Integrating Discharge-Concentration Dynamics Across Carbon Forms in a Boreal Landscape

The flux of terrestrial carbon across land-water boundaries influences the overall carbon balance of landscapes and the ecology and biogeochemistry of aquatic ecosystems. The local consequences and broader fate of carbon delivered to streams is determined by the overall composition of carbon inputs, including the balance of organic and inorganic forms. Yet, our understanding of how hydrologic fluxes across different land-water interfaces regulate carbon supply remains poor. We used 7 years of data from three boreal catchments to test how different land-water interfaces (i.e., forest, wetland, and lake) modulate concentration-discharge (C-Q) relationships for dissolved organic carbon (DOC), carbon dioxide (CO2), and methane, as well as the balance among forms (e.g., DOC:CO2). Seasonal patterns in concentrations and C-Q relationships for individual carbon forms differed across catchments. DOC varied between chemostasis and transport limitation in the forest catchment, between supply limitation and chemostasis in the wetland catchment, and was persistently chemostatic in the lake outlet stream. Carbon gases were supply limited overall, but exhibited chemostasis or transport limitation in the forest and wetland catchments linked to elevated flow in summer and autumn. Unique C-Q relationships for individual forms reflected the properties of different interfaces and underpinned changes in the composition of lateral carbon supply. Accordingly, DOC dominated the carbon flux during snowmelt, whereas gas evasion increased in relative importance during other times of the year. Integrating the C-Q dynamics of individual carbon forms provides insight into the shifting composition of lateral export, and thus helps to predict how hydrologic changes may alter the fate of carbon supplied to streams

Famílies botàniques de plantes medicinals

Facultat de Farmàcia, Universitat de Barcelona. Ensenyament: Grau de Farmàcia, Assignatura: Botànica Farmacèutica, Curs: 2013-2014, Coordinadors: Joan Simon, Cèsar Blanché i Maria Bosch.Els materials que aquí es presenten són els recull de 175 treballs d’una família botànica d’interès medicinal realitzats de manera individual. Els treballs han estat realitzat per la totalitat dels estudiants dels grups M-2 i M-3 de l’assignatura Botànica Farmacèutica durant els mesos d’abril i maig del curs 2013-14. Tots els treballs s’han dut a terme a través de la plataforma de GoogleDocs i han estat tutoritzats pel professor de l’assignatura i revisats i finalment co-avaluats entre els propis estudiants. L’objectiu principal de l’activitat ha estat fomentar l’aprenentatge autònom i col·laboratiu en Botànica farmacèutica

Dry habitats sustain high CO2 emissions from temporary ponds across seasons

Despite the increasing understanding of the magnitude and drivers of carbon gas emissions from inland waters, the relevance of water fluctuation and associated drying on their dynamics is rarely addressed. Here, we quantified CO2 and CH4 fluxes from a set of temporary ponds across seasons. The ponds were in all occasion net CO2 emitters irrespective of the presence or absence of water. While the CO2 fluxes were in the upper range of emissions for freshwater lentic systems, CH4 fluxes were mostly undetectable. Dry habitats substantially contributed to these emissions and were always a source of CO2, whereas inundated habitats acted either as a source or a sink of atmospheric CO2 along the year. Higher concentrations of coloured and humic organic matter in water and sediment were linked to higher CO2 emissions. Composition of the sediment microbial community was related both to dissolved organic matter concentration and composition, but we did not find a direct link with CO2 fluxes. The presence of methanogenic archaea in most ponds suggested the potential for episodic CH4 production and emission. Our results highlight the need for spatially and temporally inclusive approaches that consider the dry phases and habitats to characterize carbon cycling in temporary systems

Dry habitats sustain high CO2 emissions from temporary ponds across seasons

Despite the increasing understanding of the magnitude and drivers of carbon gas emissions from inland waters, the relevance of water fluctuation and associated drying on their dynamics is rarely addressed. Here, we quantified CO2 and CH4 fluxes from a set of temporary ponds across seasons. The ponds were in all occasion net CO2 emitters irrespective of the presence or absence of water. While the CO2 fluxes were in the upper range of emissions for freshwater lentic systems, CH4 fluxes were mostly undetectable. Dry habitats substantially contributed to these emissions and were always a source of CO2, whereas inundated habitats acted either as a source or a sink of atmospheric CO2 along the year. Higher concentrations of coloured and humic organic matter in water and sediment were linked to higher CO2 emissions. Composition of the sediment microbial community was related both to dissolved organic matter concentration and composition, but we did not find a direct link with CO2 fluxes. The presence of methanogenic archaea in most ponds suggested the potential for episodic CH4 production and emission. Our results highlight the need for spatially and temporally inclusive approaches that consider the dry phases and habitats to characterize carbon cycling in temporary systems

Dry habitats sustain high CO2 emissions from temporary ponds across seasons

Despite the increasing understanding of the magnitude and drivers of carbon gas emissions from inland waters, the relevance of water fluctuation and associated drying on their dynamics is rarely addressed. Here, we quantified CO2 and CH4 fluxes from a set of temporary ponds across seasons. The ponds were in all occasion net CO2 emitters irrespective of the presence or absence of water. While the CO2 fluxes were in the upper range of emissions for freshwater lentic systems, CH4 fluxes were mostly undetectable. Dry habitats substantially contributed to these emissions and were always a source of CO2, whereas inundated habitats acted either as a source or a sink of atmospheric CO2 along the year. Higher concentrations of coloured and humic organic matter in water and sediment were linked to higher CO2 emissions. Composition of the sediment microbial community was related both to dissolved organic matter concentration and composition, but we did not find a direct link with CO2 fluxes. The presence of methanogenic archaea in most ponds suggested the potential for episodic CH4 production and emission. Our results highlight the need for spatially and temporally inclusive approaches that consider the dry phases and habitats to characterize carbon cycling in temporary systems

A tale of pipes and reactors : Controls on the in-stream dynamics of dissolved organic matter in rivers

The potential for rivers to alter the flux of dissolved organic matter (DOM) from land to ocean is widely accepted. Yet anticipating when and where rivers behave as active reactors vs. passive pipes of DOM stands as a major knowledge gap in river biogeochemistry, resulting in uncertainties for global carbon models. Here, we investigate the controls on in-stream DOM dynamics by evaluating changes in DOM concentration and composition along several reaches of a medium-sized river network over one full hydrological year. Roughly half of the observations over time and space showed active reactor conditions and, among these, similar pro-portion of gains and losses was measured. High water residence times promoted the active over passive behavior of the reaches, while DOM properties and nitrate availability determined whether they supplied or removed DOM from the river. Among different DOM fractions, protein-like DOM both of terrestrial and aquatic origin seemed to drive bulk DOM patterns. Our study emphasizes the role of water residence time as a physical constraint for in-stream processes, and provides new insights into the key factors governing the net balance between in-stream gains and losses of DOM in rivers

Local and regional drivers of headwater streams metabolism : insights from the first AIL collaborative project

Streams play a key role in the global biogeochemical cycles, processing material from adjacent terrestrial systems and transporting it downstream. However, the drivers of stream metabolism, especially those acting at broad spatial scales, are still not well understood. Moreover, stream metabolism can be affected by hydrological changes associated with seasonality, and thus, assessing the temporality of metabolic rates is a key question to understand stream function. This study aims to analyse the geographical and temporal patterns in stream metabolism and to identify the main drivers regulating the whole ecosystem metabolic rates at local and regional scales. Using a coordinated distributed experiment, we studied ten headwaters streams located across five European ecoregions during summer and fall 2014. We characterized the magnitude and variability of gross primary production (GPP) and ecosystem respiration (ER) with the open-channel method. Moreover, we examined several climatic, geographical, hydrological, morphological, and physicochemical variables that can potentially control stream metabolic rates. Daily rates of stream metabolism varied considerately across streams, with GPP and ER ranging from 0.06 to 4.33 g O-2 m(-2) d(-1) and from 0.72 to 14.20 g O-2 m(-2) d(-1), respectively. All streams were highly heterotrophic (P/R < 1), except the southernmost one. We found that the drier climates tended to have the highest GPP, while humid regions presented the highest ER. Between the sampling periods no statistical differences were found. Partial-least squares models (PLS) explained similar to 80% of the variance in GPP and ER rates across headwater streams and included both local and regional variables. Rates of GPP varied primarily in response to the local variables, such as streambed substrate and stream water temperature. In contrast, regional variables, such as the mean annual temperature or the land use of the catchment, had more relevance to explain ER. Overall, our results highlight that stream metabolism depends on both local and regional drivers and show the positive experience of a young network of researchers to assess scientific challenges across large-scale geographic areas