Luciana Cristina de Sousa Vieira

Identifying suitable environmental conditions for the early development and deciding how much to shade andiroba (Carapa guianensis Aubl.) seedlings in nurseries still lacks a technical basis. This study evaluated the growth and physiological responses of seedlings grown under 0, 30, 50, and 70% shading for 300 days, with six plants per treatment, combining chlorophyll content, chlorophyll a fluorescence, gas exchange, and growth analysis. Under full sun, the Fv/Fm ratio fell from 0.79 to 0.70 from 90 days onward, signaling photoinhibition, whereas under 70% shading values remained stable and total chlorophyll content reached five times the full-sun level by the end. Photosynthesis, stomatal conductance, and transpiration were highest under 30 and 50% shading, where carbon-use efficiency was also greatest; at 90 days, intrinsic water-use efficiency was up to 33% higher than in full sun, although all treatments declined after 180 days. The higher carbon-use efficiency under moderate shading was accompanied by greater relative growth rates, and the leaf area ratio of shaded plants was about 60% higher than in full sun. Moderate shading (30–50%) is recommended for nursery production, whereas full sun is not indicated for the early phase, as it induces pho-toinhibition and limits growth.

Introduction: Cashew ( Anacardium occidentale ) is one of the most economically and socially important perennial crops in the Brazilian semiarid region, supporting rural livelihoods while also representing a native species adapted to tropical drylands. Understanding how climate change may alter the environmental suitability of native species is critical for conservation planning and sustainable land use in dryland ecosystems. Methods: Here, we modeled the current and future potential distribution of Anacardium occidentale (cashew tree) across the Caatinga biome using MaxEnt (v.3.4.4) and bioclimatic predictors derived from two CMIP6 Earth System Models (EC-Earth3-Veg and MIROC6) under the SSP2-4.5 and SSP5-8.5 emission scenarios for the baseline period and future projections (2050 and 2070). Occurrence records were compiled from GBIF, SpeciesLink, and Embrapa databases and refined through ecological filtering and pedoclimatic zoning. Results: The current model showed high predictive performance (AUC ≈ 0.88), with approximately 25% of the biome classified as highly suitable (≥ 0.5), mainly concentrated in the northern Caatinga. Suitability patterns were primarily driven by precipitation seasonality, annual rainfall, elevation (altitude), and vegetation cover, indicating strong dependence on water availability and habitat structure. Future projections revealed substantial contractions of suitable areas, particularly under SSP5-8.5, with losses ranging from 68% (EC-Earth3-Veg) to 76% (MIROC6). Both climate models consistently indicated that increasing temperatures and reduced seasonal precipitation will intensify aridification, leading to a spatial retreat of the species niche toward coastal and sub-humid zones—areas that correspond to the historical origin and current climatic refugia of the species. Discussion: These results demonstrate the high vulnerability of Anacardium occidentale to ongoing climate change and highlight the importance of conserving coastal and sub-humid microrefugia, as well as implementing climate-adaptive management strategies to support rural livelihoods and extractive systems dependent on cashew production in the Brazilian semi-arid region.

Forests function as socio-ecological systems that link human societies with ecosystems, serving as living territories that sustain the livelihoods of diverse populations. Forests may act as natural infrastructure, supporting biophysical processes that underpin climate and water regulation, thereby reinforcing the system’s resilience to external disturbances, including political instability and extreme weather events. Simultaneously, forests are viewed primarily as a territorial base for expanding energy systems and extractive activities, such as water provision, bioenergy generation, and food production, positioning them at the center of the water–energy–food nexus. These competing valuations of forest ecosystems shape land-use decisions and governance regimes, with profound implications for long-term ecosystem integrity and socio-ecological resilience. This chapter analyzes the forest–water–energy–food nexus by emphasizing the contribution of natural forests and other tree-covered lands in Brazil in sustaining water, energy, and food systems across diverse biomes and territories, and by exploring governance strategies to reconcile economic development with environmental limits.

Este estudo investiga um evento extremo de chuva ocorrido em Fortaleza em 3 de janeiro de 2015, que resultou em danos materiais significativos e impactos socioeconômicos na região. A pesquisa se concentra na aplicação do modelo numérico WRF 3.9.1 (Weather Research and Forecasting) para simular este evento, utilizando diferentes esquemas de parametrização física e realizando testes de sensibilidade. Os resultados demonstram que as parametrizações físicas testadas foram capazes de reproduzir o sistema de convecção que afetou não só Fortaleza, mas também os municípios de Paracuru, Aquiraz, Cascavel e Guanaces. Notavelmente, a simulação utilizando a microfísica de Thompson obteve uma representação mais precisa da precipitação. Esta abordagem fornece insights importantes para aprimorar a previsão e compreensão de eventos extremos de chuva, contribuindo assim para a mitigação de seus impactos.

Carapa guianensis Aubl., known as andiroba, is a multipurpose tree from the Amazon. Planted under environmental conditions, there is still no conclusive data on the light preferences of this species. Thus, the aim of this study was to evaluate growth and physio- logical variables at four shading levels (0%, 30%, 50% and 70%). In the first observation period (≤ 15 months), the relative chlorophyll content (SPAD index) indicated more efficient carbon gain by photosynthesis under shade conditions. Gas exchange measurements (20 months) allowed to conclude that the conditions of exposure to the sun caused photoinhibition. Dry matter evaluation (24 months) confirmed: 50% shade resulted in the greatest increase in dry matter for all plant parts (leaves, stems and roots). This study indicates that this species can give a greater return in relation to biomass under shading conditions, such as in secondary forest enrichment or agroforestry systems, at least in the initial phase of establishment.

Models that predict the stomatal conductance process (gs) for a given set of environmental conditions are important, as this process is the main mechanism that controls the gas exchange of terrestrial plants absorbing atmospheric CO2. This work presents the results of a simulation to observe the gs process as a function of soil water availability (WAP) using an ecosystem demography model (ED2.2). The results showed that the model was able to reproduce the seasonality of the gas observed in the field. During periods when there was WAP, gs increased and the lower availability of water in the soil for the plant led to reduced photosynthesis due to stomata closure, decreasing stomatal conductance to reduce water loss. The model results for gross primary productivity (GPP) were also similar to those observed in the field, varying around ≈24 MgC.ha-1.yr-1 for the rainy season and ≈23 MgC.ha-1.yr- 1 for the dry season (average 2002 to 2010). The assimilation of CO2 via NPP and stomatal conductance had an R2 of 0.7 indicating that the assimilation of CO2 was high when there was greater stomatal conductance, favoring the increase in aboveground biomass in the model.

A modelagem demográfica de ecossistemas é uma ferramenta importante para determinar quais fatores podem moldar a sucessão de uma floresta após eventos climáticos extremos. Os possíveis impactos da redução das chuvas, aumento da concentração de CO₂ atmosférico e o aumento da temperatura do ar devem ser estudados para se entender o que pode ocorrer com a floresta sob um cenário de mudanças climáticas. O objetivo deste trabalho foi realizar duas simulações utilizando-se condições ambientais projetadas sob os cenários RCP4.5 e RCP8.5, de aumento moderado e intenso na concentração do CO₂ atmosférico, os quais indicam mudanças simultâneas tanto de diminuição da precipitação quanto de aumento da temperatura do ar. Nas condições dos cenários de mudanças climáticas RCP4.5 e RCP8.5, a fertilização por CO₂ teve um impacto positivo na vegetação contribuindo para o aumento da biomassa cima do solo (AGB), saturando a altas temperaturas, indicando que em um clima mais seco e mais quente a floresta tropical pode reduzir o incremento de carbono em sua biomassa, desacelerando o seu crescimento e não contribuindo como um sumidouro de CO₂ para o ambiente.

Models that simulate the process of stomatal conductance (gs) for a given set of environmental conditions are important, as this process is the main mechanism that controls the gas exchange of terrestrial plants absorbing atmospheric CO2 in tropical forests. Simulations were performed for the Tapajós National Forest, in the western Brazilian Amazon, observing the gs process under the current climate scenario (control) and under the scenarios RCP4.5 and RCP8.5 (2071 - 2100), using the ED2.2 ecosystem demography model. The results showed that the lower availability of soil water for the plants reduced photosynthesis due to the closing of the stomata. The model results for gross primary productivity (GPP) are similar to those observed in the field, varying about ≈24 MgC ha-1 year-1 for the rainy season and ≈23 MgC ha-1 year-1 for the dry season (average 2002 to 2010) in the control scenario. In the RCP4.5 scenario, simulated GPP was 30.7 and 30 MgC ha-1year-1 for the rainy and dry season, respectively (30.5 and 25 MgC ha-1year-1, respectively, for the RCP8.5 scenario). Our results also show that there may be a limitation on the increase in biomass carbon with the concentration of CO2, as GPP was lower in RCP8.5, despite this scenario having a higher value of atmospheric CO2 relative to RCP4.5.

Carapa guianensis Aubl. (andiroba in Brazil) is an Amazonian multi-use tree. Due to an increased early growth (caused by large seeds reserves), no conclusive data on light preferences during initial development are available. This two-year greenhouse experiment aimed to evaluate growth and physiological variables under four levels of shading (0%, 30%, 50% and 70%). In the very-early stage of Carapa guianensis development (≤ 15 months), the growth in height, leaf number did not give conclusive results. Nevertheless, the shoot diameter and the relative chlorophyll content (SPAD) significantly indicated more efficient carbon gain by photosynthesis in high shade conditions (70%). After 15 months, significant changes suggested photoinhibition and high plasticity: i) gas exchange measurements (photosynthetic activity, stomatal conductance and transpiration) showed lower values under sun conditions, ii) the 50%-shade resulted in the highest dry matter increase (regarding leaves, stem and roots), iii) the Shoot-Root Ratio varied from 1.88 under sun exposure up to 4.73 under shade conditions. Although plantations of Carapa guianensis are often performed under open conditions, this study indicates that this species can give a higher return regarding biomass under shaded conditions, at least during the initial phase of establishment.

A produção de biomassa em áreas de Caatinga apresenta grande variação espacial e sazonal, principalmente em função da distribuição das chuvas. Diante da diminuição da vegetação de Caatinga no nordeste brasileiro e ao consequente avanço da desertificação em todo o bioma, o presente estudo analisou qual tem sido o sequestro de carbono para o período de 2001 a 2019, em quatro áreas localizadas ao norte (A1), leste (A2), sul (A3) e oeste (A4) do bioma, e o que pode estar conduzindo com maior influência seu aumento ou diminuição. Através da análise com dados de sensoriamento remoto de produtividade primária bruta (PPB) e líquida (PPL), provenientes do MODIS, e dados de clima obtidos do NCEP e estações meteorológicas, observou-se que estão havendo uma redução das chuvas em todas as áreas, um aumento da temperatura do ar e redução de absorção de carbono pela biomassa. O teste de Mann-Kendall foi aplicado para verificar o nível de significância destas mudanças e constatamos que os resultados foram estatisticamente significativos somente para A2. Também se verificou que a variável determinante no crescimento da vegetação de Caatinga é a chuva. Mesmo com baixa significância estatística para a maior parte das áreas, foi verificado que a PPB e PPL estão reduzindo para A1, A2 e A4 como possível consequência desta mudança no clima. Em A3 onde se observou aumento no sequestro de carbono, provavelmente devido a hidrologia local, o que está fazendo com que esta área de Caatinga seja resiliente mesmo em períodos de seca.