Impacts of long-term acid deposition on soil and water chemistry are of particular concern in the Great Smoky Mountains National Park (GRSM), receiving some of the highest acid deposition rates in the eastern United States and limited by inadequate acid buffering capacity. In the GRSM, the Noland Divide watershed (NDW) has been monitored since 1991 for water chemistries of precipitation, throughfall, soil, and stream. The impacts of long-term acidic deposition on stream water quality in the NDW were investigated through: 1) development of an ion input-output budget; 2) analysis of trends and seasonal patterns for major ions; 3) comparison of net export rates between baseflow and stormflow periods; and 4) characterization of soil chemistry and transport properties for various potential acid deposition scenarios. Between 1991 and 2006, throughfall deposition remained unchanged and consisted of 1,735 eq ha-1 yr-1 of SO42-, 863 eq ha-1 yr-1 of NO3-, and 284 eq ha-1 yr-1 of NH4+. Net retention of sulfate was estimated at 61% being controlled by soil adsorption, and inorganic nitrogen was retained at 32% presumably due to plant uptake. Nitrogen retention increased by 44.30 eq ha-1 yr-1 over the study period. Besides deposition, soil acidity was increased by nitrification and precipitation-driven desorption of previously accumulated sulfate. To neutralize soil acidity, Ca2+, Mg2+ and Na+ were depleted from NDW by 77, 46 and 66 eq ha-1 yr-1, respectively. Due to the continuous addition of acidity, base saturation in soil was reduced to 4% at present. Mobilization of aluminum and other metals (Mn and Zn) may be enhanced by these geochemical processes, potentially causing toxic conditions to fish and other biota in the GRSM streams. Impacts of acidic deposition on streams were confirmed by measured stream pH below 6 and acid neutralizing capacity below 0.01 meq L-1. During stormflows pH and ANC depressions occurred primarily due to increases in sulfate transport, leading to episodic acidification events. This study provides new information on hydrological and biogeochemical processes that regulate stream acidification events in the southern Appalachian region, supporting improved management strategies for GRSM streams.

Pollutants follow various subsurface and surface water pathways from sources within a catchment to its outlet and may cause detrimental effects on downstream water quality and ecosystems. Along their different transport pathways through a catchment, pollutants may be attenuated subject to different physical and biogeochemical processes. In this thesis, physical process effects on such catchment-scale pollutant transport and attenuation, resulting coastal pollutant loading and its efficient abatement are investigated. For this purpose, pollutant transport-attenuation is modeled both generically using a Lagrangian Stochastic Advective-Reactive (LaSAR) approach and site specifically for the Swedish Norrström basin using the GIS-based dynamic nitrogen transport-attenuation model POLFLOW. Furthermore, the role of such modeling for catchment-scale pollutant abatement is also investigated by use of economic optimization modeling. Results indicate that appropriate characterization of catchment-scale solute transport and attenuation processes requires accurate quantification of the specific solute pathways from different sources in a catchment, through the subsurface and surface water systems of the catchment, to the catchment outlet. The various physical processes that act on solute transported along these pathways may be quantified appropriately by use of relevant solute travel time distributions for each water subsystem that the pathways cross through the catchment. Such distributions capture the physical solute travel time variability from source to catchment outlet and its effects on reactive pollutant transport. Results of this thesis show specifically that neglect of such physical solute travel time variability in large-scale models of nitrogen transport and attenuation in catchments may yield misleading model estimates of nitrogen attenuation rates. Results for nitrogen abatement optimization in catchments further indicate that inefficient solutions for coastal nitrogen load reduction may result from simplifying physical transport assumptions made in different catchment-scale nitrogen transport-attenuation models. Modeling of possible future nitrogen management scenarios show also that slow nitrogen transport and reversible mass transfer processes in the subsurface water systems of catchments may greatly delay and temporally redistribute coastal nitrogen load effects of inland nitrogen source abatement over decades or much longer. Achievement of the national Swedish environmental objective to reduce the anthropogenic coastal nitrogen loading by 30% may therefore require up to a 40% reduction of both point sources, for achieving a fast coastal load response, and diffuse sources, for maintaining the coastal load reduction also in the long term. / QC 20100908

Chemical dynamics in the vadose zone are poorly understood due to the transient nature of chemical and hydrologic conditions, but are nonetheless critical to understanding contaminant fate and transport. This work explored the effects of soil structure (i.e. layers, lenses) on linked geochemical, hydrological, and microbiological processes under changing hydrologic conditions (e.g. rainfall, introduction of groundwater, and fluctuating water table heights). A homogenized medium-grained sand, homogenized organic-rich loam and a sand-over-loam layered column were constructed for the first series of experiments. The second series of experiments employed two soil columns with lenses that were packed identically with sterilized and untreated sediments. Each consisted of two lenses of organic-rich loam in a medium-grained sand matrix. Lenses were located at different vertical depths and were horizontally offset. In-situ collocated probes collected soil hydrologic and chemical data. In the layered column, enhanced biogeochemical cycling was observed over the texturally homogeneous soil columns. Enumerations of Fe(III) and SO42- reducing microorganisms also show 1-2 orders of magnitude greater community numbers in the layered column. The greatest concentrations of aqueous FeS clusters (FeSaq) were observed in close proximity to the soil interface. To our knowledge, this was the first documentation of FeSaq in partially saturated sediments. Mineral and soil aggregate composite layers were also most abundant near the soil layer interface; the presence of which, likely contributed to an order of magnitude decrease of hydraulic conductivity. In the live lens column, Fe-oxide bands formed at the fringes of the lenses that retarded water flow rates by an order of magnitude compared to the sterilized column. Microbial activity also produced insoluble gases and that led to the creation of a separate gas phase that reduced hydraulic conductivity. This limited the interaction between groundwater with soil-pore waters that led to the formation of geochemically distinct water masses in relatively close proximity to one another. No such changes were observed in the sterilized column. When compared to homogenous columns, the presence of soil heterogeneities altered biogeochemical and hydrologic processes considerably which highlights the need to consider soil heterogeneity in contaminant fate and transport models. These findings suggest that quantifying coupled hydrologic-biogeochemical processes occurring at small scale soil interfaces is critical to accurately describing and predicting chemical changes at the larger system scale.

This work aims to increase our understanding of the nature of large scale features of sea ice from a dynamics point of view.Sea ice plays an important part in the exchange of heat and humidity between sea and air and thus is an important component of the climate system. Its physical presence also directly impacts the various forms of life such as diatoms, polar bears and humans alike.The dynamics of sea ice affect both weather and climate, through the large scale drift in the Arctic from the Siberian coast towards Fram Strait, through creation of cracks in the ice called leads or polynyas, and through ridging and other mechanical deformations of ice floes.In this work, we have focused on modelling of ridged ice for a number of reasons. Direct observations of the internal ice state is very difficult to perform and in general, observations of sea ice are either sparse or of limited information density. Ridged ice can be seen as the memory of high ice stress events, giving us a view on these highly dynamic events. Ridging is of major importance for the ice thickness distribution, as the thickest ice can only be formed through mechanical processes. Further, ridged ice is of direct interest for anyone conducting shipping through seasonal or perennial ice covered seas as it can form impenetrable barriers or in extreme even cases crush a ship caught within the ice pack. To this end, a multi-category sea ice model, the HELsinki Multi category Ice model (HELMI), was implemented into the Rossby Centre Ocean model (RCO). HELMI has explicit formulations for ridged and rafted ice, as well as sub-grid scale ice thickness distribution (a feature shared with other multi category models) and an ice strength based on energetics. These features give RCO better representation of sub-grid scale physics and gives us the possibility to study the deformed ice in detail. In paper I we look at the change in behaviour in the Arctic as the ice becomes more mobile, leading to a slight increase in modelled ridged ice volume in the central Arctic, despite a general trend of a decreasing ice cover.Paper II takes us to the Baltic Sea and the possibilities of modelling ridge ice concentration with a statistical model.In Paper III we investigate how the diminishing ice cover in future scenarios affects the biological activity in the Baltic Sea.Finally Paper IV investigates how the ice stress and the internal ice force can be interpreted in terms of ice compression on the ship scale. / <p>At the time of the doctoral defence the following paper was unpublished and had a status as follows: Paper 4: Manuscript</p>

The concentrations of trace elements in 30 Saanich Peninsula agricultural soil samples were determined by acid digestion and inductively coupled plasma - optical emission spectroscopy (ICP-OES). A comparison of the results obtained to a 1995 BC Ministry of Environment data indicated that As, Cu, Mo, Sb, Se and Sn concentrations had increased whereas the concentrations of Ba, Be, Cd, Cr, Co, Mn, Ni, Pb, V and Zn had decreased. The principal sources of the trace elements were anthropogenic sources including fertilizer and manure application, weathering of rocks and atmospheric deposition. The concentrations changes were largely influenced by the individual properties of the elements, soil texture, soil organic matter and clay content. The mobility of the trace elements in the soils was mainly controlled by clay content and followed the order Cd> B >Mo> Cr> V> Zn> Se> Co> Cr> As> Ba> Sb> Mn> Ag, Be, Hg, Ni, Pb.

A quasi-two dimensional model for the southern Vancouver Island shelf was developed with the Regional Ocean Modelling System (ROMS) to study coupling of the carbon, oxygen, and nitrogen cycles in a summer wind-driven upwelling region. The physical model is coupled to an ecosystem module that includes a simple representation of a sediment layer and considers non-fixed C:N ratios for detritus and dissolved organic matter (i.e., explicitly modelled pools of carbon and nitrogen for those variables). The model accounts for denitrification within the sediments as well as within the water column when oxygen concentrations are low (below 5 mmol-O2 m-3). The objective is to identify the dominant processes controlling the cycles, their coupling, and their sensitivity to changes in environmental forcing. Results demonstrate how low oxygen and low pH events are tightly coupled in the coastal study region, especially through local ecosystem processes. In particular, exchange with the sediments plays a dominant role in consuming oxygen from and releasing inorganic carbon to the bottom waters on the shelf. Two key features distinguish the southern Vancouver Island shelf from other coastal regions in the California Current System and protect inner shelf waters from severe hypoxia and corrosive (i.e., undersaturated in aragonite) conditions. First, the greater width of the shelf reduces the penetration of subsurface offshore high-carbon and low-oxygen waters into shallower waters; and second, the relatively fresh Vancouver Island Coastal Current (VICC) brings oxygen-rich and carbon-poor waters to the bottom layer over the inner shelf. Sensitivity experiments show that carbon and oxygen cycles on the southern Vancouver Island shelf may be significantly affected by an altered upwelling season, a shallower offshore Oxygen Minimum Zone, a warmer ocean, and a carbon-enriched environment. Combinations of these scenarios suggest a potential increasing risk for the development of coastal hypoxia and corrosive conditions in the future. Further sensitivity simulations indicate that sedimentary denitrification provides an additional coupling between the carbon, oxygen, and nitrogen cycles. Total alkalinity generated by sediment denitrification has the potential to buffer anthropogenic ocean acidification. However, this alkalinity effect over the Vancouver Island shelf in late spring and summer simulations is small compared with studies for other locations at annual scales. Longer time scales need to be examined in this region to confirm whether the role of alkalinity generation in the sediments is significant. In conclusion, this dissertation not only demonstrates the coupled nature of biogeochemical cycles in the coastal ocean, but also the importance of this coupling as we try to estimate how coastal ecosystems will respond to human modifications of shelf waters and the climate.

I used a specific inhibitor approach to systematically measure NH4+ oxidation rates through the euphotic zone of three distinct oceanographic regimes. Study sites included Saanich Inlet, a highly productive British Columbia fjord, the Line P oceanographic transect in the NE subarctic pacific, and the Bermuda Atlantic Time-series Study (BATS) station in the oligotrophic, sub-tropical Sargasso Sea. Nitrate uptake rates were also measured at select stations on a number of research cruises. NH4+ oxidation rates were found to proceed throughout the euphotic zone in each of my study regions, and, overall, euphotic zone NH4+ oxidation rates ranged from undetectable to 203 nmol L-1 d-1. A general characterization of the rates observed in each of my study regions shows that euphotic zone NH4+ oxidation rates were typically highest in Saanich Inlet, intermediate along Line P, and lowest at BATS. The observation that NH4+ oxidation occurred throughout the euphotic zone in each of my study regions was in contrast to the traditional assumption of no euphotic zone nitrification, and it should now be considered a ubiquitous process in the euphotic regions of the ocean. Results found that euphotic zone nitrification could have potentially supported, on average, 15, 53 and 79% of the phytoplankton NO3- requirements in Saanich Inlet, and along Line P and at BATS, respectively, and this underscores the need for a major re-evaluation of the new production paradigm. Light, substrate concentrations, and potentially substrate supply rates were all found to play a role in regulating NH4+ oxidation, albeit to varying degrees, and I discuss the influence that each of these variables may have had on controlling NH4+ oxidation rates at regionally specific scales in Chapters 2 (Saanich Inlet), 3 (Line P) and 4 (BATS). Finally, a cross study-region comparison of results showed that the relative degree by which new production estimates were reduced, when euphotic zone nitrification was taken into consideration, decreased exponentially as total NO3- uptake rates increased; the relationship I describe between these two variables may potentially provide a simple and rapid means of estimating the extent to which new production may have been overestimated at regionally specific and global scales. My Line P sampling program also provided me with an opportunity to conduct the first investigation of intermediate depth N2O distributions along the Line P oceanographic transect. My results demonstrated that nitrification is the predominant production pathway for N2O in the NE subarctic Pacific. N2O distributions along Line P were variable, however, and I also consider the role of different transiting water masses and potential far-field denitrification in contributing to this variability. Finally, I estimated sea-to-air fluxes of N2O and based on these results I have demonstrated that the NE subarctic Pacific is a “hotspot” for N2O emissions to the atmosphere. / Graduate

Existe uma preocupação mundial com as mudanças climáticas causadas pelo aumento da concentração de gases do efeito estufa (GEE) e consequente acréscimo na temperatura média da superfície terrestre. A queima de combustíveis fósseis é a maior causadora do aquecimento global e responsável por danos à saúde humana. É notável o esforço global em diversificar a matriz mundial de combustíveis líquidos, priorizando a substituição de fontes fósseis por renováveis. Tal substituição reforça a necessidade de avaliações de todas as emissões de GEE na cadeia produtiva da cana-de-açúcar. O Brasil é o maior produtor de etanol proveniente de cana-de-açúcar. Um importante co-produto deste processo produtivo é a vinhaça, sendo produzida em elevadas quantidades e constituída por uma expressiva carga orgânica. Esta é comumente aplicada ao solo por fertirrigação. Apesar de atuar beneficamente no solo, pouco se sabe sobre a capacidade deste co-produto de aumentar as emissões de GEE no solo. Assim, o objetivo foi avaliar o efeito da aplicação da vinhaça nas emissões de N2O e CH4 e na comunidade de bactérias desnitrificantes e metanogênicas do solo. As amostragens de GEE e solo foram em áreas de cana sem queima a partir da aplicação de doses vinhaça (0, 150, 300 e 450 m3 ha-1). O delineamento experimental realizado foi em cinco blocos casualizados, totalizando 25 câmaras de coleta de gases do efeito estufa. Amostras de solo foram coletadas em quatro períodos de amostragem após aplicação de vinhaça (0, 7, 15 e 30 dias), em dois anos consecutivos. Foram analisados os GEE, N2O e CH4, além da abundancia de genes por meio da técnica de qPCR. A fertirrigação via aplicação de vinhaça no solo, nos dois anos, proporcionou aumento nas emissões de N-N2O, principalmente nos primeiros dias após a aplicação. Contudo os fluxos de C-CH4 oscilaram indicando a capacidade do solo de servir ora como fonte ora como sumidouro deste GEE. Os fatores de emissão obtidos para aplicação de N na forma de vinhaça, dose de 300 m3 ha-1, foram de 0,08% para o primeiro ano e 0,07% para o segundo ano. A partir da técnica de qPCR, a abundância dos genes indicou que a introdução deste resíduo ao solo pode aumentar significativamente o total de bactérias no solo e a atividade do gene nosZ, contudo o mesmo não ocorre com o potencial de desnitrificação biológica (gene nirK) e nem com o gene mcrA (redução de CH4). Os resultados demonstram que a aplicação da vinhaça no solo influencia as emissões de GEE, assim como a comunidade microbiana do solo / There is a global concern with climate change caused by increased concentration of greenhouse gases (GHG) and consequent increase in the average temperature of the Earth surface. Fossil fuels burning is the major cause of global warming and it is responsible for damages to human health. Remarkable global efforts in diversifying liquid fuels have been attempted, giving priority to the replacement of fossil fuels to renewables. Such substitution reinforces the need of an evaluation of all GHG emissions in the production chain of sugarcane. Brazil is the largest producer of ethanol with source from sugarcane. An important co-product of the production process is vinasse, which is being produced in large quantities comprising a significant organic load. This is commonly applied over the ground by fertigation. Despite being good for the soil, little is known about the ability of this co-product of increasing GHG emissions. This work aimed to evaluate the effect of the application of vinasse in the emissions of N2O and CH4 and in the soil community of denitrifying and methanogenic bacteria. Sampling of GHG and soil were performed in areas of sugarcane without burning with the application of different vinasse doses (0, 150, 300 and 450 m3 ha-1). The experiment was conducted in five blocks, totaling 25 collection chambers of greenhouse gases. Soil samples were collected in four sampling periods after application of vinasse (0, 7, 15 and 30 days), in two consecutive years. We analyzed the GHG, N2O and CH4, and the abundance of genes by qPCR technique. The fertigation via vinasse application on the ground in two years provided an increase in emissions of N-N2O, especially in the first couple of days after application. However the flow of C-CH4 was variable indicating the ability of the soil to serve either as source or as sink of this GHG. The emission factor obtained for N application in the form of vinasse dose of 300 m3 ha-1 was 0.08% for the first year and 0.07% for the second year. By qPCR technique, the abundance of the genes indicated that the use of this residue to the soil can significantly increase the amount of bacteria in the soil and nosZ gene activity. However it does not occur with the potential for biological denitrification (nirK gene) or with the gene mcrA (reduction of CH4). These results demonstrate that the application of vinasse in the soil influences GHG emissions as well as the soil microbial community

Les communautés microbiennes benthiques participent activement au recyclage de la matière organique et de fait au fonctionnement biogéochimique des écosystèmes lacustres. Ces communautés comportent de nombreux phyla mais leur diversité fonctionnelle est encore incomplètement connue. Ce travail vise à appréhender les modifications de structure et d'abondance des gènes fonctionnels en lien avec la distribution spatiale verticale (liée au gradient d'oxydoréduction), la variabilité spatiale horizontale (zone côtière vs pélagique) et la dynamique saisonnière liée au brassage de la colonne d'eau (ré-oxygénation des interfaces benthiques), de même que l'identification de la diversité des méthanotrophes et des méthanogènes.Pour cette étude, des carottes sédimentaires ont été prélevées sur un transect zone côtière – zone pélagique, à différentes dates au cours d'un cycle annuel. Chaque carotte sédimentaire a été analysée dans la verticalité entre l'interface eau-sédiment et 20 cm. Les communautés microbiennes participant au cycle du méthane ont été ciblées par 2 gènes de fonction et étudiées en termes de structure, de diversité et d'abondance; par ailleurs, des marqueurs phylogénétiques ont été utilisés pour caractériser les communautés bactériennes et archéennes totales.Les résultats de l'étude spatiale montrent que, si à l'échelle locale (station d'échantillonnage) une relative homogénéité des communautés microbiennes (totales et fonctionnelles) est observée, des variabilités fortes sont détectées d'une part à l'échelle des transects horizontaux en lien avec des changements de conditions environnementales et d'autre part dans la verticalité des sédiments sous l'effet des conditions d'oxydoréduction. La communauté bactérienne étant la plus affectée dans la verticalité, avec des changements de structure entre toutes les strates étudiées. Dans cette même étude, une analyse comparative de la structure des communautés (totales et fonctionelles) a démontré que l'analyse d'échantillons individuels permettait d'obtenir un plus grand nombre d'OTU que l'analyse des mêmes échantillons regroupés en pools.Les résultats de l'étude de la dynamique temporelle des communautés méthanogènes et méthanotrophes révèlent des changements de structure et abondance, principalement à l'interface eau - sédiment en lien avec la dynamique d'oxygénation du lac. Quant à l'analyse de la diversité, elle montre une dominance des Methanomicrobiales (Methanoregula principalement) pour les méthanogènes, mais les Methanosarcinales (Methanosarcina) et les Methanobacteriales (Methanobacterium) ont également été identifiés. Pour les méthanotrophes, la diversité est dominée par Methylobacter en zone profonde et par Methylococcus en zone côtière, les méthanotrophes de Type II (Methylosinus et Methylocystis) ont aussi été identifiés.L'ensemble de ces travaux souligne l'importance de prendre en compte, à la fois la variabilité spatiale (horizontale et verticale) et la variabilité temporelle, des communautés méthanogènes et méthanotrophes lors de l'étude de ces communautés. Les changements quant à leurs structures et leurs abondances sont des paramètres non négligeables pour comprendre les processus impliqués dans le cycle du méthane. / Benthic microbial communities are actively involved in organic matter recycling and fact biogeochemical functioning of lake ecosystems. These communities comprise many phyla but their functional diversity is still incompletely known. This study is focused on the benthic microbial communities involved in the methane cycle in lacsutrine suystems. We aimed understanding the structural and abundance changes of functional genes related to the vertical distribution (redox gradient in sediment), the horizontal variability (coastal vs. pelagic benthic zone) and seasonal dynamics related to mixing of the water column (re-oxygenation of benthic interface). The composition of methanotrophic and methanogenic communities was characterized by sequencing analyses.For this study, sedimentary cores were sampled along a transect from coastal to pelagic zone, at different times during an annual cycle. In addition, each sediment core was analyzed in its verticality from the water-sediment interface to 20 cm depth. Microbial communities involved in the cycle of methane (methanogenesis and methanotrophy) were targeted by 2 functional genes (mcrA and pmoA). Furthermore, phylogenetic markers were used to characterize the total bacterial and archaeal communities. These communities are studied in terms of structure (genotyping), diversity (sequencing) and abundance (qPCR, DNA) of their functional genes.The results of the study showed that, on a spatial scale, a low heterogeneity was detected for a given sampling station in terms of structure of microbial communities (total and functional), however, a high variability was detected both at an horizontal scale along a transect (costal vs. pelagic zone), due to contrasted environmental conditions, and at a vertical scale (upper to deeper layers in the core) under the effect of redox conditions. The bacterial community being the most affected in the verticality, with structural changes among all strata studied. In the same study, a comparative analysis of the structure (for all of the communities), between pooled samples and individual samples, demonstrated that the analysis of individual samples provided a greater number of OTU for the majority of microbial communities.Moreover the study of the temporal dynamic of methanogen and methanotroph communities revealed changes in the structure and abundance, mainly at the water - sediment interface, according to the oxygenation levels that varied through time. The analysis of diversity showed a dominance of Methanomicrobiales (Methanoregula mainly) for methanogens, but Methanosarcinales (Methanosarcina) and Methanobacteriales (Methanobacterium) were also identified. The methanotrophs' community was dominated by Methylobacter on deeper stations and by Methylococcus in coastal station. Type II methanotrophs (Methylosinus and Methylocystis) were also identified.This work highlights the importance of taking into account both the spatial variability (horizontal and vertical) and the temporal variability of methanogen and methanotroph communities. Changes on their structures and abundances are significant parameters for understanding the processes involved in the methane cycle.

Submitted by (lucia.rodrigues@ufrpe.br) on 2016-08-25T13:02:14Z No. of bitstreams: 1 Alan Caue de Holanda (1).pdf: 4278080 bytes, checksum: 564351dc83c5e00382ba808429b9f256 (MD5) / Made available in DSpace on 2016-08-25T13:02:15Z (GMT). No. of bitstreams: 1 Alan Caue de Holanda (1).pdf: 4278080 bytes, checksum: 564351dc83c5e00382ba808429b9f256 (MD5) Previous issue date: 2012-02-29 / The Caatinga is one of the only regions in Brazil where its limits are restricted to national territory, and for being the biome fourth in land area in the country, is the most neglected by the political authorities, where there is a strong anthropic disturbance and disorderly exploitation of natural resources, especially for energy, agricultural and pastoral. Given this issue, and the deficiency related to the study of vegetation, is that the present work aims to survey the vegetation in an area of Caatinga, analyze litter production and nutrient; check the rate of decomposition of leaf litterfall of ten species of greatest importance value and quantify the distribution of nutrients in the soil-vegetation. The study was conducted in the remnant forested savanna Riachão Farm located in the municipality of Pombal, PB. For sampling of the adult vegetation were installed 40 plots of 10 m x 25 m in a systematic way, where were inventoried all the individuals with CAP ≥ 10.0 cm. Natural regeneration was evaluated through the implementation of sub-plots of 5 m x 5 m located in the northwestern part of each installment, in which all individuals were sampled with a height H> 1.0 m CNB <10.0 cm. To analyze litter production were installed in the center of each sample unit a collector box with dimensions of 1.0 m2, in which monthly during the period of one year, all material in the boxes were collected and separated by fractions, and 40 plots installed, 16 were selected for realization of analyzes chemistry (N, P, K, Ca and Mg). The decomposition of leaf material was performed for the ten species of highest importance value (VI) recorded in the area in line with the soil respiration. After collecting the leaves, they were distributed in 288 litter bags, and each had a portion of 10.0 g. Samples were collected during one year at intervals of 45 days and then sent to the laboratory for chemical quantification of C and N. To analyze the distribution of nutrients in different compartments of the soilplant system, was collected recent mature leaves from the middle portion of the canopy of ten trees of most important in different orthogonal points, eight soil samples from plots at different depths (0 - 0.1 m, 0.1-0.2 m, 0.2-0.3 m) and portions of organic mantle, all the papers were forwarded to the analyzes chemical. We sampled 1338 individuals in the adult tree shrub component and 365 in natural regeneration. The Shannon diversity index calculated for the adult and regeneration was 1.67 and 1.35 nats individual-1, respectively. Were estimated deposition an annual litter of 3785.67 kg ha-1, the leaf fraction being the largest contributor with 70% and the concentration of nutrients in the litter followed the order Ca>N>K>Mg>P. It was found over a year of the study as a weight loss of 67% and with the soil respiration more intense at night. The C/N rate is relatively low, indicating a higher rate of mineralization. The remaining soil is rich in nutrients and high concentrations of nutrients in the leaves, associated with low concentrations observed in the organic mantle, may be indicative of greater efficiency of the biochemical cycle. / A Caatinga é uma das únicas regiões do Brasil em que seus limites estão restritos ao território nacional, e apesar de ser o quarto bioma em área territorial no país, é o mais negligenciado pelas autoridades políticas, onde se verifica uma forte pressão antrópica e desordenada na exploração dos recursos naturais, principalmente para fins energéticos, agrícolas e pastoris. Diante dessa problemática, e da carência em trabalhos relacionado ao estudo da vegetação, é que o presente trabalho, tem por objetivo fazer o levantamento da vegetação em uma área de Caatinga, analisar o aporte de serapilheira e nutrientes; verificar a taxa de decomposição da serapilheira foliar das dez espécies de maior valor de importância e quantificar a distribuição de nutrientes no sistema solo-vegetação. O trabalho foi conduzido em um remanescente de savana estépica florestada localizada no Sítio Riachão, município de Pombal, PB. Para amostragem da vegetação adulta, foram instaladas 40 unidades amostrais de 10 m x 25 m de forma sistemática, onde foram inventariados todos os indivíduos com CAP ≥ 10 cm. A regeneração natural foi avaliada pela implantação de sub-unidades amostrais de 5 m x 5 m instaladas na parte noroeste de cada parcela, em que foram amostrados todos os indivíduos com altura H > 1,0 m e CNB < 10,0 cm. Para analisar o aporte de serapilheira foi instalada, no centro de cada unidade amostral, uma caixa coletora com dimensões de 1,0 m2, em que mensalmente durante o período de um ano, todo material presente nas caixas foi coletado e separado por frações, e das 40 parcelas instaladas, 16 foram sorteadas para a realização das análises químicas (N, P, K, Ca e Mg). A decomposição do material foliar foi realizada para as dez espécies de maior valor de importância (VI) registradas na área em consonância com a respiração edáfica. Após a coleta das folhas, as mesmas foram distribuídas em 288 litter bags, e que cada uma tinha a porção de 10,0 g. As coletas foram realizadas no período de um ano em intervalos de 45 dias, sendo posteriormente encaminhadas ao laboratório para a quantificação química de C e N. Para analisar a distribuição dos nutrientes nos diferentes compartimentos do sistema solo-planta, coletaram-se folhas recém maduras da porção média da copa das dez árvores de maior VI, nos diferentes pontos ortogonais, amostras de solo de oito parcelas em diferentes profundidades (0-0,1 m; 0,1-0,2 m e 0,2-0,3 m) e porções de manta orgânica, posteriormente todo o material foi encaminhado para a realização das análises químicas. Foram amostrados 1338 indivíduos no componente arbustivo arbóreo adulto e 365 na regeneração natural. O índice de diversidade de Shannon calculado para o adulto e regeneração foi de 1,67 e 1,35 nats individuo-1, respectivamente. Estimou-se uma deposição anual de serapilheira de 3.785,67 kg ha-1, sendo a fração folha a maior contribuinte com 70% e a concentração de nutrientes na serapilheira seguiu a ordem Ca>N>K>Mg>P. Verificou-se ao longo de um ano de avaliação medidas de perda de massa de 67%, com a respiração edáfica sendo mais intensa no período noturno. A relação C/N foi relativamente baixa, indicativo de maior taxa de mineralização. O solo do remanescente é rico em nutrientes, e a alta concentração de nutrientes nas folhas, associada à baixa concentração observada na manta orgânica, pode ser um indicativo de maior eficiência do ciclo bioquímico.