La présence des antibiotiques à usage humain et vétérinaire dans l’écosystème aquatique, est devenue un problème écologique sérieux. En effet, ces substances résistent aux traitements des stations d’épuration, ce qui engendre leur introduction et accumulation dans l’environnement. Par conséquent, le développement de méthodes efficaces pour le traitement de ces polluants est nécessaire. La première partie de ce travail de thèse s’inscrit dans le cadre de la dégradation des antibiotiques par procédé électro-Fenton. Ce procédé consiste à produire in situ des espèces fortement oxydantes, les radicaux hydroxyle, permettant la dégradation totale des composés organiques persistants. La sulfaméthazine (SMT) et le triméthoprime (TMP) ont été choisis comme composés modèles, en raison de leur détection régulière dans les effluents des stations d’épuration, les eaux de surface et les eaux souterraines. Dans cette première partie, nous avons examiné l’influence de différents paramètres expérimentaux, sur l’efficacité du procédé électro-Fenton. Les conditions opératoires optimales nécessaires pour la dégradation totale des deux antibiotiques étudiés, ont été également déterminées. En outre, les produits intermédiaires aromatiques générés lors de la dégradation des deux antibiotiques, ont été identifiés. Leur évolution durant l’électrolyse a été également suivie. La deuxième partie est consacrée à l’étude de la minéralisation de la SMT et du TMP par procédé électro-Fenton. Les résultats obtenus indiquent que les taux de minéralisation de la SMT et du TMP sont respectivement de 91 et 85% après dix-huit heures de traitement. Les acides carboxyliques formés, ainsi que les ions inorganiques libérés ont été identifiés, leur évolution a été suivie au cours du traitement. De plus, en se basant sur les différents sous-produits générés, nous avons proposé des mécanismes réactionnels pour la minéralisation de la SMT et du TMP par procédé électro-Fenton. La troisième partie de ce travail porte sur l’étude de la minéralisation des deux antibiotiques considérés par couplage du procédé électro-Fenton et d’un traitement biologique. La SMT et le TMP, ont été prétraités par procédé électro-Fenton, ce qui a conduit à leur dégradation totale, avec des taux de minéralisation faibles. Par la suite, un traitement biologique a été effectué durant 20 jours, les taux globaux de minéralisation ont alors augmenté pour atteindre 81 et 68% pour respectivement la SMT et le TMP. Dans une dernière partie, nous avons procédé à la minéralisation de deux effluents industriels, contenant les antibiotiques étudiés, par couplage du procédé électro-Fenton et d’un traitement biologique. Les taux de minéralisation globaux obtenus sont de 81 et 89% pour respectivement l’effluent SMT et l’effluent TMP. Ce qui prouve la pertinence du procédé combiné, pour le traitement des effluents industriels. / The occurrence of human and veterinary antibiotics in the aquatic ecosystem becomes a serious environmental problem. These compounds cannot be treated by wastewater treatment plants, resulting in their entry and accumulation to measurable levels in the environment. Over the last decade, the conventional biological processes were used for wastewater treatment, but did not appear to be enough effective when dealing with wastes containing antibiotics, owing to the important recalcitrance of these compounds. Therefore, the development of efficient methods to treat antibiotics is needed. The first part of this thesis is focused on the degradation of antibiotics by electro-Fenton process. This process consists in producing in situ strongly oxidizing species, hydroxyl radicals, allowing the total degradation of persistent and toxic organic compounds. Sulfamethazine (SMT) and trimethoprim (TMP) were selected as model compounds, because of their regular detection in the effluents of sewage plants, surface water and groundwater. In this first part, we examined the influence of various operating parameters, on the efficiency of electro-Fenton process. The optimal operating conditions necessary for the removal of the studied antibiotics, were also determined. Moreover, the aromatic intermediate products, generated during antibiotics degradation, were identified. Their evolution during electrolysis was also followed. The second part is devoted to the study of mineralization, of SMT and TMP, by the electro-Fenton process. The obtained results indicate that the yields of SMT and TMP mineralization were 91 and 85%, respectively after eighteen hours of treatment. The identification and monitoring of short chain carboxylic acids and released inorganic ions during the treatment, were carried out. Furthermore, based on the identified by-products, we proposed a plausible mineralization reaction pathway for SMT and TMP. The third part of this work concerns the study of the mineralization of considered antibiotics by a combined process coupling an electro-Fenton pretreatment and a biological degradation. SMT and TMP were pretreated by the electro-Fenton process, which led to their total degradation, with low levels of mineralization, ensuring significant residual organic content for a subsequent biological treatment. Afterwards, biological treatment was performed during 20 days and showed that the level of overall mineralization increased to reach 81 and 68% for SMT and TMP, respectively. In a last part, we carried out the mineralization of two industrial effluents containing SMT and TMP, by combining electro-Fenton and activated sludge treatment. Overall mineralization yields of the combined process of 81 and 89% were obtained for SMT effluent and TMP effluent, respectively. This result confirms the relevance of combined process, even for the treatment of industrial effluents.

The Beattie syenite is composed of a series of lenticular bodies of syenitic rocks, situated immediately north of the Porcupine-Destor fault zone in the town of Duparquet, approximately 32 km north of Rouyn-Noranda in the Abitibi Subprovince. The principal body is 3.3 km long and 470 m in width and is flanked by a series of smaller lenses to the south and northeast. The intrusion has been zircon dated at 2682±1Ma and 2682.9±1.1 Ma and hosted the major part of the Au-mineralization of the now defunct Beattie mine, which was an important producer of gold in the area from 1933 to 1956 (9.66 Mt at 4.88 g/t Au). A total of 5 petrographic units are defined here, on the basis of field relationships, macroscopic textures, petrology and mineralogy: 1- The porphyritic Beattie syenite unit is composed of 2% to 10% of tabular sub- to anhedral feldspar phenocrysts about 2 mm to 10 mm in size, set in a red feldspathic and aphanitic matrix. This unit can be strongly cataclastic with abundant hydrothermal minerals. 2- The equigranular magnetite-bearing syenite unit includes few feldspar phenocrysts, about 2 mm to 10 mm in a fine-grained matrix. It is characterized by unaltered titanite, epidote, hornblende porphyroblasts and is the only unit with actinolite replacing clinopyroxene. 3- The porphyritic Central Duparquet syenite unit contains between 2% - 25% of coarse equant euhedral feldspar phenocrysts, about 5 mm to 16 mm in size, in a red or sometimes grey aphanitic matrix. 4- The megaporphyritic syenite unit is composed of very coarse alkali feldspar phenocrysts, typically 1 cm to 6 cm across, in a red aphanitic matrix. The phenocrysts often form a glomeroporphyritic texture. 5- The lath syenite unit occurs as numerous ~m-width thin dykes, which cross-cut all other petrographic units. These dykes display a characteristic trachytic texture, as defined by the preferential alignment of alkali feldspar laths, which are typically 1 cm to 3 cm in a grey or red aphanitic matrix. Petrology and geochemistry investigations revealed that the syenite intruded into the older 2720-2718 Ma volcanic Deguisier Formation and the <2687±2 Ma sediments of the Porcupine Group. Detailed geochemical analysis revealed that the Deguisier Formation is composed of three units, forming a complete tholeiitic suite. The Deguisier Formation is proposed here to have been produced in a volcanic arc setting. Detailed petrological, mineralogical and geochemical studies indicate that, the syenite is part of the alkaline series and is metaluminous to peraluminous. The syenite intruded at shallow depths through a sequence of injections, yielding the five comagmatic units. The syenite and country rocks were then subjected to a series of hydrothermal alterations and brittle deformation events, combined with metamorphism to the greenschist facies. The Au-mineralization in this region is attributed to the hydrothermal alteration with brittle deformation.

Orientadores: Alvaro Penteado Crósta, Catarina Labouré Bemfica Toledo, Adalene Moreira Silva / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Geociências / Made available in DSpace on 2018-08-27T00:13:09Z (GMT). No. of bitstreams: 1 Carrino_ThaisAndressa_D.pdf: 37700269 bytes, checksum: 1032551af9407d69e558467ba552091e (MD5) Previous issue date: 2015 / Resumo: O sul do Peru contém importantes depósitos epitermais de Au-Ag (±metais base) de pequeno a médio porte, associados com a orogenia Andina do Mioceno-Plioceno. Uma análise sinóptica da região abrangendo os alvos Chapi Chiara, Cerro Millo, San Antonio de Esquilache e Cerro Chucapaca ¿ localizados em distintos paleoestratovulcões¿, foi feita via processamento e análise de imagem do sensor ASTER. Todos estes alvos são caracterizados por extensas zonas de alteração argílica avançada (alunita-caulinita) (AAA), à exceção de San Antonio de Esquilache, cuja alteração argílica (AA) (esmectita/ilita) e argílica avançada se restringe a intrusões dioríticas aflorantes. Diferentemente, o depósito epitermal de sulfetação intermediária Canahuire (Au-(Cu, Ag)) foi discriminado por extensos afloramentos NW-SE de rochas quartzosas (Grupo Yura/Juro-Cretáceo), e rochas carbonáticas (Formação Gramadal/Grupo Yura) e brechas freáticas e freatomagmáticas pobres em sílica que hospedam a mineralização. Modelo de favorabilidade para depósitos "tipo-Canahuire" foi produzido a partir da integração dos produtos ASTER usando-se a lógica fuzzy. Estudo de detalhe foi realizado no prospecto Chapi Chiara usando-se petrografia, geoquímica, espectroscopia de reflectância, dados de susceptibilidade magnética (SM), imagens da amplitude do sinal analítico e da primeira derivada vertical do campo magnético anômalo, além do processamento de imagens do sensor HyMap. As principais rochas vulcânicas amostradas compreendem andesito porfirítico (SM ~28×10-3 SI), tufo e lapilli tufo de composição riolítica (SM~0). O setor SW do prospecto é caracterizado por três subáreas com extensa AAA, marcadas por quartzo, K-alunita, alunita intermediária, Na-alunita, caulinita, dickita (±topázio, ±huangita, ± minerais APS, ±pirofilita, ±diásporo, ±rutilo) (SM ~0 a ~0,15×10-3 SI). Restritas zonas de AA (quartzo, ilita ± , ilita paragonítica ± , esmectita, ±pirita, ±rutilo) (SM ~0,01×10-3 SI) e de alteração propilítica (clorita, quartzo, calcita, epidoto, esmectita, ±caulinita, ±pirita, ± calcopirita, ± titanomagnetita e magnetita)) (SM ~3,45×10-3 a ~36,03 × 10-3 SI) ocorrem em setores distais. O setor central é marcado por brechas hidrotermais métricas/decamétricas com SM ~0 a 0,01×10-3 SI, compostas de fragmentos de rochas ricos em quartzo vuggy. Há considerável concentração de pirita e forte associação geoquímica de Au, Ag, As, Bi, Hg, Se, Sb, e Te. Os principais minerais supergênicos compreendem jarosita e goethita. As assembléias minerais hipógenas acima mencionadas revelam a existência de um sistema epitermal de alta sulfetação similar ao do prospecto aurífero Cerro Millo e aos dos depósitos auríferos Tucari e Santa Rosa, permitindo a inferência de idade relativa do paleoestratovulcão e da concomitante atividade hidrotermal em Chapi Chiara entre ~11 e ~4 Ma. Intenso processo de lixiviação magmático-hidrotermal visto nas zonas de AAA e AA paramagnéticas e diamagnéticas gerou duas extensas zonas desmagnetizadas NW-SE, compatíveis com o sistema de falhas regionais Condoroma-Caylloma. Estruturas de menor magnitude também aparecem (e.g., NE-SW, E-W). Embora estes trends sejam interessantes vetores exploratórios, a exposição de minerais formados em condições de maior temperatura (e.g., alunita+topázio, alunita+dickita+pirofilita, diásporo, alunita intermediária no setor SW), sugere tratar-se de núcleos mais erodidos, reduzindo-se o potencial de mineralização local, e/ou indicando a proximidade do limite de transição do domínio epitermal para um mesotermal em profundidade, com a possível existência de intrusão(ões) diorítica(s) próxima(s) à superfície do prospecto, similarmente ao que já é observado no alvo análogo de San Antonio de Esquilache / Abstract: Southern Peru contains important small- to medium-sized Au-Ag (± base metals) epithermal deposits, associated with the Miocene-Pliocene Andean orogeny. A synoptic analysis of the region covering the Chapi Chiara, Cerro Millo, San Antonio de Esquilache and Cerro Chucapaca targets ¿ each one located in distinct paleostratovolcanoes ¿ was done through the processing and analysis of ASTER data. These targets are characterized by extensive advanced argillic alteration zones, except San Antonio de Esquilache, that is marked by argillic alteration (AA) (smectite-illite) and advanced argillic alteration (alunite-kaolinite) (AAA) zones restricted to outcropping diorite intrusions. Unlikely, the Canahuire intermediate sulfidation epithermal Au-(Cu, Ag) deposit was discriminated by extensive NW-SE quartz-rich rocks (Yura Group/Juro-Cretaceous), and carbonate rocks (Gramadal Formation/Yura Group) and silica-poor phreatic and phreatomagmatic breccias that host the mineralization. Favorability model for "Canahuire-type" deposits was created through the integration of ASTER data using the fuzzy logic technique. A detailed study was conducted at Chapi Chiara prospect through petrography, geochemistry, reflectance spectroscopy, magnetic susceptibility (MS), images of the amplitude of analytic signal and of first vertical derivative of the anomalous magnetic field, besides the processing of HyMap hyperspectral remote sensing data. The main sampled volcanic rocks comprise porphyritic andesite (MS ~28×10-3 SI), and rhyolitic tuff and lapilli tuf (MS~0). The SW sector of the prospect is characterized by three sub-areas with extensive AAA zones, marked by quartz, K-alunite, intermediate alunite, Na-alunite, kaolinite, dickite (±topaz, ±huangite, ±APS minerals, ±pyrophyllite, ±diaspore, ±rutile) (MS ~0 to ~0,15×10-3 SI). Restricted AA zones (quartz, illite ± , paragonitic illite ± , smectite, ±pyrite, ±rutile) (MS ~0,01×10-3 SI), and of propylitic alteration (chlorite, quartz, calcite, epidote, smectite, ±kaolinite, ±pyrite, ±chalcopyrite, ±titanomagnetite and magnetite)) (MS ~3,45×10-3 to ~36,03×10-3 SI) occur in distal sectors. The central sector is marked by metric/decametric hydrothermal breccias with MS ~0 to 0,01×10-3 SI, composed of vuggy quartz-rich fragments. There is a considerable concentration of pyrite and strong geochemical association of Au, Ag, As, Bi, Hg, Se, Sb, e Te. The main supergene minerals comprise jarosite and goethite. The above mentioned hypogene mineral assemblages reveal a high sulfidation epithermal system similar to the Cerro Millo gold prospect and to Tucari and Santa Rosa gold deposits, allowing to infer a relative age between ~11 and ~4 Ma for the paleoestratovolcano and the concomitant hydrothermal activity in Chapi Chiara. Intense magmatic-hydrotermal leaching seen in the paramagnetic and diamagnetic AAA and AA zones generated two NW-SE extensive demagnetized zones, compatible with the regional Condoroma-Caylloma fault system. Smaller structures also occur (e.g., NE-SW, E-W). Although these trends are interesting exploration vectors, the exposure of minerals formed at higher temperature (e.g., alunite+topaz, alunite+dickite+pyrophyllite, diaspore, intermediate alunite in the SW sector), suggest possible eroded cores, reducing the local potential for mineralization, and/or indicating the proximity of the limit between epithermal and mesothermal domains in depth. In addition, there is a possible proximity of dioritic intrusion(s) near the surface of the prospect, similarly to the currently exposed intrusions at the surface in the analogous target of San Antonio de Esquilache / Doutorado / Geologia e Recursos Naturais / Doutora em Ciências

A osteoaderina (OSAD) tem sido identificada nos tecidos mineralizados, porém, seu papel na mineralização óssea não está claro. Foi feita uma comparação do momento em que a OSAD aparece na ossificação intramembranosa e endocondral, em relação aos estágios iniciais de mineralização. O osso parietal de fetos de ratos Wistar com 17, 18 e 21 dias e o côndilo mandibular de ratos com 30 dias foram removidos. A expressão de OSAD foi analisada por imunocitoquímica e Western blotting. Nos dois tipos de ossificação, a imunomarcação foi detectada nos osteoblastos; porém, na matriz extracelular a OSAD apareceu somente na fase fibrilar de mineralização, mantendo-se constante posteriormente. A análise por Western blotting revelou que os fetos com 17 dias continham pouco menos OSAD que os de 18 dias, enquanto a imunorreatividade diminuía nos fetos com 21 dias. Os resultados sugerem que a OSAD tem um papel na mineralização da matriz, atuando, provavelmente como organizadora de seu arcabouço ou retendo o mineral, além de exercer atividades de adesão entre os componentes da matriz. / Osteoadherin (OSAD) had been identified in mineralized tissues, but its specific role in mineralization remains unclear. The present study compared the appearance of OSAD at early stages of mineralization during both intramembranous and endochondral ossification. Parietal bone of 17, 18 and 21 days-old fetus and mandibular condyle of 30 days-old Wistar rats were removed. The expression of OSAD was analyzed by immunocytochemistry and Western blotting. In both types of ossification the labeling was uniformly distributed in the cytoplasm of osteoblasts but it only appeared in the mineralizing matrix when the fibrilar stage was taking place, remaining as a component of the mineralized bone matrix. Western blots revealed that 17-days-old embryos contained slightly less OSAD than 18- days-old fetus, while immunoreactivity was weak in 21 days-old fetus. The results suggest that OSAD plays a role in collagen fibril mineralization maybe by organizing the matrix assembly or by retaining the mineral into the matrix, besides exerting binding activities among its components.

Made available in DSpace on 2016-07-18T17:51:14Z (GMT). No. of bitstreams: 1 Ana Carolina Monico Moreira.pdf: 1642608 bytes, checksum: 18d3912f914f7722664fc90f664a9bd5 (MD5) Previous issue date: 2016-03-23 / Sandy soils, such as the west paulista region, have some limitations for growing plants, such as the low content of clay and organic matter in the soil. The challenge from this is to accumulate organic matter in sandy textured soils to improve the production system conditions. The aim of this study was to evaluate the dynamics of nitrogen and carbon in a distroferric Red-Yellow Argisol in management system rotation/succession crops of maize, lupine, Urochloa brizantha (syn. Brachiaria) and soybeans combined with N rates in no-till system. The experiment was installed and conducted at the Faculty of Agricultural Sciences at the University of West Paulista - UNOESTE in Presidente Prudente/SP, following a randomized complete block design with four replications in a split plot, the plots consisted of three crop rotations (Maize/Lupine/Fallow/Soybean, Maize plus Urochloa brizantha/Soybean; Urochloa brizantha/Soybean) and the subplots by four N rates applied annually (50, 100, 150 and 200 kg ha-1). The main crops rotated were: hybrid corn AG 5055, soybean farming BMX Power RR and forage Urochloa brizantha (syn. Brachiaria) cv. MG-5. We evaluated the total N content and N-inorganic (NH4 + and NO3) of soil, soybean leaves, corn and Urochloa and straw; NH3 volatilization; total C content; and the contents of C and N soil microbial biomass. The management of crop rotations and N levels did not influence the N content in the soil and in the plant, but the highest concentrations of N and C soil found at 0-20 cm. / Os solos arenosos, como os da região do Oeste Paulista, apresentam algumas limitações para o cultivo de plantas, como o baixo teor de argila e de matéria orgânica no solo. O grande desafio a partir disso é acumular matéria orgânica nos solos de textura arenosa para melhorar as condições do sistema de produção. O objetivo desse trabalho foi avaliar a dinâmica do nitrogênio e do carbono em um Argissolo Vermelho distroférrico em sistema de manejo com rotação/sucessão das culturas do milho, do tremoço, da Urochloa Brizantha (syn. Brachiaria) e da soja combinadas com doses de N, em sistema de plantio direto. O experimento foi instalado e conduzido na Faculdade de Ciências Agrárias, na Universidade do Oeste Paulista - UNOESTE, em Presidente Prudente/SP, seguindo o delineamento em blocos casualizados, com quatro repetições, em esquema de parcelas subdivididas, sendo as parcelas constituídas por três rotações de culturas (Milho/Tremoço/Pousio/Soja; Milho + Urochloa brizantha/Soja; Urochloa brizantha/Soja) e as subparcelas por quatro doses de N aplicadas anualmente (50, 100, 150 e 200 kg ha-1). As culturas principais rotacionadas utilizadas foram: milho híbrido AG 5055, soja cultivar BMX Potência RR e a forrageira Urochloa brizantha (syn. Brachiaria) cv. MG-5. Foram avaliados os teores de N-total e N-inorgânico (NH4+ e NO3-) do solo, das folhas da soja, do milho e da Urochloa e da palhada; NH3 volatilizada; o teor de C-total; e os teores de C e N da biomassa microbiana do solo. Conclui-se que o manejo das rotações de culturas e as doses de N não influenciaram nos teores de N no solo e na planta, porém as maiores concentrações de N e C do solo foram encontradas na camada de 0-20 cm.

This research work discusses the removal of organic pollutants specifically diclofenac and acid blue-25 using chalcogenide semiconductors. Semiconductors are materials that absorb light of specific energy and potentially degrade these organic pollutants into smaller compounds that are not toxic such as carbon dioxide and water. / Civil and Chemical Engineering

The aim of this study was to determine the occurrence of selected toxic elements in wine. The theoretical part described technology of wine production and selected toxic elements (cadmium, lead, copper, zinc, nickel and chromium) in the terms of their impact on wine quality and their effects on the human organism. It provides an overview of instrumental analytical methods, which can be used for the analysis of toxic metals. In the experimental part inductively coupled mass spektrometry technique was used for the analysis of wine samples. The measured values are statistically processed and compared with current legislation.

L’affaissement et la dégradation des sols organiques, utilisés pour les cultures maraîchères du Québec, sont actuellement des sujets criants. Ces sols très fertiles sont utilisés pour la production d’environ 50 % des légumes au Québec. Cependant, une partie de cette ressource est perdue, à chaque année, à cause de l’érosion et de l’activité microbienne. Plusieurs mesures sont actuellement prises pour réduire ces pertes, telles que l’utilisation de brise-vent et la réduction des labours, dans le but d’augmenter la durée de vie de cette ressource. Toutefois, ces méthodes ne sont pas suffisantes et ne considèrent pas les facteurs biotiques derrière la dégradation des sols organiques. La respiration (oxydation) microbienne représente pourtant plus de 50 % de la perte totale de matière organique dans le sol. Comme les nématodes libres sont les prédateurs principaux du microbiote, leur abondance et leur diversité pourraient influencer les populations microbiennes, mais les conséquences de cette interaction sur la composition et la diversité des communautés sont peu connues. Cette étude fait ressortir le rôle indirect des nématodes dans la dégradation de la matière organique via la prédation des bactéries et des champignons dans le sol et la régulation de ces communautés. Nous avons manipulé les communautés de nématodes afin d’observer des variations de composition et de diversité dans la communauté bactérienne, ainsi que dans les processus de dégradation de la matière organique. Des variations significatives ont été observées pour la production possible d’enzymes extracellulaires provenant des bactéries, l’abondance des bactéries, la disponibilité de l’azote dans le sol et le rendement des feuilles de laitues. Ces résultats permettent de faire ressortir l’importance de la prédation des nématodes et la nécessité d’accorder à ce groupe une plus grande attention dans la mise en place de systèmes de production végétale. L’ajustement des pratiques culturales pourrait aider à maintenir des réseaux écologiques plus stables et augmenter la longévité des sols organiques. / The subsidence and degradation of organic soils, used for vegetable crops in Quebec, is currently a critical issue. These very fertile soils are used for the production of about 50% of the vegetables in Quebec. However, part of this resource is lost every year due to erosion and microbial activity. Several measures are currently being taken to reduce these losses, such as the use of windbreaks and the reduction of plowing, to increase the life span of this resource. However, these methods are not sufficient and do not consider the biotic factors behind organic soil degradation. Microbial respiration (oxidation) accounts for more than 50% of the total loss of organic matter in the soil. Free-living nematodes are the main predators of the microbiota, their abundance and diversity could influence microbial populations, but the consequences of this interaction on community composition and diversity are poorly understood. This study highlights the indirect role of nematodes in the degradation of organic matter via predation of bacteria and fungi in the soil and the regulation of these communities. We manipulated nematode communities and observed variations in composition and diversity in the bacterial community, as well as in organic matter degradation processes. Specifically, significant variations were obtained for the possible production of extracellular enzymes from bacteria, bacterial abundance, soil nitrogen availability, and lettuce leaf yield. These results serve to highlight the importance of nematode predation and the need for greater attention to this group in the development of crop production systems. Adjusting cultural practices could help maintain more stable ecological networks and increase the longevity of organic soils.

The ecological significance of coarse woody debris (CWD) is usually highlighted in forests where CWD constitutes much of an ecosystem's carbon (C) source and stores. However, a unique addition of CWD is occurring in semi-deserts for which there is no ecological analog. To stem catastrophic wildfires and create firebreaks, whole Juniperus osteosperma (Torr.) and Pinus edulis (Engelm.) trees are being mechanically shredded into CWD fragments and deposited on soils previously exposed to decades of tree-induced changes that encourage "tree islands of fertility." To investigate consequences of CWD on C and nitrogen (N) cycling, we evaluated microbial metabolic activity and N transformation rates in Juniperus and Pinus surface and subsurface soils that were either shredded or left untreated. We sampled three categories of tree cover on over 40 tree cover encroachment sites. Tree cover categories (LOW = 0-15%, MID ≥ 15-45%, HIGH ≥ 45%) were used to indicate tree island development at time of treatment. In conjunction with our microbial measurements, we evaluated the frequency of three exotic grasses, and thirty-five native perennial grasses to identify links between belowground and aboveground processes. The addition of CWD increased microbial biomass by almost two-fold and increased microbial efficiency, measured as the microbial quotient, at LOW Juniperus cover. C mineralization was enhanced by CWD only in Pinus soils at the edge of tree canopies. The addition of CWD had little impact on microbial activity in subsurface soils. CWD enhanced the availability of dissolved organic C (DOC) and phosphorus (P) but tended to decrease the overall quality of labile DOC, measured as the ratio of soil microbial biomass to DOC. This suggested that the increase in DOC alone or other environmental factors novel to CWD additions lead to the increase in biomass and efficiency. P concentrations were consistently higher following CWD additions for all encroachment levels. The CWD additions decreased N mineralization and nitrification in Juniperus and Pinus soils at LOW and MID tree cover but only in surface soils, suggesting that less inorganic N was available to establishing or residual plants. The frequency of native perennial grasses, especially Elymus elymoides (Raf.), was at least 65% higher under CWD additions for all categories of tree cover, while the frequencies of exotic annual and perennial grasses were not impacted by CWD. The frequency of all perennial grasses ranged from 10-27%. Our results suggest that CWD enhanced microbial activity even when the quality of C substrates declined requiring microbes to immobilize more N. The reduction in inorganic N may promote the establishment and growth of native perennial grasses. Ultimately, the addition of CWD improved soil conditions for microbes in tree islands of fertility.

No description available.