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The relative importance of abiotic and biotic factors in shaping forest biomass stocks and fluxes remains a controversial issue. Here, using data gathered from 39 1 ha plots located in flooded and terra firme mature tropical lowland forests of the Amazon and Orinoquia regions of Colombia, we evaluated the importance of climate, soil fertility, and flooding, as well as tree taxonomic/phylogenetic diversity and forest structural properties, in determining the aboveground biomass stocks (AGB; Mg ha−1) and aboveground woody productivity (AWP; Mg ha−1 year−1). Using information‐theoretic multimodel inference and variance partitioning we found that forest structural features such as the number of trees with diameter at breast height ≥ 70 cm, and wood density, are the main drivers of variation in AGB. However, taxonomic diversity also contributes to AGB because it is associated with more large trees in these forests. In contrast, the key drivers of AWP in these forests were soil P and Mg concentrations, with no significant effects of diversity indices. These findings emphasize the need to include major soil cations other than N and P (e.g. Mg) in experimental studies to improve our understanding about the extent to which soil fertility can modulate increases in forest AWP due to climate change. Terra firme forests had higher AGB stocks than flooded forests, but both had similar AWP; and we found similar results for the drivers of AGB and AWP between flooded and terra firme forests. Our results provide limited evidence for strong effects of plant diversity on AGB or AWP. Therefore, we call for caution on generalizations of nature‐based initiatives aiming to preserve diversity based on maximizing carbon stocks and productivity, due to the complex nature of the processes controlling carbon accumulation and carbon fluxes in tropical forests. [ABSTRACT FROM AUTHOR]

Tropical montane forests (TMFs) are biodiversity hotspots and provide vital ecosystem services, but they are disproportionately vulnerable to climate warming. In the Andes, cold‐affiliated species from high elevations are being displaced at the hot end of their thermal distributions by warm‐affiliated species migrating upwards from lower elevations, leading to compositional shifts. Leaf functional traits are strong indicators of plant performance and at the community level have been shown to vary along elevation gradients, reflecting plant adaptations to different environmental niches. However, the plastic response of such traits to relatively rapid temperature change in Andean TMF species remains unknown. We used three common garden plantations within a thermosequence in the Colombian Andes to investigate the warming and cooling responses of key leaf functional traits in eight cold‐ and warm‐affiliated species with variable thermal niches. Cold‐affiliated species shifted their foliar nutrient concentrations when exposed to warming, while all other traits did not significantly change; contrastingly, warm‐affiliated species were able to adjust structural, nutrient and water‐use efficiency traits from acquisitive to conservative strategies in response to cooling. Our findings suggest that cold‐affiliated species will struggle to acclimate functional traits to warming, conferring warm‐affiliated species a competitive advantage under climate change. Summary Statement: In Andean montane forests, species from lower, warmer elevations are more able to acclimate a variety of leaf functional traits (structural, nutrient and water‐use efficiency) to rapid temperature change than species from higher, colder elevations. This could confer a competitive advantage upon warm‐affiliated species under climate warming, potentially leading to compositional shifts in these ecosystems. [ABSTRACT FROM AUTHOR]

The extent to which historical dispersal, environmental features and geographical barriers shape the phylogenetic structure and turnover of tree communities in northwestern Amazonia at multiple spatial scales remains poorly understood.We used 85 floristically standardized 0.1‐ha plots (DBH ≥ 2.5 cm) distributed in three subregions of northwestern (NW) Amazonia across three main habitat types (floodplain, swamp and terra firme forests) to hypothesize that (a) historical dispersal overcome geographical barriers, which meant low local phylogenetic relatedness and low phylogenetic turnover. (b) Geographical barriers triggered dispersal limitation, causing high local and subregional phylogenetic clustering and high regional phylogenetic turnover. (c) Edaphic properties and flooding were negatively associated with stem size and determined the tree phylogenetic structure and turnover at local and regional scales in Amazon forests.We found that the extent to which environmental or evolutionary features shaped the phylogenetic structure and phylogenetic similarity of tree communities in NW Amazonia was scale dependent. Specifically, we show that the relative importance of environmental factors increases as spatial scale and species pool decreases. Furthermore, we find that these results are generally robust for both adult and juvenile trees.Synthesis. Our analysis at the regional (NW Amazon) scale lends support to the idea of Amazonian forests as a large meta‐community primarily structured by historical dispersal at large spatial scales with an increasing importance of environmental factors at finer spatial scales. The convergence of ancestral lineages across habitat types may have been due to the relatively recent formation of geographical barriers that promoted local isolation and allopatric speciation. [ABSTRACT FROM AUTHOR]

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The diameter growth rates of tropical trees are essential information for understanding the dynamics of tropical forests, to study the ontogenetic growth of trees, planning restoration programs, and developing sustainable forest management. The growth is measured as the change in the diameter of the trunk (mm yr-1) between two measurements. Thus, there is a resulting relationship between the size and age, a basic assumption of the models that use initial diameter as time surrogate. However, the tree size is not an age surrogate, being an assumption which must be evaluated. We analyzed the growth as a function of the initial diameter. The tree growth data are obtained from permanent plots, where individuals of different sizes coexist. We propose new method to standardize tree growth data: to eliminate measurement errors and the effect of the sick trees, we split data for diameter class, and then we eliminate zero values and negative growth rate. Also, we eliminate the same number of data in the upper limit of the distribution, following the assumption that errors are normally distributed; but also, that both possible measurement errors by default (zero or negative growth rates), and by the excess (very high growth rates) are equally likely to occur (50%). Before, we applied two transformations to the absolute growth rates (relative growth rates and log-transformed relative growth rates). Then, wefit the data to the von Bertalanffy differential growth equation using non-linear models and chose the best model based on the AIC. We gathered functional traits (wood density), climate, and position of the adult trees in the vertical structure of the forests that potentially influence tree performance and biomass storage and these were included in the models. We used a portion of data to test the performance of the resulting models. Finally, the resulting differential equations were integrated in order to obtain models of the diameter as a function of age. We statistically fit diametric growth models and determine some ontogenetic traits both for 100 species groups and for 10 individual species. We found that log-transformed relative growth rate showed the better fit. Also, we found that data standardization procedure proposed by us showed better fit than raw data. Finally, we found that wood density affect the tree growth rate negatively. Here, we showed that trees growth rates produce biased results when they are used to fit growth models if data are used in their raw form. The power increase in the model predictability is a greater advance in the methods to estimate tree growth rates and their change on time. Also, we propose that these method used in this study allow us to predict and increase the credibility of models of tropical species. [ABSTRACT FROM AUTHOR]