Leveraging Signatures of Plant Functional Strategies in Wood Density Profiles of African Trees to Correct Mass Estimations From Terrestrial Laser Data

peer reviewedWood density (WD) relates to important tree functions such as stem mechanics and resistance against pathogens. This functional trait can exhibit high intraindividual variability both radially and vertically. With the rise of LiDAR-based methodologies allowing nondestructive tree volume estimations, failing to account for WD variations related to tree function and biomass investment strategies may lead to large systematic bias in AGB estimations. Here, we use a unique destructive dataset from 822 trees belonging to 51 phylogenetically dispersed tree species harvested across forest types in Central Africa to determine vertical gradients in WD from the stump to the branch tips, how these gradients relate to regeneration guilds and their implications for AGB estimations. We find that decreasing WD from the tree base to the branch tips is characteristic of shade-tolerant species, while light-demanding and pioneer species exhibit stationary or increasing vertical trends. Across all species, the WD range is narrower in tree crowns than at the tree base, reflecting more similar physiological and mechanical constraints in the canopy. Vertical gradients in WD induce significant bias (10%) in AGB estimates when using database-derived species-average WD data. However, the correlation between the vertical gradients and basal WD allows the derivation of general correction models. With the ongoing development of remote sensing products providing 3D information for entire trees and forest stands, our findings indicate promising ways to improve greenhouse gas accounting in tropical countries and advance our understanding of adaptive strategies allowing trees to grow and survive in dense rainforests. © 2020, The Author(s)

Consistent patterns of common species across tropical tree communities

Trees structure the Earth’s most biodiverse ecosystem, tropical forests. The vast number of tree species presents a formidable challenge to understanding these forests, including their response to environmental change, as very little is known about most tropical tree species. A focus on the common species may circumvent this challenge. Here we investigate abundance patterns of common tree species using inventory data on 1,003,805 trees with trunk diameters of at least 10 cm across 1,568 locations1,2,3,4,5,6 in closed-canopy, structurally intact old-growth tropical forests in Africa, Amazonia and Southeast Asia. We estimate that 2.2%, 2.2% and 2.3% of species comprise 50% of the tropical trees in these regions, respectively. Extrapolating across all closed-canopy tropical forests, we estimate that just 1,053 species comprise half of Earth’s 800 billion tropical trees with trunk diameters of at least 10 cm. Despite differing biogeographic, climatic and anthropogenic histories7, we find notably consistent patterns of common species and species abundance distributions across the continents. This suggests that fundamental mechanisms of tree community assembly may apply to all tropical forests. Resampling analyses show that the most common species are likely to belong to a manageable list of known species, enabling targeted efforts to understand their ecology. Although they do not detract from the importance of rare species, our results open new opportunities to understand the world’s most diverse forests, including modelling their response to environmental change, by focusing on the common species that constitute the majority of their trees.Publisher PDFPeer reviewe

Consistent patterns of common species across tropical tree communities

Trees structure the Earth’s most biodiverse ecosystem, tropical forests. The vast number of tree species presents a formidable challenge to understanding these forests, including their response to environmental change, as very little is known about most tropical tree species. A focus on the common species may circumvent this challenge. Here we investigate abundance patterns of common tree species using inventory data on 1,003,805 trees with trunk diameters of at least 10 cm across 1,568 locations1,2,3,4,5,6 in closed-canopy, structurally intact old-growth tropical forests in Africa, Amazonia and Southeast Asia. We estimate that 2.2%, 2.2% and 2.3% of species comprise 50% of the tropical trees in these regions, respectively. Extrapolating across all closed-canopy tropical forests, we estimate that just 1,053 species comprise half of Earth’s 800 billion tropical trees with trunk diameters of at least 10 cm. Despite differing biogeographic, climatic and anthropogenic histories7, we find notably consistent patterns of common species and species abundance distributions across the continents. This suggests that fundamental mechanisms of tree community assembly may apply to all tropical forests. Resampling analyses show that the most common species are likely to belong to a manageable list of known species, enabling targeted efforts to understand their ecology. Although they do not detract from the importance of rare species, our results open new opportunities to understand the world’s most diverse forests, including modelling their response to environmental change, by focusing on the common species that constitute the majority of their trees

Consistent patterns of common species across tropical tree communities

Trees structure the Earth's most biodiverse ecosystem, tropical forests. The vast number of tree species presents a formidable challenge to understanding these forests, including their response to environmental change, as very little is known about most tropical tree species. A focus on the common species may circumvent this challenge. Here we investigate abundance patterns of common tree species using inventory data on 1,003,805 trees with trunk diameters of at least 10 cm across 1,568 locations1-6 in closed-canopy, structurally intact old-growth tropical forests in Africa, Amazonia and Southeast Asia. We estimate that 2.2%, 2.2% and 2.3% of species comprise 50% of the tropical trees in these regions, respectively. Extrapolating across all closed-canopy tropical forests, we estimate that just 1,053 species comprise half of Earth's 800 billion tropical trees with trunk diameters of at least 10 cm. Despite differing biogeographic, climatic and anthropogenic histories7, we find notably consistent patterns of common species and species abundance distributions across the continents. This suggests that fundamental mechanisms of tree community assembly may apply to all tropical forests. Resampling analyses show that the most common species are likely to belong to a manageable list of known species, enabling targeted efforts to understand their ecology. Although they do not detract from the importance of rare species, our results open new opportunities to understand the world's most diverse forests, including modelling their response to environmental change, by focusing on the common species that constitute the majority of their trees

La distribution spatiale des Acanthaceae dans les secteurs phytogéographiques de Ndjele (1988) en RD Congo

peer reviewe

Tropical tree allometry and crown allocation, and their relationship with species traits in central Africa

Common allometric patterns have been reported across the tropics and good performance on independent data was retrieved for the most recent pantropical model predicting tree aboveground biomass (AGB) from stem diameter, wood density and total height. General models are undoubtedly useful for the estimation and monitoring of biomass and carbon stocks in tropical forests, however specific allometry, allocation, and traits, are at the core of many models of vegetation dynamics, and there is lack of such information for some regions and species. In this study, we specifically evaluated how size-dependent changes in above-ground biomass and biomass allocation to crown relate to other allometric and life-history traits for tropical tree species. We gathered destructive data available in eight terra firme forest sites across central Africa and the combined dataset consisted of 1,023 trees belonging to 54 tropical tree species phylogenetically dispersed, with only two congeneric species. A huge body of field and laboratory measurements was used for computing AGB and crown mass ratio (CMR) at the tree level, and to derive key allometric traits at the species level. For the latter, species-specific relationships between tree diameter and total height, crown exposure to light, wood density, and bark thickness were fitted for 50 species. Our results show interspecific variation in the relationships relating tree diameter to both AGB and CMR, and including species traits in a multi-specific AGB model confirmed that interspecific variation in biomass allometry is primarily determined by species wood density. We also showed that the allocation of biomass to crown increases linearly with tree diameter for most species, and that interspecific variation in the CMR model is associated with the species dispersal mode and maximum height. Trait covariations among our set of tropical tree species widespread and/or locally abundant in central Africa, revealed a continuum between large-statured species, which tended to be light-demanding, deciduous and wind-dispersed, and species with opposite attributes. Information on allometry, allocation, and traits provided here could further be used in comparative ecology and for parameterizing dynamic and succession models. Also importantly, the species-specific AGB models fitted for major tree species, including most timber species of central Africa, will help improve biomass estimates

Tropical tree allometry and crown allocation, and their relationship with species traits in central Africa

peer reviewedCommon allometric patterns have been reported across the tropics and good performance on independent data was retrieved for the most recent pantropical model predicting tree aboveground biomass (AGB) from stem diameter, wood density and total height. General models are undoubtedly useful for the estimation and monitoring of biomass and carbon stocks in tropical forests, however specific allometry, allocation, and traits, are at the core of many models of vegetation dynamics, and there is lack of such information for some regions and species. In this study, we specifically evaluated how size-dependent changes in above-ground biomass and biomass allocation to crown relate to other allometric and life-history traits for tropical tree species. We gathered destructive data available in eight terra firme forest sites across central Africa and the combined dataset consisted of 1,023 trees belonging to 54 tropical tree species phylogenetically dispersed, with only two congeneric species. A huge body of field and laboratory measurements was used for computing AGB and crown mass ratio (CMR) at the tree level, and to derive key allometric traits at the species level. For the latter, species-specific relationships between tree diameter and total height, crown exposure to light, wood density, and bark thickness were fitted for 50 species. Our results show interspecific variation in the relationships relating tree diameter to both AGB and CMR, and including species traits in a multi-specific AGB model confirmed that interspecific variation in biomass allometry is primarily determined by species wood density. We also showed that the allocation of biomass to crown increases linearly with tree diameter for most species, and that interspecific variation in the CMR model is associated with the species dispersal mode and maximum height. Trait covariations among our set of tropical tree species widespread and/or locally abundant in central Africa, revealed a continuum between large-statured species, which tended to be light-demanding, deciduous and wind-dispersed, and species with opposite attributes. Information on allometry, allocation, and traits provided here could further be used in comparative ecology and for parameterizing dynamic and succession models. Also importantly, the species-specific AGB models fitted for major tree species, including most timber species of central Africa, will help improve biomass estimates