1,721,025 research outputs found
Riparian zone heterogeneity influences the amount and fate of biodegradable dissolved organic carbon at the land-water interface
No full textThe transport of biodegradable dissolved organic carbon (bDOC) across land-water boundaries is central to supporting the ecological and biogeochemical functioning of freshwater ecosystems. Yet, we know little about how the generation and supply of terrestrial bDOC to streams and lakes is regulated by the physical, biological, and hydrological properties of the riparian interface. Here, we assessed how terrestrial, groundwater, and aquatic bDOC differ along flowpaths connecting riparian soils to a headwater boreal stream. We further tested how bDOC generation and supply differs among interfaces with distinct hydrogeomorphologies, as reflected by differences in soil properties, groundwater dynamics, and hydrological connectivity to the stream. We found that bDOC quantity declined sharply from terrestrial sources, to groundwater, to aquatic systems, and that these differences were associated with changes in the optical and chemical properties of the dissolved organic matter pool. However, bDOC generation and potential transport in groundwater varied across site types and reflected local differences in soil organic matter storage, depth to groundwater, and soil microbial community activity. Interface zones with organic-rich soils but weak hydrological connections had a large capacity to produce bDOC, but likely only laterally contributed organic resources during floods. By contrast, sites with stronger lateral hydrological connectivity served as persistent conduits for organic resources generated further upslope, even if the capacity to generate bDOC locally was weak. Overall, our results illustrate how hydrogeomorphic heterogeneity at the land-water interface can add spatial and temporal complexity to the generation and transfer of bDOC from soils to the inland water continuum
Stream metabolism (as resazurin-resorufin transformation) along a boreal headwater stream and its relation to groundwater organic matter supply
No full textDatasets supporting the manuscript entitled "Groundwater-stream connections shape the spatial patterns and rates of aquatic metabolism", published in Limnology and Oceanography Letters. Three datasets are available:
"Groundwater_Characterization.csv": dissolved organic matter characterization of and heterotrophic activity associated with, the major water sources discharging into a headwater boreal stream during summer 2017. Major water sources are: lake water and five discrete groundwater inflows (here named as discrete riparian inflow points).
"Raz_Additions.csv": Constant-rate additions of resazurin performed in a boreal headwater stream (Krycklan catchment, Sweden) during seven dates of summer 2017. Data contains resazurin and resorufin concentrations from the surface and hyporheic water at 18 stations along a 90-m long reach.
"Raz_transformation_metric.csv": Hydrologic and metabolic characterization of the 90-m long reach for the seven resazurin additions conducted in summer 2017.
More information about the data can be found in the document "Metadata.doc". Information about field and laboratory procedures can be found in the main manuscript or in the document "Supporting_Information.doc"
Groundwater-stream connections shape the spatial pattern and rates of aquatic metabolism
Full text linkA longstanding challenge in stream ecology is to understand how landscape configuration organizes spatial patterns of ecosystem function via lateral groundwater connections. We combined laboratory bioassays and field additions of a metabolic tracer (resazurin) to test how groundwater-stream confluences, or “discrete riparian inflow points” (DRIPs), regulate heterotrophic microbial activity along a boreal stream. We hypothesized that DRIPs shape spatial patterns and rates of aquatic heterotrophic microbial activity by supplying labile dissolved organic matter (DOM) to streams. Laboratory bioassays showed that the potential influence of DRIPs on heterotrophic activity varied spatially and temporally, and was related to their DOM content and composition. At the reach scale, DRIP-stream confluences elevated the spatial heterogeneity and whole-reach rates of heterotrophic activity, especially during periods of high land–water hydrological connectivity. Collectively, our results show how the arrangement of lateral groundwater connections influence heterotrophic activity in streams with implications for watershed biogeochemical cycles
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Groundwater inflows control patterns and sources of greenhouse gas emissions from streams
No full textHeadwater streams can be important sources of carbon dioxide (CO2) and methane (CH4) to the atmosphere. However, the influence of groundwater–stream connectivity on the patterns and sources of carbon (C) gas evasion is still poorly understood. We explored these connections in the boreal landscape through a detailed study of a 1.4 km lake outlet stream that is hydrologically fed by multiple topographically driven groundwater input zones. We measured stream and groundwater dissolved organic C (DOC), CO2, and CH4 concentrations every 50 m biweekly during the ice-free period and estimated in-stream C gas production through a mass balance model and independent estimates of aquatic metabolism. The spatial pattern of C gas concentrations was consistent over time, with peaks of both CH4 and CO2 concentrations occurring after each groundwater input zone. Moreover, lateral C gas inputs from riparian soils were the major source of CO2 and CH4 to the stream. DOC mineralization and CH4 oxidation within the stream accounted for 17–51% of stream CO2 emissions, and this contribution was the greatest during relatively higher flows. Overall, our results illustrate how the nature and arrangement of groundwater flowpaths can organize patterns of stream C concentrations, transformations, and emissions by acting as a direct source of gases and by supplying organic substrates that fuel aquatic metabolism. Hence, refined assessments of how catchment structure influences the timing and magnitude of groundwater–stream connections are crucial for mechanistically understanding and scaling C evasion rates from headwaters.inancial supported was provided by the Swedish Research Foundation (VR) through SITES, Future Forests, Kempe Foundation, FOMA (SLU), Formas, and SKB. Anna Lupon and Blaize Denfeld were supported by a Kempe Foundation stipend.Peer reviewe
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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