An estimate of the number of tropical tree species

The high species richness of tropical forests has long been recognized, yet there remains substantial uncertainty regarding the actual number of tropical tree species. Using a pantropical tree inventory database from closed canopy forests, consisting of 657,630 trees belonging to 11,371 species, we use a fitted value of Fisher’s alpha and an approximate pantropical stem total to estimate the minimum number of tropical forest tree species to fall between ∼40,000 and ∼53,000, i.e. at the high end of previous estimates. Contrary to common assumption, the Indo-Pacific region was found to be as species-rich as the Neotropics, with both regions having a minimum of ∼19,000–25,000 tree species. Continental Africa is relatively depauperate with a minimum of ∼4,500–6,000 tree species. Very few species are shared among the African, American, and the Indo-Pacific regions. We provide a methodological framework for estimating species richness in trees that may help refine species richness estimates of tree-dependent taxa

Pervasive gaps in Amazonian ecological research

Biodiversity loss is one of the main challenges of our time,1,2 and attempts to address it require a clear un derstanding of how ecological communities respond to environmental change across time and space.3,4 While the increasing availability of global databases on ecological communities has advanced our knowledge of biodiversity sensitivity to environmental changes,5–7 vast areas of the tropics remain understudied.8–11 In the American tropics, Amazonia stands out as the world’s most diverse rainforest and the primary source of Neotropical biodiversity,12 but it remains among the least known forests in America and is often underrepre sented in biodiversity databases.13–15 To worsen this situation, human-induced modifications16,17 may elim inate pieces of the Amazon’s biodiversity puzzle before we can use them to understand how ecological com munities are responding. To increase generalization and applicability of biodiversity knowledge,18,19 it is thus crucial to reduce biases in ecological research, particularly in regions projected to face the most pronounced environmental changes. We integrate ecological community metadata of 7,694 sampling sites for multiple or ganism groups in a machine learning model framework to map the research probability across the Brazilian Amazonia, while identifying the region’s vulnerability to environmental change. 15%–18% of the most ne glected areas in ecological research are expected to experience severe climate or land use changes by 2050. This means that unless we take immediate action, we will not be able to establish their current status, much less monitor how it is changing and what is being lostinfo:eu-repo/semantics/publishedVersio

The Amazon Tall Tower Observatory (ATTO): Overview of pilot measurements on ecosystem ecology, meteorology, trace gases, and aerosols

The Amazon Basin plays key roles in the carbon and water cycles, climate change, atmospheric chemistry, and biodiversity. It has already been changed significantly by human activities, and more pervasive change is expected to occur in the coming decades. It is therefore essential to establish long-term measurement sites that provide a baseline record of present-day climatic, biogeochemical, and atmospheric conditions and that will be operated over coming decades to monitor change in the Amazon region, as human perturbations increase in the future. The Amazon Tall Tower Observatory (ATTO) has been set up in a pristine rain forest region in the central Amazon Basin, about 150 km northeast of the city of Manaus. Two 80 m towers have been operated at the site since 2012, and a 325 m tower is nearing completion in mid-2015. An ecological survey including a biodiversity assessment has been conducted in the forest region surrounding the site. Measurements of micrometeorological and atmospheric chemical variables were initiated in 2012, and their range has continued to broaden over the last few years. The meteorological and micrometeorological measurements include temperature and wind profiles, precipitation, water and energy fluxes, turbulence components, soil temperature profiles and soil heat fluxes, radiation fluxes, and visibility. A tree has been instrumented to measure stem profiles of temperature, light intensity, and water content in cryptogamic covers. The trace gas measurements comprise continuous monitoring of carbon dioxide, carbon monoxide, methane, and ozone at five to eight different heights, complemented by a variety of additional species measured during intensive campaigns (e.g., VOC, NO, NO2, and OH reactivity). Aerosol optical, microphysical, and chemical measurements are being made above the canopy as well as in the canopy space. They include aerosol light scattering and absorption, fluorescence, number and volume size distributions, chemical composition, cloud condensation nuclei (CCN) concentrations, and hygroscopicity. In this paper, we discuss the scientific context of the ATTO observatory and present an overview of results from ecological, meteorological, and chemical pilot studies at the ATTO site. © Author(s) 2015

Pervasive gaps in Amazonian ecological research

Biodiversity loss is one of the main challenges of our time,1,2 and attempts to address it require a clear understanding of how ecological communities respond to environmental change across time and space.3,4 While the increasing availability of global databases on ecological communities has advanced our knowledge of biodiversity sensitivity to environmental changes,5,6,7 vast areas of the tropics remain understudied.8,9,10,11 In the American tropics, Amazonia stands out as the world's most diverse rainforest and the primary source of Neotropical biodiversity,12 but it remains among the least known forests in America and is often underrepresented in biodiversity databases.13,14,15 To worsen this situation, human-induced modifications16,17 may eliminate pieces of the Amazon's biodiversity puzzle before we can use them to understand how ecological communities are responding. To increase generalization and applicability of biodiversity knowledge,18,19 it is thus crucial to reduce biases in ecological research, particularly in regions projected to face the most pronounced environmental changes. We integrate ecological community metadata of 7,694 sampling sites for multiple organism groups in a machine learning model framework to map the research probability across the Brazilian Amazonia, while identifying the region's vulnerability to environmental change. 15%–18% of the most neglected areas in ecological research are expected to experience severe climate or land use changes by 2050. This means that unless we take immediate action, we will not be able to establish their current status, much less monitor how it is changing and what is being lost

Comparação florística e estrutural entre florestas de igapó e campinarana ao longo de gradientes hidro-edáficos na Reserva de Desenvolvimento Sustentável do Uatumã, Amazônia Central

Amazonian igapó and campinarana are considered low-productivity systems and contain forests located upon soils with low nutrient availability and subject to periodical floods. Their species composition, diversity, forest structure and biomass may be equally limited by nutrient availability and some studies suggest a close relationship between their floras. The aim of this study was to describe and to compare the species composition, diversity, forest structure and biomass in an igapó and a campinarana in Central Amazonia and to test its dependence on soil texture, soil nutrients and hydric factors. We inventoried all individuals ≥ 10 cm DBH, distributed along six 0.5 ha plots in each ecosystem. We also calculated trees heights and basal areas. We estimated the above ground wood biomass (AGWB). Tree biomass was estimated based on two allometric models, which consider DBH, wood specific density (ρ) and tree heights, while palm biomass was estimated using an allometric model that considers only individual s height. We sampled 2163 individuals in the igapó and 1849 in the campinarana. Both ecosystems are characterized by high acidity and nutrient-poor soils, being the soil clayish in the igapó and sandy in the campinarana. Mean duration of flooding in igapó plots varied between 10 and 202 days year-1. Mean water table depth in campinarana plots varied between 39.7 and 245.5 cm during the rainy season and between 92.0 and 315.7 cm during the dry season. Although the campinarana was richer in tree species, mean Fisher s alpha diversity was not significantly different between both ecosystems. Floristic similarity between both ecosystems was extremely low (Bray-Curtis dissimilarity index 0.97). Floristic patterns were neither related to edaphic or hydric gradients in both ecosystems. Amanoa cf. guianensis was the most important species in igapó while Aldina heterophylla was the most important species in campinarana. Both ecosystems are similar in structure, with dominance of individuals of low heights and small diameters. They are also similar on biomass: AGWB amounted to 141 - 152 Mg ha-1 in the igapó and to 152 - 164 Mg ha-1 in the campinarana. Flood duration was negatively related to the biomass accumulation in the igapó. In both ecosystems, no dependence of biomass on edaphic gradients was detected. The low biomass found for the igapó and the campinarana when compared to other Amazonian ecosystems, seems to reflect the nutrient-poor soils.Na Amazônia, florestas de igapó e campinarana são sistemas de baixa produtividade, localizados sobre solos com baixa disponibilidade de nutrientes e sujeitos à saturação do solo por água e/ou alagamentos periódicos. A composição e diversidade de espécies, a estrutura florestal e a biomassa destes dois ecossistemas podem ser igualmente limitadas pela disponibilidade de nutrientes dos solos nos quais se desenvolvem e alguns estudos sugerem que suas floras são altamente relacionadas. O objetivo do presente estudo foi descrever e comparar a composição e diversidade florística, estrutura e biomassa de um igapó e uma campinarana na Amazônia Central e determinar sua relação com os fatores de textura e nutrientes do solo, duração da inundação (no igapó) e profundidade do lençol freático (na campinarana). Foram inventariados todos os indivíduos com DAP ≥ 10 cm, distribuídos em seis parcelas de 0,5 ha em cada ecossistema. Foram calculadas a altura e área basal para todos os indivíduos. Foi estimada a biomassa lenhosa acima do solo (AGWB Above Ground Wood Biomass), sendo a biomassa arbórea estimada com base em dois modelos alométricos que consideram DAP, densidade específica da madeira (ρ) e altura dos indivíduos e a biomassa de palmeiras estimada com base em um modelo que considera apenas a altura dos indivíduos. Foram encontrados 2163 indivíduos no igapó e 1849 indivíduos na campinarana. Os dois ecossistemas apresentaram solos com elevada acidez e pobres em nutrientes, sendo o igapó argiloso e a campinarana arenosa. A inundação média nas parcelas do igapó variou entre 10 e 202 dias ano-1. A profundidade média do lençol freático na campinarana variou entre 39,7 e 245,5 cm no período chuvoso e entre 92,0 e 315,7 cm no período de estiagem. Embora a campinarana tenha apresentado maior número de espécies, a diversidade alfa de Fisher média não diferiu significativamente entre os dois ecossistemas. A similaridade florística entre ecossistemas revelou-se extremamente baixa (índice de dissimilaridade de Bray-Curtis 0,97). Não houve relação entre os padrões florísticos e os gradientes edáficos e hídricos nos dois ecossistemas. Amanoa cf. guianensis foi a espécie mais importante no igapó e Aldina heterophylla foi a espécie mais importante na campinarana. Os dois ecossistemas são semelhantes quanto à estrutura da vegetação, apresentando porte baixo e elevado número de indivíduos com DAP pequeno. São semelhantes também quanto à biomassa: AGWB variou entre 141 e 152 Mg ha-1 no igapó e entre 152 e 164 Mg ha-1 na campinarana. A biomassa não foi relacionada ao gradiente edáfico nos dois ecossistemas e à profundidade do lençol freático na campinarana, mas foi negativamente relacionada à duração da inundação no igapó. Os baixos valores de biomassa encontrados para o igapó e a campinarana, quando comparados a outros ecossistemas amazônicos, são provavelmente um reflexo da escassez de nutrientes dos solos nos quais se desenvolvem

The Brazilian freshwater wetscape: Changes in tree community diversity and composition on climatic and geographic gradients

<div><p>Wetlands harbor an important compliment of regional plant diversity, but in many regions data on wetland diversity and composition is still lacking, thus hindering our understanding of the processes that control it. While patterns of broad-scale terrestrial diversity and composition typically correlate with contemporary climate it is not clear to what extent patterns in wetlands are complimentary, or conflicting. To elucidate this, we consolidate data from wetland forest inventories in Brazil and examine patterns of diversity and composition along temperature and rainfall gradients spanning five biomes. We collated 196 floristic inventories covering an area >220 ha and including >260,000 woody individuals. We detected a total of 2,453 tree species, with the Amazon alone accounting for nearly half. Compositional patterns indicated differences in freshwater wetland floras among Brazilian biomes, although biomes with drier, more seasonal climates tended to have a larger proportion of more widely distributed species. Maximal alpha diversity increased with annual temperature, rainfall, and decreasing seasonality, patterns broadly consistent with upland vegetation communities. However, alpha diversity-climate relationships were only revealed at higher diversity values associated with the uppermost quantiles, and in most sites diversity varied irrespective of climate. Likewise, mean biome-level differences in alpha-diversity were unexpectedly modest, even in comparisons of savanna-area wetlands to those of nearby forested regions. We describe attenuated wetland climate-diversity relationships as a shifting balance of local and regional effects on species recruitment. Locally, excessive waterlogging strongly filters species able to colonize from regional pools. On the other hand, increased water availability can accommodate a rich community of drought-sensitive immigrant species that are able to track buffered wetland microclimates. We argue that environmental conditions in many wetlands are not homogeneous with respect to regional climate, and that responses of wetland tree communities to future climate change may lag behind that of non-wetland, terrestrial habitat.</p></div

Variation in Fisher’s alpha along four climate gradients.

<p>Quantile regression fits are indicated with solid (tau = 0.1, 0.5, and 0.9) and dashed lines (tau = 0.3, 0.7). The color scheme matches biome colors in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0175003#pone.0175003.g001" target="_blank">Fig 1</a>.</p

Regional wetland diversity in Brazilian biomes (<i>sensu</i> Veloso [38]).

<p>Random curves were generated by repeated re-sampling of pooled sites within biomes (colored curves) or all sites combined (grey curve). The x-axis is rescaled to the number of individuals, based on the average number of stems per site of each biome.</p

For each biome, the number (and proportion) of tree species occurring in one, two, or more biomes (<i>sensu</i> Veloso [38]).

<p>For each biome, the number (and proportion) of tree species occurring in one, two, or more biomes (<i>sensu</i> Veloso [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0175003#pone.0175003.ref038" target="_blank">38</a>]).</p