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Author: Nathaniel Kiel
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ISBN:
Category :
Languages : en
Pages : 0
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Changing global drivers are eroding ecosystem resilience. As change continues, determining the implications of ecosystem transformations must be coupled with "climate change education" and evidence-based undergraduate biology curricula to train the next generation of scientists. My dissertation addresses each need in turn. First, I use remote sensing and field studies to understand the drivers and effects of poor subalpine forest recovery following large, stand-replacing wildfire in the U.S. Northern Rocky Mountains. I ask: (1) how extensive is forest conversion to sparse or non-forest three decades after the 1988 Yellowstone fires, and what drives its distribution? (2) how does forest conversion affect subalpine forest understory plant communities, aboveground carbon stocks, and the potential for forest recovery? and (3) how do anomalously frequent (30-year fire-return interval) stand-replacing wildfires in forests adapted to historically infrequent (125-year fire-return interval) fires alter understory plant communities? I complement these studies with the development and assessment of new undergraduate curricula on systems thinking and biogeochemical cycling, incorporating gameplay and simple simulation modeling to ask: how do student attitudes toward and understanding of the nitrogen cycle change following game- and inquiry-based learning? Subalpine forest conversion 30 years after the 1988 fires was extensive, covering ~41,000 hectares of previously forested area primarily at higher elevations and further from surrounding unburned forest. While much of this area appears "locked in" to sparse or non-forest, other areas may yet recover to forest owing to seed pressure from ex situ and in situ sources. Understory plant communities increasingly resembled meadow communities where tree densities were lowest, and aboveground carbon stock recovery was diminished. Understory communities were also affected by minimal forest recovery following anomalously frequent fire, with shifts toward shade-intolerant species and species from lower elevation zones adapted to drier conditions. Finally, undergraduate students in an intermediate general ecology course self-identified improved attitudes toward and understanding of the nitrogen cycle, largely attributing these changes to gameplay of "The N Game" and active lecture. This research elucidates how changing climate and disturbance will alter forest ecosystems and how evidence-based teaching approaches may help train undergraduate students to address these and other global challenges.
Author: Nathaniel Kiel
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Book Description
Changing global drivers are eroding ecosystem resilience. As change continues, determining the implications of ecosystem transformations must be coupled with "climate change education" and evidence-based undergraduate biology curricula to train the next generation of scientists. My dissertation addresses each need in turn. First, I use remote sensing and field studies to understand the drivers and effects of poor subalpine forest recovery following large, stand-replacing wildfire in the U.S. Northern Rocky Mountains. I ask: (1) how extensive is forest conversion to sparse or non-forest three decades after the 1988 Yellowstone fires, and what drives its distribution? (2) how does forest conversion affect subalpine forest understory plant communities, aboveground carbon stocks, and the potential for forest recovery? and (3) how do anomalously frequent (30-year fire-return interval) stand-replacing wildfires in forests adapted to historically infrequent (125-year fire-return interval) fires alter understory plant communities? I complement these studies with the development and assessment of new undergraduate curricula on systems thinking and biogeochemical cycling, incorporating gameplay and simple simulation modeling to ask: how do student attitudes toward and understanding of the nitrogen cycle change following game- and inquiry-based learning? Subalpine forest conversion 30 years after the 1988 fires was extensive, covering ~41,000 hectares of previously forested area primarily at higher elevations and further from surrounding unburned forest. While much of this area appears "locked in" to sparse or non-forest, other areas may yet recover to forest owing to seed pressure from ex situ and in situ sources. Understory plant communities increasingly resembled meadow communities where tree densities were lowest, and aboveground carbon stock recovery was diminished. Understory communities were also affected by minimal forest recovery following anomalously frequent fire, with shifts toward shade-intolerant species and species from lower elevation zones adapted to drier conditions. Finally, undergraduate students in an intermediate general ecology course self-identified improved attitudes toward and understanding of the nitrogen cycle, largely attributing these changes to gameplay of "The N Game" and active lecture. This research elucidates how changing climate and disturbance will alter forest ecosystems and how evidence-based teaching approaches may help train undergraduate students to address these and other global challenges.
Author:
Publisher:
ISBN:
Category : Botany
Languages : en
Pages : 372
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Author: William H. Romme
Publisher:
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Category : Fire
Languages : en
Pages : 25
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Young, recently burned forests are increasingly widespread throughout western North America, but forest development after large wildfires is not fully understood, especially regarding effects of variable burn severity, environmental heterogeneity, and changes in drivers over time. We followed development of subalpine forests after the 1988 Yellowstone fires by periodically re-sampling permanent plots established soon after the fires. We asked two questions about patterns and processes over the past 25 years: (1) Are plant species richness and community composition converging or diverging across variation in elevation, soils, burn severity, and post-fire lodgepole pine (Pinus contorta var. latifolia) density? (2) What are the major controls on post-fire species composition, and has the relative importance of controls changed over time? For question 1, we sampled 10-m2 plots (n=552) distributed among three geographic areas that differ in elevation and substrate; plots spanned the spectrum of fire severities and were re-sampled periodically from 1991-2013. For question 2, we sampled 0.25-ha plots (n=72), broadly distributed across areas that burned as stand-replacing fire, in 1999 and 2012. Richness and species composition diverged early on between infertile low-elevation areas (lower richness) and more fertile high-elevation areas (greater richness). Richness increased rapidly for the first five years post-fire, then leveled off or increased only slowly thereafter. Only 6% of 227 recorded species were non-native. Some annuals and species with heat-stimulated soil seed banks were associated with severely burned sites. However, most post-fire species had been present before the fire; many survived as roots or rhizomes and regenerated rapidly by sprouting. Among the 72 plots, substrate, temperature, and precipitation (the abiotic template) were consistently important drivers of community composition in 1999 and 2012. Post-fire lodgepole pine abundance was not significant in 1999 but was the most important driving variable by 2012, with a negative effect on presence of most understory species, especially annuals and shade-intolerant herbs. Burn severity was significant in 1999 but not in 2012, and distance to unburned forest had no influence in either year. The 1988 fires did not fundamentally alter subalpine forest community assemblages in Yellowstone, and ecological memory conferred resilience to high-severity fire.
Author: Linda L. Wallace
Publisher: Yale University Press
ISBN: 0300127758
Category : Nature
Languages : en
Pages : 400
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Book Description
Americans currently choose their president through the electoral college, an extraordinarily complex mechanism that may elect a candidate who does not receive the most votes. In this provocative book, George Edwards III argues that, contrary to what supporters of the electoral college claim, there is no real justification for a system that might violate majority rule. Drawing on systematic data, Edwards finds that the electoral college does not protect the interests of small states or racial minorities, does not provide presidents with effective coalitions for governing, and does little to protect the American polity from the alleged harms of direct election of the president. In fact, the electoral college distorts the presidential campaign so that candidates ignore most small states and some large ones and pay little attention to minorities, and it encourages third parties to run presidential candidates and discourages party competition in many states. Edwards demonstrates effectively that direct election of the president without a runoff maximizes political equality and eliminates the distortions in the political system caused by the electoral college.
Author: Diana F. Tomback
Publisher:
ISBN:
Category : Greater Yellowstone Ecosystem
Languages : en
Pages : 26
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Author: Jason M. Greenlee
Publisher:
ISBN:
Category : Botany
Languages : en
Pages : 252
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Author: Emily Mary Booth
Publisher:
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Category :
Languages : en
Pages : 310
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Wildland fires are becoming more frequent and more severe in the United States, due in part to climate change and in part to long-term fire suppression and the subsequent build-up of fuels. Following wildfires of greater severity than what were historically present in an area, plant community recovery trajectories may diverge from the pre-disturbance plant community. The Lost Pines region of central Texas supported the westernmost stands of loblolly pine (Pinus taeda) in the United States. In 2011, a wildfire burned most of Bastrop State Park (BSP), located in the Lost Pines. Pre-fire, BSP was a mostly closed-canopy forest dominated by loblolly pine and several species of oak (Quercus spp.), with sparse herbaceous vegetation and a dense mid-canopy of yaupon (Ilex vomitoria). Most plants in BSP were either killed or top-killed in the wildfire. We studied pre- and post-fire plant community dynamics to understand and predict post-fire plant community recovery trajectories. Top-killed oak species sprouted vigorously in more severely-burned plots (Chapter 1, Chapter 2); yaupon sprouted in all burn severity classes (Chapter 3). Loblolly pine, which can only recruit from seed, established more slowly than sprouting species, in part due to the transitory inhibitory effect of an erosion control product (Chapter 3). In the first year after the fire, it appeared that oak sprouts might out-compete loblolly pine seedling recruitment. However, in 2015, a large loblolly pine recruitment event occurred following a year of unusually high precipitation (Chapter 1, Chapter 2). These results indicate recovery trajectories towards continued survival of the loblolly pine population in BSP, although with a potentially greater abundance of oak species than what was present pre-fire. Furthermore, yaupon is likely to re-form dense thickets such as those present pre-fire without measures to prevent woody plant encroachment. Immediately post-fire, the herbaceous plant community increased in abundance, richness and diversity, likely due to greater canopy openness (Chapter 4). Very few invasive species were present either pre- or post-fire (Chapter 5). Alternate trajectories towards open-canopy savanna with a diverse understory community and lower mid-story tree abundance could be maintained by management actions such as prescribed fire or mechanical thinning.
Author: Don G. Despain
Publisher: Roberts Rinehart Publishers
ISBN:
Category : Nature
Languages : en
Pages : 268
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A comprehensive view of vegetation types, distribution, and the natural forces that influence plant succession in Yellowstone.
Author:
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Category : Animal ecology
Languages : en
Pages : 92
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Author: Monica Goigel Turner
Publisher:
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Category : Biomass
Languages : en
Pages : 14
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Disturbance and succession have long been of interest in ecology, but how landscape patterns of ecosystem structure and function evolve following large disturbances is poorly understood. After nearly 25 years, lodgepole pine ( Pinus contorta var. latifolia) forests that regenerated after the 1988 Yellowstone Fires (Wyoming, USA) offer a prime opportunity to track the fate of disturbance-created heterogeneity in stand structure and function in a wilderness setting. In 2012, we resampled 72 permanent plots to ask (1) How have postfire stand structure and function changed between 11 and 24 yr postfire, and what variables explain these patterns and changes? (2) How has landscape-level (among-stand) variability in postfire stand structure and function changed between 11 and 24 yr postfire? We expected to see evidence of convergence beginning to emerge, but also that initial postfire stem density would still determine trajectories of biomass accumulation. After 24 yr, postfire lodgepole pine density remained very high (mean = 21,738 stems/ha, range = 0-344,067 stems/ha). Stem density increased in most plots between 11 and 24 yr postfire, but declined sharply where 11-yr-postfire stem density was >72,000 stems/ha. Stems were small in high-density stands, but stand-level lodgepole pine leaf area, foliage biomass, and live aboveground biomass increased over time and with increasing stem density. After 24 yr, mean annual lodgepole pine aboveground net primary production ( ANPP) was high (mean = 5 Mg?ha?1?yr?1, range = 0-16.5 Mg?ha?1?yr?1). Among stands, lodgepole pine ANPP increased with stem density, which explained 69% of the variation; another 8% of the variation was explained by environmental covariates. Early patterns of postfire lodgepole pine regeneration, which were contingent on prefire serotiny and fire severity, remained the dominant driver of stand structure and function. We observed mechanisms that would lead to convergence in stem density (structure) over time, but it was landscape variation in functional variables that declined substantially. Stand structure and function have not converged across the burned landscape, but our evidence suggests function will converge sooner than structure.
