1. Large-scale data compilation is increasing steadily in tropical forest research, but the lack of standardized methods for data collection limits drawing inference from large datasets and cross-biome analyses. Different inclusion methods and minimum tree diameter threshold are among these varying factors. To tackle this issue, we evaluated how different approaches for tree sampling affects our understanding of diversity and functioning in different tropical vegetation types.2. We used a unique dataset of 44 inventory plots (43.54 ha) encompassing an aridity gradient: evergreen moist forests, semideciduous and deciduous tropical forests.Data were collected using the by-tree inclusion method, in which, all stems are measured if the equivalent diameter of the tree reaches the minimum threshold.We simulated the impact of adopting different inclusion methods (by-stem and by-tree) and different minimum diameter thresholds on the estimation of number of trees and stems, biomass and species richness. We used linear and nonlinear mixed models to investigate the effect of minimum diameter threshold and inclusion method on our different response variables. We also evaluated species chance to be sampled under different minimum inclusion criteria.3. Inclusion method and minimum diameter threshold mainly affect the estimation of number of trees and stems and species richness, especially in deciduous and semideciduous forests, where resprouting is a prevalent strategy. In these forests, many trees that have several stems do not reach the minimum size individually when adopting the by-stem method, yet they do reach the minimum size threshold when all stems are considered together. For these environments under water stress, our analysis showed that using large minimum sizes, such as the 10 cm typically used in rainforests, implies large sampling losses, especially when used jointly with the by-stem inclusion method.4. The by-tree inclusion method represents an alternative approach that offers a more reliable sampling in different vegetation types, particularly in those habitats where resprouting is a widely encountered strategy along all age classes. 2018 | Methods in Ecology and Evoluঞon de SOUZA et Al.
Tropical forests have played an important role as a carbon sink over time. However, the carbon dynamics of Brazilian non-Amazon tropical forests are still not well understood. Here, we used data from 32 tropical seasonal forest sites, monitored from 1987 to 2020 (mean site monitoring length, ~15 years) to investigate their long-term trends in carbon stocks and sinks. Our results highlight a long-term decline in the net carbon sink (0.13 Mg C ha−1 year−1) caused by decreasing carbon gains (2.6% by year) and increasing carbon losses (3.4% by year). The driest and warmest sites are experiencing the most severe carbon sink decline and have already moved from carbon sinks to carbon sources. Because of the importance of the terrestrial carbon sink for the global climate, policies are needed to mitigate the emission of greenhouse gases and to restore and protect tropical seasonal forests.
Soil is a relevant driver of taxonomic, functional and phylogenetic composition at local scales. However, the mechanisms by which the soil act in these components or how these components interact with each other are not elucidated. Herein, we propose to understand the role of soil (environmental filtering) on the turnover of taxonomic and phylogenetic components and their role in determining the functional composition of Seasonally Dry Tropical Forest (SDTF) communities. We sampled all the arboreal individuals with Diameter at Breast Height equal to or higher than 3 cm and collected soil variables of 25 units from five SDTF fragments located in the Brazilian Caatinga Domain. These data enabled us to obtain the taxonomic, functional and phylogenetic composition of each plot, which were then analyzed by Structural Equation Models jointly with the soil variables. Our results suggest that the soil conditions select specific phylogenetic lineages from a regional species pool according to the adaptive potential, which affects the distribution and abundance of species (taxonomic composition). However, it was not possible to establish a direct relationship between the phylogenetic composition and the taxonomic composition, possibly due to the use of labile functional traits in the analysis. We also found that soil acts directly on the functional composition, leading to a differential success of individuals which would represent a direct and indirect effect of taxonomic composition on the functional composition. Thus, we found community aspects result from different ecological mechanisms which act in a continuous and progressive way between functional, phylogenetic and taxonomic composition.
This work reports the isolation of the sesquiterpene lactone 15-deoxygoyazensolide from the stems of Minasia alpestris and the evaluation of its antimicrobial activity against the following oral pathogens: Enterococcus faecalis, Streptococcus salivarius, Streptococcus sobrinus, Streptococcus mutans, Streptococcus mitis, Streptococcus sanguinis, and Lactobacillus casei. Despite the cytotoxicity and genotoxicity of other sesquiterpene lactones of the furanoheliangolide-type, our results revealed that this compound exhibits low antibacterial activity against the evaluated oral pathogens; however, an interesting selectivity against E. faecalis (minimum inhibitory concentration [MIC]=40 µg mL(-1)) and S. sobrinus (MIC=60 µg mL(-1)) was observed.
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