Antonio Celso Dantas Antonino

Caatinga, the Brazilian dry tropical forest: can it tolerate climate changes?

Our review focuses on the projections of climate change in the Brazilian semiarid region, the Caatinga, based on recent publications about global climate change and biology. We found several vulnerable points in the initial estimates, the main one being that the data were collected and analyzed without a multidisciplinary knowledge. This review discusses several studies that show the current knowledge in many semiarid regions around the world. Some of these studies argue for the increase in vegetation greenness responses even under severe and prolonged drought, based on the high resilience the Caatinga native species show under severe drought conditions over the years. Additionally, we include in this review recent data produced by our group on key ecophysiological variables under drought conditions. We also show successful examples of deforested areas recovery in the semiarid region of the Central America. It is critical that the recovery of semiarid areas is coupled with the implementation of socio-environmental policies, engaging the local population and providing subsidies for life wealth improvement. These are key aspects for a long-term recovery and conservation of the Brazilian dry tropical forest.

Water budget in a soil with food crops in the semi-arid region of northeast Brazil.

Considering that water is a limiting factor and there are few studies on water balance in the semi-arid Northeastern Brazil, an experiment was established at Coxixola, PB, Brazil, with four treatments (corn and beans crops, bare soil and soil covered with mulch), in plots of 7.7 x 10 m and plant spacing of 1.1 x 1.0 m. Rainfall, evaporation (Class A tank) and soil water (neutron probe) were monitored. Low (212 mm) and irregular rainfall resulted in water deficit towards the final period of the experiment and was responsible for the low water use efficiencies and low productivity of corn (grain and total biomass, 282 and 1141 kg ha-1) and beans (166 and 558 kg ha-1). Bare soil and mulch had similar results, with high water losses, 1.57 and 1.48 mm day-1, respectively, and only small increases in stored soil water (28 and 35 mm, respectively) were observed at the end of experiment. Mulching does not seem to be a promising practice in the area due to this small increase and the difficulty in obtaining plant residues.

Residual N and P fertilizer effect and fertilizer recovery on intercropped and sole-cropped corn and bean in semiarid northeast Brazil

The effects of a single 15N and P fertilizer application (16 and 12 kg ha–1) on intercropped and sole-cropped corn and beans was followed over three consecutive years. Grain (0.1–0.9 ton ha–1 yr–1) and straw productions (0.2–2.5 ton ha–1 yr–1) were limited by rainfall and showed small responses to fertilizer. In the first year, plant N uptake was more than twice the fertilizer amounts, while P uptake was less than half the fertilizer amounts. Plant N derived from fertilizer was low (9–19%). Sole corn took up more (34%) than beans (16%) and the combined intercrop (26%) and also had higher recovery of fertilizer in the soil than single beans (50% against 28%). The distribution of fertilizer N and P in the soil showed a similar pattern in all treatments, with a high concentration around the application spot and decreasing concentrations at greater distances and above and below this point. Total P increases in a soil volume 10 cm around the application spot corresponded to 60% of the amount applied. Fertilizer contributions to the second crop were < 3% of total plant N and represented <6% of the applied amount. Therefore, the residual fertilizer effect on production was attributable to P. The patterns of fertilizer N and P distribution in the soil remained similar but N recoveries decreased 14–18%. Despite low rainfall, low productivities and reasonable proportions of fertilizer N remaining in the soil, the residual effects of the applied fertilizer N were too low to justify a fertilizer recommendation based on economic returns on the investment.

Análise quantitativa de parâmetros biofísicos de bacia hidrográfica obtidos por sensoriamento remoto

The objective of this work was to quantitatively evaluate the biophysical parameters, obtained by remote sensing, for the range area of the Tapacura River Basin, in Pernambuco state, Brazil. Landsat 5‑TM images of 7/10/1989, 7/6/2005, and 8/29/2007 were used. The images were registered with a polynomial geometric correction of first order. Radiometric calibration, reflectance, transmittance and planetary albedo were calculated and, subsequently, thematic maps of surface albedo, surface temperature and enhanced vegetation index (EVI) were generated. The surface albedo showed increasing average values between the 1989 and 2005 images, which indicates the urban territorial expansion. The image of 8/29/2007 showed the highest land surface temperature, followed by the temperatures showed in the images of 7/10/1989 and 7/6/2005, and the highest values were those of the urban networks. The 1989 image showed the highest average value for EVI, which indicates that there was a higher vegetation presence in that date.

Condutividade hidráulica não saturada de um podzólico amarelo da zona da mata norte de Pernambuco

The determination of the hydraulic conductivity of a Yellow Podzolic soil was carried out during an experiment in a plot measuring 3.5 m x 3.5 m, at the Estacao Experimental de Itapirema, Goiana, in the State of Pernambuco, Brazil. The internal drainage method was used to obtain the hydraulic conductivity (K(q)) as a function of soil water content, in the three main horizons of the soil. In relation to the methodological aspects, processing of data from internal drainage experiments, including the initial phase of fast drainage, the adjustment of the required parameters, it is necessary to use functions that reproduce the distinct transition between the fast and slow phases of drainage. From all five tested functions, those of power, sum of two exponentials and sum of three exponentials, especially this last one, adjusted well to this distinct transition. Three main horizons of the Yellow Podzolic soil were investigated for hydraulic conductivity. The sandy A horizon, with large pores, has a high conductivity while the BA horizon, with massive structure and few visible pores, has a low infiltration rate. The hydraulic dynamics of the Bt horizon is more complex due to its heterogeneity. The precise characterization of the A and BA horizons, which are the most important to agriculture and soil conservation, makes it possible to elaborate numeric simulation models of the water transference process in the surface horizons of this type of soil.

Reactivity of the plant growth regulator paclobutrazol (cultar) with two tropical soils of the northeast semiarid region of Brazil.

The reactivity of paclobutrazol (PBZ, a plant growth retardant) with a Yellow Ultisol and a Vertisol from the semiarid northeast region of Brazil was evaluated through batch sorption experiments and modeling. Although not instantaneous, the sorption kinetic of PBZ (pure and formulated) was fast (a few hours) in both soils. The sorption kinetics were well described by a second-order (dS(t)/dt=k(2)(S(e2)-S(t))(2)) but not by a first-order model. The sorption isotherms were found to be linear and the calculated K(D) values were 8.8 +/- 0.11 and 7.4 +/- 0.2 L kg(-1) for pure PBZ in the Ultisol and the Vertisol, respectively. The corresponding K(OC) values were 1275 +/- 34 (logK(OC) = 3.11) and 1156 +/- 49 (logK(OC) = 3.06) L kg(-1), respectively. Considering the very different texture of the two soils and the similar K(OC) values determined, these results showed that in both soils, the sorption of PBZ is dominantly controlled by organic matter, although some interactions of PBZ with iron oxides (goethite) were observed in the Ultisol. Based on these sorption parameters a low leachability potential of PBZ in soils is anticipated, as they correspond to a groundwater ubiquity score (GUS) ranging from 2.0 to 2.7, i.e., moderately to not mobile, in contradiction with the actual groundwater situation in Brazil. This work stresses the need to evaluate and predict the risk associated with aquifer contamination by this widely used plant growth regulator.

Transporte do paclobutrazol em colunas de solos

Paclobutrazol (PBZ) is a post-emergence plant growth regulator used in agricultural systems with the objective of vegetative control growth, thereby increasing the reproductive capacity of the plant. This growth regulator remains active in the soil for several years being detrimental to subsequent tillage and contamination of groundwater through leaching. The objective of this work was to study the mechanisms involved in the transport and sorption of PBZ in an Ultisol and a Vertisol, both of the San Francisco Valley, Brazil. Column breakthrough experiments were performed with a water tracer (Bromide) and with PBZ at 0.4 e 1.6 cm3.min-1 in the two soils. Hydrodispersive parameters of both soils were obtained by fitting the tracer breakthrough curves (BTC) with the convection-dispersion (CDE) model, whereas the parameters of PBZ reactive transport were obtained with the CDE-2 sorption sites model, through the CXTFIT code. PBZ presents a lower retardation factor in the Vertisol than in the Ultisol. The water flow was found to strongly affect PBZ mass balance, mainly because of sorption/desorption hysteresis, suggesting partial irreversible sorption of the chemical. The two sites model fitted well the tracer and PBZ breakthrough curves. The results showed that PBZ transport is strongly influenced by its interactions with the soil matrix through rate-limited sorption. The determined transport parameters indicate that PBZ applied to the two tropical soils cultivated with Mango presents an important leaching potential and contamination risk of the groundwater of the San Francisco Valley.

DETERMINAÇÃO DA CONDUTIVIDADE HIDRÁULICA E DA SORVIDADE DE UM SOLO NÃO-SATURADO UTILIZANDO-SE PERMEÂMETRO A DISCO

Dois metodos, utilizando permeâmetros a disco, foram usados para medir a sorvidade e a condutividade hidraulica em tres horizontes de um solo de Santa Maria da Boa Vista, Pernambuco, utilizando-se potenciais de fornecimento de agua de 0, -2,5, -5 e -10 cm de agua. No primeiro metodo, a condutividade hidraulica foi obtida atraves de estimativas da sorvidade e do fluxo estacionario, utilizando-se apenas um permeâmetro. No segundo, as medidas da sorvidade e da condutividade hidraulica foram feitas utilizando-se valores dos fluxos estacionarios, obtidos a partir de dois permeâmetros de diferentes raios. Esse segundo metodo apresentou resultados mais consistentes dos tempos ¾ gravitacional e geometrico ¾, e do raio caracteristico de poros que o primeiro metodo. A sorvidade foi tao importante quanto a condutividade hidraulica para caracterizar o processo de infiltracao. A reducao brusca dos valores dos raios caracteristicos de poros do horizonte A2/B, com mudancas no potencial de fornecimento de agua, revelou a heterogeneidade da estrutura deste horizonte, permitindo identificar a influencia dos volumes argilosos compactados sobre o processo de infiltracao.Sorptivity and hydraulic conductivity were determined by two methods using disc permeameters. Infiltration experiments were carried out on three horizons of a representative soil of the semi-arid region, located in Santa Maria da Boa Vista, State of Pernambuco, Brazil. Water was supplied to this soil by disc permeameters at potentials of 0, -2.5, -5 and -10 cm of water. In the first method, hydraulic conductivity was measured using estimates of sorptivity and steady state fluxes. In the second, sorptivity and hydraulic conductivity were determined using measurements of steady state fluxes with two disc permeameters of different radius. Results of the second method, regarding characteristic times and characteristic pore radius, were more consistent than those of the first one. Sorptivity was as important as hydraulic conductivity to characterize the infiltration process. The abrupt reduction of the characteristic pore radius in the horizon A2/B with changes in the water supply potential indicates the structure heterogeneity of this horizon and allows the identification of the role of the clay compact volumes on the infiltration process.

BALANÇO HÍDRICO EM NEOSSOLO REGOLÍTICO CULTIVADO COM BRAQUIÁRIA (Brachiaria decumbens Stapf)

Um dos principais fatores de producao para as culturas e a disponibilidade de agua no solo, de forma que a quantificacao das entradas e saidas dessa agua, por meio do metodo do balanco hidrico, pode ser um instrumento valioso para melhorar o manejo dado a ela. Desse modo, este trabalho teve como objetivo analisar os componentes do balanco hidrico (variacao do armazenamento de agua no solo, drenagem, ascensao capilar e evapotranspiracao) e o perfil do sistema radicular em Brachiaria decumbens, em nove meses do ano de 2011 (marco a novembro). Tambem foi avaliada a razao entre evapotranspiracao (ET) e evapotranspiracao de referencia (ETo). Esta pesquisa foi realizada na fazenda Riacho do Papagaio, em Sao Joao, na mesorregiao do Agreste do Estado de Pernambuco, onde foram instalados sensores automatizados para medicao da umidade volumetrica do solo nas profundidades de 0,10; 0,20; 0,30; e 0,40 m. A precipitacao pluvial foi monitorada por meio de um pluviografo automatizado instalado numa torre no centro da area. Para a determinacao da drenagem e da ascensao capilar, foram realizados ensaios de infiltracao para obtencao da condutividade hidraulica do solo, alem da determinacao da curva de retencao, em laboratorio. A ET foi obtida como termo residual da equacao do balanco hidrico e a ETo, pelo metodo de Penman-Monteith. O volume de controle utilizado para o balanco hidrico teve como limite superior a superficie do solo e como limite inferior a profundidade de 0,30 m. Tambem foi analisado o perfil do sistema radicular da braquiaria, mensalmente. Observou-se que os periodos com elevadas pluviosidades resultaram num maior armazenamento de agua no solo, em maiores valores de drenagem e de evapotranspiracao. O fluxo de agua no limite inferior (z = 0,30 m) do solo ocorreu somente no sentido descendente, sendo perdidos 103,14 mm de agua por drenagem, o que representa 24,12 % de toda a agua fornecida a cultura. A evapotranspiracao total da Brachiaria decumbens Stapf foi de 324,96 mm, com valor medio de 1,2 mm d-1. A pastagem sofreu estresse hidrico, em quase todo periodo experimental, tendo em vista os valores da relacao ET/ETo serem inferiores a 1. Os baixos valores da razao ET/ETo indicaram a necessidade de se realizar irrigacao para se diminuir o deficit hidrico. No entanto, em razao dos elevados valores de drenagem, recomendam-se praticas de manejo que aumentem a retencao de agua pelo solo.

Telhado verde: desempenho do sistema construtivo na redução do escoamento superficial

Na atualidade, metade da populacao mundial reside em centros urbanos, e os impactos negativos decorrentes de eventos hidrologicos tem sido recorrentes, visto que, com o aumento da impermeabilizacao, ha reducao nas taxas de infiltracao, levando a diminuicao da recarga dos aquiferos e a diminuicao do escoamento de base. Consequentemente, o escoamento superficial e intensificado, aumentando a frequencia e a magnitude dos picos de cheia, o que pode resultar na ocorrencia de inundacoes, especialmente nos centros urbanos. Por outro lado, verifica-se ja ha algum tempo o emprego de telhados verdes em varias partes do mundo para contribuicao arquitetonica estetica e melhoria do conforto ambiental. Alem desses enfoques, esta solucao vem sendo tratada, tambem, como uma estrutura de controle do escoamento pluvial. Considerando caracteristicas reais e os dados obtidos em campo, foi realizada a simulacao da dinâmica da agua em dois telhados verdes, com o emprego do codigo computacional Hydrus-1D, para diferentes intensidades de precipitacao, visando verificar o desempenho desse sistema construtivo na reducao do escoamento superficial. Os hidrogramas de saida mostraram-se qualitativamente adequados e quantitativamente coerentes e pode-se concluir que os telhados verdes constituem importantes dispositivos no amortecimento do escoamento superficial oriundo dos telhados, para as condicoes climaticas da area investigada.