Estimation of slow- and fast-cycling soil organic carbon pools from 6N HCI hydrolysis

Includes bibliographical references (pages 238-239).Acid hydrolysis is used to fractionate the soil organic carbon pool into relatively slow- and fast-cycling compartments on soils from Arizona, the Great Plains states and Michigan collected for carbon isotope tracer studies related to soil carbon sequestration, for studies of shifts in C3/C4 vegetation, and for "pre-bomb" soil-carbon inventories. Prior to hydrolysis, soil samples are first treated with cold 0.5-1N HCl to remove soil carbonates if necessary. Samples are then dispersed in a concentrated NaCI solution (p~1.2 g cm-3) and floated plant fragments are skimmed off the surface. After rinsing and drying, all remaining recognizable plant fragments are picked from the soil under 20x magnification. Plant-free soils, and hot, 6NHCl acid-hydrolysis residue and hydrolyzate fractions are analyzed for carbon content, δ 13C and 14C age, and the carbon distribution is verified within 1-2% by stable-carbon isotope mass balance. On average, the recalcitrant residue fraction is 1800 year older and 2.6‰ more 13C-depleted than total soil organic carbon. A test of hydrolysis with fresh plant fragments produced as much as 71-76% in the acid-hydrolysis residue pool. Thus, if plant fragments are not largely removed prior to hydrolysis, the residue fraction may date much younger than it actually is.Publisher version: https://journals.uair.arizona.edu/index.php/radiocarbon/article/view/1903/1904

Nontarget Effects—The Achilles’ Heel of Biological Control? Retrospective Analyses to Reduce Risk Associated with Biocontrol Introductions

Controversy exists over ecological risks in classical biological control. We reviewed 10 projects with quantitative data on nontarget effects. Ten patterns emerged: (a) Relatives of the pest are most likely to be attacked; (b) host-specificity testing defines physiological host range, but not ecological range; (c) prediction of ecological consequences requires population data; (d) level of impact varied, often in relation to environmental conditions; (e) information on magnitude of nontarget impact is sparse; ( f ) attack on rare native species can accelerate their decline; (g) nontarget effects can be indirect; (h) agents disperse from agroecosystems; (i) whole assemblages of species can be perturbed; and ( j ) no evidence on adaptation is available in these cases. The review leads to six recommendations: Avoid using generalists or adventive species; expand host-specificity testing; incorporate more ecological information; consider ecological risk in target selection; prioritize agents; and pursue genetic data on adaptation. We conclude that retrospective analyses suggest clear ways to further increase future safety of biocontrol

Carbon isotope ratios of Great Plains soils and in wheat-fallow systems

Includes bibliographical references (pages 1076-1077).The purposes of this study were to improve knowledge of regional vegetation patterns of C3 and C4 plants in the North American Great Plains and to use δ13C methodology and long-term research sites to determine contributions of small-grain crops to total soil organic carbon (SOC) now present. Archived and recent soil samples were used. Detailed soil sampling was in 1993 at long-term sites near Akron, CO, and Sidney, NE. After soil sieving, drying, and deliming, SOC and δ13C were determined using an automated C/N analyzer interfaced to an isotope-ratio mass spectrometer. Yield records from long-term experimental sites were used to estimate the amount of C3 plant residue C returned to the soil. Results from δ13C analyses of soils from near Waldheim, Saskatchewan, to Big Springs, TX, showed a strong north to south decrease in SOC derived from C3 plants and a corresponding increase from C4 plants. The δ13C analyses gave evidence that C3 plant residue C (possibly from shrubs) is increasing at the Big Springs, TX, and Lawton, OK, sites. Also, δ13C analyses of subsoil and topsoil layers shows evidence of a regional shift to more C3 species, possibly because of a cooler climate during the past few hundreds to thousands of years. Data from long-term research sites indicate that the efficiency of incorporation of small-grain crop residue C was about 5.4% during 84 year at Akron, CO, and about 10.5% during 20 year at Sidney, NE. The 14C age of the SOC at 0- to 10-cm depth was 193 year and at 30 to 45 cm was 4000 yr; 14C age of nonhydrolyzable C was 2000 and 7000 year for these same two respective depths. Natural partitioning of the 13C isotope by the photosynthetic pathways of C3 and C4 plants provides a potentially powerful tool to study SOC dynamics at both regional and local scales

Deaf Smith County, Texas: Records of wells, driller's logs, water analyses, and map showing location of wells

Data complied regarding wells and other water resources, including water quality analysis, measurements, and other relevant information

Nutrient composition of selected traditional United States Northern Plains Native American plant foods

Ten wild plants (cattail broad leaf shoots, chokecherries, beaked hazelnuts, lambsquarters, plains prickly pear, prairie turnips, stinging nettles, wild plums, raspberries, and rose hips) from three Native American reservations in North Dakota were analyzed to expand composition information of traditional foraged plants. Proximates, dietary fiber (DF), vitamins, minerals, carotenoids, and folate vitamers were assayed using standard methods and reference materials. Per serving, all were rich in Mn (100–2808 mg). Several provided \u3e10% DRI of Fe (cattail shoots, steamed lambsquarters, and prairie turnips), Ca (steamed lambsquarters, prickly pear, and prairie turnips), Mg (cattail shoots, lambsquarters, prickly pear, and prairie turnips), vitamins B6 (chokecherries, steamed lambsquarters, broiled prickly pear, and prairie turnips), C (raw prickly pear, plums, raspberries, rose hips (426 mg/100 g), and K (cattail shoots, chokecherries, lambsquarters, plums, rose hips, and stinging nettles). DF was \u3e10 g/serving in chokecherries, prairie turnips, plums and raspberries. Rose hips, plums, lambsquarters, and stinging nettles were carotenoid-rich (total, 3.2–11.7 mg/100 g; b-carotene, 1.2–2.4 mg/100 g; lutein/zeaxan- thin, 0.9–6.2 mg/100 g) and lycopene (rose hips only, 6.8 mg/100 g). Folate (primarily 5-methylte- trahydrofolate) was highest in raw lambsquarters (97.5 mg/100 g) and notable in cattail shoots, raw prairie turnips, and blanched stinging nettles (10.8, 11.5, and 24.0 mg/100 g, respectively). Results, provided to collaborating tribes and available in the National Nutrient Database of the United States Department of Agriculture (USDA) (www.ars.usda.gov/nutrientdata), support reintroduction or increased consumption of foraged plants

Saturation of the Two-Plasmon Decay Instability in Long-Scale-Length Plasmas Relevant to Direct-Drive Inertial Confinement Fusion

Measurements of the hot-electron generation by the two-plasmon-decay instability are made in plasmas relevant to direct-drive inertial confinement fusion. Density-scale lengths of 400 {micro}m at n{sub cr}/4 in planar CH targets allowed the two-plasmon-decay instability to be driven to saturation for vacuum intensities above ~3.5 x 10{sup 14} W cm{sup -2}. In the saturated regime, ~1% of the laser energy is converted to hot electrons. The hot-electron temperature is measured to increase rapidly from 25 to 90 keV as the laser beam intensity is increased from 2 to 7 x 10{sup 14} W cm{sup -2}. This increase in the hot-electron temperature is compared with predictions from nonlinear Zakharov models