A dinâmica do C e do N dentro do ecossistema engloba os processos fisiológicos que ocorrem na planta e no solo. Utilizando o sistema Trop-T-FACE no campus da USP de Ribeirão Preto, que combina os sistemas FACE (Free-air carbon dioxide enrichment) e T-FACE (Temperature free-air controlled enhancement), para enriquecimento e controle do CO2 e da elevada temperatura (aquecimento), respectivamente, foram realizados dois experimentos com duas forrageiras tropicais, Stylosanthes capitata Vogel (leguminosa C3) e Panicum maximum Jacq. (gramínea C4). O primeiro experimento envolveu o aquecimento de 2°C no dossel de plantas S. capitata Vogel e resultou em uma intensificação do ciclo do N em curto prazo provavelmente devido à uma maior fixação biológica de N2 pela leguminosa, além de maiores taxas respiratórias do solo e reduzidas taxas de atividade enzimática do solo. No segundo experimento, plantas de S. capitata e P. maximum foram submetidas a quatro tratamentos: controle, com condições de CO2 e temperatura ambiente; aquecimento de 2°C e concentração de CO2 ambiente (eT), temperatura ambiente e concentração de CO2 elevada em 600 µmol mol-1 (eC) e aquecimento de 2°C e concentração de CO2 elevada em 600 µmol mol-1 (eC+eT). Os resultados da respiração do solo indicaram um efeito do aquecimento sobre os processos biológicos do solo devido ao aumento das temperaturas do solo. Análises isotópicas das plantas mostraram, a partir do 3° dia de experimento, o decréscimo do 13C em ambas espécies nos tratamentos com elevado CO2 como consequência da incorporação do C novo assimilado. Quanto ao 15N, este apresentou apenas valores positivos nas C3, enquanto nas C4 houve tanto valores negativos como positivos, mas ambos não indicaram um padrão muito claro quanto a diferenças entre tratamentos. Análises enzimáticas não revelaram alterações específicas no metabolismo do C no solo, mas foram encontradas alterações no metabolismo do N que indicam uma influência direta deste nutriente no potencial do solo em armazenar C. / The C and N dynamics may be interpreted as a flow within the ecosystem that encompasses the physiological processes that occur in plants and soil. In this study, we used of a new combined FACE and T-FACE system, to allow plants of Stylosanthes capitata Vogel (C3) and Panicum maximum Jacq. (C4) to be exposed to higher CO2 concentrations and temperatures, respectively. The system named Trop-T-FACE was established at the Ribeirão Preto campus of the University of São Paulo (USP). Two experiments were conducted using this system; the first involved the warming of 2° C in the plant canopy of Stylosanthes capitata Vogel and resulted in an intensification of N short term cycle probably due to greater biological N2 fixation by legumes, plus larger soil respiration rates and reduced rates of soil enzymatic activity. In the second experiment, plants of S. capitata and P. maximum were exposed to 4 treatments: a control (ambient temperature and ambient CO2); eT (ambient CO2 concentration and a canopy temperature of 2 °C greater than the ambient temperature), eC (600 µmol mol-1 CO2 and ambient temperature), and eC + eT (600 µmol mol-1 CO2 and a canopy temperature of 2 °C greater than the ambient temperature). Results from soil respiration indicated an effect of warming on soil respiration by effect of increment in soil temperature. Isotopic analysis showed, from the third day of the experiment, the decay of 13C values in both species in the treatments with elevated CO2 as a result of assimilation of the new C. Whereas 15N showed only positive values in C3, in C4 we found negative and positive values, but both did not indicate a clear pattern among treatments. Enzymatic analyzes revealed no specific changes in C metabolism in the soil, but changes in N metabolism might indicate a direct influence of this nutrient in the potential of the soil to store C.

No description available.

Les nanomatériaux sont de plus en plus présents dans les produits consommables du quotidien. L’argent est le métal le plus utilisé en nanotechnologie pour ses propriétés antimicrobiennes. Par différentes voies d’entrée, les nanoparticules d’argent (nAg) se retrouvent dans l’environnement en quantité significative, notamment dans les sols suite à la valorisation agricole des biosolides municipaux. Il est prévu qu’une interaction négative sur la communauté microbienne terrestre ait des répercussions sur la fertilité du sol et les processus biogéochimiques. Les mesures de l’activité enzymatique ont déjà montré leur efficacité et leur sensibilité dans la détection d’une perturbation physique et chimique du sol. Les effets potentiels des nAg sur l’écosystème terrestre ont été évalués en mesurant l’activité des enzymes β-D-glucosidase (EC 3.2.1.21), leucine-aminopeptidase (EC 3.4.11.1), phosphomonoesterase (EC 3.1.3) et arylsulfatase (EC 3.1.6.1) intervenant dans les cycles des éléments essentiels C, N, P et S, respectivement. L’activité enzymatique est mesurée à l’aide d’une technique basée sur la fluorescence qui requière des substrats synthétiques liés à un fluorophore. Un sol de type sableux a été échantillonné au Campus Macdonald de l’Université McGill (Sainte-Anne-de-Bellevue, Qc) puis exposé aux nAg (taille ~20 nm) ou à la forme ionique Ag+ (Ag-acetate) à des concentrations nominales de 1,25 × 10-3, 1,25 × 10-2, 0,125, 1,25, 6,25 et 31,25 mg Ag kg-1 sol. De plus, le rôle de la matière organique (MO) a été évalué en effectuant un amendement du sol avec un compost de feuilles. Pour mieux comprendre les effets observés, des analyses de spéciation de l’Ag ont été réalisées. Les concentrations en Ag dissous ont été déterminées après filtration à travers des membranes de 0,45 µm ou de 3 kDa (~1 nm, ultrafiltration) pour séparer la phase particulaire des ions dissous. De façon générale, une inhibition de l’activité enzymatique a été observée pour les 4 enzymes en fonction de l’augmentation de la concentration en Ag (totale et dissoute) mais elle est significativement moins importante avec l’ajout de la MO. Les résultats suggèrent que l’inhibition de l’activité des enzymes aux faibles expositions aux nAg est due aux nanoparticules puisqu’une très faible fraction des nAg est réellement dissoute et aucun effet significatif n’a été observé pour les sols traités à des concentrations similaires en Ag+. Par contre, les effets mesurés aux concentrations plus élevées en nAg sont semblables aux expositions à l’Ag+ et suggèrent un rôle de l’Ag colloïdale dans l’inhibition du processus enzymatique des sols. / Nanomaterials are increasingly included in manufactured consumable products. Silver is the metal that is most often used in nanotechnology for its antimicrobial properties. By different pathways, silver nanoparticles (nAg) can end up in the environment, in significant quantities. They are especially expected to be found in soils due to the use of landfills. In the presence of silver (Ag) negative effects on the terrestrial microbial communities with a subsequent impact on soil fertility and biogeochemical processes are expected. Measurements of enzyme activity have already shown their effectiveness and sensitivity in the detection of chemical and physical disturbances of soils. In this document, the potential effects of nAg on the terrestrial ecosystem have been evaluated by measuring the activities of the enzymes β-D-glucosidase (EC 3.2.1.21), leucine aminopeptidase (EC 3.4.11.1), phosphomonoesterase (EC 3.1.3) and arylsulfatase (EC 3.1.6.1), which are involved in the cycling of the essential elements C, N, P and S, respectively. The enzyme activity is measured using a fluorescence based technique that employs synthetic substrates linked to a fluorophore. A sandy soil was sampled at Macdonald Campus of McGill University (Ste-Anne-de-Bellevue, Qc) and then exposed to nAg (size ~ 20 nm) or free silver (Ag+, as Ag-acetate) at nominal concentrations of 1.25 × 10-3, 1.25 × 10-2, 0.125, 1.25, 6.25 and 31.25 mg Ag kg-1 soil. The role of organic matter (OM) was evaluated by adding leaf compost to the soil. The proportion of the toxicity that could be attributed to the nAg was evaluated by performing Ag speciation analyses in all soil samples. Dissolved Ag concentrations were determined after filtration through a 0.45 µm membrane or a 3 kDa ultrafiltration membrane (~ 1 nm) in order to separate the particulate phase from the dissolved ions. In general, inhibition of the enzyme activities was observed for the four enzymes as a function of increasing Ag concentrations (total and dissolved), however effects were significantly less dramatic in the OM-amended soil. The results suggested that the inhibition of enzyme activities at low-concentrations of nAg appeared to be due to the nanoparticles since a very small fraction of the nAg was actually dissolved and no significant effect was observed for soils treated with similar concentrations of Ag+. On the other hand, the effects measured at high concentrations of Ag were similar for the exposures to both nAg and Ag+, suggesting that, at these concentrations, colloidal Ag may have played a role in the inhibition of the soil enzymatic processes.

Les nanomatériaux sont de plus en plus présents dans les produits consommables du quotidien. L’argent est le métal le plus utilisé en nanotechnologie pour ses propriétés antimicrobiennes. Par différentes voies d’entrée, les nanoparticules d’argent (nAg) se retrouvent dans l’environnement en quantité significative, notamment dans les sols suite à la valorisation agricole des biosolides municipaux. Il est prévu qu’une interaction négative sur la communauté microbienne terrestre ait des répercussions sur la fertilité du sol et les processus biogéochimiques. Les mesures de l’activité enzymatique ont déjà montré leur efficacité et leur sensibilité dans la détection d’une perturbation physique et chimique du sol. Les effets potentiels des nAg sur l’écosystème terrestre ont été évalués en mesurant l’activité des enzymes β-D-glucosidase (EC 3.2.1.21), leucine-aminopeptidase (EC 3.4.11.1), phosphomonoesterase (EC 3.1.3) et arylsulfatase (EC 3.1.6.1) intervenant dans les cycles des éléments essentiels C, N, P et S, respectivement. L’activité enzymatique est mesurée à l’aide d’une technique basée sur la fluorescence qui requière des substrats synthétiques liés à un fluorophore. Un sol de type sableux a été échantillonné au Campus Macdonald de l’Université McGill (Sainte-Anne-de-Bellevue, Qc) puis exposé aux nAg (taille ~20 nm) ou à la forme ionique Ag+ (Ag-acetate) à des concentrations nominales de 1,25 × 10-3, 1,25 × 10-2, 0,125, 1,25, 6,25 et 31,25 mg Ag kg-1 sol. De plus, le rôle de la matière organique (MO) a été évalué en effectuant un amendement du sol avec un compost de feuilles. Pour mieux comprendre les effets observés, des analyses de spéciation de l’Ag ont été réalisées. Les concentrations en Ag dissous ont été déterminées après filtration à travers des membranes de 0,45 µm ou de 3 kDa (~1 nm, ultrafiltration) pour séparer la phase particulaire des ions dissous. De façon générale, une inhibition de l’activité enzymatique a été observée pour les 4 enzymes en fonction de l’augmentation de la concentration en Ag (totale et dissoute) mais elle est significativement moins importante avec l’ajout de la MO. Les résultats suggèrent que l’inhibition de l’activité des enzymes aux faibles expositions aux nAg est due aux nanoparticules puisqu’une très faible fraction des nAg est réellement dissoute et aucun effet significatif n’a été observé pour les sols traités à des concentrations similaires en Ag+. Par contre, les effets mesurés aux concentrations plus élevées en nAg sont semblables aux expositions à l’Ag+ et suggèrent un rôle de l’Ag colloïdale dans l’inhibition du processus enzymatique des sols. / Nanomaterials are increasingly included in manufactured consumable products. Silver is the metal that is most often used in nanotechnology for its antimicrobial properties. By different pathways, silver nanoparticles (nAg) can end up in the environment, in significant quantities. They are especially expected to be found in soils due to the use of landfills. In the presence of silver (Ag) negative effects on the terrestrial microbial communities with a subsequent impact on soil fertility and biogeochemical processes are expected. Measurements of enzyme activity have already shown their effectiveness and sensitivity in the detection of chemical and physical disturbances of soils. In this document, the potential effects of nAg on the terrestrial ecosystem have been evaluated by measuring the activities of the enzymes β-D-glucosidase (EC 3.2.1.21), leucine aminopeptidase (EC 3.4.11.1), phosphomonoesterase (EC 3.1.3) and arylsulfatase (EC 3.1.6.1), which are involved in the cycling of the essential elements C, N, P and S, respectively. The enzyme activity is measured using a fluorescence based technique that employs synthetic substrates linked to a fluorophore. A sandy soil was sampled at Macdonald Campus of McGill University (Ste-Anne-de-Bellevue, Qc) and then exposed to nAg (size ~ 20 nm) or free silver (Ag+, as Ag-acetate) at nominal concentrations of 1.25 × 10-3, 1.25 × 10-2, 0.125, 1.25, 6.25 and 31.25 mg Ag kg-1 soil. The role of organic matter (OM) was evaluated by adding leaf compost to the soil. The proportion of the toxicity that could be attributed to the nAg was evaluated by performing Ag speciation analyses in all soil samples. Dissolved Ag concentrations were determined after filtration through a 0.45 µm membrane or a 3 kDa ultrafiltration membrane (~ 1 nm) in order to separate the particulate phase from the dissolved ions. In general, inhibition of the enzyme activities was observed for the four enzymes as a function of increasing Ag concentrations (total and dissolved), however effects were significantly less dramatic in the OM-amended soil. The results suggested that the inhibition of enzyme activities at low-concentrations of nAg appeared to be due to the nanoparticles since a very small fraction of the nAg was actually dissolved and no significant effect was observed for soils treated with similar concentrations of Ag+. On the other hand, the effects measured at high concentrations of Ag were similar for the exposures to both nAg and Ag+, suggesting that, at these concentrations, colloidal Ag may have played a role in the inhibition of the soil enzymatic processes.

Resumo: A derrubada da vegetação nativa e o uso do solo para atividades agropecuárias podem causar alterações nos atributos do solo que variam de intensidade, em função do tipo de manejo adotado. É importante o acompanhamento na variação dos atributos do solo no sentido de detectar alterações que venham em detrimento do potencial produtivo, as propriedades biológicas são as que primeiro se alteram, sendo de grande validade na detecção de impactos negativos no solo pelo uso. O objetivo deste estudo foi verificar alterações em atributos biológicos, comparando áreas sob vegetação nativa com áreas cultivadas com cana-de-açúcar, milho, pastagem e citros. A partir de um ponto georreferenciado, cada área amostrada foi dividida em três sub áreas com 100 m2 (10 x 10 m), sendo coletadas 20 amostras simples em cada uma delas na profundidade 0-0,20 m, que foram misturadas para formar uma amostra composta. As áreas em estudo incluíram onze Latossolos, seis Argissolos, três Neossolos, dois Nitossolos, um Gleissolo, um Organossolo, um Cambissolo e um Chernossolo, solos estes situados em diferentes municípios do Estado de São Paulo. Nas amostras de solo foram avaliados: carbono e nitrogênio da biomassa microbiana, respiração basal, quociente metabólico (qCO2) e atividade das enzimas amilase, arilsulfatase, celulase, desidrogenase, fosfatase ácida, protease e o potencial de hidrólise do diacetato de fluoresceína (FDA). As atividades de arilsulfatases e desidrogenases foram as que melhor refletiram alterações antrópicas sofridas pelos solos em estudo. A matéria orgânica e a capacidade de troca catiônica foram às propriedades químicas do solo que melhor se correlacionaram com os atributos biológicos e bioquímicos avaliados. / Abstract: The removal of the natural vegetation and the use of the soil for agricultural purposes may cause deep alterations in the soil properties depending on the management applied. It is important periodic evaluations of soil properties in order to detect alterations that can degrade the soil. Among soil properties, soil biological activities are those that first indicate soil modifications. The objective of this study was to evaluate changes in soil biological attributes, comparing areas under native forests with areas with the same soils and cultivated with sugarcane or maize. From a georeferenced point, each selected area was divided into three plots with 100 m2 (10 x 10 m), and 20 simple samples were collected in the 0-0.20 m depth, which were mixed to form a composed sample. The studied areas included the eleven different Oxisols, Ultisols six, three Neossolos two Alfisols, an Ultisol, a Organosol a Cambisol and a Chernosol, these soils located in different districts all in São Paulo State. The following soil attributes were evaluated in the soil samples: carbon and nitrogen in the soil microbial biomass, basal respiration, metabolic quotient (qCO2), the activity of the enzymes amylases, arylsulphatase, cellulose, dehydrogenases, phosphatase acid, proteases and the hydrolysis of fluorescein diacetate (FDA). The activities of arylsulfatase and dehydrogenase were the ones that best reflected changes undergone by anthropogenic soils in the study. Organic matter associated and cation exchange capacity were the soil properties that best correlated with the biological and biochemical attributes evaluated. / Orientador: Wanderley José de Melo / Coorientador: Gabriel Maurício Peruca de Melo / Banca: José Frederico Centurion / Banca: Marcus Vinícius Vieitas Ramos / Mestre

Made available in DSpace on 2015-04-20T12:22:47Z (GMT). No. of bitstreams: 1 REAN A ZANINETTI.pdf: 1994412 bytes, checksum: 1ed1f5ec80f6dcfa0641503d9071f8dc (MD5) Previous issue date: 2012-05-04 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The cultivation of natural rubber can be an important alternative to planting large tracts of land degraded in the country, as they have good development in Oxisols, accumulating organic matter and improving nutrient cycling. Therefore the objective of this study was to evaluate through chemical and biological soil attributes, the potential of rubber in the balance, in stock and cycling of nutrients. For this, we studied a chronosequence consisting of a primary forest of reference and areas of rubber trees planted 5, 18, 19, 20 and 44 years ago, where it was taken five soil samples in each area, in 0-10 cm, 11-20 cm and 21-40 cm of depth, in this samples were determined the soil fertility, microbial biomass, organic matter fractionation and enzymatic activity. The results showed that removal of the forest resulted in an average reduction of 46% of the stock of organic carbon in soil, with respect to microbial biomass carbon, this reduction was 32%, regardless of age of the plantation. There was a predominance of the humin fraction, followed by humic and fulvic acids and enzyme activity was higher in soil under primary forest. The succession of primary forest to rubber plantations cause an increase in the microbial activity and does not make much change to the soil fertility. After 18 years of the cultivation there is recovery of half of the content of organic soil matter. / A heveicultura pode constituir importante alternativa de plantio para grandes extensões de terras degradadas pelo País, pois possuem bom desenvolvimento em Latossolos, acumulando matéria orgânica e melhorando a ciclagem de nutrientes. Por isto, o objetivo desse trabalho foi avaliar através de atributos químicos e biológicos do solo, o potencial da seringueira no equilíbrio, no estoque e na ciclagem de nutrientes. Para isso, foi estudada uma cronossequencia formada por uma floresta primária de referência e em áreas de cultivo de seringueira (Hevea spp.) plantadas há 5, 18, 19, 20 e 44 anos, onde foram coletadas cinco amostras de solo em cada área, nas profundidades 0-10 cm; 11-20 cm e 21-40 cm, nas quais foram determinada a fertilidade do solo, biomassa microbiana, fracionamento da matéria orgânica e atividade enzimática. Os resultados mostraram que a remoção da floresta ocasionou em diminuição média de 46% do estoque de carbono orgânico no solo, com relação ao C da biomassa microbiana, essa redução foi de 32%, independente da idade do seringal. Verificou-se o predomínio da fração humina, seguida pelas frações dos ácidos húmicos e ácidos fúlvicos e atividade enzimática sendo mais elevada nos solo sob floresta primária. A sucessão floresta primária para seringais causa aumento da atividade microbiana e pouco altera a fertilidade do solo. Após o décimo oitavo ano de idade do seringal há recuperação de metade do teor de matéria orgânica do solo.