Influence of Tillage and Liming on N2O emission from a rainfed crop

Nitrous oxide (N2O) is the main greenhouse gas (GHG) produced by agricultural soils due to microbial processes. The application of N fertilizers is associated with an increase of N2O losses. However, it is possible to mitigate these emissions by the introduction of adequate management practices (Snyder et al., 2009). Soil conservation practices (i.e.no tillage, NT) have recently become widespread because they promote several positive effects (increases in soil organic carbonand soil fertility, reduction of soil erosion, etc). In terms of GHG emissions, there is no consensus in the literature on the effects of tillage on N2O. Several studies found that NT can produce greater (Baggs et al., 2003), lower (Malhi et al., 2006) or similar (Grandey et al., 2006) N2O emissions compared to traditional tillage (TT). This large uncertainty is associated with the duration of tillage practices and climatic variability. Liming is widely use to solve problems of soil acidity (Al toxicity, yield penalties, etc). Several studies show a decrease in N2O emissions with liming (Barton et al., 2013) whereas no significant effects or increases were observed in others (Galbally et al., 2010). The aim of this work was to evaluate the effects of tillage (NT vs TT) and liming application or not of Ca-amendment) on N2O emissions from an acid soil during a rainfed crop.

Biogeochemical indicators of elevated nitrogen deposition in semiarid Mediterranean ecosystems

Nitrogen (N) deposition has doubled the natural N inputs received by ecosystems through biological N fixation and is currently a global problem that is affecting the Mediterranean regions. We evaluated the existing relationships between increased atmospheric N deposition and biogeochemical indicators related to soil chemical factors and cryptogam species across semiarid central, southern, and eastern Spain. The cryptogam species studied were the biocrust-forming species Pleurochaete squarrosa (moss) and Cladonia foliacea (lichen). Sampling sites were chosen in Quercus coccifera (kermes oak) shrublands and Pinus halepensis (Aleppo pine) forests to cover a range of inorganic N deposition representative of the levels found in the Iberian Peninsula (between 4.4 and 8.1 kg N ha(-1) year(-1)). We extended the ambient N deposition gradient by including experimental plots to which N had been added for 3 years at rates of 10, 20, and 50 kg N ha(-1) year(-1). Overall, N deposition (extant plus simulated) increased soil inorganic N availability and caused soil acidification. Nitrogen deposition increased phosphomonoesterase (PME) enzyme activity and PME/nitrate reductase (NR) ratio in both species, whereas the NR activity was reduced only in the moss. Responses of PME and NR activities were attributed to an induced N to phosphorus imbalance and to N saturation, respectively. When only considering the ambient N deposition, soil organic C and N contents were positively related to N deposition, a response driven by pine forests. The PME/NR ratios of the moss were better predictors of N deposition rates than PME or NR activities alone in shrublands, whereas no correlation between N deposition and the lichen physiology was observed. We conclude that integrative physiological measurements, such as PME/NR ratios, measured on sensitive species such as P. squarrosa, can provide useful data for national-scale biomonitoring programs, whereas soil acidification and soil C and N storage could be useful as additional corroborating ecosystem indicators of chronic N pollution.

A host–guest system to study structure–function relationships of membrane fusion peptides

We designed a host–guest fusion peptide system, which is completely soluble in water and has a high affinity for biological and lipid model membranes. The guest sequences are those of the fusion peptides of influenza hemagglutinin, which are solubilized by a highly charged unstructured C-terminal host sequence. These peptides partition to the surface of negatively charged liposomes or erythrocytes and elicit membrane fusion or hemolysis. They undergo a conformational change from random coil to an obliquely inserted (≈33° from the surface) α-helix on binding to model membranes. Partition coefficients for membrane insertion were measured for influenza fusion peptides of increasing lengths (n = 8, 13, 16, and 20). The hydrophobic contribution to the free energy of binding of the 20-residue fusion peptide at pH 5.0 is −7.6 kcal/mol (1 cal = 4.18 J). This energy is sufficient to stabilize a “stalk” intermediate if a typical number of fusion peptides assemble at the site of membrane fusion. The fusion activity of the fusion peptides increases with each increment in length, and this increase strictly correlates with the hydrophobic binding energy and the angle of insertion.

Dopamine transporters are markedly reduced in Lesch-Nyhan disease in vivo.

Dopamine (DA) deficiency has been implicated in Lesch-Nyhan disease (LND), a genetic disorder that is characterized by hyperuricemia, choreoathetosis, dystonia, and compulsive self-injury. To establish that DA deficiency is present in LND, the ligand WIN-35,428, which binds to DA transporters, was used to estimate the density of DA-containing neurons in the caudate and putamen of six patients with classic LND. Comparisons were made with 10 control subjects and 3 patients with Rett syndrome. Three methods were used to quantify the binding of the DA transporter so that its density could be estimated by a single dynamic positron emission tomography study. These approaches included the caudate- or putamen-to-cerebellum ratio of ligand at 80-90 min postinjection, kinetic analysis of the binding potential [Bmax/(Kd x Vd)] using the assumption of equal partition coefficients in the striatum and the cerebellum, and graphical analysis of the binding potential. Depending on the method of analysis, a 50-63% reduction of the binding to DA transporters in the caudate, and a 64-75% reduction in the putamen of the LND patients was observed compared to the normal control group. When LND patients were compared to Rett syndrome patients, similar reductions were found in the caudate (53-61%) and putamen (67-72%) in LND patients. Transporter binding in Rett syndrome patients was not significantly different from the normal controls. Finally, volumetric magnetic resonance imaging studies detected a 30% reduction in the caudate volume of LND patients. To ensure that a reduction in the caudate volume would not confound the results, a rigorous partial volume correction of the caudate time activity curve was performed. This correction resulted in an even greater decrease in the caudate-cerebellar ratio in LND patients when contrasted to controls. To our knowledge, these findings provide the first in vivo documentation of a dopaminergic reduction in LND and illustrate the role of positron emission tomography imaging in investigating neurodevelopmental disorders.

Estudo da dinâmica e destino ambiental dos fluidos usados na usinagem industrial de peças metálicas

Este estudo consistiu na investigação sobre a interação dos lubrificantes empregados na usinagem de metais com a matéria orgânica natural (substâncias húmicas), a sua mobilidade no solo, a degradação microbiológica e a remoção dos mesmos do solo. Realizou-se, também, um estudo sobre as mudanças nas características dos fluidos após a sua utilização. Para o processo de degradação das amostras de fluido, submetidos aos efeitos de diferentes fatores ambientais, foram utilizados quatro tratamentos : (i) microrganismos nativos, chamada amostra controle; (ii) amostra controle com matéria orgânica proveniente de turfa; (iii) amostra controle acrescida de microrganismos existentes nos efluentes de máquinas de corte; e (iv) amostra controle com adição de microrganismos de compostagem. Para a pesquisa da degradação sem o efeito dos parâmetros climáticos, foram utilizadas amostras de solo contaminadas mantendo-se em estufa, e a inoculação dos microrganismos em meios de cultura com e sem acréscimo de fonte alternativa de carbono. Como técnicas analíticas, foram utilizadas a CG-DIC e a CG-EM. Essas técnicas são indicadas tanto para estudar a composição dos fluidos quanto dos produtos de degradação microbiológica, tendo sido otimizados métodos analíticos para serem empregados no monitoramento ambiental e de estudos de degradação. As análises por IVTF e por EF também foram empregadas na identificação e quantificação dos fluidos. Observou-se uma considerável interação dos fluidos solúveis com a matéria orgânica do solo, embora tenham se apresentado com alta mobilidade para alguns constituintes, bem como um acelerado processo de degradação durante o uso. De outro modo, os fluidos insolúveis se apresentaram mais imóveis, ficando retidos na matéria orgânica do solo, entretanto, foram mais prontamente degradados no ambiente que os solúveis. A adição de matéria orgânica e de microrganismos de compostagem acelerou o processo de degradação para todos os fluidos de corte investigados.

Química da matéria orgânica e pedogênese em Latossolos húmicos sob vegetação de cerrado

A matéria orgânica do solo (MOS) representa um importante reservatório de carbono (C) nos ecossistemas terrestres. O conteúdo de C estocado no solo pode ser liberado para a atmosfera na forma de CO2, com a decomposição da MOS, ou pode ser aumentado com a entrada de resíduos e retenção da MOS. Nesse sentido, é importante entender os mecanismos de estabilidade e retenção da MOS para predizer como os solos respondem a mudanças, quer sejam elas induzidas por alterações climáticas ou por práticas de manejo. Dentro dos Latossolos, classe que ocupa cerca de 32 % do território brasileiro, há aqueles que possuem horizonte A húmico hiper espesso e, portanto, com maior estoque de C. Aspectos sobre a origem, formação e preservação do horizonte A húmico destes solos em suas ocorrências em diferentes biomas ainda não foram completamente elucidados e estão estritamente ligados à fonte, dinâmica e mecanismos de preservação e distribuição da MOS no solo. O objetivo deste trabalho é entender a gênese da MO dos Latossolos húmicos que ocorrem no Bioma Cerrado, por meio da caracterização molecular pela técnica da pirólise acoplada à cromatografia gasosa e espectroscopia de massas (pirólise - CG/EM). Para isso, foram coletadas amostras dos horizontes A em dois perfis de Latossolos com horizonte A húmico (LH1, LH2) e um perfil de Latossolo com horizonte A moderado (solo de referência; LNH) situados em superfície de aplanamento adjacente à Serra do Espinhaço, no município de Grão Mogol - MG, sob clima tropical semi-úmido e vegetação de cerrado sensu strictu. Por meio da descrição morfológica dos solos em diferentes níveis de observação (campo, lupa e microscópio) procurou-se entender melhor os mecanismos de espessamento do horizonte A e a distribuição de partículas de carvão ao longo do perfil. As amostras dos horizontes foram submetidas ao fracionamento físico e extração da MOS, gerando as seguintes frações: fração leve livre (FLL); fração leve oclusa (FLO), fração extraível com NaOH (EXT) e resíduo (RES). A morfologia dos perfis evidencia a intensa e longa atividade biológica (fauna e raízes) a que esses solos foram e estão submetidos. Isso explica a abundância de microagregados e a consequente macropososidade elevada, assim como a ampla distribuição de fragmentos de carvão em todo o horizonte A, e parte do B, com dimensões milimétricas a submilimétricas, sugerindo a fragmentação destes ao longo do tempo. Foi evidenciado o maior conteúdo de carvões nos dois LHs em comparação ao LNH. A distribuição da MOS nas frações estudadas foi a mesma para os três perfis estudados: RES>EXT>FLL>FLO, que mostra a importância da fração RES para estes solos. Produtos da carbonização (Black carbon; BC: hidrocarbonetos poliaromáticos) foram mais abundantes na fração RES e FLO, no entanto, a maior diferença qualitativa entre a MOS de LHs e LNH diz respeito à abundância de BC na fração RES, que é maior em LHs do que LNH; confirmando a maior quantidade de carvões em LHs verificada na morfologia. Um índice de degradação do BC foi estabelecido com base em análise fatorial com os todas as frações estudadas e produtos poliaromáticos. Este índice, aplicado às frações EXT e RES, mostrou que a degradação do BC aumenta com a profundidade/idade, e não houve diferenças significativas entre os perfis estudados. Portanto, LHs provavelmente tem maior entrada de carvões, o que deve estar ligado a um histórico de maior incidência de incêndios ou maior abundância local de espécies arbóreas.

Community dynamics of stabilized dune xerophytic shrubs

Tese de doutoramento, Biologia (Ecologia), Universidade de Lisboa, Faculdade de Ciências, 2016

Age determination and paleotemperatures of sediment cores TTR17-1_384B and TTR17-1_436B in the Alboran Sea

Climate conditions in the westernmost Mediterranean (Alboran Sea basin) over the last two millennia have been reconstructed through integration of molecular proxies applied for the first time in this region at such high resolution. Two temperature proxies, one based on isoprenoid membrane lipids of marine Thaumarchaeota (TEXH86-tetraether index of compounds consisting of 86 carbons) and the other on alkenones produced by haptophytes (UK'37 ratio) were applied to reconstruct sea surface temperature (SST). Both records reveal a progressive long term decline in SST over the last two millennia and an increased rate of warming during the second half of the twentieth century. This is in accord with previous temperature reconstructions for the Northern Hemisphere. TEXH86 temperature values are higher than those inferred from UK'37, probably due to differences in the bloom season of haptophytes and Thaumarchaeota, and reflect summer SST. The branched vs. isoprenoid tetraether index (BIT index) suggests a low contribution of soil organic matter (OM) to the sedimentary OM. The stable carbon isotopic composition of long chain n-alkanes indicates a predominant C3 plant contribution, with no major change in vegetation over the last 2000 yr. The distribution of long chain 1,14-diols (most likely sourced by Proboscia species in this setting) provided insight into variation in upwelling conditions during the last 2000 yr and depicts a correlation with the North Atlantic Oscillation (NAO) index, providing evidence of enhanced wind induced upwelling during periods of a persistent positive mode of the NAO.

Characteristics of samples obtained during the expedition to Bolshoy Lyakhovsky Island in July/August 2014

The German-Russian project CARBOPERM - Carbon in Permafrost, origin, quality, quantity, and degradation and microbial turnover - is devoted to studying soil organic matter history, degradation and turnover in coastal lowlands of Northern Siberia. The multidisciplinary project combines research from various German and Russian institutions and runs from 2013 to 2016. The project aims assessing the recent and the ancient trace gas budget over tundra soils in northern Siberia. Studied field sites are placed in the permafrost of the Lena Delta and on Bol'shoy Lyakhovsky, the southernmost island of the New Siberian Archipelago in the eastern Laptev Sea. Field campaigns to Bol'shoy Lyakhovsky in 2014 (chapter 2) were motivated by research on palaeoenvironmental and palaeoclimate reconstruction, sediment dating, near surface geophysics and microbiological research. In particular the field campaigns focussed on: - coring Quaternary strata with a ages back to ~200.000 years ago as found along the southern coast; they allow tracing microbial communities and organic tracers (i.e. lipids and biomarkers, sedimentary DNA) in the deposits across two climatic cycles (chapter 3), - instrumenting a borehole with a thermistor chain for measuring permafrost temperatures (chapter 3), - sampling Quaternary strata for dating permafrost formation periods based on the optical stimulated luminescence (OSL) technique (chapter 4), - sampling soil and geologic formations for carbon content in order to highlight potential release of CO2 and methane based on incubation experiments (chapter 5), - profiling near surface permafrost using ground-penetrating radar and geoelectrics for defining the spatial depositional context, where the cores are located (chapters 6 + 7).

Plant species, biomass and environmental characteristics of relevés along the North America Arctic bioclimate gradient

Question: How do interactions between the physical environment and biotic properties of vegetation influence the formation of small patterned-ground features along the Arctic bioclimate gradient? Location: At 68° to 78°N: six locations along the Dalton Highway in arctic Alaska and three in Canada (Banks Island, Prince Patrick Island and Ellef Ringnes Island). Methods: We analysed floristic and structural vegetation, biomass and abiotic data (soil chemical and physical parameters, the n-factor [a soil thermal index] and spectral information [NDVI, LAI]) on 147 microhabitat releves of zonalpatterned-ground features. Using mapping, table analysis (JUICE) and ordination techniques (NMDS). Results: Table analysis using JUICE and the phi-coefficient to identify diagnostic species revealed clear groups of diagnostic plant taxa in four of the five zonal vegetation complexes. Plant communities and zonal complexes were generally well separated in the NMDS ordination. The Alaska and Canada communities were spatially separated in the ordination because of different glacial histories and location in separate floristic provinces, but there was no single controlling environmental gradient. Vegetation structure, particularly that of bryophytes and total biomass, strongly affected thermal properties of the soils. Patterned-ground complexes with the largest thermal differential between the patterned-ground features and the surrounding vegetation exhibited the clearest patterned-ground morphologies.

Permafrost cores and active layer pits on Herschel Island: core attributes

Twelve permafrost cores and active layer pits were drilled/dug on Herschel Island in order to estimate the soil organic carbon and total nitrogen contents in the first 30, 100 and 200 cm of ground. The data are the core information obtained during sampling.

Spatial distribution and morphometric analysis of thermokarst lakes and other water bodies : Case study from the sporadic permafrost region, Tavvavuoma, Sweden

Projected air and ground temperatures are expected to be higher in Arctic and sub-Arcticlatitudes and with temperatures already close to the limit where permafrost can exist,resistance against degradation is low. With thawing permafrost, the landscape is modifiedwith depression in which thermokarst lakes emerge. In permafrost soils a considerableamount of soil organic carbon is stored, with the potential of altering climate even furtherif expansion and formation of new thermokarst lakes emerge, as decay releasesgreenhouse gases (C02 and CH4) to the atmosphere. Analyzing the spatial distribution andmorphometry over time of thermokarst lakes and other water bodies, is of importance inaccurately predict carbon budget and feedback mechanisms, as well as to assess futurelandscape layout and these features interaction. Different types of high-spatial resolutionaerial and satellite imageries from 1963, 1975, 2003, 2010 and 2015, were used in bothpre- and post-classification change detection analyses. Using object oriented segmentationin eCognition combined with manual adjustments, resulted in digitalized water bodies>28m2 from which direction of change and morphometric values were extracted. Thequantity of thermokarst lakes and other water bodies was in 1963 n=92, with succeedingyears as a trend decreased in numbers, until 2010-2015 when eleven water bodies wereadded in 2015 (n=74 to n=85). In 1963-2003, area of these water bodies decreased with50 651m2 (189 446-138 795m2) and continued to decrease in 2003-2015 ending at 129337m2. Limnicity decreased from 19.9% in 1963 to 14.6% in 2003 (-5.3%). In 2010 and2015 13.7-13.6%. The late increase in water bodies differs from an earlier hypothesis thatsporadic permafrost regions experience decrease in both area and quantity of thermokarstlakes and water bodies. During 1963-2015, land gain has been in dominance of the ratiobetween the two competing processes of expansion and drainage. In 1963-1975, 55/45%,followed by 90/10% in 1975-2003. After major drainage events, land loss increased to62/38% in 2010-2015. Drainage and infilling rates, calculated for 15 shorelines werevaried across both landscape and parts of shorelines, with in average 0.17/0.15/0.14m/yr.Except for 1963-1975 when rate of change in average was in opposite direction (-0.09m/yr.), likely due to evident expansion of a large thermokarst lake. Using a squaregrid, distribution of water bodies was determined, with an indistinct cluster located in NEand central parts. Especially for water bodies <250m2, which is the dominant area classthroughout 1963-2015 ranging from n=39-51. With a heterogeneous composition of bothsmall and large thermokarst lakes, and with both expansion and drainage altering thelandscape in Tavvavuoma, both positive and negative climate feedback mechanisms are inplay - given that sporadic permafrost still exist.