1,721,084 research outputs found
Raw data to peat cosm analysis from the Meadowlands in Minnesota, USA
No full textGlobally important carbon (C) stores in northern peatlands are vulnerable to oxidation in a changing climate. A growing body of literature draws attention to the importance of dissolved organic matter (DOM) in governing anaerobic metabolism in organic soil, but exactly how the reduction-oxidation (redox) activities of DOM, and particularly the phenolic fraction, are likely to change in an altered climate remain unclear. We used large mesocosms in the PEATcosm experiment to assess changes in peatland DOM and redox potential in response to experimental manipulations of water table (WT) position and plant functional groups (PFGs). WT position and PFGs interacted in their effects on redox potential and quantity and quality of DOM. Phenolics were generally of higher molecular weight and more oxidized with sedges in lowered water tables. Altered DOM character included changes in dissolved nitrogen (N), with higher N:phenolics with higher E4:E6 (absorbance ratio = 465:665) DOM in the lowered WT and sedge PFG treatments. Conversely, biomolecular assignments to free amino-sugars were largely absent from low WT treatments. Drainage resulted in the creation of unique N compounds which were more condensed (lower H:C), that changed with depth and PFG. The accumulation of oxidized compounds with low WT and in sedge rhizospheres could be very important pools of electron acceptors beneath the water table, and their mechanisms of formation are discussed. This work suggests the effects of changes in vegetation communities can be as great as WT position in directly and interactively mediating peat redox environment and the redox-activity of DOM
Genet diversity, genetic structure, and trait expression of trembling aspen (Populus tremuloides michx.) after clear-cut harvesting and post-harvest soil treatments
No full text© 2017, Canadian Science Publishing. All rights reserved. Trembling aspen is a fast growing, broadly distributed tree in North America that reproduces by root suckers (clonally) and by seeds (sexually). Since timber harvesting can affect both reproduction pathways by changing the soil properties, we assessed genet diversity, genetic structure, and phenotypic trait expression of trembling aspen populations after clear-cut harvesting in a long-term soil productivity study site in Michigan. A total of 323 stems in replicated plots having heavy soil compaction and surface organic matter (OM) removed, and the untreated controls, were analyzed at microsatellites and for phenotypic traits. Overall, higher spatial aggregation of ramets from the same genet, a greater spatial separation of different genets, and a very good phenotypic separation among genets was observed in the treatment plots. In contrast, for plots with spatially intermixed clones phenotypic separation was much lower. Genetic differentiation was high between individual plots, but soil compaction and OM removal had little effect on genetic differentiation and diversity. One treatment plot was strongly differentiated phenotypically, but not genetically, from all other plots. Consequently, microenvironmental and genetic differences should be considered when forest management effects on trait expressions and productivity are analyzed. Overall, heavy soil compaction and OM removal in fine-textured soil seemed to have restricted the spread of aspen clones
FTIR spectral data and derivative indices produced across peatland forestation gradient and depth profiles for 30 peatlands in the midwest United States
No full textPeatlands contain enormous carbon stocks, but the stability of this carbon is variable. Peatlands can vary in tree cover from completely open to forested with associated differences in peat quality. Peat quality, or potential for mineralization, is a contributing factor affecting how the carbon balance of peatland ecosystems could change with climate or land use changes. We compared the peat quality of open peatlands dominated by Sphagnum mosses to forested, or silvic, peatlands dominated by black spruce and tamarack or northern white cedar to quantify the effects of different carbon sources on peat quality. We used Fourier-transform infrared spectrometry (FTIR) to analyze peat properties throughout the depth profile of 30 peat cores across the hemi-boreal Upper Great Lakes region. We found that tree cover was associated with differences in both surficial and deep peat quality. Silvic peat had lower peat quality than Sphagnum peat as shown by FTIR indices. Sphagnum peat also had significantly higher peat quality at the surface compared to at depth. However, silvic peat showed no significant difference with depth in any indices. Our results indicate that the dominant plant functional type is a strong driver of peat quality as we identified key differences between silvic and Sphagnum peatlands. These relatively local differences are similar in magnitude to those found across biomes comparing tropical swamps to boreal Sphagnum peatlands. This implies that the dominant plant functional type (e.g. tree, shrub, graminoid, or moss) may be more important to peat quality than species identity - or even latitude - in peatlands
Streamflow, snow measurements, soil moisture, air temperature, absorption and fluorescence indices at Brooks Gorge Research Watershed in 2016
No full textIn many northern watersheds, runoff occurring with snowmelt brings the largest pulse of dissolved organic matter (DOM) and other solutes from soils to streams. Yet, exactly how DOM fractions are altered with movement through soils and into streams is not well understood, particularly with changes in snowmelt timing and magnitude. We studied the optical character of DOM as it moved through a northern forested watershed, from contrasting aspects with different snowmelt rates, and into a small headwater stream. We found significant differences among optical characteristics of leaf leachates, DOM within soil horizons on contrasting north-facing and south-facing aspects, and stream DOM
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
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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