1,721,665 research outputs found
Long-term grazing negatively affects nitrogen dynamics in Northern Patagonian wet meadows
No full textWet meadows are seasonally saturated wetlands that can develop in arid and semi-arid areas. In the semi-arid region of North Patagonia, Argentina wet meadows are islands of high net primary productivity surrounded by low productivity steppe vegetation. Because of this, Patagonian wet meadows have been heavily grazed by livestock for more than a century. It has been shown that overgrazed wet meadows have lower soil carbon, however, little is known about how overgrazing impacts N dynamics. To this end, we measured ammonium (NH4+), nitrate (NO3−), and total nitrogen (Nt) in paired wet meadows that varied in long-term grazing intensity (heavy vs. light). Results indicate that heavily grazed sites had on average 43% less Nt and 57% less NH4+ than lightly grazed sites. Soil NH4+ concentrations were always significantly greater than NO3− concentrations, being the later often below detection levels. In addition, NH4+ concentrations were correlated with soil moisture in lightly grazed sites, but not in heavily grazed sites. These findings indicate that implementation of better management practices are currently needed to promote more sustainable grazing in semi-arid wet meadows of North PatagoniaEEA BarilocheFil: Enriquez, Andrea Soledad. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Bariloche; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Chimner, Rodney Allen. Michigan Technological University. School of Forest Resources and Environmental Science; Estados UnidosFil: Cremona, Maria Victoria. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Bariloche; Argentin
Grazing intensity levels influence C reservoirs of wet and mesic meadows along a precipitation gradient in Northern Patagonia
Full text linkWet meadows are important ecosystems for forage production and as carbon reservoirs in semi-arid areas. In Patagonia, Argentina, large areas of wet meadows have been classified as overgrazed by livestock. The objective of this study was to determine whether long-term overgrazing has affected carbon (C) storage in plant and soil pools in wet and mesic meadows. The study occurred in Northern Patagonia, in three study sites located along a precipitation gradient. Our results indicate that long-term overgrazing reduced, on average, 35 % of the total ecosystem C pool. There was significantly lower aboveground and belowground plant production in heavily grazed compared to lightly grazed sites, 419 ± 262 – 128 ± 110 g m2 year−1 and 3796 ± 2622 – 1702 ± 1012 g m2 year−1, respectively. Soil C concentrations were also less in heavily grazed sites (184 ± 98 – 105 ± 58 g kg−1 at 1 m depth, respectively). The response of meadows to long-term heavy grazing also appears to be influenced by different levels of precipitation, with sites in drier areas being apparently more susceptible to overgrazing. Our results indicate that new management and restoration practices are needed to stop and reverse meadow deterioration in degraded meadows of Northern Patagonia.Fil: Enriquez, Andrea Soledad. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Patagonia Norte. Estación Experimental Agropecuaria San Carlos de Bariloche; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Chimner, Rodney A.. Michigan Technological University; Estados UnidosFil: Cremona, Victoria. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Buenos Aires Sur. Estación Experimental Agropecuaria Bordenave; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Diehl, Paula. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Patagonia Norte. Estación Experimental Agropecuaria San Carlos de Bariloche; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Bonvissuto, Griselda Luz. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Buenos Aires Sur. Estación Experimental Agropecuaria Bordenave; Argentin
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
Dinámica de los flujos de metano y del carbono orgánico disuelto en agua en diferentes tipos de turbera en la cuenca Pastaza-Marañón de la amazonía peruana
Full text linkEl metano (CH4) es un gas de efecto invernadero que retiene más calor que el dióxido de carbono (25-38 veces), pero permanece menos tiempo en la atmósfera. Mientras, el carbono orgánico disuelto (DOC) es uno de los componentes menos estudiados del ciclo de carbono en turberas tropicales. Se determinó las tasas de emisión de CH4 y la concentración de DOC en suelos de las turberas presentes en la cuenca de los ríos Pastaza y Marañón (C-PM). Basados en la literatura previa se evaluó si algunas variables bióticas (tipo de vegetación, tipo de planta, densidad de neumatóforos) y abióticas (microtopografía, profundidad de napa freática, temperatura de aire y de suelo) están asociadas a las emisiones de CH4 y la cantidad de DOC: Las emisiones de CH4 (~70 mg m-2 d-1) de C-PM son altas comparadas con otras turberas tropicales. Mientras que la cantidad de DOC (~30 mg L-1) es menor que lo reportado en turberas de Indonesia. La densidad de neumatóforos (raíces especiales de la palmera aguaje) está asociada a ambos componentes del ciclo de carbono, sugiriendo un rol relevante del sistema raíz-suelo-microbios en la variación de las emisiones de CH4 y la concentración de DOC.Estados Unidos. Sustainable Wetlands Adaptation and Mitigation Program (SWAMP)Tesi
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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