Índices de vegetação na diagnose nutricional de povoamentos híbridos de Eucalyptus urophylla S. T. Blake

Remote sensing through band ratio techniques for nutritional monitoring of clonal eucalyptus plantations is essential to guarantee health and productivity, reducing costs of forestry enterprises. The objective was to apply vegetation indices from high resolution satellite images in the nutritional diagnosis of macronutrients in plantations of clonal hybrids of Eucalyptus urophylla S. T. Blake. The study was carried out in 62 areas of six municipalities in the state of Bahia under cultivation of homogeneous eucalyptus plantations, aged between 1.3 and 1.8 years. The design was completely randomized with six treatments constituted by the rainfall regime (1000 to 1300 mm year-1 and 1300 to 1600 mm year-1) and soil types (class and texture). The nutritional diagnosis of nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg) and sulfur (S) was performed from leaf analysis and determination of vegetation indices: normalized difference vegetation (NDVI), normalized difference water index (NDWI) and soil adjusted vegetation index (SAVI). The evaluated areas have high vigor (NDVI > 0.70) and the highest values were observed in the rainy regions (1300 to 1600 mm year-1) (mean of 0.78). The NDWI index presents the highest correlation for the average levels of Ca and Mg. The NDVI, NDWI and SAVI indexes present a strong correlation with each other (-0.97 to 1.00) and can help in mapping vigor and consequently in eucalyptus productivity.O sensoriamento remoto, por meio das técnicas de razão de bandas para o monitoramento nutricional de plantios clonais de eucalipto, é fundamental para garantir a sanidade, produtividade e reduzir custos de empreendimentos florestais. Objetivou-se aplicar índices de vegetação a partir de imagens de satélite de alta resolução na diagnose nutricional de macronutrientes em plantios de híbridos clonais de Eucalyptus urophylla S. T. Blake. O estudo foi realizado em 62 áreas de seis municípios do estado da Bahia sob cultivo de plantios homogêneos de eucalipto, com idades entre 1,3 e 1,8 anos. O delineamento foi inteiramente casualizado com seis tratamentos constituídos pelo regime pluviométrico (1000 a 1300 mm ano-1 e 1300 a 1600 mm ano-1) e tipos de solo (classe e textura). A diagnose nutricional de nitrogênio (N), fósforo (P), potássio (K), cálcio (Ca), magnésio (Mg) e enxofre (S) foi realizada a partir da análise foliar e da determinação dos índices de vegetação: índice de vegetação por diferença normalizada (NDVI), índice de diferença normalizada da água (NDWI) e índice de vegetação ajustado ao solo (SAVI). As áreas avaliadas possuem alto vigor (NDVI > 0,70) e os maiores valores foram observados nas regiões chuvosas (1300 a 1600 mm ano-1) (médio de 0,78). O índice NDWI apresenta maior correlação para os teores médios de Ca e Mg. Os índices NDVI, NDWI e SAVI apresentam forte correlação entre si (-0,97 a 1,00) e podem auxiliar no mapeamento do vigor e consequentemente na produtividade de eucalipto

Modeling of Soil Losses on a Yellow Argisol Under Planted Forest

ABSTRACT Erosion prediction models are a useful tool for soil use planning and soil conservation. This study aimed to apply the Universal Soil Loss Equation (USLE) in an experimental sub-basin located in the municipality of Teixeira de Freitas, in the southern end of the state of Bahia, Brazil. The following variables were calculated: rainfall erosivity factor, using the precipitation data; soil erodibility factor, by the correlation between erosivity and soil losses obtained from a standard plot installed in the field; topographic factor; vegetation cover and management factor; and conservation practices factor. The product of these factors corresponded to the soil losses in the sub-basin. Data from erosion plots were used to validate the model. The USLE predicted higher soil losses than that observed in the plots, and the eucalyptus proved to be efficient at reducing soil losses by erosion

Erosão hídrica associada a padrões de chuva no extremo Sul da Bahia em pós-plantio de eucalipto

Soil and water losses caused by water erosion represent a risk of environmental damage and loss of soil productivity, with economic, social and environmental consequences. Plant cover is an important ally against water erosion, together with the knowledge of rainfall characteristics. Thus, this study aimed to evaluate the soil and water losses and to determine rainfall patterns in two homogeneous eucalyptus plantations; one in Yellow Argisol, located in Teixeira de Freitas, and another in Humiluvic Spodosol, located in Caravelas, both in the Extreme South of the state of Bahia. Erosion plots were installed, and consisted of three treatments: bare soil, eucalyptus, and native forest. Rainfall data was obtained from an automatic gauging station, with 10 minute registration interval for erosivity (erosivity index EI30) and rainfall pattern analyses. Higher soil losses were observed in Yellow Argisol, and the advanced rainfall pattern was predominant. Eucalyptus minimum tillage was efficient in reducing soil and water losses by water erosion.As perdas de solo e de água por erosão hídrica representam risco de dano ambiental e redução da produtividade dos solos, sendo uma das principais formas de degradação com consequências econômicas, sociais e ambientais. A cobertura vegetal é um importante aliado no combate à erosão hídrica, assim como o conhecimento das características da chuva. Deste modo, o presente estudo teve como objetivo avaliar as perdas de solo e água e determinar os padrões de chuva em floresta homogênea de eucalipto em Argissolo Amarelo, no município de Teixeira de Freitas, e em Espodossolo Humilúvico, no município de Caravelas, ambas no Extremo Sul da Bahia. Parcelas de perdas de solo foram instaladas envolvendo três tratamentos: solo descoberto, Eucalipto e Mata nativa (área em equilíbrio), em ambas as classes de solo avaliadas. Para a erosividade, obtida pelo índice de erosividade em 30 minutos (EI30), e para os padrões de chuva dos eventos erosivos foram considerados dados pluviométricos obtidos em estação climatológica automatizada, com intervalos de registro de 10 minutos. As maiores perdas de solo foram observadas no Argissolo Amarelo e o padrão de chuva predominante foi o avançado. O cultivo mínimo de eucalipto mostrou-se eficiente na redução das perdas de solo e de água por erosão hídrica

Soil compaction caused by harvest and logging operations in eucalyptus forests in coarse-textured soils from northeastern Brazil

ABSTRACT Planted forests occupy more than 6.5 million ha in Brazil, where harvest and logging operations are performed with increasingly heavier machinery, increasing the risk of soil compaction. Soil compaction can be avoided if soil load bearing capacity is not exceeded, what makes it important to assess both the soil strength and the impact of different operations. The aim of this study was to evaluate the load bearing capacity of some coarse textured soils (two Hapludult and one Haplorthod) in two soil horizons (BA and B), from northeastern Brazil; and to assess the impact of harvest and logging operations performed with harvester and forwarder. Although the Haplorthod presented higher load bearing capacity in both the BA horizon (for the whole moisture range) and the B horizon (for higher water contents), it suffered the greatest soil compaction. Traffic with the harvester resulted in soil compaction in both the BA and the B horizons, but the increase in bulk density was higher on the later, reaching 18.7% in the Haplorthod. The forwarder traffic intensity and the presence of plant residue cover significantly affected the occurrence of soil compaction. In the BA horizon, the increase in soil bulk density for different forwarder traffic intensities was 3 passes ~ 6 passes < 12 passes ~ 16 passes. The increase in bulk density was higher in the Haplorthod, reaching 32% after 16 forwarder passes over bare soil. Significant linear regressions were obtained from the number of forwarder passes and the increase in bulk density