Características foliares e trocas gasosas em arvoretas de espécies nativas da Amazônia Central

Global climate models predict changes on the length of the dry season in the Amazon which may affect tree physiology. The aims of this work were to determine the effect of the rainfall regime and fraction of sky visible (FSV) at the forest understory on leaf traits and gas exchange of ten rainforest tree species in the Central Amazon, Brazil. We also examined the relationship between specific leaf area (SLA), leaf thickness (LT), and leaf nitrogen content on photosynthetic parameters. Data were collected in January (rainy season) and August (dry season) of 2008. A diurnal pattern was observed for light saturated photosynthesis (Amax) and stomatal conductance (gs), and irrespective of species, Amax was lower in the dry season. However, no effect of the rainfall regime was observed on gs nor on the photosynthetic capacity (Apot, measured at saturating [CO2]). Apot and leaf thickness increased with FSV, the converse was true for the FSV-SLA relationship. Also, a positive relationship was observed between Apot per unit leaf area and leaf nitrogen content, and between Apot per unit mass and SLA. Although the rainfall regime only slightly affects soil moisture, photosynthetic traits seem to be responsive to rainfall-related environmental factors, which eventually lead to an effect on Amax. Finally, we report that little variation in FSV seems to affect leaf physiology (Apot) and leaf anatomy (leaf thickness)

VELOCIDADE DE CARBOXILAÇÃO DA RUBISCO E TRANSPORTE DE ELÉTRONS EM ESPÉCIES ARBÓREAS EM RESPOSTA A FATORES DO AMBIENTE NA AMAZÔNIA CENTRAL

Light availability is one of the main factors that limits photosynthetic rates in saplings in the forest understory. The aims of this study were to determine how photosynthetic parameters (maximum carboxylation velocity of Rubisco – V c-max and maximum rate of electron transport – J max ) respond to irradiance, temperature and diurnal variations in the physical environment. Gas exchange data were collected between 08h00 and 16h00, and from September to November (2010) under ambient conditions, temperature of 27± 2 ºC and relative humidity of 70 ± 3%. CO 2 saturated photosynthesis (A pot ) was measured under light saturation and [CO 2 ] of 2000 μ mol mol -1 . Data were subjected to analysis of variance and then the Tukey test was used for mean separations. V c-max and J max correlated with photosynthetic rates at [CO 2 ] of 380 μ mol mol -1 (A 380 ) and A pot . The increase in intercellular CO 2 concentration (C i ) led to increase in photosynthetic rates, up to the point of photosynthesis limitation by the electron transport rate. Below the collimation point (300-569 μmol mol -1) photosynthetic rates were limited by V c-max . Increases in irradiance and temperature in the forest understory led to increasing the values of A 380 , A pot , V c-max and J max . However, the effect of time of day on V c-max and J max was not significant ( p > 0.05). Absence of an effect of time of day on V c-max and J max is important for the leaf to efficiently use the sun flecks that occasionally puncture the forest floor

Crescimento e eficiência fotossintética de uso do nitrogênio e fósforo em espécies florestais da amazônia na fase juvenil

In the Amazon Rainforest, photosynthesis and tree growth may be limited by the availability of nutrient. Thus, the objectives of this study were to determine the effect of leaf N and P content on photosynthesis, and to assess plant growth in response to understory light in ten tree species in Central Amazonia. Data were collected in January 2008. The photosynthetic capacity (Apot) of leaves positively increased with foliar N and P content, but it was only responsive to P use efficiency. The contents of N and P increased as understory irradiance increased. In addition, we found a positive relationship between N content and the N/P ratio. On the contrary, the relationship between P content and the N/P ratio was negative. Specific leaf area was negatively correlated with N and P. N use efficiency declined with increases with the N/P ratio, but the N/P ratio had no significant effect on P use efficiency. Growth in diameter increased with understory light. In conclusion, saplings were highly sensitive to variations in light intensity, and P was used with high efficiency in studied species

VELOCIDADE DE CARBOXILAÇÃO DA RUBISCO E TRANSPORTE DE ELÉTRONS EM ESPÉCIES ARBÓREAS EM RESPOSTA A FATORES DO AMBIENTE NA AMAZÔNIA CENTRAL

Light availability is one of the main factors that limits photosynthetic rates in saplings in the forest understory. The aims of this study were to determine how photosynthetic parameters (maximum carboxylation velocity of Rubisco – Vc-max and maximum rate of electron transport – Jmax) respond to irradiance, temperature and diurnal variations in the physical environment. Gas exchange data were collected between 08h00 and 16h00, and from September to November (2010) under ambient conditions, temperature of 27± 2 ºC and relative humidity of 70 ± 3%. CO2 saturated photosynthesis (Apot) was measured under light saturation and [CO2] of 2000 μmol mol-1. Data were subjected to analysis of variance and then the Tukey test was used for mean separations. Vc-max and Jmax correlated with photosynthetic rates at [CO2] of 380 μmol mol-1 (A380)and Apot. The increase in intercellular CO2 concentration (Ci) led to increase in photosynthetic rates, up to the point of photosynthesis limitation by the electron transport rate. Below the mutual limitation point (300-569 μmol mol-1) photosynthetic rates were limited by Vc-max. Increases in irradiance and temperature in the forest understory led to increasing the values of A380, Apot, Vc-max and Jmax. However, the effect of time of day on Vc-max and Jmax was not significant (p > 0.05). Absence of an effect of time of day on Vc-max and Jmax is important for the leaf to efficiently use the sun flecks that occasionally puncture the forest floor.A disponibilidade de luz é um dos fatores que mais limita a fotossíntese de árvores juvenis no sub-bosque da floresta. Os objetivos deste estudo foram determinar como os parâmetros fotossintéticos (velocidade máxima de carboxilação da Rubisco – Vc-max e as taxas máximas de transporte de elétrons – Jmax) respondem à irradiância, temperatura e horário do dia no interior da floresta. Os dados foram coletados nos meses de setembro a novembro de 2010, entre 08h00 e 16h00, em condições ambientais de temperatura (27 ± 2ºC) e umidade relativa do ar (70 ± 3%). Fotossíntese saturada por CO2 (Apot) foi mensurada em luz saturante e [CO2] de 2000 μmol mol-1.Os dados foram submetidos à análise de variância, o teste de Tukey foi utilizado para separação de médias. Vc-max e Jmax correlacionaram com a fotossintese em [CO2] de 380 μmol mol-1  (A380) e Apot. O aumento de Ci causou o aumento da fotossíntese, até o ponto da limitação da fotossíntese por Jmax. Abaixo do ponto de colimitação (300 a 569 μmol mol-1), as taxas fotossintéticas foram limitadas por Vc-max. Aumentos da irradiância e temperatura no sub-bosque aumentaram os valores de A380, Apot, Vc-max e Jmax. Entretanto, não houve efeito significativo (p > 0,05) do horário do dia em Vc-max e Jmax. Ausência de efeito do horário do dia é importante para a folha poder utilizar com alta eficiência os feixes de luz direta que ocasionalmente atingem o sub-bosque da florest

Social Participation in the Brazilian National Biodiversity Monitoring Program Leads to Multiple Socioenvironmental Outcomes

The Brazilian Biodiversity Monitoring Program (Monitora Program) is a long-term large-scale program aimed at monitoring the state of biodiversity and associated ecosystem services in the protected areas (PAs) managed by Instituto Chico Mendes de Conservação da Biodiversidade (ICMBio). Encouraging qualified social participation is one of Monitora Program’s guiding principles. In this case study, we describe how citizen participation occurs in various stages of the Monitora Program, including planning, data collection, interpretation, and discussion of results. Aspects that are crucial for a legitimate and continuous involvement and participation are described. We also illustrate some of the results from the Program and discuss how the program can contribute to Brazil’s achievement of the United Nations (UN) Sustainable Development Goals (SDGs). In 2022, the program was implemented in 113 of the 334 protected areas managed by ICMBio, most of them in the Amazon. The program results are aligned to 12 of the 17 SDGs, influencing changes that move society closer to these goals at the local scale. Data from the Monitora Program can be used to support Brazilian SDG reporting, but this requires further developments. Social participation in Monitora Program has strengthened links between institutions and people of different profiles, enhancing participation in protected area (PA) management and generating multiple local impacts, while producing quality biodiversity information to inform decision-making in conservation

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

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

Is stomatal conductance of Central Amazonian saplings influenced by circadian rhythms under natural conditions?

Stomata control CO2 uptake and transpirational water loss, and their functioning is closely regulated by external factors, such as light, CO2 concentration, air vapor pressure deficit, and temperature. In addition, endogenous factors (e.g. biological clock) also affect stomatal movement. In comparison with ambient factors, internal factors have received less attention in Amazonian tree species. The aim of this study was to determine how stomatal functioning and photosynthesis respond to continuous light exposure during a circadian cycle. We collected data from July to September 2010 in four saplings of Amphirrhox surinamensis. Stomatal conductance (g s50) and photosynthesis at a constant photosynthetically active radiation of 50 μmol m-2 s-1 (P N50) were measured continuously during a circadian period (24 h, day and night) under a [CO2] of 380 μmol mol-1, temperature of 25 ± 2 °C, air relative humidity of 73 ± 3 %. The highest values of g s50 and P N50 were observed before 02:00 pm. Values of these parameters decreased toward the end of the afternoon and night until reaching steady state around midnight. Stomatal reopening (inferred by the increase in g s values) began after midnight (01:00 am-02:00 am) when lower temperatures were recorded. Cooler temperatures observed after midnight and higher vapor pressure deficit values recorded early in the morning should promote closing rather than stomatal opening. Stomatal reopening in the early predawn hours suggests the involvement of an endogenous timer (circadian clock) in stomatal functioning. © 2014 Brazilian Society of Plant Physiology