Biomass and vegetation index by remote sensing in different caatinga forest areas / Relação entre biomassa e índices de vegetação por sensoriamento remoto em diferentes áreas de florestas de caatinga

Continued unsustainable exploitation of natural resources promotes environmental degradation and threatens the preservation of dry forests around the world. This situation exposes the fragility and the necessity to study landscape transformations. In addition, it is necessary to consider the biomass quantity and to establish strategies to monitor natural and anthropic disturbances. Thus, this research analyzed the relationship between vegetation index and the estimated biomass using allometric equations in different Brazilian caatinga forest areas from satellite images. This procedure is performed by estimating the biomass from 9 dry tropical forest fragments using allometric equations. Area delimitations were obtained from the Embrapa collection of dendrometric data collected in the period between 2011 and 2012. Spectral variables were obtained from the orthorectified images of the RapidEye satellite. The aboveground biomass ranged from 6.88 to 123.82 Mg.ha-1. SAVI values were L = 1 and L = 0.5, while NDVI and EVI ranged from 0.1835 to 0.4294, 0.2197 to 0.5019, 0.3622 to 0.7584, and 0.0987 to 0.3169, respectively. Relationships among the estimated biomass and the vegetation indexes were moderate, with correlation coefficients (Rs) varying between 0.64 and 0.58. The best adjusted equation was the SAVI equation, for which the coefficient of determination was R² = 0.50, R2aj = 0.49, RMSE = 17.18 Mg.ha-1 and mean absolute error of prediction (MAE) = 14.07 Mg.ha-1, confirming the importance of the Savi index in estimating the caatinga aboveground biomass.

A exploração contínua e insustentável dos recursos naturais promove a degradação ambiental e ameaça a conservação das florestas secas no mundo. Essa situação expõe a fragilidade e a necessidade de estudar as transformações da paisagem. É necessário considerar o quantitativo de biomassa e o estabelecimento de estratégias para monitorar distúrbios naturais e antrópicos. Assim, este trabalho teve como objetivo analisar a relação entre o índice de vegetação e a biomassa estimada por meio de equações alométricas em diferentes áreas da caatinga brasileira a partir de imagens de satélite. Este procedimento é realizado estimando-se a biomassa de nove fragmentos de floresta tropical seca com o uso em equações alométricas. As delimitações das áreas foram obtidas da coleção da Empresa Brasileira de Pesquisa Agropecuária, a partir dos dados dendrométricos coletados no período entre 2011 e 2012. As variáveis espectrais foram obtidas a partir das imagens ortorretificadas do satélite RapidEye. A biomassa acima do solo variou de 6,88 a 123,82 Mg.ha-1. Os valores de SAVI para os coeficientes L = 1 e L = 0,5, NDVI e EVI variaram de 0,1835 a 0,4294, 0,2197 a 0,5019, 0,3622 a 0,7584 e 0,0987 a 0,3169, respectivamente. As relações entre a biomassa estimada e os índices de vegetação foram moderadas, com coeficiente de correlação (rs) variando entre 0,64 e 0,58. A equação mais bem ajustada foi a Equação do SAVI, com coeficiente de determinação foi R² = 0,50, R2aj = 0.49, RMSE = 17.18 Mg.ha-1 e erro médio absoluto de predição (MAE) = 14.07 Mg.ha-1, confirmando a importância do índice SAVI na estimativa da biomassa aérea da Caatinga.

Optimizing multifunctional agroecosystems in irrigated dryland agriculture to restore soil carbon - Experiments and modelling.

Irrigated dryland agroecosystems could become more sustainable if crop and soil management enhanced soil organic carbon (SOC). We hypothesized that combining high inputs from cover crops with no-tillage will increase long-term SOC stocks. Caatinga shrublands had been cleared in 1972 for arable crops and palm plantations before implementing field experiments on Mango and Melon systems (established in 2009 and 2012, respectively). Each of the two experiments were managed with no-till (NT) or conventional till (CT), and three types of cover cropping, either a plant mixture of 75% (PM1) or 25% (PM2) legumes, or spontaneous vegetation (SV). The RothC model was used with a daily timestep to simulate the soil moisture dynamics and C turnover for this dry climate. Carbon inputs were between 2.62 and 5.82 Mg C ha-1 year-1 and increased the depleted SOC stocks by 0.08 to 0.56 Mg C ha-1 year-1. Scenarios of continuous biomass inputs of ca. 5 Mg C ha-1 year-1 for 60 years are likely to increase SOC stocks in the mango NT beyond the original Caatinga SOC by between 19.2 and 20.5 Mg C ha-1. Under CT similar inputs would increase SOC stocks only marginally above depletion (2.75 to 2.47 Mg C ha-1). Under melon, annual carbon inputs are slightly greater (up to 5.5 Mg C ha-1 year-1) and SOC stocks would increase on average by another 8% to 22.3 to 20.6 Mg C ha-1 under NT and by 8 Mg C ha-1 under CT. These long-term simulations show that combining NT with high quality cover crops (PM1, PM2) would exceed SOC stocks of the initial Caatinga within 20 and 25 years under irrigated melon and mango cultivation, respectively. These results present a solution to reverse prior loss of SOC by replacing CT dryland agriculture with irrigated NT plus high input cover crops agroecosystems.

Physical attributes of Ultisol of Brazil's northeastern semiarid under organic farming of wine grapes.

The purpose of this study was to evaluate the effects of organic farming of wine grapes under physical and chemical characteristics of Ultisol Brazil's northeastern semiarid region. The samples of soil were collected from the row and interrow of the farming and from the fallow area, at the depths of 0.0-0.10, 0.10-0.20, 0.20-0.30 and 0.30-0.60 m. The samples were collected at six and twelve months after the culture implementation to evaluate the state of aggregation, bulk density and total soil porosity, flocculation index and organic matter contents, calcium, magnesium, and sodium. The results were submitted to statistical analysis. The adoption of organic farming contributed to the soil aggregation process. The bulk density and total soil porosity did not differ significantly between the evaluations, but were within the critical limits for sandy soils. The index flocculation did not have a great influence on the aggregates formation, being this process influenced by organic matter. The period of one year was considered short to obtain conclusive results in improving the soil quality by organic farming, since there are difficulties in tropical soils in promoting significant increases in organic matter content in short time.

Relação entre alumínio e silício em genótipos de milho resistente e sensível a toxidez de alumínio / Relation between aluminum and silicon in maize genotypes resistant and sensitive at aluminum toxicity

A fim de obter informações sobre a relação entre alumínio e silício no crescimento de dois genótipos de milho, sendo um tolerante e outro sensível a toxidez de alumínio, foi realizado um estudo em casa de vegetação, na presença e ausência de alumínio e silício em dois genótipos de milho. Os tratamentos utilizados foram uma solução de 2,0 mmol L-1 de cálcio (CaCl2), na presença e na ausência de alumínio (0,025 mmol L-1- AlCl3) e de silício (0,14 mmol L-1 a partir de uma solução de SiO2). O experimento foi conduzido por um período de cinco dias e no final foram avaliados o comprimento de raiz, as concentrações de silício, alumínio e cálcio na parte aérea e nas raízes e o índice mitótico de células meristemáticas das raízes. O silício reduziu o efeito tóxico do alumínio no crescimento radicular dos genótipos de milho independente da sensibilidade ao alumínio.

To verify the relation between aluminum and silicon in the growth of two maize genotypes resistant and sensitive at toxicity aluminum was carried out in the greenhouse a bioensaio involving the treatments presence and absence of aluminum and silicon in corn genotypes. The treatments were compound for solutions of 2.0 mmol L-1 calcium (CaCl2) without and with aluminum (0.025 mmol L-1 AlCl3) and silicon (0.14 mmol L-1, to part solution SiO2). The experiment was carried out for five days and for assess the treatments effect were evaluated root length, silicon, aluminum and calcium concentrations in the shoots and in the roots and the mitotic index of meristematic cells of roots. Silicon reduced the toxic effect of aluminum in corn genotypes as evaluated through root length.