Controls on ecosystem respiration of carbon dioxide across a boreal wetland gradient in Interior Alaska

Thesis (M.S.) University of Alaska Fairbanks, 2012Permafrost and organic soil layers are common to most wetlands in interior Alaska, where wetlands have functioned as important long-term soil carbon sinks. Boreal wetlands are diverse in both vegetation and nutrient cycling, ranging from nutrient-poor bogs to nutrient- and vascular-rich fens. The goals of my study were to quantify growing season ecosystem respiration (ER) along a gradient of vegetation and permafrost in a boreal wetland complex, and to evaluate the main abiotic and biotic variables that regulate CO₂ release from boreal soils. Highest ER and root respiration were observed at a sedge/forb community and lowest ER and root respiration were observed at a neighboring rich fen community, even though the two fens had similar estimates of root biomass and vascular green area. Root respiration also contributed approximately 40% to ER at both fens. These results support the conclusion that high soil moisture and low redox potential may be limiting both heterotrophic and autotrophic respiration at the rich fen. This study suggests that interactions among soil environmental variables are important drivers of ER. Also, vegetation and its response to soil environment determines contributions from aboveground (leaves and shoots) and belowground (roots and moss) components, which vary among wetland gradient communities.Introduction -- Introduction to boreal wetlands -- Ecosystem respiration and its role in peatland function -- Brief rationale for this study -- Goals, objectives, and hypotheses -- Methods -- Description of study site and the gradient design -- Atmospheric and soil environmental variables -- Ecosystem respiration fluxes -- Root respiration fluxes and aboveground vegetation measurements -- Results -- Soil environmental variables along the gradient -- Ecosystem respiration -- Contributions of root respiration to ER -- Discussion -- Patterns of ecosystem respiration along the wetland gradient -- The role of roots in ecosystem respiration of CO₂ -- Study limitations and ideas for future research -- Conclusions

Controls on ecosystem respiration of carbon dioxide across a boreal wetland gradient in Interior Alaska

Thesis (M.S.) University of Alaska Fairbanks, 2012Permafrost and organic soil layers are common to most wetlands in interior Alaska, where wetlands have functioned as important long-term soil carbon sinks. Boreal wetlands are diverse in both vegetation and nutrient cycling, ranging from nutrient-poor bogs to nutrient- and vascular-rich fens. The goals of my study were to quantify growing season ecosystem respiration (ER) along a gradient of vegetation and permafrost in a boreal wetland complex, and to evaluate the main abiotic and biotic variables that regulate CO₂ release from boreal soils. Highest ER and root respiration were observed at a sedge/forb community and lowest ER and root respiration were observed at a neighboring rich fen community, even though the two fens had similar estimates of root biomass and vascular green area. Root respiration also contributed approximately 40% to ER at both fens. These results support the conclusion that high soil moisture and low redox potential may be limiting both heterotrophic and autotrophic respiration at the rich fen. This study suggests that interactions among soil environmental variables are important drivers of ER. Also, vegetation and its response to soil environment determines contributions from aboveground (leaves and shoots) and belowground (roots and moss) components, which vary among wetland gradient communities.Introduction -- Introduction to boreal wetlands -- Ecosystem respiration and its role in peatland function -- Brief rationale for this study -- Goals, objectives, and hypotheses -- Methods -- Description of study site and the gradient design -- Atmospheric and soil environmental variables -- Ecosystem respiration fluxes -- Root respiration fluxes and aboveground vegetation measurements -- Results -- Soil environmental variables along the gradient -- Ecosystem respiration -- Contributions of root respiration to ER -- Discussion -- Patterns of ecosystem respiration along the wetland gradient -- The role of roots in ecosystem respiration of CO₂ -- Study limitations and ideas for future research -- Conclusions

The radio luminosity distribution of pulsars in 47 Tucanae

We have used the Australia Telescope Compact Array to seek the integrated radio flux from all the pulsars in the core of the globular cluster 47 Tucanae. We have detected an extended region of radio emission and have calibrated its flux against the flux distribution of the known pulsars in the cluster. We find the total 20-cm radio flux from the cluster's pulsars to be S = 2.0 +/- 0.3 mJy. This implies the lower limit to the radio luminosity distribution to be L_1400 = 0.4 mJy kpc^2 and the size of the observable pulsar population to be N < 30.Comment: 7 pages, 4 figures, MNRAS in pres

Hey Look at Me: The Effect of Giving Circles on Giving

Theories abound for why individuals give to charity. We conduct a field experiment with donors to a Yale University service club to test the impact of a promise of public recognition on giving. Some may claim that they respond to an offer of public recognition not to improve their social standing, but rather to motivate others to give. To tease apart these two theories, we conduct a laboratory experiment with undergraduates, and find no evidence to support the alternative, altruistic motivation. We conclude that charitable gifts increase in response to the promise of public recognition primarily because of individuals' desire to improve their social image.

Relations between extensional tectonics and magmatism within the Southern Oklahoma aulacogen

Variations in the geometry, distribution and thickness of Cambrian igneous and sedimentary units within southwest Oklahoma are related to a late Proterozoic - early Paleozoic rifting event which formed the Southern Oklahoma aulacogen. These rock units are exposed in the Wichita Mountains, southwest Olkahoma, located on the northern margin of a Proterozoic basin, identified in the subsurface by COCORP reflection data. Overprinting of the Cambrian extensional event by Pennyslvanian tectonism obsured the influence of pre-existing basement structures and contrasting basement lithologies upon the initial development of the aulacogen

Has inventory volatility returned? A look at the current cycle

The massive liquidation of inventories during the 2001 recession contrasts sharply with the more moderate inventory movements observed in recent decades. While the rundown might be seen as evidence that firms are not managing their inventories as effectively as some economists have claimed, a careful analysis of inventory behavior in 2001 suggests that during much of the recession, firms were successfully regulating their inventories to avoid a large buildup of excess stock.Inventories ; Recessions

The Trade-off between Private Lots and Public Open Space in Subdivisions at the Urban-Rural Fringe

In many communities on the urban–rural fringe, subdivisions are subject to “clustering” rules, in which houses must be located on a portion of the total land area and the remainder of the land is left as open space. This open space may be undisturbed forest or pastureland, or it may include recreation facilities and trails. In some communities, the open space may remain in agricultural use as pasture or cropland. Although the open space may provide benefits to subdivision residents, it means that those residents are living in a higher-density setting than people living in conventional subdivisions. It is unclear whether the benefits offset the loss experienced by smaller lots and higher density. This trade-off is the focus of our study. We use data on subdivision house sales occurring between 1981 and 2001 in a county on the fringe of the Washington, DC, metropolitan area to estimate a hedonic price model. We examine how households value being adjacent to open space and having more open space in the subdivision, and how they may be willing to trade off those amenities with their own private lot space. We find that private acreage matters to households—a 10 percent larger lot leads to about a 0.6 percent higher house price, all else being equal. Subdivision open space is also valuable to households, but the marginal effect is much smaller than the marginal effect of private lot space. We also find that subdivision open space does substitute for private land, but the extent of the trade-off is small. We use the results of the estimated hedonic model to simulate the effects on prices of jointly increasing open space and reducing average lot size, holding the size of the subdivision constant. We find that average house prices are lower with clustering, particularly for interior lots that are not adjacent to open space.subdivisions, clustering, hedonic property values, open space

Atmospheric Escape from Hot Jupiters

The extra-solar planet HD209458b has been found to have an extended atmosphere of escaping atomic hydrogen (Vidal-Madjar et al. 2003), suggesting that ``hot Jupiters'' closer to their parent stars could evaporate. Here we estimate the atmospheric escape (so called evaporation rate) from hot Jupiters and their corresponding life time against evaporation. The calculated evaporation rate of HD209458b is in excellent agreement with the HI Lyman-alpha observations. We find that the tidal forces and high temperatures in the upper atmosphere must be taken into account to obtain reliable estimate of the atmospheric escape. Because of the tidal forces, we show that there is a new escape mechanism at intermediate temperatures at which the exobase reaches the Roche lobe. From an energy balance, we can estimate plausible values for the planetary exospheric temperatures, and thus obtain typical life times of planets as a function of their mass and orbital distance.Comment: A&A Letters, in pres

A survey of the networks bringing a knowledge of optical glass-working to the London trade, 1500-1800

In October 2013, esteemed scientific instrument scholar Anita McConnell contacted the Whipple Museum, wanting to know if there was any way of putting online an unpublished work she had completed in 1997 on "how the technology of glass working for optical purposes reached Britain, 1600-1800." This work had long been recognized by colleagues as an important account of glass-making technique, but access had been limited to those few who had seen the limited number of privately printed copies in circulation

Acute cardiorespiratory responses to inspiratory pressure threshold loading

This is a non-final version of an article (under the working title "Acute cardiovascular and ventilatory responses to inspiratory pressure threshold loading") published in final form in Medicine & Science in Sports & Exercise, 42(9), 1696-1703, 2010 .Purpose: We tested the acute responses to differing pressure threshold inspiratory loading intensities in well-trained rowers. The purpose of this study was to evaluate 1) how the magnitude of inspiratory pressure threshold loading influences repetition maximum (RM), tidal volume (VT), and external work undertaken by the inspiratory muscle; and 2) whether the inspiratory muscle metaboreflex is activated during acute inspiratory pressure threshold loading. Methods: Eight males participated in seven trials. Baseline measurements of maximal inspiratory pressure (PImax), resting tidal volume (VT), and forced vital capacity (FVC) were made. During the remaining sessions, participants undertook a series of resistive inspiratory breathing tasks at loads corresponding to 50%, 60%, 70%, 80%, and 90% of PImax using a pressure threshold inspiratory muscle trainer. The number of repetitions completed at each load, VT, heart rate (fc), and measures of arterial blood pressure was assessed continuously during each trial. Results: A standardized cutoff of 10% FVC was used to define the RM, which decreased as loading intensity increased (P < 0.05). This response was nonlinear, with an abrupt decrease in RM occurring at loads ≥70% of PImax. The most commonly used inspiratory muscle training regimen of 30RM corresponded to 62.5% ± 4.6% of PImax and also resulted in the highest external work output. Tidal volume (VT) decreased significantly over time at 60%, 70%, and 80% of PImax (P < 0.05), as did the amount of external work completed (P<0.05). Conclusions: Although all loads elicited a sustained increase in fc, only the 60% load elicited a sustained rise in mean arterial blood pressure (P = 0.016), diastolic blood pressure (P = 0.015), and systolic blood pressure (P = 0.002), providing evidence for a metaboreflex response at this load