The combination of a strict labor legislation with daily and weekly time-dependent demand patterns has meant that transit companies tend to suffer significant inefficiencies; indeed, as more drivers than the minimum required are hired, providing services at off-peak periods, many tend to be inactive during these periods. To attack this problem, two strategies have been proposed. The first is using flexible shifts that may change daily according to a predefined contract. The other is using split shifts in which drivers' working hours are split in two to serve both the morning and afternoon peak periods. However, evidence of driver acceptance of these strategies is lacking. This paper presents a methodology to identify which characteristics of a shift are important for drivers (considering their socioeconomic characteristics) and to quantify their impact. Such information would allow transit operators to offer better working shifts to their drivers, with mutual benefits. The approach includes estimation of a mixed logit model based on stated preference data for choice of working shift; the context definition, shift attributes, and in general the experimental design were quite involved. A sample of 436 drivers working at two important operators in Santiago were interviewed. Our modelling results show considerable heterogeneity in drivers' preferences and also show that a significant number of them would be prepared to participate in flexible shifts. Our method allows operators to determine the economic incentives they should attach to such shifts for them to be accepted by the required fraction of their drivers.
Em vista à importância da dinâmica de matéria orgânica para a ecologia florestal, o presente trabalho analisou a influência topografia sobre os processos de produção e estocagem de serapilheira em área de Floresta Atlântica Ombrófila pertencente ao PARNA-Tijuca, RJ. A pesquisa englobou aspectos da vegetação, a produção, redistribuição e estocagem de serapilheira, além de características do solo como presença de matéria orgânica e fertilidade. Tais variáveis foram comparadas entre as condições de divisor de drenagem, alta e baixa encostas e o fundo de vale. O divisor de drenagem destaca-se apresentando vegetação mais baixa, com dossel um pouco mais aberto, maior densidade de indivíduos e favorável às palmeiras, em comparação às demais áreas. As variações encontradas na estrutura da vegetação não se materializaram em diferenças significativas entre as posições na encosta em relação à massa de detritos orgânicos aportados ao solo durante um ano. A redistribuição de serapilheira pela topografia é essencialmente associada ao momento da queda dos detritos, e o material já depositado no solo também pode ser mobilizado para o movimento encosta abaixo. Condicionadas pelo gradiente de umidade vinculado à topografia, taxas de decomposição diferenciadas resultam em estoques de serapilheira significativamente menos espesso no fundo de vale onde a decomposição é mais rápida. O divisor de drenagem, menos úmido, apresenta estoque mais espesso. Os estoques foram similares e intermediários na alta e baixa encosta. Como provável reflexo da decomposição mais lenta da serapilheira, o divisor de drenagem apresentou pior condição de fertilidade, com alta acidez e presença de alumínio.
O fluxo de matéria orgânica é um componente importante da dinâmica de ecossistemas e dos impactos ambientais. A água da chuva, ao percolar os ambientes terrestres, transporta partículas orgânicas das quais as menores têm maior mobilidade espacial e são mais ativas do ponto de vista ecológico, sendo chamadas de dissolvidas quando menores que 0,45 µm na maioria dos estudos recentes. A dinâmica de carbono orgânico dissolvido (COD) inclui entradas atmosféricas de moléculas alóctones, tanto pela deposição úmida vinculada à chegada direta via chuva e que pode ser observada pela concentração de COD na precipitação inicial, quanto pela deposição seca originada pela lavagem da biomassa viva onde se acumulam poeiras orgânicas de origem atmosférica, a qual pode ser observada na precipitação atravessada. Nesta segunda, também há a presença de COD originado por exsudatos solúveis secretados pela própria vegetação. Nas deposições úmida e seca, é mais relevante a condição atmosférica vinculada à influência de atividades industriais e centros urbanos, do que a produtividade dos ecossistemas em si. Ao percolar e lixiviar os estoques de serrapilheira a água da chuva atinge as maiores concentrações de COD, onde a dinâmica de produtividade e decomposição de cada ecossistema torna-se preponderante. Quando infiltra o horizonte mineral do solo o COD pode adsorver-se às partículas minerais, reduzindo sua concentração na solução do solo gradativamente com o aumento da profundidade. Quando ocorrem escoamentos superficiais, ficam reduzidas as oportunidades de adsorção do COD ao solo, resultando em aumento das transferências dos ecossistemas terrestres para os aquáticos. A B S T R A C TThe flows of organic matter are an important part of the ecosystem dynamics and environmental impacts. Rainwater, when percolating through terrestrial environments, transports organic particles, of which the smallest ones have greater spatial mobility and are more ecologically active. These particles are considered dissolved when smaller than 0.45 μm in most recent studies. The dynamics of dissolved organic carbon (DOC) involves the atmospheric input of allochthonous molecules, due to the wet deposition associated with rainfall, which can be observed in the DOC concentration in the initial precipitation, as well as by the dry deposition caused by the washing of living biomass where organic dust of atmospheric origin accumulates, which can be observed in the throughfall fluxes. In the later, there is also the presence of DOC originated by soluble exudates secreted by the vegetation itself. About wet and dry depositions, the atmospheric condition associated with the influence of industrial activities and urban centers is more relevant than the productivity of the ecosystems themselves. When percolating and leaching the litter stocks, rainwater reaches the highest concentrations of DOC, where the dynamics of productivity and decomposition of each ecosystem becomes preponderant. When it infiltrates the soil mineral horizon the DOC can adsorb to the mineral particles, reducing its concentration in the soil solution gradually as the depth increases. With the occurrence of surface runoff, opportunities for adsorption of DOC to the soil are reduced, resulting in increased transfer from terrestrial to aquatic ecosystems.Key-words: Dissolved organic carbon; forest leaching; geoecology
Considering the importance of dissolved organic carbon (DOC) flows for the carbon biogeochemical cycle, and a set of organic matter (OM) ecosystem services, our work aimed to analyze and discuss water DOC concentrations from different forest compartments: bulk precipitation, throughfall, soil solution, and stream water, in a mountainous rainforest in southeastern Brazil (Atlantic Forest). A hillslope-scale spatial design aimed to add to the discussion an analysis linked to the litter decomposition heterogeneity observed between different hillslope positions for DOC leaching. A temporal analysis was carried out by comparing rainfall events, which are different about their rainfall characteristics and antecedent humidity context. A dilution effect associated with rainfall intensity was observed in wet and dry depositions, being more pronounced on the dry deposition, which also showed a pre-wash effect linked to the previous rainfall-volume, with the time range of 15-days of previous rainfall as more relevant. Under-litter DOC concentrations showed no dilution or pre-wash effects. While in the throughfall there was no spatial difference in a hillslope-scale, the litter leaching showed great spatial variation, so that the intermediate stocks (and decomposition rates) of the mid-hillslope areas presented higher concentrations, which it is due to a balance between accumulation of material on the soil (little loss by microbiota respiration) and chemical rework on the material (new solubles) that favors the DOC leaching. In the soil solution, there is a tendency to decrease concentrations in depth. However, in events with greater rainfall intensity, soil packages with a higher OM incorporated can change from an adsorption environment to a desorption environment. The stream water showed, under baseflow condition, lower concentrations of DOC than observed in the bulk precipitation, highlighting the soil role for the organic carbon retention, where a high water infiltration capacity and OM decomposition efficiency may have key-role.
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