Degradation of Caatinga biome has created desertification processes in several areas, inducing big microclimate and surface changes. Therefore, it is fundamental develop research methods capable of identifying areas under degradation process. Satellite images in different spatial, temporal, radiometric and spectral resolutions are being used to monitor big areas from several biomes worldwide. The objective of this study was to evaluate and quantify the degree of degradation and preservation of the Caatinga biome, using geoprocessing methods and remote sensing products , using surface data and Landsat-8 images for 2013, 2014 and 2015. Remote sensing methods were used to estimate the Normalized Difference Vegetation Index (NDVI), surface albedo (α) and Moving Standard Deviation Index (MDSI). The results showed that the vegetation indexes and the techniques of degradation and change detection satisfactorily identified the behavior of the surrounding vegetation in the study area, standing out as good indices for degradation processes in the semiarid. It was concluded that change detection and classification by decision tree methods were efficient in the identif ication of anthropized areas during the experimental period.
Determining actual crop evapotranspiration (ETa) is paramount for irrigation management. The principal measurement methods and physical models generally require crop and weather data that are not readily available. We determined the crop coefficient (Kc) of sweet oranges during the initial development stage and evaluated the performance of the Poulovassilis semi-empirical model coupled with a simple soil water balance for estimating the ETa. The ETa was inferred from the variation in the soil water content over time, measured by time-domain reflectometry. In the Poulovassilis model, the ETa is obtained by multiplying the crop evapotranspiration (ETc) by an adjustment coefficient (ca), which accounts for a reduction in the evapotranspiration caused by soil water depletion. Soil water storage was obtained using the daily and 10-day soil water balances, computed by considering inputs and outputs of water from the system. The empirical parameter, ca, was determined using inverse modeling. The optimal ca value obtained through inverse modeling was 0.05 and 0.03 for the daily and 10-day soil water balances, respectively. The model performed better for the daily soil water balance than the 10-day balance, with performance comparable with the other ETa models. Average Kc during the sweet orange initial crop stage was 0.85.
AGRONOMIA -FITOTECNIA Caracterização e produtividade de cultivares de milho doce em fileiras duplas sob diferentes espaçamentos entre plantas Characterization and yield of double-row sweet corn cultivars under different plant spacings
O Instituto de Conservação Internacional do Brasil estima uma redução da Caatinga de 90% no estado de Alagoas. Logo, o reflorestamento surge como uma medida para recuperação destas áreas. No entanto, sabe-se que a época de coleta das sementes de plantas nativas é muito variável. Dessa forma, o armazenamento de sementes surge como um processo imprescindível em programas de reflorestamento. O objetivo deste estudo foi verificar a interferência de um período de armazenamento de seis meses em diferentes embalagens (plástico grosso e papel kraft) e dois locais (laboratório e condições controladas de temperatura e umidade) sob sementes de Pau Ferro. O trabalho foi realizado no Laboratório de Fisiologia Vegetal do Campus Arapiraca da Universidade Federal de Alagoas. As variáveis estudadas visando obter a qualidade das sementes após o armazenamento foram: porcentagem de germinação, índice de velocidade de germinação, tempo médio de germinação, plântulas normais, anormais e sementes dormentes e mortas. Utilizou-se o delineamento inteiramente casualizados na montagem dos testes de germinação, com oito repetições, sendo 25 sementes por repetição, os dados obtidos foram submetidos a análise de variância por programa estatístico e quando significativos pelo teste F (p<0,05), tiveram suas médias comparadas pelo teste de Tukey (p<0,05). De maneira geral, o ambiente sob condições controladas de temperatura e umidade mostrou-se superior ao ambiente laboratorial. O plástico grosso mostra-se como uma alternativa mais viável para o acondicionamento de sementes e armazenamento.
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