a large dataset of 2,410 trees ‡ 5 cm diameter, directly harvested in 27 study sites across the tropics. Proportional rela- tionships between aboveground biomass and the prod- uct of wood density, trunk cross-sectional area, and total height are constructed. We also develop a regres- sion model involving wood density and stem diameter only. Our models were tested for secondary and old- growth forests, for dry, moist and wet forests, for low- land and montane forests, and for mangrove forests. The most important predictors of AGB of a tree were, in decreasing order of importance, its trunk diameter, wood specific gravity, total height, and forest type (dry, moist, or wet). Overestimates prevailed, giving a bias of 0.5-6.5% when errors were averaged across all stands. Our regression models can be used reliably to predict aboveground tree biomass across a broad range of tropical forests. Because they are based on an unprece- dented dataset, these models should improve the quality

Tree allometry and improved estimation of carbon stocks and balance in tropical forests

La phytomasse épigée d'une forêt dense en Guyane française

Role de divers groupes de plantes (nomades, dryades) dans la mosaique forestiere. Relations entre la mosaique forestiere, les phases successives de cette mosaique, divers processus dont les plus importants sont la dissemination et la dynamique de la croissance et qui s'expriment naturellement lorsqu'apparaissent des chablis. Illustrations photographiques, diagrammes, schemas

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La dynamique de la forêt naturelle

La degradation croissante des paysages tropicaux et l'erosion de leur biodiversite sont un des problemes environnementaux les plus cruciaux. Les forets tropicales recelent la plus large diversite specifique connue : elles contiennent plus de la moitie des especes animales et vegetales de la planete. Quelle est la signification de la richesse specifique dans les forets tropicales ? L'exemple des forets du sud du Mexique permet d'analyser les consequences de la deforestation sur l'extinction des especes. Les mecanismes qui interviennent dans le maintien de la biodiversite sont analyses: les caracteristiques du milieu y sont optimales pour l'evolution et les extinctions d'especes sont minimales. La richesse specifique y est le produit de la contribution spontanee de speciations et des possibilites de mutations qui sont immenses. La flore et la faune mexicaines sont parmi les plus riches du monde mais elles sont menacees surtout dans les forets tropicales, qui, avec un taux de deforestation de 4,3 % par an, auront disparu dans environ 25 ans. Les evaluations des pertes de biodiversite sont de 0,5 a 1 % par an pour les zones tropicales.

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Diversité spécifique et déforestation : l'exemple des forêts tropicales humides du Mexique

Firstly we propose a model of flowering and fruiting for the trees of the French Guyana rain forests. Flowering and fruiting can be: continuous, discontinuous, pluriannual and regular or irregular. In any of these patterns, flowering is generally synchronous for individuals of a same species. Secondly we analyse and discuss the characteristics of seasonality, its relationships to the biological types and fruit dissemination patterns. Flowering is at its height during the long dry season (August November), fruit production at a maximum in the middle of the rainy season (March April). No difference in the timing of fruit production was found between canopy and understory species. If we consider solely the canopy trees, Anemochorous and specially Autochorous species are more seasonal in their fruit production than Zoochorous species.

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H. Puig

Papers

Tree allometry and improved estimation of carbon stocks and balance in tropical forests

La phytomasse épigée d'une forêt dense en Guyane française

La dynamique de la forêt naturelle

Diversité spécifique et déforestation : l'exemple des forêts tropicales humides du Mexique

Phénologie et saisonnalité de la floraison et de la fructification en forêt dense guyanaise