32 results on '"McGuire, A. David"'
Search Results
2. Assessing dynamic vegetation model parameter uncertainty across Alaskan arctic tundra plant communities.
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Euskirchen, Eugénie S., Serbin, Shawn P., Carman, Tobey B., Fraterrigo, Jennifer M., Genet, Hélène, Iversen, Colleen M., Salmon, Verity, and McGuire, A. David
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TUNDRAS ,PLANT communities ,HETEROTROPHIC respiration ,TEMPERATURE control ,DYNAMIC models ,COASTAL plains ,PRIMARY productivity (Biology) - Abstract
As the Arctic region moves into uncharted territory under a warming climate, it is important to refine the terrestrial biosphere models (TBMs) that help us understand and predict change. One fundamental uncertainty in TBMs relates to model parameters, configuration variables internal to the model whose value can be estimated from data. We incorporate a version of the Terrestrial Ecosystem Model (TEM) developed for arctic ecosystems into the Predictive Ecosystem Analyzer (PEcAn) framework. PEcAn treats model parameters as probability distributions, estimates parameters based on a synthesis of available field data, and then quantifies both model sensitivity and uncertainty to a given parameter or suite of parameters. We examined how variation in 21 parameters in the equation for gross primary production influenced model sensitivity and uncertainty in terms of two carbon fluxes (net primary productivity and heterotrophic respiration) and two carbon (C) pools (vegetation C and soil C). We set up different parameterizations of TEM across a range of tundra types (tussock tundra, heath tundra, wet sedge tundra, and shrub tundra) in northern Alaska, along a latitudinal transect extending from the coastal plain near Utqiaġvik to the southern foothills of the Brooks Range, to the Seward Peninsula. TEM was most sensitive to parameters related to the temperature regulation of photosynthesis. Model uncertainty was mostly due to parameters related to leaf area, temperature regulation of photosynthesis, and the stomatal responses to ambient light conditions. Our analysis also showed that sensitivity and uncertainty to a given parameter varied spatially. At some sites, model sensitivity and uncertainty tended to be connected to a wider range of parameters, underlining the importance of assessing tundra community processes across environmental gradients or geographic locations. Generally, across sites, the flux of net primary productivity (NPP) and pool of vegetation C had about equal uncertainty, while heterotrophic respiration had higher uncertainty than the pool of soil C. Our study illustrates the complexity inherent in evaluating parameter uncertainty across highly heterogeneous arctic tundra plant communities. It also provides a framework for iteratively testing how newly collected field data related to key parameters may result in more effective forecasting of Arctic change. [ABSTRACT FROM AUTHOR]
- Published
- 2022
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3. Carbon release through abrupt permafrost thaw
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Turetsky, Merritt R., Abbott, Benjamin W., Jones, Miriam C., Anthony, Katey Walter, Olefeldt, David, Schuur, Edward A. G., Grosse, Guido, Kuhry, Peter, Hugelius, Gustaf, Koven, Charles, Lawrence, David M., Gibson, Carolyn, Sannel, A. Britta K., and McGuire, A. David
- Abstract
The permafrost zone is expected to be a substantial carbon source to the atmosphere, yet large-scale models currently only simulate gradual changes in seasonally thawed soil. Abrupt thaw will probably occur in <20% of the permafrost zone but could affect half of permafrost carbon through collapsing ground, rapid erosion and landslides. Here, we synthesize the best available information and develop inventory models to simulate abrupt thaw impacts on permafrost carbon balance. Emissions across 2.5 million km2of abrupt thaw could provide a similar climate feedback as gradual thaw emissions from the entire 18 million km2permafrost region under the warming projection of Representative Concentration Pathway 8.5. While models forecast that gradual thaw may lead to net ecosystem carbon uptake under projections of Representative Concentration Pathway 4.5, abrupt thaw emissions are likely to offset this potential carbon sink. Active hillslope erosional features will occupy 3% of abrupt thaw terrain by 2300 but emit one-third of abrupt thaw carbon losses. Thaw lakes and wetlands are methane hot spots but their carbon release is partially offset by slowly regrowing vegetation. After considering abrupt thaw stabilization, lake drainage and soil carbon uptake by vegetation regrowth, we conclude that models considering only gradual permafrost thaw are substantially underestimating carbon emissions from thawing permafrost.
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- 2020
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4. Large loss of CO2in winter observed across the northern permafrost region
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Natali, Susan M., Watts, Jennifer D., Rogers, Brendan M., Potter, Stefano, Ludwig, Sarah M., Selbmann, Anne-Katrin, Sullivan, Patrick F., Abbott, Benjamin W., Arndt, Kyle A., Birch, Leah, Bjo¨rkman, Mats P., Bloom, A. Anthony, Celis, Gerardo, Christensen, Torben R., Christiansen, Casper T., Commane, Roisin, Cooper, Elisabeth J., Crill, Patrick, Czimczik, Claudia, Davydov, Sergey, Du, Jinyang, Egan, Jocelyn E., Elberling, Bo, Euskirchen, Eugenie S., Friborg, Thomas, Genet, Hélène, Göckede, Mathias, Goodrich, Jordan P., Grogan, Paul, Helbig, Manuel, Jafarov, Elchin E., Jastrow, Julie D., Kalhori, Aram A. M., Kim, Yongwon, Kimball, John S., Kutzbach, Lars, Lara, Mark J., Larsen, Klaus S., Lee, Bang-Yong, Liu, Zhihua, Loranty, Michael M., Lund, Magnus, Lupascu, Massimo, Madani, Nima, Malhotra, Avni, Matamala, Roser, McFarland, Jack, McGuire, A. David, Michelsen, Anders, Minions, Christina, Oechel, Walter C., Olefeldt, David, Parmentier, Frans-Jan W., Pirk, Norbert, Poulter, Ben, Quinton, William, Rezanezhad, Fereidoun, Risk, David, Sachs, Torsten, Schaefer, Kevin, Schmidt, Niels M., Schuur, Edward A. G., Semenchuk, Philipp R., Shaver, Gaius, Sonnentag, Oliver, Starr, Gregory, Treat, Claire C., Waldrop, Mark P., Wang, Yihui, Welker, Jeffrey, Wille, Christian, Xu, Xiaofeng, Zhang, Zhen, Zhuang, Qianlai, and Zona, Donatella
- Abstract
Recent warming in the Arctic, which has been amplified during the winter1–3, greatly enhances microbial decomposition of soil organic matter and subsequent release of carbon dioxide (CO2)4. However, the amount of CO2released in winter is not known and has not been well represented by ecosystem models or empirically based estimates5,6. Here we synthesize regional in situ observations of CO2flux from Arctic and boreal soils to assess current and future winter carbon losses from the northern permafrost domain. We estimate a contemporary loss of 1,662?TgC per year from the permafrost region during the winter season (October–April). This loss is greater than the average growing season carbon uptake for this region estimated from process models (-1,032?TgC per year). Extending model predictions to warmer conditions up to 2100 indicates that winter CO2emissions will increase 17% under a moderate mitigation scenario—Representative Concentration Pathway 4.5—and 41% under business-as-usual emissions scenario—Representative Concentration Pathway 8.5. Our results provide a baseline for winter CO2emissions from northern terrestrial regions and indicate that enhanced soil CO2loss due to winter warming may offset growing season carbon uptake under future climatic conditions.
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- 2019
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5. Assessing historical and projected carbon balance of Alaska: A synthesis of results and policy/management implications.
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McGuire, A. David, Striegl, Robert, Wylie, Bruce K., Zhou, Xiaoping, Zhu, Zhiliang, Genet, Hélène, Lyu, Zhou, He, Yujie, Zhuang, Qianlai, Pastick, Neal, Stackpoole, Sarah, Birdsey, Richard, D'Amore, David, and Rupp, T. Scott
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CARBON cycle ,TAIGAS ,CLIMATE change ,AQUATIC ecology ,PERMAFROST - Abstract
Abstract: We summarize the results of a recent interagency assessment of land carbon dynamics in Alaska, in which carbon dynamics were estimated for all major terrestrial and aquatic ecosystems for the historical period (1950–2009) and a projection period (2010–2099). Between 1950 and 2009, upland and wetland (i.e., terrestrial) ecosystems of the state gained 0.4 Tg C/yr (0.1% of net primary production, NPP), resulting in a cumulative greenhouse gas radiative forcing of 1.68 × 10
−3 W/m2 . The change in carbon storage is spatially variable with the region of the Northwest Boreal Landscape Conservation Cooperative (LCC) losing carbon because of fire disturbance. The combined carbon transport via various pathways through inland aquatic ecosystems of Alaska was estimated to be 41.3 Tg C/yr (17% of terrestrial NPP). During the projection period (2010–2099), carbon storage of terrestrial ecosystems of Alaska was projected to increase (22.5–70.0 Tg C/yr), primarily because of NPP increases of 10–30% associated with responses to rising atmospheric CO2 , increased nitrogen cycling, and longer growing seasons. Although carbon emissions to the atmosphere from wildfire and wetland CH4 were projected to increase for all of the climate projections, the increases in NPP more than compensated for those losses at the statewide level. Carbon dynamics of terrestrial ecosystems continue to warm the climate for four of the six future projections and cool the climate for only one of the projections. The attribution analyses we conducted indicated that the response of NPP in terrestrial ecosystems to rising atmospheric CO2 (~5% per 100 ppmv CO2 ) saturates as CO2 increases (between approximately +150 and +450 ppmv among projections). This response, along with the expectation that permafrost thaw would be much greater and release large quantities of permafrost carbon after 2100, suggests that projected carbon gains in terrestrial ecosystems of Alaska may not be sustained. From a national perspective, inclusion of all of Alaska in greenhouse gas inventory reports would ensure better accounting of the overall greenhouse gas balance of the nation and provide a foundation for considering mitigation activities in areas that are accessible enough to support substantive deployment. [ABSTRACT FROM AUTHOR]- Published
- 2018
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6. The role of environmental driving factors in historical and projected carbon dynamics of wetland ecosystems in Alaska.
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Lyu, Zhou, He, Yujie, Zhuang, Qianlai, Genet, Hélène, Clein, Joy, Euskirchen, Eugénie S., McGuire, A. David, Bennett, Alec, Breen, Amy, Kurkowski, Tom, Rupp, T. Scott, Johnson, Kristofer, Pastick, Neal J., Wylie, Bruce K., and Zhu, Zhiliang
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ENVIRONMENTAL risk ,CARBON & the environment ,WETLAND ecology ,SIMULATION methods & models ,CARBON cycle ,ATMOSPHERIC carbon dioxide ,CLIMATE change ,GLOBAL warming - Abstract
Abstract: Wetlands are critical terrestrial ecosystems in Alaska, covering ~177,000 km
2 , an area greater than all the wetlands in the remainder of the United States. To assess the relative influence of changing climate, atmospheric carbon dioxide (CO2 ) concentration, and fire regime on carbon balance in wetland ecosystems of Alaska, a modeling framework that incorporates a fire disturbance model and two biogeochemical models was used. Spatially explicit simulations were conducted at 1‐km resolution for the historical period (1950–2009) and future projection period (2010–2099). Simulations estimated that wetland ecosystems of Alaska lost 175 Tg carbon (C) in the historical period. Ecosystem C storage in 2009 was 5,556 Tg, with 89% of the C stored in soils. The estimated loss of C as CO2 and biogenic methane (CH4 ) emissions resulted in wetlands of Alaska increasing the greenhouse gas forcing of climate warming. Simulations for the projection period were conducted for six climate change scenarios constructed from two climate models forced under three CO2 emission scenarios. Ecosystem C storage averaged among climate scenarios increased 3.94 Tg C/yr by 2099, with variability among the simulations ranging from 2.02 to 4.42 Tg C/yr. These increases were driven primarily by increases in net primary production (NPP) that were greater than losses from increased decomposition and fire. The NPP increase was driven by CO2 fertilization (~5% per 100 parts per million by volume increase) and by increases in air temperature (~1% per °C increase). Increases in air temperature were estimated to be the primary cause for a projected 47.7% mean increase in biogenic CH4 emissions among the simulations (~15% per °C increase). Ecosystem CO2 sequestration offset the increase in CH4 emissions during the 21st century to decrease the greenhouse gas forcing of climate warming. However, beyond 2100, we expect that this forcing will ultimately increase as wetland ecosystems transition from being a sink to a source of atmospheric CO2 because of (1) decreasing sensitivity of NPP to increasing atmospheric CO2 , (2) increasing availability of soil C for decomposition as permafrost thaws, and (3) continued positive sensitivity of biogenic CH4 emissions to increases in soil temperature. [ABSTRACT FROM AUTHOR]- Published
- 2018
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7. Fuel-reduction management alters plant composition, carbon and nitrogen pools, and soil thaw in Alaskan boreal forest.
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Melvin, April M., Celis, Gerardo, Johnstone, Jill F., McGuire, A. David, Genet, Helene, Schuur, Edward A. G., Rupp, T. Scott, and Mack, Michelle C.
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TAIGAS ,BLACK spruce ,FUEL reduction (Wildfire prevention) ,CHEMICAL composition of plants ,THAWING ,CARBON content of plants ,NITROGEN content of plants - Abstract
Increasing wildfire activity in Alaska's boreal forests has led to greater fuel-reduction management. Management has been implemented to reduce wildfire spread, but the ecological impacts of these practices are poorly known. We quantified the effects of hand-thinning and shearblading on above- and belowground stand characteristics, plant species composition, carbon (C) and nitrogen (N) pools, and soil thaw across 19 sites dominated by black spruce ( Picea mariana) in interior Alaska treated 2-12 years prior to sampling. The density of deciduous tree seedlings was significantly higher in shearbladed areas compared to unmanaged forest (6.4 vs. 0.1 stems/m
2 ), and unmanaged stands exhibited the highest mean density of conifer seedlings and layers (1.4 stems/m2 ). Understory plant community composition was most similar between unmanaged and thinned stands. Shearblading resulted in a near complete loss of aboveground tree biomass C pools while thinning approximately halved the C pool size (1.2 kg C/m2 compared to 3.1 kg C/m2 in unmanaged forest). Significantly smaller soil organic layer ( SOL) C and N pools were observed in shearbladed stands (3.2 kg C/m2 and 116.8 g N/m2 ) relative to thinned (6.0 kg C/m2 and 192.2 g N/m2 ) and unmanaged (5.9 kg C/m2 and 178.7 g N/m2 ) stands. No difference in C and N pool sizes in the uppermost 10 cm of mineral soil was observed among stand types. Total C stocks for measured pools was 2.6 kg C/m2 smaller in thinned stands and 5.8 kg C/m2 smaller in shearbladed stands when compared to unmanaged forest. Soil thaw depth averaged 13 cm deeper in thinned areas and 46 cm deeper in shearbladed areas relative to adjacent unmanaged stands, although variability was high across sites. Deeper soil thaw was linked to shallower SOL depth for unmanaged stands and both management types, however for any given SOL depth, thaw tended to be deeper in shearbladed areas compared to unmanaged forest. These findings indicate that fuel-reduction management alters plant community composition, C and N pools, and soil thaw depth, with consequences for ecosystem structure and function beyond those intended for fire management. [ABSTRACT FROM AUTHOR]- Published
- 2018
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8. The role of driving factors in historical and projected carbon dynamics of upland ecosystems in Alaska.
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Genet, Hélène, He, Yujie, Lyu, Zhou, McGuire, A. David, Zhuang, Qianlai, Clein, Joy, D'Amore, David, Bennett, Alec, Breen, Amy, Biles, Frances, Euskirchen, Eugénie S., Johnson, Kristofer, Kurkowski, Tom, (Kushch) Schroder, Svetlana, Pastick, Neal, Rupp, T. Scott, Wylie, Bruce, Zhang, Yujin, Zhou, Xiaoping, and Zhu, Zhiliang
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ECOLOGY ,ECOSYSTEM dynamics ,ATMOSPHERIC carbon dioxide ,CARBON in soils ,CARBON cycle ,CLIMATE change ,UPLANDS - Abstract
It is important to understand how upland ecosystems of Alaska, which are estimated to occupy 84% of the state (i.e., 1,237,774 km
2 ), are influencing and will influence state-wide carbon (C) dynamics in the face of ongoing climate change. We coupled fire disturbance and biogeochemical models to assess the relative effects of changing atmospheric carbon dioxide (CO2 ), climate, logging and fire regimes on the historical and future C balance of upland ecosystems for the four main Landscape Conservation Cooperatives (LCCs) of Alaska. At the end of the historical period (1950-2009) of our analysis, we estimate that upland ecosystems of Alaska store ~50 Pg C (with ~90% of the C in soils), and gained 3.26 Tg C/yr. Three of the LCCs had gains in total ecosystem C storage, while the Northwest Boreal LCC lost C (−6.01 Tg C/yr) because of increases in fire activity. Carbon exports from logging affected only the North Pacific LCC and represented less than 1% of the state's net primary production (NPP). The analysis for the future time period (2010-2099) consisted of six simulations driven by climate outputs from two climate models for three emission scenarios. Across the climate scenarios, total ecosystem C storage increased between 19.5 and 66.3 Tg C/yr, which represents 3.4% to 11.7% increase in Alaska upland's storage. We conducted additional simulations to attribute these responses to environmental changes. This analysis showed that atmospheric CO2 fertilization was the main driver of ecosystem C balance. By comparing future simulations with constant and with increasing atmospheric CO2 , we estimated that the sensitivity of NPP was 4.8% per 100 ppmv, but NPP becomes less sensitive to CO2 increase throughout the 21st century. Overall, our analyses suggest that the decreasing CO2 sensitivity of NPP and the increasing sensitivity of heterotrophic respiration to air temperature, in addition to the increase in C loss from wildfires weakens the C sink from upland ecosystems of Alaska and will ultimately lead to a source of CO2 to the atmosphere beyond 2100. Therefore, we conclude that the increasing regional C sink we estimate for the 21st century will most likely be transitional. [ABSTRACT FROM AUTHOR]- Published
- 2018
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9. Historical and projected trends in landscape drivers affecting carbon dynamics in Alaska.
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Pastick, Neal J., Duffy, Paul, Genet, Hélène, Rupp, T. Scott, Wylie, Bruce K., Johnson, Kristofer D., Jorgenson, M. Torre, Bliss, Norman, McGuire, A. David, Jafarov, Elchin E., and Knight, Joseph F.
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CLIMATE change ,ATMOSPHERIC temperature ,PERMAFROST ,DECIDUOUS forests ,TAIGAS - Abstract
Modern climate change in Alaska has resulted in widespread thawing of permafrost, increased fire activity, and extensive changes in vegetation characteristics that have significant consequences for socioecological systems. Despite observations of the heightened sensitivity of these systems to change, there has not been a comprehensive assessment of factors that drive ecosystem changes throughout Alaska. Here we present research that improves our understanding of the main drivers of the spatiotemporal patterns of carbon dynamics using in situ observations, remote sensing data, and an array of modeling techniques. In the last 60 yr, Alaska has seen a large increase in mean annual air temperature (1.7°C), with the greatest warming occurring over winter and spring. Warming trends are projected to continue throughout the 21st century and will likely result in landscape-level changes to ecosystem structure and function. Wetlands, mainly bogs and fens, which are currently estimated to cover 12.5% of the landscape, strongly influence exchange of methane between Alaska's ecosystems and the atmosphere and are expected to be affected by thawing permafrost and shifts in hydrology. Simulations suggest the current proportion of near-surface (within 1 m) and deep (within 5 m) permafrost extent will be reduced by 9-74% and 33-55% by the end of the 21st century, respectively. Since 2000, an average of 678 595 ha/yr was burned, more than twice the annual average during 1950-1999. The largest increase in fire activity is projected for the boreal forest, which could result in a reduction in late-successional spruce forest (8-44%) and an increase in early-successional deciduous forest (25-113%) that would mediate future fire activity and weaken permafrost stability in the region. Climate warming will also affect vegetation communities across arctic regions, where the coverage of deciduous forest could increase (223-620%), shrub tundra may increase (4-21%), and graminoid tundra might decrease (10-24%). This study sheds light on the sensitivity of Alaska's ecosystems to change that has the potential to significantly affect local and regional carbon balance, but more research is needed to improve estimates of land-surface and subsurface properties, and to better account for ecosystem dynamics affected by a myriad of biophysical factors and interactions. [ABSTRACT FROM AUTHOR]
- Published
- 2017
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10. Permafrost collapse is accelerating carbon release
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Turetsky, Merritt R., Abbott, Benjamin W., Jones, Miriam C., Walter Anthony, Katey, Olefeldt, David, Schuur, Edward A. G., Koven, Charles, McGuire, A. David, Grosse, Guido, Kuhry, Peter, Hugelius, Gustaf, Lawrence, David M., Gibson, Carolyn, and Sannel, A. Britta K.
- Abstract
The sudden collapse of thawing soils in the Arctic might double the warming from greenhouse gases released from tundra, warn Merritt R. Turetsky and colleagues. The sudden collapse of thawing soils in the Arctic might double the warming from greenhouse gases released from tundra, warn Merritt R. Turetsky and colleagues.
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- 2019
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11. Responses of High Latitude Ecosystems to Global Change: Potential Consequences for the Climate System.
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Canadell, Josep G., Pataki, Diane E., Pitelka, Louis F., McGuire, A. David, Chapin, F. S., Wirth, Christian, Apps, Mike, Bhatti, Jagtar, Callaghan, Terry, Christensen, Torben R., Clein, Joy S., Fukuda, Masami, Maximov, Trofim, Onuchin, Alexander, Shvidenko, Anatoly, and Vaganov, Eugene
- Published
- 2007
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12. Palaeodata-informed modelling of large carbon losses from recent burning of boreal forests
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Kelly, Ryan, Genet, Hélène, McGuire, A. David, and Hu, Feng Sheng
- Abstract
Wildfires play a key role in the boreal forest carbon cycle, and models suggest that accelerated burning will increase boreal C emissions in the coming century. However, these predictions may be compromised because brief observational records provide limited constraints to model initial conditions. We confronted this limitation by using palaeoenvironmental data to drive simulations of long-term C dynamics in the Alaskan boreal forest. Results show that fire was the dominant control on C cycling over the past millennium, with changes in fire frequency accounting for 84% of C stock variability. A recent rise in fire frequency inferred from the palaeorecord led to simulated C losses of 1.4 kg C m−2(12% of ecosystem C stocks) from 1950 to 2006. In stark contrast, a small net C sink of 0.3 kg C m−2occurred if the past fire regime was assumed to be similar to the modern regime, as is common in models of C dynamics. Although boreal fire regimes are heterogeneous, recent trends and future projections point to increasing fire activity in response to climate warming throughout the biome. Thus, predictions that terrestrial C sinks of northern high latitudes will mitigate rising atmospheric CO2may be over-optimistic.
- Published
- 2016
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13. Trajectory of the Arctic as an integrated system.
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Hinzman, Larry D., Deal, Clara J., McGuire, A. David, Mernild, Sebastian H., Polyakov, Igor V., and Walsh, John E.
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WATER conservation ,ENVIRONMENTAL engineering ,ATMOSPHERIC water vapor ,SEA ice ,ATMOSPHERIC temperature - Abstract
Although much remains to be learned about the Arctic and its component processes, many of the most urgent scientific, engineering, and social questions can only be approached through a broader system perspective. Here, we address interactions between components of the Arctic system and assess feedbacks and the extent to which feedbacks (1) are now underway in the Arctic and (2) will shape the future trajectory of the Arctic system. We examine interdependent connections among atmospheric processes, oceanic processes, sea-ice dynamics, marine and terrestrial ecosystems, land surface stocks of carbon and water, glaciers and ice caps, and the Greenland ice sheet. Our emphasis on the interactions between components, both historical and anticipated, is targeted on the feedbacks, pathways, and processes that link these different components of the Arctic system. We present evidence that the physical components of the Arctic climate system are currently in extreme states, and that there is no indication that the system will deviate from this anomalous trajectory in the foreseeable future. The feedback for which the evidence of ongoing changes is most compelling is the surface albedo-temperature feedback, which is amplifying temperature changes over land (primarily in spring) and ocean (primarily in autumn-winter). Other feedbacks likely to emerge are those in which key processes include surface fluxes of trace gases, changes in the distribution of vegetation, changes in surface soil moisture, changes in atmospheric water vapor arising from higher temperatures and greater areas of open ocean, impacts of Arctic freshwater fluxes on the meridional overturning circulation of the ocean, and changes in Arctic clouds resulting from changes in water vapor content. [ABSTRACT FROM AUTHOR]
- Published
- 2013
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14. Insights and issues with simulating terrestrial DOC loading of Arctic river networks.
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Kicklighter, David W., Hayes, Daniel J., McClelland, James W., Peterson, Bruce J., McGuire, A. David, and Melillo, Jerry M.
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CARBON compounds ,HYDROLOGY ,WATERSHEDS ,FORESTED wetlands ,CARBON dioxide ,INFORMATION sharing - Abstract
Terrestrial carbon dynamics influence the contribution of dissolved organic carbon (DOC) to river networks in addition to hydrology. In this study, we use a biogeochemical process model to simulate the lateral transfer of DOC from land to the Arctic Ocean via riverine transport. We estimate that, over the 20th century, the pan-Arctic watershed has contributed, on average, 32 Tg C/yr of DOC to river networks emptying into the Arctic Ocean with most of the DOC coming from the extensive area of boreal deciduous needle-leaved forests and forested wetlands in Eurasian watersheds. We also estimate that the rate of terrestrial DOC loading has been increasing by 0.037 Tg C/yr² over the 20th century primarily as a result of climate-induced increases in water yield. These increases have been offset by decreases in terrestrial DOC loading caused by wildfires. Other environmental factors (C0
2 fertilization, ozone pollution, atmospheric nitrogen deposition, timber harvest, agriculture) are estimated to have relatively small effects on terrestrial DOC loading to Arctic rivers. The effects of the various environmental factors on terrestrial carbon dynamics have both offset and enhanced concurrent effects on hydrology to influence terrestrial DOC loading and may be changing the relative importance of terrestrial carbon dynamics on this carbon flux. Improvements in simulating terrestrial DOC loading to pan-Arctic rivers in the future will require better information on the production and consumption of DOC within the soil profile, the transfer of DOC from land to headwater streams, the spatial distribution of precipitation and its temporal trends, carbon dynamics of larch-dominated ecosystems in eastern Siberia, and the role of industrial organic effluents on carbon budgets of rivers in western Russia. [ABSTRACT FROM AUTHOR]- Published
- 2013
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15. The carbon budget of the northern cryosphere region.
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McGuire, A David, Macdonald, Robie W, Schuur, Edward AG, Harden, Jennifer W, Kuhry, Peter, Hayes, Daniel J, Christensen, Torben R, and Heimann, Martin
- Abstract
The northern cryosphere is undergoing substantial warming of permafrost and loss of sea ice. Release of stored carbon to the atmosphere in response to this change has the potential to affect the global climate system. Studies indicate that the northern cryosphere has been not only a substantial sink for atmospheric CO
2 in recent decades, but also an important source of CH4 because of emissions from wetlands and lakes. Analyses suggest that the sensitivity of the carbon cycle of the region over the 21st Century is potentially large, but highly uncertain because numerous pathways of response will be affected by warming. Further research should focus on sensitive elements of the carbon cycle such as the consequences of increased fire disturbance, permafrost degradation, and sea ice loss in the northern cryosphere region. [ABSTRACT FROM AUTHOR]- Published
- 2010
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16. Changing feedbacks in the climate-biosphere system.
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Chapin III, F. Stuart, Randerson, James T., McGuire, A. David, Foley, Jonathan A., and Field, Christopher B.
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BIOTIC communities ,CLIMATE change ,CLIMATOLOGY ,DEFORESTATION ,SOLAR energy ,UNITED Nations Framework Convention on Climate Change (1992). Protocols, etc., 1997 December 11 ,CONTROL of forest degradation ,ALBEDO ,CARBON - Abstract
Ecosystems influence climate through multiple pathways, primarily by changing the energy, water, and greenhouse- gas balance of the atmosphere. Consequently, efforts to mitigate climate change through modification of one pathway, as with carbon in the Kyoto Protocol, only partially address the issue of ecosystem-climate interactions. For example, the cooling of climate that results from carbon sequestration by plants may be partially offset by reduced land albedo, which increases solar energy absorption and warms the climate. The relative importance of these effects varies with spatial scale and latitude. We suggest that consideration of multiple interactions and feedbacks could lead to novel, potentially useful climate-mitigation strategies, including greenhouse-gas reductions primarily in industrialized nations, reduced desertification in arid zones, and reduced deforestation in the tropics. Each of these strategies has additional ecological and societal benefits. Assessing the effectiveness of these strategies requires a more quantitative understanding of the interactions among feedback processes, their consequences at local and global scales, and the teleconnections that link changes occurring in different regions. [ABSTRACT FROM AUTHOR]
- Published
- 2008
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17. Planning for resilience: modeling change in human-fire interactions in the Alaskan boreal forest.
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Chapin III, F. Stuart, Rupp, T. Scott, Starfield, Anthony M., DeWilde, La-ona, Zavaleta, Erika S., Fresco, Nancy, Henkelman, Jonathon, and McGuire, A. David
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TAIGAS ,FORESTS & forestry ,SOCIAL scientists ,WILDFIRES - Abstract
The development of policies that promote ecological, economic, and cultural sustainability requires collaboration between natural and social scientists. We present a modeling approach to facilitate this communication and illustrate its application to studies of wildfire in the interior of Alaska. We distill the essence of complex fire-vegetation interactions that occur in the real world into a simplified landscape model, and describe how equally complex fire-human interactions could be incorporated into a similar modeling framework. Simulations suggest that fire suppression is likely to increase the proportion of flammable vegetation on the landscape and reduce the long-term effectiveness of wildfire suppression. Simple models that test the consequences of assumptions help natural and social scientists to communicate objectively when exploring the long-term consequences of alternative policy scenarios. [ABSTRACT FROM AUTHOR]
- Published
- 2003
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18. Temporal uncertainties of integrated ecological/economic assessments at the global and regional scales.
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Perez-Garcia, John, Joyce, Linda A., and McGuire, A. David
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FOREST microclimatology ,CLIMATE change ,DECISION making - Abstract
Over the past several years, research using the Center for International Trade in Forest Products (CINTRAFOR) Global Trade Model (CGTM) and the Terrestrial Ecosystem Model (TEM) has estimated the potential effects of climate change on the global forest sector. The process of linking these two models—many model runs with alternative economic, ecological and climate scenarios—provides useful information on (i) the behavior of the economic model under alternative assumptions, (ii) integrated economic/ecological results and (iii) their implication for decision makers. Previous works indicate that assumptions on economic behavior and ecology interactions are important when estimating the economic effects of climate change on the forest sector. This paper estimates the economic effects associated with alternative transient paths of change in climate and CO
2 on the forest sector. The results indicate economic welfare measures change significantly under two alternative assumptions of the path that changes in climate and CO2 may take. An assumption of a pseudo-transient constant rate of change to reach an equilibrium endpoint produces larger global welfare changes over the time period than a “true” transient change in climate by an average US$ 2 billion over the period 1994–2040. In addition, regional and market segment impacts are not uniformly distributed and should also be considered when programmatic needs are identified. [Copyright &y& Elsevier]- Published
- 2002
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19. The impact of lower sea-ice extent on Arctic greenhouse-gas exchange
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Parmentier, Frans-Jan W., Christensen, Torben R., Sørensen, Lise Lotte, Rysgaard, Søren, McGuire, A. David, Miller, Paul A., and Walker, Donald A.
- Abstract
In September 2012, Arctic sea-ice extent plummeted to a new record low: two times lower than the 1979–2000 average. Often, record lows in sea-ice cover are hailed as an example of climate change impacts in the Arctic. Less apparent, however, are the implications of reduced sea-ice cover in the Arctic Ocean for marine–atmosphere CO2exchange. Sea-ice decline has been connected to increasing air temperatures at high latitudes. Temperature is a key controlling factor in the terrestrial exchange of CO2and methane, and therefore the greenhouse-gas balance of the Arctic. Despite the large potential for feedbacks, many studies do not connect the diminishing sea-ice extent with changes in the interaction of the marine and terrestrial Arctic with the atmosphere. In this Review, we assess how current understanding of the Arctic Ocean and high-latitude ecosystems can be used to predict the impact of a lower sea-ice cover on Arctic greenhouse-gas exchange.
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- 2013
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20. The Effect of Moisture Content on the Thermal Conductivity of Moss and Organic Soil Horizons From Black Spruce Ecosystems in Interior Alaska
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O'Donnell, Jonathan A., Romanovsky, Vladimir E., Harden, Jennifer W., and McGuire, A. David
- Abstract
Organic soil horizons function as important controls on the thermal state of near-surface soil and permafrost in high-latitude ecosystems. The thermal conductivity of organic horizons is typically lower than mineral soils and is closely linked to moisture content, bulk density, and water phase. In this study, we examined the relationship between thermal conductivity and soil moisture for different moss and organic horizon types in black spruce ecosystems of interior Alaska. We sampled organic horizons from feather moss-dominated and Sphagnum-dominated stands and divided horizons into live moss and fibrous and amorphous organic matter. Thermal conductivity measurements were made across a range of moisture contents using the transient line heat source method. Our findings indicate a strong positive and linear relationship between thawed thermal conductivity (Kt) and volumetric water content. We observed similar regression parameters ( or slope) across moss types and organic horizons types and small differences in 0(yintercept) across organic horizon types. Live Sphagnumspp. had a higher range of Ktthan did live feather moss because of the field capacity (laboratory based) of live Sphagnumspp. In northern regions, the thermal properties of organic soil horizons play a critical role in mediating the effects of climate warming on permafrost conditions. Findings from this study could improve model parameterization of thermal properties in organic horizons and enhance our understanding of future permafrost and ecosystem dynamics.
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- 2009
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21. A first-order analysis of the potential rôle of CO2fertilization to affect the global carbon budget: a comparison of four terrestrial biosphere models
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Kicklighter, David W., Bruno, Michele, DZönges, Silke, Esser, Gerd, Heimann, Martin, Helfrich, John, Ift, Frank, Joos, Fortunat, Kaduk, Jörg, Kohlmaier, Gundolf H., McGuire, A. David, Melillo, Jerry M., Meyer, Robert, III, Berrien Moore, Nadler, Andreas, Prentice, I. Colin, Sauf, Walter, Schloss, Annette L., Sitch, Stephen, Wittenberg, Uwe, and Würth, Gudrun
- Abstract
We compared the simulated responses of net primary production, heterotrophic respiration, net ecosystem production and carbon storage in natural terrestrial ecosystems to historical (1765 to 1990) and projected (1990–2300) changes of atmospheric CO2concentration of four terrestrial biosphere models: the Bern model, the Frankfurt Biosphere Model (FBM), the High-Resolution Biosphere Model (HRBM) and the Terrestrial EcosystemModel (TEM). The results of the model intercomparison suggest that CO2fertilization of natural terrestrial vegetation has the potential to account for a large fraction of the so-called “missing carbon sink” of 2.0 Pg C in 1990. Estimates of this potential are reduced when the models incorporate the concept that CO2fertilization can be limited by nutrient availability. Although the model estimates differ on the potential size (126 to 461 Pg C) of the future terrestrial sink caused by CO2fertilization, the results of the four models suggest that natural terrestrial ecosystems will have a limited capacity to act as a sink of atmospheric CO2in the future as a result of physiological constraints and nutrient constraints on NPP. All the spatially explicit models estimate a carbon sink in both tropical and northern temperate regions, but the strength of these sinks varies over time. Differences in the simulated response of terrestrial ecosystems to CO2fertilization among the models in this intercomparison study reflect the fact that the models have highlighted different aspects of the effect of CO2fertilization on carbon dynamics of natural terrestrial ecosystems including feedback mechanisms. As interactions with nitrogen fertilization, climate change and forest regrowth may play an important role in simulating the response of terrestrial ecosystems to CO2fertilization, these factors should be included in future analyses. Improvements in spatially explicit data sets, whole-ecosystem experiments and the availability of net carbon exchange measurements across the globe will also help to improve future evaluations of the role of CO2fertilization on terrestrial carbon storage.
- Published
- 1999
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22. A first‐order analysis of the potential rôle of CO2fertilization to affect the global carbon budget: a comparison of four terrestrial biosphere models
- Author
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KICKLIGHTER, DAVID W., BRUNO, MICHELE, DÖNGES, SILKE, ESSER, GERD, HEIMANN, MARTIN, HELFRICH, JOHN, IFT, FRANK, JOOS, FORTUNAT, KADUK, JÖRG, KOHLMAIER, GUNDOLF H., McGUIRE, A. DAVID, MELILLO, JERRY M., MEYER, ROBERT, III, BERRIEN MOORE, NADLER, ANDREAS, PRENTICE, I. COLIN, SAUF, WALTER, SCHLOSS, ANNETTE L., SITCH, STEPHEN, WITTENBERG, UWE, and WÜRTH, GUDRUN
- Abstract
We compared the simulated responses of net primary production, heterotrophic respiration, net ecosystem production and carbon storage in natural terrestrial ecosystems to historical (1765 to 1990) and projected (1990–2300) changes of atmospheric CO2concentration of four terrestrial biosphere models: the Bern model, the Frankfurt Biosphere Model (FBM), the High‐Resolution Biosphere Model (HRBM) and the Terrestrial EcosystemModel (TEM). The results of the model intercomparison suggest that CO2fertilization of natural terrestrial vegetation has the potential to account for a large fraction of the so‐called ‘‘missing carbon sink’′ of 2.0 Pg C in 1990. Estimates of this potential are reduced when the models incorporate the concept that CO2fertilization can be limited by nutrient availability. Although the model estimates differ on the potential size (126 to 461 Pg C) of the future terrestrial sink caused by CO2fertilization, the results of the four models suggest that natural terrestrial ecosystems will have a limited capacity to act as a sink of atmospheric CO2in the future as a result of physiological constraints and nutrient constraints on NPP. All the spatially explicit models estimate a carbon sink in both tropical and northern temperate regions, but the strength of these sinks varies over time. Differences in the simulated response of terrestrial ecosystems to CO2fertilization among the models in this intercomparison study reflect the fact that the models have highlighted different aspects of the effect of CO2fertilization on carbon dynamics of natural terrestrial ecosystems including feedback mechanisms. As interactions with nitrogen fertilization, climate change and forest regrowth may play an important role in simulating the response of terrestrial ecosystems to CO2fertilization, these factors should be included in future analyses. Improvements in spatially explicit data sets, whole‐ecosystem experiments and the availability of net carbon exchange measurements across the globe will also help to improve future evaluations of the role of CO2fertilization on terrestrial carbon storage.
- Published
- 1999
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23. Modeled responses of terrestrial ecosystems to elevated atmospheric CO2: a comparison of simulations by the biogeochemistry models of the Vegetation/Ecosystem Modeling and Analysis Project (VEMAP)
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Pan, Yude, Melillo, Jerry M., McGuire, A. David, Kicklighter, David W., Pitelka, Louis F., Hibbard, Kathy, Pierce, Lars L., Running, Steven W., Ojima, Dennis S., Parton, William J., and Schimel, David S.
- Abstract
Abstract: Although there is a great deal of information concerning responses to increases in atmospheric CO
2 at the tissue and plant levels, there are substantially fewer studies that have investigated ecosystem-level responses in the context of integrated carbon, water, and nutrient cycles. Because our understanding of ecosystem responses to elevated CO2 is incomplete, modeling is a tool that can be used to investigate the role of plant and soil interactions in the response of terrestrial ecosystems to elevated CO2 . In this study, we analyze the responses of net primary production (NPP) to doubled CO2 from 355 to 710 ppmv among three biogeochemistry models in the Vegetation/Ecosystem Modeling and Analysis Project (VEMAP): BIOME-BGC (BioGeochemical Cycles), Century, and the Terrestrial Ecosystem Model (TEM). For the conterminous United States, doubled atmospheric CO2 causes NPP to increase by 5% in Century, 8% in TEM, and 11% in BIOME-BGC. Multiple regression analyses between the NPP response to doubled CO2 and the mean annual temperature and annual precipitation of biomes or grid cells indicate that there are negative relationships between precipitation and the response of NPP to doubled CO2 for all three models. In contrast, there are different relationships between temperature and the response of NPP to doubled CO2 for the three models: there is a negative relationship in the responses of BIOME-BGC, no relationship in the responses of Century, and a positive relationship in the responses of TEM. In BIOME-BGC, the NPP response to doubled CO2 is controlled by the change in transpiration associated with reduced leaf conductance to water vapor. This change affects soil water, then leaf area development and, finally, NPP. In Century, the response of NPP to doubled CO2 is controlled by changes in decomposition rates associated with increased soil moisture that results from reduced evapotranspiration. This change affects nitrogen availability for plants, which influences NPP. In TEM, the NPP response to doubled CO2 is controlled by increased carboxylation which is modified by canopy conductance and the degree to which nitrogen constraints cause down-regulation of photosynthesis. The implementation of these different mechanisms has consequences for the spatial pattern of NPP responses, and represents, in part, conceptual uncertainty about controls over NPP responses. Progress in reducing these uncertainties requires research focused at the ecosystem level to understand how interactions between the carbon, nitrogen, and water cycles influence the response of NPP to elevated atmospheric CO2 .- Published
- 1998
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24. EXPERIMENTAL ASSESSMENT OF REPRODUCTIVE INTERACTIONS BETWEEN SYMPATRIC ASTER AND ERIGERON (ASTERACEAE) IN INTERIOR ALASKA
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Armbruster, W. Scott and McGuire, A. David
- Abstract
Erigeron glabellusand Aster sibiricushave similar flowers, share pollinators, but bloom sequentially in interior Alaska. Both species depend on insect pollination for seed set: the Erigeronis self‐incompatible, and the Asteris apparently self‐compatible but allogamous. To test the hypothesis that sequential blooming is maintained by natural selection generated by reproductive interference, we manipulated the flowering time of Erigeron, forcing it to bloom simultaneously with Aster, and measured female fecundity in both species. We found no evidence of reduced female fecundity in either species caused by the presence of the sympatric “competitor” or by artificial pollination with the heterospecific pollen prior to conspecific pollination. Two‐species mixtures of simultaneously blooming Asterand Erigeronexperienced significant interspecific visitation, which may, under natural conditions, cause loss of pollen to alien stigmas and depressed male fecundity, at least in Erigeron. We found no evidence that sequential blooming in Erigeronand Asteris maintained by depressed female fecundity through pollinator sharing. If sequential blooming is maintained by natural selection, it seems more likely to be the result of selection generated by depressed male fitness through pollen loss to alien stigmas.
- Published
- 1991
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25. EFFECTS OF SNOWPACK ON TIMING AND ABUNDANCE OF FLOWERING IN DELPHINIUM NELSONII (RANUNCULACEAE): IMPLICATIONS FOR CLIMATE CHANGE
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Inouye, David W. and McGuire, A. David
- Abstract
Delphinium nelsoniiis an early‐blooming herbaceous perennial of montane western North America, which we studied in dry subalpine meadows in the Colorado Rocky Mountains. We examined the effects of variation in annual snowfall between 1973 and 1989 on the timing and abundance of flowering. During years of lower snow accumulation, D. nelsoniiplants experienced colder temperatures between the period of snowmelt and flowering. Also, flowering was delayed, floral production was lower, and flowering curves were more negatively skewed; damage during floral development probably occurred in years of low snowfall. If climate change results in decreased mean annual snowfall for the Rocky Mountains, then the seed production of D. nelsoniiwill probably be adversely affected. Decreased snowfall may also indirectly lower the seed production of later‐blooming species by decreasing populations of bumblebees and hummingbirds that forage on D. nelsoniiflowers. Decreased snowfall has the potential to reduce the number and relative proportions of species in the herbaceous flora in our study area.
- Published
- 1991
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26. INTERACTIONS FOR POLLINATION BETWEEN TWO SYNCHRONOUSLY BLOOMING HEDYSARUM SPECIES (FABACEAE) IN ALASKA
- Author
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McGuire, A. David
- Abstract
In interior and arctic Alaska, Hedysarum borealeand H. alpinum(Fabaceae) occur sympatrically, bloom nearly synchronously, have similar floral morphology and color, and require pollination by insects to set seed. I studied the pollination ecology of these species at a site where they occur sympatrically near Fairbanks, Alaska, to determine if pollination interactions play a role in maintaining overlapping blooming times. Seed set in each species was apparently neither enhanced nor reduced by the presence of the other species. Seed set of H. borealewas positively related to visitation rates by female Megachile giliae, the most abundant visitor to H. boreale.This bee showed no preference between the two Hedysarumspecies. However, worker Bombus flavifrons, the most abundant visitor to H. alpinum, preferred to forage on H. alpinum.The exhibition of strong floral constancy by visitors to the two Hedysarumspecies suggests that interspecific pollination may not be strong enough to cause divergence in blooming times. I found no evidence that the presence of one Hedysarumspecies enhances visitation to the other species. Instead, because visitation by worker B. flavifronsto H. alpinumwas reduced on sympatric plots, H. alpinummay have to tolerate overlap with H. borealeto take advantage of worker B. flavifronsactivity. The results of this study suggest that the two Hedysarumspecies may simply bloom when their best pollinators are most active.
- Published
- 1993
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27. STUDIES ON EXPERIMENTAL SHIGELLOSIS
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McGuire, C. David and Floyd, Thomas M.
- Abstract
Host resistance to Shigella infections can be decreased by non-specific physical stress. Fasting lowers the number of Shigella required for a parenteral LD50 dose. While the LD50 by the oral route is larger in fasted than in nonfasted animals, the fasted host's susceptibility to oral infection is increased as evidenced by the increased fecal Shigella carrier state, duration of intestinal infection, and increased incidence of Shigella bacteriemia. Fatigue also increases the animal's susceptibility to shigellosis, but to a lesser extent than does fasting.
- Published
- 1958
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28. STUDIES ON EXPERIMENTAL SHIGELLOSIS
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McGuire, C. David and Floyd, Thomas M.
- Abstract
Experimental Shigella flexneri 3 infections produced in normal mice have been described. The passage of viable Shigella through the stomach of orally infected animals, and the persistence of the organisms in the intestine for periods of 5 to 7 days, with an increase in bacterial numbers, indicated that true infection was produced. Blood culture studies showed that a Shigella bacteriemia occurred after either oral or parenteral administration of Shigella to normal mice. Mice infected orally revealed mild, but consistent pathological changes, including mesenteric hemorrhage, liver and spleen hypertrophy, and occasional diarrhea.
- Published
- 1958
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29. Identification of Group A Streptococci: Bacitracin Disc and Fluorescent Antibody Techniques Compared with the Lancefield Precipitin Method
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STREAMER, CHARLES W., WILLIAMS, PAUL M., LOU WANG, WEN LAN, JOHNSON, R. SAMUEL, McGUIRE, C. DAVID, ABELOW, IRENE J., and GLASER, ROBERT J.
- Abstract
During the course of a project which had as its primary objective the evaluation of a streptococcal disease control program,1 an opportunity was presented to compare the efficacy of (a) the bacitracin disc method and (b) the fluorescent antibody method of identifying Group A streptococci with the Lancefield precipitin technique. The results which were obtained and are here presented are confirmatory of previous work2,3 and show that both the bacitracin disc and the fluorescent antibody techniques are highly reliable. Each, therefore, represents a useful method for the identification of Group A streptococci in clinical laboratories. METHODS A total of 776 strains of streptococci was subjected to study; 669 (90%) were isolated from patients who were seen on the clinical services of the Denver General Hospital, while 69 strains (10%) were obtained from household contacts of patients included in the study. Of the streptococcal isolations, 76% were made from
- Published
- 1962
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30. Author Correction: Large loss of CO2in winter observed across the northern permafrost region
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Natali, Susan M., Watts, Jennifer D., Rogers, Brendan M., Potter, Stefano, Ludwig, Sarah M., Selbmann, Anne-Katrin, Sullivan, Patrick F., Abbott, Benjamin W., Arndt, Kyle A., Birch, Leah, Björkman, Mats P., Bloom, A. Anthony, Celis, Gerardo, Christensen, Torben R., Christiansen, Casper T., Commane, Roisin, Cooper, Elisabeth J., Crill, Patrick, Czimczik, Claudia, Davydov, Sergey, Du, Jinyang, Egan, Jocelyn E., Elberling, Bo, Euskirchen, Eugenie S., Friborg, Thomas, Genet, Hélène, Göckede, Mathias, Goodrich, Jordan P., Grogan, Paul, Helbig, Manuel, Jafarov, Elchin E., Jastrow, Julie D., Kalhori, Aram A. M., Kim, Yongwon, Kimball, John S., Kutzbach, Lars, Lara, Mark J., Larsen, Klaus S., Lee, Bang-Yong, Liu, Zhihua, Loranty, Michael M., Lund, Magnus, Lupascu, Massimo, Madani, Nima, Malhotra, Avni, Matamala, Roser, McFarland, Jack, McGuire, A. David, Michelsen, Anders, Minions, Christina, Oechel, Walter C., Olefeldt, David, Parmentier, Frans-Jan W., Pirk, Norbert, Poulter, Ben, Quinton, William, Rezanezhad, Fereidoun, Risk, David, Sachs, Torsten, Schaefer, Kevin, Schmidt, Niels M., Schuur, Edward A. G., Semenchuk, Philipp R., Shaver, Gaius, Sonnentag, Oliver, Starr, Gregory, Treat, Claire C., Waldrop, Mark P., Wang, Yihui, Welker, Jeffrey, Wille, Christian, Xu, Xiaofeng, Zhang, Zhen, Zhuang, Qianlai, and Zona, Donatella
- Abstract
An amendment to this paper has been published and can be accessed via a link at the top of the paper.
- Published
- 2019
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31. Comparison of pigeon guillemot, Cepphus columba, blood parameters from oiled and unoiled areas of Alaska eight years after the Exxon Valdez oil spill
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Litzow, M. A., Golet, G. H., Duffy, L. K., Roby, D. D., McGuire, A. David, and Seiser, P. E.
- Subjects
BIRDS ,HEMATOLOGY ,MARINE pollution ,OIL spills - Abstract
In 1997, we compared the haematological and plasma biochemical profiles among populations of pigeon guillemots, Cepphus columba, in areasoiled and not oiled by the 1989 Exxon Valdez oil spill (EVOS) that occurred in Prince William Sound (PWS), Alaska. Pigeon guillemot populations in PWS were injured by EVOS and have not returned to pre-spilllevels. If oil contamination is limiting recovery of pigeon guillemots in PWS, then we expected that blood parameters of pigeon guillemots would differ between oiled and unoiled areas and that these differences would be consistent with either toxic responses or lower fitness. We collected blood samples from chicks at approximately 20 and 30 days after hatching. Physiological changes associated with chick growth were noted in several blood parameters. We found that only calcium and mean cell volume were significantly different between the chicks in oiled and unoiled areas. Despite these differences, blood biomarkers provided little evidence of continuing oil injury to pigeon guillemot chicks, eight years after the EVOS. Preliminary data from adults indicated elevated aspartate aminotransferase activity in the adults from the oiled area, which is consistent with hepatocellular injury. Because adults have greater opportunities for exposure to residual oil than nestlings, we recommend studies that fully evaluate the healthof adults residing in oiled areas. [ABSTRACT FROM AUTHOR]
- Published
- 2000
32. IN VIVO CHANGE OF SEROLOGICAL SPECIFICITY IN SHIGELLA FLEXNERI
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McGuire, C. David and Floyd, Thomas M.
- Published
- 1958
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