Amazonian Tree Research Articles

Forest type affects the capacity of Amazonian tree species to store carbon as woody biomass

For tropical tree species, wood density can vary greatly both within and between species depending on environmental conditions. In Amazonian seasonally flooded forests, yearly flood pulses influence tree growth and floodplain trees have developed specialised strategies to cope with prolonged submersion during flooding. We therefore hypothesised that seasonal floods significantly affect the capacity of trees to store carbon as woody biomass per unit volume and that forest hydrology would be an important factor in determining above-ground woody biomass and carbon stocks across the Amazon Basin. To test these hypotheses, we collected and analysed wood cores from 44 species occurring in both seasonally flooded (várzea) forests and adjacent unflooded (terra firme) forests along the Juruá River, western Brazilian Amazon. We used wood specific gravity (WSG) as a proxy of woody biomass and carbon. We compared WSG values within species, genera and families and found higher WSG in unflooded forest trees compared to their conspecifics in seasonally flooded várzea. Moreover, the effect of forest type on WSG was strongest at the family level and weakest at the species level. We further assessed the implications of WSG accuracy on above-ground woody tree biomass and found significant differences in AGWB as a function of WSG. Again, the differences became greater with lower taxonomic specificity, but also increased with lower site-specificity and greater tree dimensions. In conclusion, habitat specific WSG is important to quantify and map the spatial distribution of above-ground woody biomass and carbon in Amazonian forests.

Biased-corrected richness estimates for the Amazonian tree flora

Amazonian forests are extraordinarily diverse, but the estimated species richness is very much debated. Here, we apply an ensemble of parametric estimators and a novel technique that includes conspecific spatial aggregation to an extended database of forest plots with up-to-date taxonomy. We show that the species abundance distribution of Amazonia is best approximated by a logseries with aggregated individuals, where aggregation increases with rarity. By averaging several methods to estimate total richness, we confirm that over 15,000 tree species are expected to occur in Amazonia. We also show that using ten times the number of plots would result in an increase to just ~50% of those 15,000 estimated species. To get a more complete sample of all tree species, rigorous field campaigns may be needed but the number of trees in Amazonia will remain an estimate for years to come.

Flood-pulse disturbances as a threat for long-living Amazonian trees.

The long-lived tree species Eschweilera tenuifolia (O. Berg) Miers is characteristic of oligotrophic Amazonian black-water floodplain forests (igapó), seasonally inundated up to 10months per year, often forming monodominant stands. We investigated E.tenuifolia' growth and mortality patterns in undisturbed (Jaú National Park - JNP) and disturbed igapós (Uatumã Sustainable Development Reserve - USDR, downstream of the Balbina hydroelectric dam). We analysed age-diameter relationships, basal area increment (BAI) through 5-cm diameter classes, growth changes and growth ratios preceding death, BAI clustering, BAI ratio, and dated the individual year of death (14 C). Growth and mortality patterns were then related to climatic or anthropogenic disturbances. Results were similar for both populations for estimated maximum ages (JNP, 466yr; USDR, 498yr, except for one USDR tree with an estimated age of 820yr) and slightly different for mean diameter increment (JNP: 2.04mm; USDR: 2.28mm). Living trees from JNP showed altered growth post-1975 and sparse tree mortality occurred at various times, possibly induced by extreme hydroclimatic events. In contrast with the JNP, abrupt growth changes and massive mortality occurred in the USDR after the dam construction began (1983). Even more than 30yr after dam construction, flood-pulse alteration continues to affect both growth and mortality of E.tenuifolia. Besides its vulnerability to anthropogenic disturbances, this species is also susceptible to long-lasting dry and wet periods induced by climatic events, the combination of both processes may cause its local and regional extinction.

The contribution of multiple barriers to reproduction between edaphically divergent lineages in the Amazonian tree Protium subserratum (Burseraceae).

Disentangling the strength and importance of barriers to reproduction that arise between diverging lineages is central to our understanding of species origin and maintenance. To date, the vast majority of studies investigating the importance of different barriers to reproduction in plants have focused on short‐lived temperate taxa while studies of reproductive isolation in trees and tropical taxa are rare. Here, we systematically examine multiple barriers to reproduction in an Amazonian tree, Protium subserratum (Burseraceae) with diverging lineages of soil specialist ecotypes. Using observational, molecular, distributional, and experimental data, we aimed to quantify the contributions of individual prezygotic and postzygotic barriers including ecogeographic isolation, flowering phenology, pollinator assemblage, pollen adhesion, pollen germination, pollen tube growth, seed development, and hybrid fitness to total reproductive isolation between the ecotypes. We were able to identify five potential barriers to reproduction including ecogeographic isolation, phenological differences, differences in pollinator assemblages, differential pollen adhesion, and low levels of hybrid seed development. We demonstrate that ecogeographic isolation is a strong and that a combination of intrinsic and extrinsic prezygotic and postzygotic barriers may be acting to maintain near complete reproductive isolation between edaphically divergent populations of the tropical tree, P. subserratum.

Pao Pereira extract suppresses benign prostatic hyperplasia by inhibiting inflammation-associated NF\u03baB signaling

BackgroundOur previous study revealed the extract from the bark of an Amazonian tree Pao Pereira can suppress benign prostatic hyperplasia (BPH) in a rat model. Herein, we examined its inhibitory effects on human BPH cells and dissect its molecular mechanism.MethodsWe applied Pao extract to human BPH epithelial BPH-1 and prostate myofibroblast WPMY-1 cells. Cell viability, apoptosis and immunoblotting were performed, followed by gene expression profiling and gene set enrichment analysis (GSEA) to detect the differentially expressed genes and signaling pathway induced by Pao extract. Human ex vivo BPH explant organ culture was also used to examine the effects of Pao extract on human BPH tissues.ResultsPao extract treatment inhibited viability and induced apoptosis in human BPH-1 and WPMY-1 cells. Gene expression profiling and the following validation indicated that the expression levels of pro-apoptotic genes (eg. PCDC4, CHOP and FBXO32) were induced by Pao extract in both two cell lines. GSEA further revealed that Pao extract treatment was negatively associated with the activation of NFκB signaling. Pao extract suppressed the transcriptional activity of NFκB and down-regulated its target genes involved in inflammation (CXCL5, CXCL6 and CXCL12) and extracellular matrix (ECM) remodeling (HAS2, TNC and MMP13) in both cultured cells and human ex vivo BPH explants.ConclusionIn both BPH epithelial and stromal cells, Pao extract induces apoptosis by upregulating the pro-apoptotic genes and inhibiting the inflammation-associated NFκB signaling via reducing phosphorylation of NFκB subunit RelA. Our data suggest that Pao extract may be a promising phytotherapeutic agent for BPH.

Photosynthetic quantum efficiency in south-eastern Amazonian trees may be already affected by climate change.

Tropical forests are experiencing unprecedented high-temperature conditions due to climate change that could limit their photosynthetic functions. We studied the high-temperature sensitivity of photosynthesis in a rainforest site in southern Amazonia, where some of the highest temperatures and most rapid warming in the Tropics have been recorded. The quantum yield (Fv /Fm ) of photosystem II was measured in seven dominant tree species using leaf discs exposed to varying levels of heat stress. T50 was calculated as the temperature at which Fv /Fm was half the maximum value. T5 is defined as the breakpoint temperature, at which Fv /Fm decline was initiated. Leaf thermotolerance in the rapidly warming southern Amazonia was the highest recorded for forest tree species globally. T50 and T5 varied between species, with one mid-storey species, Amaioua guianensis, exhibiting particularly high T50 and T5 values. While the T50 values of the species sampled were several degrees above the maximum air temperatures experienced in southern Amazonia, the T5 values of several species are now exceeded under present-day maximum air temperatures.

Amazonia trees have limited capacity to acclimate plant hydraulic properties in response to long-term drought.

The fate of tropical forests under future climate change is dependent on the capacity of their trees to adjust to drier conditions. The capacity of trees to withstand drought is likely to be determined by traits associated with their hydraulic systems. However, data on whether tropical trees can adjust hydraulic traits when experiencing drought remain rare. We measured plant hydraulic traits (e.g. hydraulic conductivity and embolism resistance) and plant hydraulic system status (e.g. leaf water potential, native embolism and safety margin) on >150 trees from 12 genera (36 species) and spanning a stem size range from 14 to 68cm diameter at breast height at the world's only long-running tropical forest drought experiment. Hydraulic traits showed no adjustment following 15years of experimentally imposed moisture deficit. This failure to adjust resulted in these drought-stressed trees experiencing significantly lower leaf water potentials, and higher, but variable, levels of native embolism in the branches. This result suggests that hydraulic damage caused by elevated levels of embolism is likely to be one of the key drivers of drought-induced mortality following long-term soil moisture deficit. We demonstrate that some hydraulic traits changed with tree size, however, the direction and magnitude of the change was controlled by taxonomic identity. Our results suggest that Amazonian trees, both small and large, have limited capacity to acclimate their hydraulic systems to future droughts, potentially making them more at risk of drought-induced mortality.

The hyperdominant tropical tree Eschweilera coriacea (Lecythidaceae) shows higher genetic heterogeneity than sympatric Eschweilera species in French Guiana

Background and aims – The evolutionary history of Amazonia’s hyperabundant tropical tree species, also known as “hyperdominant” species, remains poorly investigated. We assessed whether the hyperdominant Eschweilera coriacea (DC.) S.A.Mori (Lecythidaceae) represents a single genetically cohesive species, and how its genetic constitution relates to other species from the same clade with which it occurs sympatrically in French Guiana.Methods – We sampled 152 individuals in nine forest sites in French Guiana, representing 11 species of the genus Eschweilera all belonging to the Parvifolia clade, with emphasis on E. coriacea. Samples were genotyped at four simple sequence repeat (SSR) markers. We delimited gene pools, i.e., genetically coherent putative taxa, using STRUCTURE software and principal component analysis. We compared the genetic assignment of individuals with their morphological species determination and estimated genetic diversity and differentiation for gene pools and species. We also estimated genome size using flow cytometry.Key results – SSR profiles commonly displayed up to four alleles per genotype, suggesting that the investigated Eschweilera species bear a paleopolyploid signature. Flow cytometry suggested that the studied species are diploid with haploid genome sizes of 871–1046 Mbp. We detected five gene pools and observed a good correspondence between morphological and genetic delimitation for Eschweilera sagotiana Miers and the undescribed morphospecies E. sp. 3 (which resembles E. grandiflora (Aubl.) Sandwith), and to a lesser extent for E. decolorans Sandwith and E. micrantha (O.Berg) Miers. Eschweilera coriacea was the most genetically diverse species and included individuals assigned to each gene pool. Conclusions – We found no conclusive evidence for cryptic species within E. coriacea in French Guiana. SSRs detected fewer gene pools than expected based on morphology in the Parvifolia clade but discriminated evolutionary relationships better than available plastid markers. A positive trend between demographic abundance of species and allelic richness illustrates that hyperdominants may have a high evolutionary potential. This hypothesis can be tested using more powerful genomic data in combination with tree phenotypic trait variation and characterization of niche breadth, to enhance our understanding of the causes of hyperdominance in Amazonian trees.

Modelling the distribution of Amazonian tree species in response to long‐term climate change during the Mid‐Late Holocene

AbstractAimTo (a) assess the environmental suitability for rainforest tree species of Moraceae and Urticaceae across Amazonia during the Mid‐Late Holocene and (b) determine the extent to which their distributions increased in response to long‐term climate change over this period.LocationAmazonia.TaxonTree species of Moraceae and Urticaceae.MethodsWe used MaxEnt and inverse distance weighting interpolation to produce environmental suitability and relative abundance models at 0.5‐degree resolution for tree species of Moraceae and Urticaceae, based on natural history collections and a large plot dataset. To test the response of the Amazon rainforest to long‐term climate change, we quantified the increase in environmental suitability and modelled species richness for both families since the Mid‐Holocene (past 6,000 years). To test the correlation between the relative abundance of these species in modern vegetation versus modern pollen assemblages, we analysed the surface pollen spectra from 46 previously published paleoecological sites.ResultsWe found that the mean environmental suitability in Amazonia for species of Moraceae and Urticaceae showed a slight increase (6.5%) over the past 6,000 years, although southern ecotonal Amazonia and the Guiana Shield showed much higher increases (up to 68%). The accompanied modelled mean species richness increased by as much as 120% throughout Amazonia. The mean relative abundance of Moraceae and Urticaceae correlated significantly with the modern pollen assemblages for these families.Main ConclusionsIncreasing precipitation between the Mid‐ and Late Holocene expanded suitable environmental conditions for Amazonian humid rainforest tree species of Moraceae and Urticaceae, leading to rainforest expansion in ecotonal areas of Amazonia, consistent with previously published fossil pollen data.

How does bark contribution to postural control change during tree ontogeny? A study of six Amazonian tree species.

Recent works revealed that bark is able to produce mechanical stress to control the orientation of young tilted stems. Here we report how the potential performance of this function changes with stem size in six Amazonian species with contrasted bark anatomy. The potential performance of the mechanism depends both on the magnitude of bark stress and the relative thickness of the bark. We measured bark longitudinal residual strain and density, and the allometric relationship between bark thickness and stem radius over a gradient of tree sizes. Constant tensile stress was found in species that rely on bark for the control of stem orientation in young stages. Other species had increasing compressive stress, associated with increasing density attributed to the development of sclereids. Compressive stress was also associated with low relative bark thickness. The relative thickness of bark decreased with size in all species, suggesting that a reorientation mechanism based on bark progressively performs less well as the tree grows. However, greater relative thickness was observed in species with more tensile stress, thereby evidencing that this reduction in performance is mitigated in species that rely on bark for reorientation.

Composition, thermal behavior and antioxidant activity of pracaxi (Pentaclethra macroloba) seed oil obtained by supercritical CO2

Abstract The Amazonian tree Pentaclethra macroloba (pracaxi) has pod-shaped fruits with flattened seeds mostly composed of lipids, carbohydrates, and proteins, besides secondary compounds, which provide potential use by many industries. This study evaluated the supercritical carbon dioxide (SC-CO2) extraction of pracaxi seed oil (PSO) at different conditions of pressure (200–300 bar) and temperature (40–60 °C). The PSO was assessed for its fatty acids and triacylglycerols (TAG) compositions, total phenolic content and antioxidant activity, as well as the oxidative stability and thermal behavior. SC-CO2 extractions provided oil yields (Ye) from 12 to 42 g/100 g, which represented up to 79% of the Ye obtained with hexane (Soxhlet). The pressure was the only significant variable (p

Styrylpyrone, isolated from an Amazon plant, induces cell cycle arrest and autophagy in Leishmania amazonensis

The search for bioactive compounds against diseases is imperative and the richness of the Amazon provides a large source to be explored. Current therapies for the treatment of parasitic infections have severe side effects and low efficacy, which makes the development of an effective chemotherapy extremely important. In this study, we describe the isolation of styrylpyrone 4-methoxy-6-(11,12-methylenedioxy-trans-styryl)-2-pyrone (SP), from the Amazonian tree species, Aniba panurensis, the in vitro activity against Leishmania amazonensis promastigotes, and its in silico pharmacokinetics properties. The results showed morphological and ultrastructural alterations, cell cycle impairment, increased reactive oxygen species production, accumulation of lipid bodies and formation of autophagic vacuoles in SP-treated parasites. In silico studies revealed that the compound has a high drug-score, which is encouraging for further investigation. Our results indicate that SP is a promising drug candidate, which induces alterations in L. amazonensis leading to parasite death through cell cycle arrest and autophagy.

A New Combination in Garcinia (Clusiaceae) Based on Rheedia martinii, a Tree Species from Suriname

Several new combinations were recently proposed to merge species of Rheedia into Garcinia. Because some species were not part of larger taxonomic treatments, revisions, or local floras, new combinations for them were not proposed. Garcinia martinii is a new combination based on the basionym Rheedia martinii, an Amazonian tree species from the high mountains of Suriname, in South America.

WOOD COLORIMETRY FOR THE CHARACTERIZATION OF AMAZONIAN TREE SPECIES: A SUBSIDY FOR A MORE EFFICIENT CLASSIFICATION

ABSTRACT The wood of different species may present macroscopic similarities, which hinders a reliable differentiation between the specie. This can be a problem, especially in the tropics, given the high species diversity in this region. To overcome this problem of wood identification, colorimetric criteria can be applied, aiming at a better and more objective classification, as opposed to the traditional anatomic criteria. Therefore, the aim of this research was to analyze the variability of the wood color considering the cutting planes (tangential and radial) and to determine its correlation with the wood basic density of ten Amazonian tree species. The following species were studied: Apuleia leiocarpa (amarelao), Hymenolobium modestum (angelim-pedra), Anadenanthera columbrina (angico), Dipteryx odorata (cumaru), Pouteria pachycarpa (goiabao), Mezilaurus itauba (itauba), Hymenaea courbaril (jatoba), Simarouba amara (marupa), Astronium leicontei (muiracatiara) and, Bowdichia nitida (sucupira). The CIEL*a*b* system was used to determine the colorimetric parameters (L*, a*, b*, C*, and h*), which were obtained through a portable colorimeter. The species were classified in six color specific groups: light yellow, olive brown, yellowish olive, olive light, grayish white and reddish brown. We observed statistical effect of the cut planes only for luminosity, with higher mean for radial face. The correlation analyses between color and basic density showed that the denser woods are darker and have more red pigment (a*). There is negative correlation between luminosity (L*) and wood basic density (-0.78). The colorimetric parameter a* presented positive correlation with the basic density (r = 0.80).

The Brazilian development agenda driving Amazon devastation

The Brazilian development agenda driving Amazon devastation

Effect of rosewood plantation chronosequence on soil attributes in Central Amazonia

Rosewood (Aniba rosaeodora Ducke) is an endangered Amazonian tree species that produces a commercially valuable essential oil, used mainly in cosmetics and fine fragrances production. The species can also be used in reforestation programs, which generate jobs and as a source of income and reduce the pressure of exploitation on natural rosewood populations. The objective of this study was to verify the influence of rosewood stands on physical and chemical soil attributes. This study was conducted at a rural farm in the Maués municipality, 350 km from Manaus, Amazonas State, Brazil. Samples were collected in five areas; 4-, 10- and 20-year-old rosewood stands, and 15- and 60-year-old secondary forests. The latter two served as control treatments, reflecting natural spontaneous succession conditions over time. Soil was sampled at 10 equidistant points within each area to measure physicochemical attributes, and at the center of each one, a soil profile was dug for description and classification of morphological characteristics. Based on the profile description, the soils were classified as Xanthic Hapludox. The results show that soil conditions under 20-year-old rosewood stand resembled those beneath the 60-year-old secondary forest, and likewise for the soil under the 10-year-old rosewood stand and the 15-year-old secondary forest. The soil bulk density ranged from 0.81 to 0.99 g cm−3 among all areas and no significant difference was found (P = 0.052). With exception to 4-year-old stand, the organic matter (2.68–5.87%) and carbon stock (18.57–31.71 Mg ha−1) did not differ significantly between stands and control treatments. For the soil macronutrients, nitrogen (0.10–0.22%), phosphorus (1.17–11.70 mg kg−1), calcium (0.03–0.31 mg kg−1) and magnesium (0.02–0.16 mg kg−1) were higher or equal in the rosewood stands in comparison to the two controls, while the potassium values (0.03–0.36 mg kg−1) were significantly higher in 60-year-old secondary forests only compared to the 10-year-old rosewood stands (P = 0.005). The soil beneath the 4-year-old rosewood stand, however, differed from the other four areas, having significantly higher natural clay content (>600 g kg−1) and higher topsoil chemical concentrations, associated with the more recent burning. This result represents the first step in addressing concern about sustainable soil use in rosewood forestry economics. Consequently, this kind of rosewood plantation can be recommended as an appropriate use of historically exploited areas, providing economic return from local biodiversity.

Amazonian trees show increased edge effects due to Atlantic Ocean warming and northward displacement of the Intertropical Convergence Zone since 1980.

Recent investigations indicate a warming of Atlantic Ocean surface waters since 1980, probably influenced by anthropic actions, inducing rainfall intensification mainly during the rainy season and slight reductions during the dry season in the Amazon. Under these climate changes, trees in upland forests (terra firme) could benefit from the intensification of the hydrological cycle and could also be affected by the reduction of precipitation during the dry season. Results of dendrochronological analyses, spatial correlations and structural equation models, showed that Scleronema micranthum (Ducke) Ducke (Malvaceae) trees exposed in fragmented areas and to edge effects in Central Amazonian terra firme forest were more sensitive to the increase in the Atlantic Ocean surface temperature and consequent northward displacement of the Intertropical Convergence Zone, mainly during the dry season. Therefore, we proved that in altered and potentially more stressful environments such as edges of fragmented forests, recent anthropogenic climatic changes are exerting pressure on tree growth dynamics, inducing alterations in their performance and, consequently, in essential processes related to ecosystem services. Changes that could affect human well-being, highlighting the need for strategies that reduce edge areas expansion in Amazon forests and anthropic climate changes of the Anthropocene.

Hendrik Poorter.

Hendrik Poorter.

Tropical tree cover in a heterogeneous environment: A reaction-diffusion model.

Observed bimodal tree cover distributions at particular environmental conditions and theoretical models indicate that some areas in the tropics can be in either of the alternative stable vegetation states forest or savanna. However, when including spatial interaction in nonspatial differential equation models of a bistable quantity, only the state with the lowest potential energy remains stable. Our recent reaction-diffusion model of Amazonian tree cover confirmed this and was able to reproduce the observed spatial distribution of forest versus savanna satisfactorily when forced by heterogeneous environmental and anthropogenic variables, even though bistability was underestimated. These conclusions were solely based on simulation results for one set of parameters. Here, we perform an analytical and numerical analysis of the model. We derive the Maxwell point (MP) of the homogeneous reaction-diffusion equation without savanna trees as a function of rainfall and human impact and show that the front between forest and nonforest settles at this point as long as savanna tree cover near the front remains sufficiently low. For parameters resulting in higher savanna tree cover near the front, we also find irregular forest-savanna cycles and woodland-savanna bistability, which can both explain the remaining observed bimodality.

Amazonian tree species threatened by deforestation and climate change

Deforestation is currently the major threat to Amazonian tree species but climate change may surpass it in just a few decades. Here, we show that climate and deforestation combined could cause a decline of up to 58% in Amazon tree species richness, whilst deforestation alone may cause 19–36% and climate change 31–37% by 2050. Quantification is achieved by overlaying species distribution models for current and future climate change scenarios with historical and projected deforestation. Species may lose an average of 65% of their original environmentally suitable area, and a total of 53% may be threatened according to IUCN Red List criteria; however, Amazonian protected area networks reduce these impacts. The worst-case combined scenario—assuming no substantial climate or deforestation policy progress—suggests that by 2050 the Amazonian lowland rainforest may be cut into two blocks: one continuous block with 53% of the original area and another severely fragmented block. This outlook urges rapid progress to zero deforestation, which would help to mitigate climate change and foster biodiversity conservation.