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Modeling Hydrologic Simulations for Past & Future Conditions across the Conterminous US
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This data release contains inputs for and outputs from hydrologic simulations for the conterminous United States (CONUS) using the Precipitation Runoff Modeling System (PRMS) version 5.1.0 and the USGS National Hydrologic Model Infrastructure (NHMI).
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Modeling sediment accumulation in North American playa wetlands in response to climate change, 1940–2100
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Playa wetlands on the west-central Great Plains of North America are vulnerable to sediment infilling from upland agriculture, putting at risk several important ecosystem services as well as essential habitats and food resources of diverse wetland-dependent biota. Climate predictions for this semi-arid area indicate reduced precipitation which may alter rates of erosion, runoff, and sedimentation of playas. We forecasted erosion rates, sediment depths, and resultant playa wetland depths across the west-central Great Plains and exam- ined the relative roles of land use context and projected changes in precipitation in the sedimentation process. We estimated erosion with the Revised Universal Soil Loss Equation (RUSLE) using historic values and downscaled precipitation predictions from three general circulation models and three emissions scenarios. We calibrated RUSLE results using field sediment measurements. RUSLE is appealing for regional scale modeling because it uses climate forecasts with monthly resolution and other widely available values including soil texture, slope and land use. Sediment accumulation rates will continue near historic levels through 2070 and will be sufficient to cause most playas (if not already filled) to fill with sediment within the next 100 years in the absence of mitigation. Land use surrounding the playa, whether grassland or tilled cropland, is more influential in sediment accumulation than climate-driven precipitation change.
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Modell 1942.pdf
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MIL-MUR
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Modelling the long-term response to positive and negative priming of soil organic carbon by black carbon
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bserved increases in the mineralization rate of labile organic carbon (LOC) in the presence of black carbon (BC) have led to speculation that corresponding decreases in non-pyrogenic (i.e. non- BC) soil organic carbon (npSOC) could significantly reduce or negate the C sequestration benefit of BC in soils. Here we show that the potential effect of an increased LOC decomposition rate on long-term npSOC stocks is negligible, even when using assump- tions that would favour large losses, potentially causing no more than 3–4 % loss of npSOC over 100 years if 50 % of above-ground crop residues were converted to BC annually. Conversely, if the BC- stimulated enhanced stabilization of npSOC that has been observed in laboratory trials is extrapolated to the long-term, it would greatly increase soil carbon stocks by 30–60 %. Annual additions of BC derived from crop residues would increase total SOC (including both BC and npSOC) by an amount five times greater than the potential increase from enhanced stabilization and an order of magnitude greater than losses of npSOC caused by annual removals of biomass to provide BC feedstock.
Keywords Black carbon Soil organic carbon Terrestrial carbon cycle Fire Biochar
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Mohan 1992.pdf
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Mohr, Helen H
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Moisture transport across Central America as a positive feedback on abrupt climatic changes
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Moisture transport from the Atlantic to the Pacific ocean across Central America leads to relatively high salinities in the North Atlantic Ocean1 and contributes to the formation of North Atlantic Deep Water2. This deep water formation varied strongly between Dansgaard/Oeschger interstadials and Heinrich events— millennial-scale abrupt warm and cold events, respectively, during the last glacial period3. Increases in the moisture transport across Central America have been proposed to coincide with northerly shifts of the Intertropical Convergence Zone and with Dansgaard/ Oeschger interstadials, with opposite changes for Heinrich events4. Here we reconstruct sea surface salinities in the eastern equatorial Pacific Ocean over the past 90,000 years by comparing palaeotemperature estimates from alkenones and Mg/Ca ratios with foraminiferal oxygen isotope ratios that vary with both tem- perature and salinity. We detect millennial-scale fluctuations of sea surface salinities in the eastern equatorial Pacific Ocean of up to two to four practical salinity units. High salinities are associated with the southward migration of the tropical Atlantic Intertropical Convergence Zone, coinciding with Heinrich events and with Greenland stadials5. The amplitudes of these salinity variations are significantly larger on the Pacific side of the Panama isthmus, as inferred from a comparison of our data with a palaeoclimate record from the Caribbean basin6. We conclude that millennial- scale fluctuations of moisture transport constitute an important feedback mechanism for abrupt climate changes, modulating the North Atlantic freshwater budget and hence North Atlantic Deep Water formation.
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Molecular study of worldwide distribution and diversity of soil animals
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The global distribution of soil animals and the relationship of below-ground biodiversity to above-ground biodiversity are not well understood. We examined 17,516 environmental 18S rRNA gene sequences representing 20 phyla of soil animals sampled from 11 locations covering a range of biomes and latitudes around the world. No globally cosmopolitan taxa were found and only 14 of 2,259 operational taxonomic units (OTUs) found were common to four or more locations. Half of those were circumpolar and may reflect higher connectivity among circumpolar locations compared with other locations in the study. Even when OTU assembly criteria were relaxed to approximate the family taxo- nomic level, only 34 OTUs were common to four or more locations. A comparison of our diversity and community structure data to environmental factors suggests that below-ground animal diver- sity may be inversely related to above-ground biodiversity. Our data suggest that greater soil inorganic N and lower pH could explain the low below-ground biodiversity found at locations of high above-ground biodiversity. Our locations could also be characterized as being dominated by microarthropods or domi- nated by nematodes. Locations dominated by arthropods were primarily forests with lower soil pH, root biomass, mean annual temperature, low soil inorganic N and higher C:N, litter and moisture compared with nematode-dominated locations, which were mostly grasslands. Overall, our data indicate that small soil animals have distinct biogeographical distributions and provide unique evidence of the link between above-ground and below- ground biodiversity at a global scale.
cosmopolitan species | endemism
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Moles 1983.pdf
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Moles Layzer 2008.pdf
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