Suspended sediment and bedload discharges in sand-bed rivers shape semi-arid landscapes and impact sediment delivery from these landscapes, but are still incompletely understood. Suspended sediment and bedload fluxes of the intermittent Exu River, Brazil, were sampled by direct measurements. The highest suspended sediment concentration observed was 4847.4 mg L-1 and this value was possibly associated with the entrainment of sediment that was deposited in the preceding year. The bedload flux was well related to the stream power and the river efficiently transported all available bedload with a mean rate of 0.0047 kg m-1 s-1 , and the percentage of bedload to suspended sediment varied between 4 and 12.72. The bed sediment of Exu River was prone to entrainment and showed a proclivity for transport. Thus, sand-bed and gravel-bed rivers of arid environments seem to exhibit the same mobility in the absence of armour layer.

Conservation systems for less soil movement and when associated with previous crops may reduce the effects of soil compaction. The objective of this work was to evaluate soil mechanical resistance penetration (MRP) in different cropping systems associated with previous corn crop after fifteen years. The experimental design was composed of experimental strips with subdivided plots, combining three soils management systems: CC- conventional cultivation, MC- minimum cultivation and NT- no-tillage, and four species of crops antecedent to maize for the production of commercial ears of green corn. In the determination of soil MRP, the electronic penetrometer (FALKER model SoloTrack PLG 5200) was used, with readings up to a depth of 400 mm. The results showed that there was a significant effect on the MRP values of the soil when submitted to the different cropping systems and previous crops at the end of fifteen years. The lowest MRP values were located in the superficial layers in the CC and MC. The NT cultivar system showed higher MRP values, at depth 0-100 mm. At conditions of tableland, after fifteen years, it was observed that the NT system provides better corn productivity levels combined with lower MRP values along the profile.

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This study evaluates the insolation calculations and their analysis soon after plotting their respective local historical average graph from 1962 to 2019 for some municipalities in Pernambucana. Monthly and annual insolation data for the study period was obtained from the National Institute of Meteorology.After homogenization, data consistency and failure filling of each series, the spatial and temporal insolation densities were performed for municipalities like Arcoverde, Cabrobó, Garanhuns, Ouricuri, Petrolina, Recife, Surubim and Triunfo. The average and its historical average were calculated and appropriate analysis was performed. The spatial distribution of the monthly insolation data showed great variability for the months studied, ranging from approximately 3 to 4 hours. The median values ​​ most likely occured during the months for the eight municipalities under study. The municipality of Garanhuns presented higher insolation values ​​than Petrolina. Comparing the values ​​obtained in this study with the values ​​of the Solarimetric Atlas of Brazil, indicated a good similarity of the recorded data.

Studies assessing technologies to design riparian strips using plant covers, based on sediment yield in river basins, are required for environmental protection. The removal of semi-shrubby, native vegetation in the Brazilian semiarid region, has contributed to the degradation of semiarid basins. The aim of this study was to design a riparian strip for the Jacu River in the semiarid region of Pernambuco as a function of sediment yield. Experiments were conducted during the years 2008-

Data regarding trace element concentrations and fluxes in suspended sediments and bedload are scarce. To fill this gap and meet the international need to include polluted rivers in future world estimation of trace element fluxes, this study aimed to determine the trace element fluxes in suspended sediment and bedload of an environmentally impacted river in Brazil. Water, suspended sediment, and bedload from both the upstream and the downstream cross sections were collected. To collect both the suspended sediment and water samples, we used the US DH-48. Bedload measurements were carried out using the US BLH 84 sampler. Concentrations of Cd, Cr, Cu, Fe, Mn, Ni, Pb, and Zn were determined by inductively coupled plasma (ICP-OES). As and Hg were determined by an atomic absorption spectrophotometer (AA-FIAS). The suspended sediments contributed more than 99 % of the trace element flux. By far Pb and to a less extent Zn at the downstream site represents major concerns. The yields of Pb and Zn in suspended sediments were 4.20 and 2.93 kg km(2) year(-1), respectively. These yields were higher than the values reported for Pb and Zn for Tuul River (highly impacted by mining activities), 1.60 and 1.30 kg km(2) year(-1), respectively, as well as the Pb yield (suspended + dissolved) to the sea of some Mediterranean rivers equal to 3.4 kg km(2) year(-1). Therefore, the highest flux and yield of Pb and Zn in Ipojuca River highlighted the importance to include medium and small rivers-often overlooked in global and regional studies-in the future estimation of world trace element fluxes in order to protect estuaries and coastal zones.

RESUMOA serapilheira é uma das principais vias de retorno de nutrientes no sistema planta-solo-planta e sua determinação permite analisar a reestruturação de ambientes florestais antropizados. O conhecimento da produção da serapilheira é fundamental para determinar o potencial de regeneração de uma área por meio do aporte e ciclagem dos nutrientes. Objetivou-se neste estudo quantificar a produção de serapilheira e o aporte de carbono e dos nutrientes da fração foliar em áreas de ocorrência de Neossolos Quartzarênicos, com vegetação em diferentes estágios de regeneração, no Parque Nacional Serra de Itabaiana, em Sergipe. Em cada uma das áreas de Areias Brancas Abertas (ABA), Areias Brancas Intermediárias (ABI) e Areias Brancas Fechadas (ABF) instalaram-se coletores nos quais a serapilheira foi coletada mensalmente, de janeiro a dezembro de 2011. Em subamostras da serapilheira foram determinadas as quantidades de carbono (C), nitrogênio (N) e fósforo (P). Com a ação do fogo nas áreas de Areias Brancas do Parque da Serra de Itabaiana, ficou evidente que o mesmo altera o estado de equilíbrio dinâmico alcançado pelo ecossistema, logo, as condições nutricionais do solo são modificadas. Os acúmulos de C, N e P não apresentaram variação sazonal significativa, de acordo com a produção da serapilheira em cada área estudada, sendo que a área ABF proporcionou os maiores acúmulos destes elementos ao longo do período de avaliação. Palavras-chave: Mata Atlântica; perturbação antrópica; matéria orgânica; processo de regeneração. ABSTRACTLitter is a major route of return of nutrients in the system plant-soil -plant and its determination allows to analyze the restructuring of anthropogenic forest environments. Knowledge of litter production is a critical in determining the potential for regeneration of an area through the intake and nutrient cycling. This study aimed to quantify the litter production and the carbon contribution and leaf fraction nutrients in areas of occurrence of Quartzipsamments with vegetation at different stages of regeneration in National Park Serra de Itabaiana in Sergipe, state. In each of the areas of Areia Branca Aberta (ABA), Areia Branca Intermediaria (ABI) and Areia Branca Fechada (ABF), settled collectors where the litter was collected monthly from January to December 2011. In the litter subsamples amounts of carbon (C), nitrogen (N) and

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