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Vulnerabilidade à erosão na ilha do Maranhão: influência do clima e das mudanças de uso e cobertura do solo

Thu, 28 Aug 2025 00:00:00 GMT

Título: Vulnerabilidade à erosão na ilha do Maranhão: influência do clima e das mudanças de uso e cobertura do solo Abstact: Coastal zones, such as São Luís Island, face challenges related to unplanned urbanization and erosive processes, exacerbated by forest degradation and changes in surface runoff. This study analyzed the relationship between anthropization and socio-environmental and climatic vulnerability in the region, investigating how changes in land use and vegetation intensify erosive processes and impact the local microclimate. The research considered variables such as soils, land use and cover, precipitation, geomorphology, and geology to identify areas susceptible to erosion. Two methodological approaches were adopted: first, maps were created through geoprocessing to delineate areas vulnerable to erosion, taking into account the characteristics of the meteorological stations of the Eastern Amazon; second, urban growth, loss of natural areas, and climatic variations over 30 years were analyzed. The results indicated a high vulnerability to erosion in São Luís Island, with significant impacts of land use on the microclimate, as evidenced by variations in precipitation and temperatures (maximum, minimum, and average). The study highlighted the need to strengthen territorial planning, particularly in the municipalities of Paço do Lumiar, Raposa, and São José de Ribamar, through instruments such as the Master Plan and the creation of conservation units. It is also essential to preserve protected areas threatened by deforestation and promote sustainable urbanization integrated with forest conservation. To improve environmental balance and quality of life, especially in communities dependent on agriculture and fishing, it is crucial to value the traditional knowledge of fishing communities. Future studies should focus on extreme climatic events to mitigate erosive impacts. The research reinforces the importance of integrated actions to address the environmental and socioeconomic challenges of São Luís Island.

Mediadores do acúmulo e da estabilidade do carbono orgânico do solo no trópico úmido

Wed, 07 Jan 2026 00:00:00 GMT

Título: Mediadores do acúmulo e da estabilidade do carbono orgânico do solo no trópico úmido Abstact: Sustainable management and the assessment of soil health indicators in the humid tropics are urgent and necessary. Historically, this region has faced food insecurity, rural poverty, and degradation of natural resources. Simple fertilization is not sufficient to improve soil health due to rapid nutrient losses and accelerated organic matter decomposition, making integrated strategies necessary for more efficient agricultural systems. In this context, this research aims to (i) estimate the effect of polyvalent cations on the accumulation and stability of soil organic carbon in tropical regions; (ii) determine key indicators of soil health in the humid tropics; and (iii) understand the dynamics of Ca and Si on ecophysiological indices, stabilized soil organic carbon (SOC) fractions, and nitrogen use efficiency in soils of the Amazonian periphery. In Chapter 1, a meta-analysis was conducted based on 14 studies published between 2003 and 2023, using random-effects models to evaluate the influence of the polyvalent cations Al, Fe, Mg, and Ca on SOC concentration. The results revealed distinct effects among the cations (p < 0.001), with Al being the most strongly associated with increases in SOC, followed by Mg and Ca. In contrast, Fe showed the smallest effect. Heterogeneity among studies (I² = 77.01%) indicated that factors such as soil class, pH, texture, and land use significantly modulate cation effects. Soils with pH between 4 and 6 and clay contents above 600 g kg⁻¹ favored SOC concentrations > 30 g kg⁻¹, particularly in the presence of Ca contents exceeding 40,000 mg kg⁻¹. For the subsequent chapters, a field experiment was conducted in the municipality of São Luís, Maranhão, Brazil, from October 2021 to July 2024. A randomized complete block design (RCBD) was adopted with four replicates and eight treatments: (1) urea; (2) legume; (3) legume + urea; (4) calcium + legume; (5) silicon + legume; (6) calcium + legume + urea; (7) silicon + legume + urea; and (8) calcium + silicon + legume + urea, under maize cultivation. In Chapter 2, the contribution of 17 edaphic variables to SOC and maize productivity was investigated using multivariate analyses (PCA, RDA, decision trees, and regression). Chemical variables—especially MAOC, Si, and, to a lesser extent, Ca—exerted the greatest effects on SOC and productivity. MAOC was highly significant (p < 0.001) and showed a strong correlation (R² = 0.87) with total SOC, whereas physical and biological variables, such as macroporosity and microbial respiration, showed secondary influence. In the final chapter, the response of the ecophysiological indices qCO₂ and qMIC, as well as SOC fractions (POC and MAOC) and nitrogen, to the studied treatments was evaluated. The results demonstrated that Ca and Si contributed to increases in the stable carbon fraction (MAOC) (p < 0.05), with Si standing out by promoting MAOC contents 32% higher than Ca when combined with legumes. Nitrogen concentration in maize plants was 72% higher under Si + legume than under Ca + legume (p < 0.05). Silicon also showed greater efficiency in the use of biological nitrogen, in contrast to Ca, which depended on synthetic N to achieve a similar effect. Overall, the results of this research reinforce that sustainable management strategies prioritizing the addition of stabilizing cations and Si, the promotion of MAOC, and the use of biological N sources can improve soil health, increase agricultural productivity, and contribute to carbon storage and stability in soils. These strategies are fundamental to mitigating climate change impacts and ensuring the long-term resilience of tropical agroecosystems.

Aspectos morfofisiológicos e anatômicos de plântulas de Handroanthus impetiginosus: reguladores de crescimento, trocas gasosas e enriquecimento de CO2 no cultivo in vitro

Tue, 30 Sep 2025 00:00:00 GMT

Título: Aspectos morfofisiológicos e anatômicos de plântulas de Handroanthus impetiginosus: reguladores de crescimento, trocas gasosas e enriquecimento de CO2 no cultivo in vitro Abstact: Handroanthus impetiginosus, popularly known as ipê roxo (purple trumpet tree), is a woody species with significant pharmacological, timber, and ornamental potential; however, it faces propagation limitations. In vitro cultivation techniques—such as germination, multiplication, rooting, and CO2 enrichment—offer excellent alternatives for propagating this species. Thus, this study aimed to establish, multiply, and root the species in vitro, as well as to analyze the impact of sucrose and CO2 enrichment on the development and anatomy of ipê roxo. Chapter I presents the theoretical background, addressing key topics regarding the species' in vitro cultivation. Chapter II details the in vitro seed germination, multiplication (using stem segments), and rooting (using shoots) of ipê roxo. Seeds were surface-sterilized and inoculated onto ½ MS culture medium without growth regulators. WPM medium supplemented with the cytokinins m-TP and BAP (0, 2.5, and 5 μM) was used for stem segment multiplication, while WPM medium with the auxins NAA and IBA (0, 3, and 6 μM) was used for rooting. After 45 days of cultivation, 5 μM m-TP emerged as the superior cytokinin for ipê roxo multiplication, and IBA at moderate concentrations proved effective as a root inducer in micropropagation protocols. In Chapter III, stem segments derived from the multiplication phase—inoculated onto WPM medium supplemented with sucrose (0, 10, and 20 g L⁻¹) and 5 μM m-TP—were placed in two climate chambers: one with ambient CO2 concentration (420 ± 30 μmol mol⁻¹) and the other with elevated CO2 concentration (800 ± 30 μmol mol⁻¹). After 35 days of culture, it was observed that 10 g L⁻¹ sucrose + 800 μmol mol⁻¹ CO₂ maximized growth and photosynthetic efficiency during the in vitro culture of ipê roxo (purple trumpet tree), particularly during the transition phases to autotrophy, while 20 g L⁻¹ sucrose + 800 μmol mol⁻¹ CO₂ influenced the species' anatomy. This study presented interesting results that enable the establishment of a protocol for the multiplication and rooting of ipê roxo, which can serve as a basis for large-scale plant propagation. The findings also indicate the possibility that H. impetiginosus exhibits a degree of physiological and anatomical plasticity in response to high CO₂ concentrations—such as those predicted in climate change scenarios—suggesting the species possesses adaptive potential.

Distribuição da Assembleia de Odonata (INSECTA) em riachos com diferentes níveis de conservação em uma região de Ecótono Amazônia - Cerrado

Mon, 30 Jun 2025 00:00:00 GMT

Título: Distribuição da Assembleia de Odonata (INSECTA) em riachos com diferentes níveis de conservação em uma região de Ecótono Amazônia - Cerrado Abstact: Transitions between large biomes, known as ecotones, have unique environmental conditions that support high biodiversity, but they also suffer intensely from agricultural expansion and environmental degradation. This dissertation investigated the influence of different levels of environmental conservation on the Odonata community (dragonflies and damselflies) in streams located in the ecotone between the Amazon and Cerrado biomes, in the southwest and north of the states of Maranhão and Tocantins, respectively. The approach was carried out through standardized sampling in 30 stream reaches distributed among environments classified as conserved, altered, and impacted, evaluating environmental variables and their relationship with the composition, richness, and abundance of Odonata species. Multivariate analyses were applied, including Generalized Linear Models (GLMs) and Threshold Indicator Taxa Analysis (TITAN), in addition to Principal Component Analysis (PCA). The results indicate that environmental integrity significantly influences the structure of the assemblages, with greater richness and abundance of Zygoptera in conserved environments, while Anisoptera showed greater tolerance to altered environments. The indicator species analysis identified sensitive taxa associated with preserved plant cover and a stable microclimate, while TITAN revealed ecological thresholds related to the variables temperature, electrical conductivity, and habitat integrity index. The diversity of Odonata proved to be an efficient bioindicator tool for the environmental quality of the evaluated streams, reinforcing the importance of preserving riparian vegetation and controlling agricultural expansion in the region. In the end, the study shows that ecotones, despite their complexity and richness, remain underexplored in ecological research and demand greater attention in conservation strategies.