1,720,982 research outputs found
Coupling GIPL Permafrost and Plant Hydraulics Model to Estimate Ecohydrological Responses to Climate Warming in Boreal Forests
Get PDFIn Arctic and Sub-Arctic regions, the existence of permafrost, a layer of soil below the earth’s surface that stays below the freezing point of 0°C for two consecutive years, depends largely on air surface temperatures. Therefore, with the occurrence of climate warming, permafrost extent and depth is changing throughout vulnerable regions located within and near the Arctic. With these regions heating up at more than twice the speed of the global average, it is becoming increasingly important to understand the dynamics of permafrost thaw and freeze cycles, as active layer thickness (ALT), which is defined as the height of the subsurface layer that freezes and thaws above the permafrost on an annual basis, affects infrastructure, methane, and carbon emissions. The vegetation that exists in permafrost regions is expected to play a large role in the progression of permafrost degradation, as plant hydraulics interact with the soil moisture, affecting characteristics such as thermal conductivity. Here, we analyze these predicted interactions between plant hydraulics and permafrost depth by coupling the GIPL soil temperature model and a plant hydraulics model. Using a robust soil, atmospheric, and plant hydraulic dataset collected at a site near Fairbanks, Alaska, independent and coupled real-world scenarios were tested. With plant hydraulics, we find that frozen soil depth has an impact on plant water stress. For frozen soil depth, we find that soil moisture impacts soil temperatures. However, sensitivity tests suggest that the thermo-physical properties of organic soils are not accurately captured by the GIPL model without further calibration.No embargoAcademic Major: Earth Science
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Sustainable Agroforestry for Climate-Stressed Farming Communities in the Sahel
Get PDFForest Gardens are a sustainable agroforestry farming practice implemented in regions around the world experiencing varying climate regimes. They utilize multiple canopy layers, the lower canopy being crops, and the other canopies being a combination of trees, shrubs, or other vegetation types. Forest Gardens are motivated by the goals of increasing ecosystem carbon sequestration, and alleviating heat and moisture stress through modulated microclimates. However, the extent to which ecosystem functions, including plant water use, carbon sequestration, and crop yield, could benefit from the implementation of Forest Gardens has not been quantified. The success of Forest Gardens also depends on sustainable irrigation strategies to optimize management goals, which requires mechanistic quantification. Here, focusing on a typical Forest Garden located in Senegal, I used in situ collected meteorological and soil moisture conditions to characterize microclimates in multi-layer canopies. The dataset was used to force an ecohydrological model to simulate soil evaporation loss, plant water use, and plant carbon sequestration under varying microclimate conditions. Specifically, I implemented two canopy structures, one with single canopy layer representing a traditional farm set up and the other with dual canopy layers representing the structure of a typical Forest Garden. I tested the impacts of dual canopy structure on ecosystem water consumption, carbon uptake and water use efficiency. Different water use strategies of trees and crops were also evaluated by modulating plant hydraulic traits. The results show that a dual-layer canopy structure of Forest Gardens alleviates the heat and atmospheric moisture stress for plants and reduces soil evaporation loss. As a result, Forest Gardens offer higher ecosystem water use efficiency, stronger carbon sink. The crop yield also likely exceeds that of traditional farms when provided with sufficient irrigation, especially for crops with an aggressive water use strategy. Nevertheless, when irrigation supply is limited, aggressive water using plants in Forest Gardens likely suffer stomatal closure, thereby restricting carbon uptake and increasing the risk of plant mortality. The findings provide support for the benefit of Forest Gardens on increasing carbon sequestration and reducing water loss. Due to tradeoffs among ecosystem functions, optimal and plant water use and irrigation strategies irrigation should be identified based on specific objectives and priorities among multiple objectives. Further in situ measurements are required to assess model uncertainties to provide robust scientific support for sustainable agroforestry management.Sustainability InstituteUndergraduate Research ScholarshipNo embargoAcademic Major: Earth Science
Multi-Decadal Recovery of Post-Wildfire Gross Primary Productivity in North-Central-Colorado
Get PDFWildfires abruptly reduce vegetation cover and gross primary productivity (GPP), a measure of photosynthesis, with the complete recovery process extending beyond a decade. Post-fire recovery of vegetation in mountainous ecosystems is particularly complex due to topography’s influence on local hydrology and climate. Most existing studies on post-fire vegetation recovery primarily focus on the short-term response while neglecting long-term legacy effects and use vegetation metrics other than GPP. Here, we address these gaps by using long-term records of remotely sensed burn area and GPP from the Landsat Burned Area Product and MODIS GPP in a space-for-time substitution approach to analyze the spatial-temporal patterns of recovery over multi-decadal periods in North-Central Colorado. We further examine how climate, environmental, and fire-related conditions contribute to the observed variation in recovery by running 17 such predictors in a Random Forest machine learning regression model. We find that GPP in burned areas within the study area recovers more slowly under conditions that are hotter, more arid, and that burned under higher severity fires, with maximum temperature anomalies being the most important predictor of post-fire GPP recovery. As post-fire climatic conditions are identified as the most important predictors of GPP recovery, these findings suggest that increasing temperatures under climate change are expected to inhibit post-fire GPP recovery, especially compounded with drought and severe burns, pointing to the value in considering post-fire climate to evaluate the impact of wildfires on terrestrial carbon budgets.No embargoAcademic Major: Earth Science
Variations on the Author
Get PDF“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
Get PDFWe 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
Get PDFWe 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
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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