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.

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

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