ESTIMATIVA DE PARÂMETROS BIOFÍSICOS E EVAPOTRANSPIRAÇÃO REAL NO SEMIÁRIDO PERNAMBUCANO UTILIZANDO SENSORIAMENTO REMOTO  FREDERICO ABRAÃO COSTA LINS1; DIEGO CEZAR DOS SANTOS ARAÚJO2; JHON LENNON BEZERRA DA SILVA2; PABRÍCIO MARCOS OLIVEIRA LOPES3; JOSÉ DIORGENES ALVES OLIVEIRA2 E ANDREY THYAGO CARDOSO SANTOS GOMES DA SILVA1 1 Mestrandos em Engenharia Agrícola – Departamento de Engenharia Agrícola, Universidade Federal Rural de Pernambuco (UFRPE). Av. D. Manoel de Medeiros, SN; Dois Irmãos, Recife, Pernambuco, Brasil; CEP: 52171-900. E-mail: frederico_acl@hotmail.com (Autor para correspondência); andreythyago@gmail.com; 2 Mestres em Engenharia Agrícola e Doutorandos – Departamento de Engenharia Agrícola da UFRPE. E-mail: diego@agro.eng.br; jhonlennoigt@hotmail.com; josediorgenes@gmail.com; 3 Doutor em Sensoriamento Remoto; Professor adjunto da Universidade Federal Rural de Pernambuco (UFRPE), Recife, Pernambuco, Brasil. E-mail: pabriciope@gmail.com.   1        RESUMO Objetivou-se estimar e avaliar a distribuição espaço-temporal de parâmetros biofísicos e a evapotranspiração real diária para o município de Arcoverde, Pernambuco, durante estações seca e chuvosa, utilizando imagens orbitais do satélite Landsat-8 de sensores OLI/TIRS, para as datas de passagem: 14/01/2015 e 02/12/2016, processadas com o algoritmo SEBAL. Foram gerados os seguintes mapas temáticos: Índice de Vegetação da Diferença Normalizada (NDVI), Índice de Área Foliar (IAF), albedo e temperatura de superfície (Ts), saldo de radiação instantâneo (Rn) e evapotranspiração real diária (ETr). O NDVI foi maior em janeiro de 2015 e o albedo e Ts foram maiores em 2016 (0,23 e 37,44 °C), ao passo que em 2015, os valores foram de 0,20 e 34,11 °C, relacionando-se às condições meteorológicas e uso do solo. O Rn variou de 520,06 a 540,22 W m-2 nos dois anos e, para a ETr, verificou-se a maior média em janeiro de 2015 (3,41 mm dia-1), devido ao maior NDVI e precipitações, evidenciando maior disponibilidade de água na vegetação e no solo. As técnicas de sensoriamento remoto possibilitaram o monitoramento do município de Arcoverde-PE, determinando os parâmetros biofísicos nos diferentes usos do solo, predizendo os processos futuros de degradação e consequente desertificação na localidade. Palavras-chave: caatinga, vegetação, monitoramento ambiental, uso do solo, agrometeorologia.  LINS, F. A. C.; ARAÚJO, D. C. dos S.; SILVA, J. L. B. da; LOPES, P. M. O.; OLIVEIRA, J. D. A.; SILVA, A. T. C. S. G. daBIOPHYSICAL PARAMETERS ESTIMATE AND ACTUAL EVAPOTRANSPIRATION IN THE SEMIARID REGION OF THE STATE OF PERNAMBUCO, BRAZIL, USING REMOTE SENSING                                                     2        ABSTRACT The purpose of this paper is to estimate and evaluate the spatial-temporal distribution of biophysical parameters and the actual daily evapotranspiration index for the municipality of Arcoverde, Pernambuco, during the dry and rainy season, using orbital images from the Landsat-8 satellite and OLI/TIRS sensors for the following dates in which the satellite passed over the region: 01/14/2015 and 02/12/2016, processed using the SEBAL algorithm. The following thematic maps were generated: Normalized Difference Vegetation Index (NDVI), Leaf Area Index (LAI), albedo and surface temperature (Ts), Net radiation (Rn) and daily reference evapotranspiration (ETr). The NDVI was higher on January 2015 and the albedo and Ts were higher in 2016 (0.23 and 37.44 °C), whereas in 2015, the values were 0.20 and 34.11 °C, related to the meteorological conditions and the land use. The Rn ranged from 520.06 to 540.22 W m-² in two years of study and, for the ETr, the highest average was recorded on January 2015 (3.41 mm day-1), due to the higher NDVI and rainfall index, evidencing greater availability of water in the vegetation and soil. The remote sensing techniques allowed the monitoring of the municipality of Arcoverde, determining the biophysical parameters in the different uses of soil, anticipating the future degradation processes and consequent desertification in the place. Keywords: caatinga, vegetation, environmental monitoring, use of the soil, agrometeorology.

The aim of this study was to monitor and evaluate the Caatinga vegetation cover in a municipality from the Brazilian semi-arid through of the spatial-temporal distribution of vegetation indexes by remote sensing. The study was developed using six satellite images which covers the municipality of Iguatu, Ceará. Thematic maps of the SAVI and LAI vegetation indexes were developed and evaluated by descriptive statistics and according to their spatial-temporal variability. Maps of the SAVI and LAI showed high heterogeneity in the spatial-temporal distribution pattern, classified as medium variability (CV = 35 to 57%) and high variability (CV = 63 to 104%), respectively. The indexes provided answers as to the land uses behavior pattern, highlighting conditions of changes in the Caatinga vegetation. In general, the SAVI and LAI indexes showed a low condition of the vegetal biomass over time, a typical spatial-temporal dynamics characteristic in the dry season of the semi-arid. The vegetation indexes detected a remarkable sensitivity of the Caatinga vegetation to the presence and/or absence of rainfall, owing a high resilience capacity in response to intense rainfall. The semi-arid region becomes more vulnerable due to the intensification of drought events.

Abstract. Hydrological studies in small basins are essential for investigating the role of distinct processes on water resources conservation and to assess the impact of the natural ecosystems on improving water security especially in semiarid environments. In Brazil, the cooperative hydrological Network REHISA (“REde de HIdrologia do SemiÁrido”) comprises hydrologists from several universities of Brazil, focusing on field measurements, monitoring and modeling activities in well instrumented experimental rural catchments located at different regions and biomes in Semiarid environment. Water scarcity is a common aspect among the catchments, as well as risks of soil and water degradation. The objective of this work is to present assessments of near surface soil moisture spatial-temporal distribution, and to evaluate the impact of soil conservation techniques in reducing runoff, using small-scale experimental plots in a representative catchment of the Pernambuco State, Brazil. The study catchment is located in Alto Ipanema River Basin (AIRB) (with an area of 150 km2), which is located at the semiarid region of the São Francisco River (area of 641 000 km2). Soil and water monitoring was performed in experimental plots with different soil cover conditions (Bare soil plots; Plots with natural cover – Caatinga Biome vegetation; Plots with cactus Palma barriers; and Plots with mulch cover – Dry grass mulch at 4 t ha−1), where probes were installed for high resolution soil moisture assessment. In addition, regular soil moisture monitoring campaigns were conducted at 7 different locations, using a capacitance probe, with arboreal and shrub Caatinga vegetation, pasture and bare soil, predominantly Brachiaria decumbens. Mulch cover runs close to the Caatinga cover, but still with higher runoff generation, and presenting lower soil moisture temporal mean values. Caatinga was highly effective in terms of soil and water conservation at the small basin scale for both the dry and the wet season, resulting in a positive nexus between vegetation and water availability at the region.

The High Ipanema watershed is located in a semiarid region and because of this, becomes more vulnerable and susceptible to the effects of environmental changes and the degradation process, it has serious economic and socio-environmental implications. In recent years with the advancement of remote sensing based on satellite imagery or other platforms, it has become possible to monitor different and large areas of the various biomes in the world. The objective of this study was to identify changes in the vegetation cover conditions in the Alto Ipanema watershed, using spectral analyzes of Landsat-8 OLI / TIRS satellite images, using remote sensing techniques. Landsat-8 OLI / TIRS satellite images were obtained from the United States Geological Survey – USGS, on 10/12/2013, 14/01/2015 and 12/08/2016, where they were processed from ERDAS IMAGINE® Software, version 9.1. The thematic maps of biophysical parameters were processed by ArcGis® 10.2.2 Software. With the biophysical parameters analyzed, it was found that the northwest portion of the watershed presents a considerable area of exposed soils with indication of a high degree of susceptibility to degradation and that the biophysical parameters evaluated by the SEBAL algorithm are efficient in understanding the dynamics of spatial and temporal areas of semiarid environments.

The objective was to verify possible modifications of the soil structure and the pattern of the spectral response of pasture vegetation cover to animal trampling. The study was carried out on a farm in the Agreste region of Pernambuco, Brazil in an area with continuous grazing by heifers. Soil samples were collected at 36 regular points, before and after the grazing period, where the physical properties of the soil were determined at a 0.00—0.10 m depth. Before and after grazing, images of the Sentinel-2A satellite were also obtained to observe the pasture vegetation response pattern over time through Vegetation Indexes. The soil attribute data were submitted to multivariate factorial analysis. The vegetation index maps were evaluated for spatial variability. The results showed that after the grazing, there was a significant change in soil attributes and pasture, which can indicate possible degradation processes.