scholarly journals Patterns and predictors of soil organic carbon storage across a continental-scale network

2021 ◽  
Author(s):  
L. E. Nave ◽  
M. Bowman ◽  
A. Gallo ◽  
J. A. Hatten ◽  
K. A. Heckman ◽  
...  
Keyword(s):  
The United States ◽  
Climate Gradients ◽  
Continental Scale ◽  
Drainage Class ◽  
C Cycle ◽  
Physicochemical Factors ◽  
Soil Carbon Stocks ◽  
Scale Network ◽  
Organic Carbon Storage ◽  
Soc Stocks

AbstractThe rarity of rapid campaigns to characterize soils across scales limits opportunities to investigate variation in soil carbon stocks (SOC) storage simultaneously at large and small scales, with and without site-level replication. We used data from two complementary campaigns at 40 sites in the United States across the National Ecological Observatory Network (NEON), in which one campaign sampled profiles from closely co-located intensive plots and physically composited similar horizons, and the other sampled dozens of pedons across the landscape at each site. We demonstrate some consistencies between these distinct designs, while also revealing that within-site replication reveals patterns and predictors of SOC stocks not detectable with non-replicated designs. Both designs demonstrate that SOC stocks of whole soil profiles vary across continental-scale climate gradients. However, broad climate patterns may mask the importance of localized variation in soil physicochemical properties, as captured by within-site sampling, especially for SOC stocks of discrete genetic horizons. Within-site replication also reveals examples in which expectations based on readily explained continental-scale patterns do not hold. For example, even wide-ranging drainage class sequences within landscapes do not duplicate the clear differences in profile SOC stocks across drainage classes at the continental scale, and physicochemical factors associated with increasing B horizon SOC stocks at continental scales frequently do not follow the same patterns within landscapes. Because inferences from SOC studies are a product of their context (where, when, how), this study provides context—in terms of SOC stocks and the factors that influence them—for others assessing soils and the C cycle at NEON sites.

Effect of Hydrologic Export on Soil Carbon Turnover Rates

2020 ◽  
Author(s):  
Oleksandra Hararuk ◽  
Stuart Jones ◽  
Christopher Solomon
Keyword(s):  
Weighted Average ◽  
The United States ◽  
Substantial Effect ◽  
Quality Data ◽  
United States Geological Survey ◽  
Turnover Rates ◽  
Water Quality Data ◽  
Soil C ◽  
C Cycle ◽  
Soc Stocks

<p>Soil is the largest terrestrial carbon (C) reservoir and is an important component of climate-carbon feedbacks, potentially sequestering or releasing large amounts CO<sub>2</sub> from or to the atmosphere. In global land models soil C dynamics is determined by the long-term balance between C inputs and turnover rates, and the latter are usually a function of soil texture, temperature, and soil moisture, which represents environmental limitation of microbial soil organic carbon (SOC) mineralization. Hydrologic C export is often overlooked in the terrestrial C cycle models, likely because proportionally soils contain a very small amount of C that can be exported with runoff, contributing around 2.9 Pg C yr<sup>-1</sup> to aquatic systems globally. However, ignoring hydrologic C export in areas, where it has substantial effect on SOC turnover rate, could result in systematic overestimation of SOC stocks and inaccurate simulation of SOC responses to changing environmental conditions. We combined water quality data from the United States Geological Survey with hydrologic and soil chemistry data products to estimate the relative contribution of hydrologic export to bulk soil turnover rates across the continental USA. The catchment area weighted average of hydrologic export effect on SOC turnover was 5.2%. Hydrologic export accounted for 0-2% of the bulk SOC turnover in arid regions, 2-15% - in forests, and 20-40% - in wetland-rich areas. The SOC stocks generated for the continental U.S. using microbe-mediated turnover alone amounted to 88.3 Pg C and were 15.4% higher than the amount reported in the Harmonized World Soil Database (76.5 Pg C), thus illustrating the importance of accounting for hydrologic C export when simulating SOC dynamics.</p>

scholarly journals Regional environmental controllers influence continental scale soil carbon stocks and future carbon dynamics

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Daniel Ruiz Potma Gonçalves ◽  
Umakant Mishra ◽  
Skye Wills ◽  
Sagar Gautam
Keyword(s):  
Environmental Factors ◽  
Land Cover ◽  
Environmental Conditions ◽  
Climate Feedback ◽  
Soil Types ◽  
Climatic Data ◽  
Earth System ◽  
Land Cover Types ◽  
Continental Scale ◽  
Soc Stocks

AbstractUnderstanding the influence of environmental factors on soil organic carbon (SOC) is critical for quantifying and reducing the uncertainty in carbon climate feedback projections under changing environmental conditions. We explored the effect of climatic variables, land cover types, topographic attributes, soil types and bedrock geology on SOC stocks of top 1 m depth across conterminous United States (US) ecoregions. Using 4559 soil profile observations and high-resolution data of environmental factors, we identified dominant environmental controllers of SOC stocks in 21 US ecoregions using geographically weighted regression. We used projected climatic data of SSP126 and SSP585 scenarios from GFDL-ESM 4 Earth System Model of Coupled Model Intercomparison Project phase 6 to predict SOC stock changes across continental US between 2030 and 2100. Both baseline and predicted changes in SOC stocks were compared with SOC stocks represented in GFDL-ESM4 projections. Among 56 environmental predictors, we found 12 as dominant controllers across all ecoregions. The adjusted geospatial model with the 12 environmental controllers showed an R2 of 0.48 in testing dataset. Higher precipitation and lower temperatures were associated with higher levels of SOC stocks in majority of ecoregions. Changes in land cover types (vegetation properties) was important in drier ecosystem as North American deserts, whereas soil types and topography were more important in American prairies. Wetlands of the Everglades was highly sensitive to projected temperature changes. The SOC stocks did not change under SSP126 until 2100, however SOC stocks decreased up to 21% under SSP585. Our results, based on environmental controllers of SOC stocks, help to predict impacts of changing environmental conditions on SOC stocks more reliably and may reduce uncertainties found in both, geospatial and Earth System Models. In addition, the description of different environmental controllers for US ecoregions can help to describe the scope and importance of global and local models.

Late-summer carbon fluxes from Canadian forests and peatlands along an east–west continental transect

2006 ◽  
Vol 36 (3) ◽  
pp. 783-800 ◽  
Author(s):  
Carole Coursolle ◽  
Hank A Margolis ◽  
Alan G Barr ◽  
T Andrew Black ◽  
Brian D Amiro ◽  
...  
Keyword(s):  
Large Scale ◽  
Ecosystem Respiration ◽  
Late Summer ◽  
Ecosystem Productivity ◽  
Diurnal Courses ◽  
Continental Scale ◽  
Young Forest ◽  
C Cycle ◽  
Use Efficiency ◽  
East West

Net ecosystem productivity (NEP) during August 2003 was measured by using eddy covariance above 17 forest and 3 peatland sites along an east–west continental-scale transect in Canada. Measured sites included recently disturbed stands, young forest stands, intermediate-aged conifer stands, mature deciduous stands, mature conifer stands, fens, and an open shrub bog. Diurnal courses of NEP showed strong coherence within the different ecosystem categories. Recently disturbed sites showed the weakest diurnal cycle; and intermediate-aged conifers, the strongest. The western treed fen had a more pronounced diurnal pattern than the eastern shrub bog or the Saskatchewan patterned fen. All but three sites were clearly afternoon C sinks. Ecosystem respiration was highest for the young fire sites. The intermediate-aged conifer sites had the highest maximum NEP (NEPmax) and gross ecosystem productivity (GEPmax), attaining rates that would be consistent with the presence of a strong terrestrial C sink in regions where these types of forest are common. These results support the idea that large-scale C cycle modeling activities would benefit from information on the age-class distribution and disturbance types within larger grid cells. Light use efficiency followed a pattern similar to that of NEPmax and GEPmax. Four of the five recently disturbed sites and all three of the peatland sites had low water use efficiencies.

USA and Empire in the 19th Century

2020 ◽  
Author(s):  
Christa Dierksheide
Keyword(s):  
British Empire ◽  
19Th Century ◽  
The United States ◽  
The Philippines ◽  
Santo Domingo ◽  
Continental Scale ◽  
Land Mass ◽  
Human Cost ◽  
The 19Th Century ◽  
American Nation

During the course of the 19th century, the United States forged an empire on a continental scale and also made significant territorial gains overseas. While it had taken the British Empire a little over two centuries to settle the swath of land stretching between the Appalachian Mountains and the Atlantic Ocean, the fledgling postcolonial American nation managed to colonize a land mass several times larger in a fraction of the time. But all this expansion came at an enormous human cost, resulting in the death or removal of countless native peoples, the enslavement of millions of African Americans, and sectional tensions that led to the American Civil War. During the latter part of the century, Americans began pursuing an imperial project beyond the continent, waging war or initiating annexation projects in Santo Domingo, Cuba, Hawaii, Puerto Rico, and the Philippines. The sources collected here reflect the dynamism, contingency, and tragedy of American colonization efforts between 1776 and 1900.

scholarly journals La collaboration scientifique et technologique en Amérique du Nord : un point de vue Canadien

2005 ◽  
Vol 24 (2) ◽  
pp. 269-296
Author(s):  
Charles H. David ◽  
Paul Dufour ◽  
Janet Halliwell
Keyword(s):  
United States ◽  
Open Economy ◽  
North American ◽  
Small Open Economy ◽  
Innovation System ◽  
The United States ◽  
Technology And Innovation ◽  
Continental Scale ◽  
Science Technology ◽  
Science Technology And Innovation

Canada, as a country with a small, open economy, faces the immediate challenge of learning to shape dynamic comparative advantage in the emerging international economy. About 75 % of Canada's trade linkages are with the United States, and a very large component of the Canadian experience of « globalization » is driven by North American economic integration. This integration is taking place in the absence of institutions and policy mechanisms to promote and manage science, technology, and innovation relations on a continental scale. Bilateral s & T arrangements centered on the United States presently characterize the North American innovation System. Circumstances in North America pose three sets of challenges to Canadian s & T policy. 1) Science and technology are increasing in importance in international trade, environmental, and social/cultural matters. This means that Canada must learn to improve its management of an increasingly internationalized domestic s & T System. 2) Canada must cultivate mutually beneficial bilateral s & T relationships with its two partners in NAFTA, Mexico and the United States. 3) Canada must identify where its interests lie in the development and governance of trilateral and international rules and arrangements for science, technology, and innovation.

scholarly journals Continental-Scale Increase in Lake and Stream Phosphorus: Are Oligotrophic Systems Disappearing in the United States?

2016 ◽  
Vol 50 (7) ◽  
pp. 3409-3415 ◽  
Author(s):  
John L. Stoddard ◽  
John Van Sickle ◽  
Alan T. Herlihy ◽  
Janice Brahney ◽  
Steven Paulsen ◽  
...  
Keyword(s):  
United States ◽  
The United States ◽  
Continental Scale

The role of soil drainage class in carbon dioxide exchange and decomposition in boreal black spruce (Picea mariana) forest stands

2010 ◽  
Vol 40 (11) ◽  
pp. 2123-2134 ◽  
Author(s):  
Kimberly P. Wickland ◽  
Jason C. Neff ◽  
Jennifer W. Harden
Keyword(s):  
Carbon Dioxide ◽  
Soil Respiration ◽  
Picea Mariana ◽  
Black Spruce ◽  
Soil Drainage ◽  
Forest Stands ◽  
Drainage Class ◽  
Surface Decomposition ◽  
Soc Stocks

Black spruce (Picea mariana (Mill.) B.S.P.) forest stands range from well drained to poorly drained, typically contain large amounts of soil organic carbon (SOC), and are often underlain by permafrost. To better understand the role of soil drainage class in carbon dioxide (CO2) exchange and decomposition, we measured soil respiration and net CO2 fluxes, litter decomposition and litterfall rates, and SOC stocks above permafrost in three Alaska black spruce forest stands characterized as well drained (WD), moderately drained (MD), and poorly drained (PD). Soil respiration and net CO2 fluxes were not significantly different among sites, although the relation between soil respiration rate and temperature varied with site (Q10: WD > MD > PD). Annual estimated soil respiration, litter decomposition, and groundcover photosynthesis were greatest at PD. These results suggest that soil temperature and moisture conditions in shallow organic horizon soils at PD were more favorable for decomposition compared with the better drained sites. SOC stocks, however, increase from WD to MD to PD such that surface decomposition and C storage are diametric. Greater groundcover vegetation productivity, protection of deep SOC by permafrost and anoxic conditions, and differences in fire return interval and (or) severity at PD counteract the relatively high near-surface decomposition rates, resulting in high net C accumulation.

scholarly journals Population Genetics of Hirsutella rhossiliensis, a Dominant Parasite of Cyst Nematode Juveniles on a Continental Scale

2016 ◽  
Vol 82 (21) ◽  
pp. 6317-6325 ◽  
Author(s):  
Niuniu Wang ◽  
Yongjie Zhang ◽  
Xianzhi Jiang ◽  
Chi Shu ◽  
M. Imran Hamid ◽  
...  
Keyword(s):  
Genetic Variation ◽  
Biocontrol Agent ◽  
Nematode Species ◽  
The United States ◽  
Heterodera Schachtii ◽  
Parasitic Nematodes ◽  
Content Type ◽  
Continental Scale ◽  
History Of ◽  
Hirsutella Rhossiliensis

ABSTRACTHirsutella rhossiliensisis a parasite of juvenile nematodes, effective against a diversity of plant-parasitic nematodes. Its global distribution on various nematode hosts and its genetic variation for several geographic regions have been reported, while the global population genetic structure and factors underlying patterns of genetic variation ofH. rhossiliensisare unclear. In this study, 87H. rhossiliensisstrains from five nematode species (Globoderasp.,Criconemella xenoplax,Rotylenchus robustus,Heterodera schachtii, andHeterodera glycines) in Europe, the United States, and China were investigated by multilocus sequence analyses. A total of 280 variable sites (frequency, 0.6%) at eight loci and six clustering in high accordance with geographic populations or host nematode-associated populations were identified. AlthoughH. rhossiliensisis currently recognized as an asexual fungus, recombination events were frequently detected. In addition, significant genetic isolation by geography and nematode hosts was revealed. Overall, our analyses showed that recombination, geographic isolation, and nematode host adaptation have played significant roles in the evolutionary history ofH. rhossiliensis.IMPORTANCEH. rhossiliensishas great potential for use as a biocontrol agent to control nematodes in a sustainable manner as an endoparasitic fungus. Therefore, this study has important implications for the use ofH. rhossiliensisas a biocontrol agent and provides interesting insights into the biology of this species.

Taxonomy, ultrastructure, and distribution of some gomphonemoid diatoms (Bacillariophyceae: Gomphonemataceae) from rivers in the United States

1999 ◽  
Vol 77 (5) ◽  
pp. 686-705 ◽  
Author(s):  
J P Kociolek ◽  
J C Kingston
Keyword(s):  
Water Quality ◽  
Quality Assessment ◽  
North American ◽  
Large Scale ◽  
Taxonomic Status ◽  
Water Quality Assessment ◽  
The United States ◽  
Great Promise ◽  
Continental Scale ◽  
National Water

Using the continental-scale collections of the U.S. Geological Survey's National Water-Quality Assessment (NAWQA) Program, we examined selected members of the family Gomphonemataceae to expand the current state of knowledge of diatom taxonomy, morphology, and distribution. Ten taxa in the genera Gomphonema, Gomphoneis, and Gomphosphenia are examined. The taxonomic status of two taxa is revised, and one new species is described. Two new features are described for the genus Gomphonema: slit-like areolae and ridge-like flaps or flanges on pseudosepta. Many North American gomphonemoid species appear to be restricted to certain geographic regions; the differences between western and eastern North America are striking. Trained analysts have had difficulty identifying and discriminating many of these taxa. We believe that this difficulty, in large part, results from our poor knowledge of the North American flora. Large-scale monitoring programs such as NAWQA, when teamed up with research organizations with common interests, hold great promise to expand our knowledge of the biodiversity of North American ecosystems.Key words: biogeography, Gomphoneis, Gomphonema, Gomphosphenia, National Water-Quality Assessment (NAWQA) Program, taxonomy; ultrastructure.

scholarly journals The Impact of Movements and Animal Density on Continental Scale Cattle Disease Outbreaks in the United States

PLoS ONE ◽  
2014 ◽  
Vol 9 (3) ◽  
pp. e91724 ◽  
Author(s):  
Michael G. Buhnerkempe ◽  
Michael J. Tildesley ◽  
Tom Lindström ◽  
Daniel A. Grear ◽  
Katie Portacci ◽  
...  
Keyword(s):  
United States ◽  
Disease Outbreaks ◽  
The United States ◽  
Continental Scale ◽  
Cattle Disease ◽  
Animal Density ◽  
The Impact
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