32 research outputs found

    Integrating plant physiology into simulation of fire behavior and effects

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    Wildfires are a global crisis, but current fire models fail to capture vegetation response to changing climate. With drought and elevated temperature increasing the importance of vegetation dynamics to fire behavior, and the advent of next generation models capable of capturing increasingly complex physical processes, we provide a renewed focus on representation of woody vegetation in fire models. Currently, the most advanced representations of fire behavior and biophysical fire effects are found in distinct classes of fine-scale models and do not capture variation in live fuel (i.e. living plant) properties. We demonstrate that plant water and carbon dynamics, which influence combustion and heat transfer into the plant and often dictate plant survival, provide the mechanistic linkage between fire behavior and effects. Our conceptual framework linking remotely sensed estimates of plant water and carbon to fine-scale models of fire behavior and effects could be a critical first step toward improving the fidelity of the coarse scale models that are now relied upon for global fire forecasting. This process-based approach will be essential to capturing the influence of physiological responses to drought and warming on live fuel conditions, strengthening the science needed to guide fire managers in an uncertain future

    Effects of canopy midstory management and fuel moisture on wildfire behavior

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    Wildfires burning more and more areas in North America can partly be attributed to fire exclusion activities in the past few decades which led to higher fuel accumulation. Mechanical thinning and prescribed burns are effective techniques to manage fuel loads and to establish a higher degree of control over future fire risk as well as to restore fire prone landscapes to their natural states of succession. However, given the complexity of interactions between fine scale fuel heterogeneity and wind, it is difficult to assess the success of thinning operations and prescribed burns. The present work addresses this issue systematically by simulating a fire starting from a simple fire line and moving through a vegetative environment where the midstory has been cleared in different degrees, leading to a canopy with almost no midstory, another with a sparse midstory and another with a thick midstory. The simulations are conducted for these three canopies under two different conditions, where the fuel moisture is high and where it is low. These six sets of simulations show widely different fire behavior, in terms of fire intensity, spread rate and consumption. To understand the physical mechanisms that lead to these differences, detailed analyses are conducted to look at wind patterns, mean flow and turbulent fluxes of momentum and energy. The analyses also lead to improved understanding of processes leading to high intensity crowning behavior in presence of a dense midstory. Moreover, this work highlights the importance of considering fine scale fuel heterogeneity, seasonality, wind effects and the associated fire-canopy-atmosphere interactions while considering prescribed burns and forest management operations

    Control of Metal Sulfide Deposits in Geothermal Binary Plants

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    ABSTRACT Geothermal power generation is growing due to the need for clean renewable energy. Traditional dry steam generation plants have been in operation in countries where Geothermal dry steam is prevalent for several decades e.g., New Zealand, Iceland, Philippines. However as the cost and environmental impact of fossil fuel power generation is realized, more effort is being placed into more complex geothermal use such as low enthalpy power plants and EGS or Hot Rock technology plants. These latter technologies bring a raft of chemical complexity to power generation in particular Silica and metal Sulfides. Whilst Silica and Arsenic Sulfides are well researched, comparatively little is known about Antimony Sulfide. The absence of chemical inhibitors for the sulfide compounds has resulted in significant fouling of some geothermal plants causing losses of power output, thereby reducing the economic viability of these plants. Recent developmental work at the Ngawha Generation site in New Zealand has shown a significant step forward in the control of Antimony Sulfide deposition in binary plant heat exchangers. This plant was taking generation units off line for cleans every 12 weeks due to the loss of power production resulting from Antimony Sulfide scale. This paper outlines how these metal Sulfides have been prevented from depositing, providing improved power output, reduced need for cleaning and, subsequent, minimization of handling these toxics deposits. There may be important implications for EGS technologies as the toxic metal Sulfides have presented a barrier to consistent power production in at least one test site

    Complementary approaches to diagnosing marine diseases: a union of the modern and the classic

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    Linking marine epizootics to a specific etiology is notoriously difficult. Recent diagnostic successes show that marine disease diagnosis requires both modern, cutting-edge technology (e.g. metagenomics, quantitative realtime PCR) and more classic methods (e.g. transect surveys, histopathology and cell culture). Here, we discuss how this combination of traditional and modern approaches is necessary for rapid and accurate identification of marine diseases, and emphasize how sole reliance on any one technology or technique may lead disease investigations astray. We present diagnostic approaches at different scales, from the macro (environment, community, population and organismal scales) to the micro (tissue, organ, cell and genomic scales). We use disease case studies from a broad range of taxa to illustrate diagnostic successes from combining traditional and modern diagnostic methods. Finally, we recognize the need for increased capacity of centralized databases, networks, data repositories and contingency plans for diagnosis and management of marine disease
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