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Good management of rangelands promotes C sequestration and reduces the likelihood of these ecosystems becoming net sources of CO2 As part of an ongoing study, soil was sampled in 2003 to investigate the long‐term effects of different livestock grazing treatments on soil organic carbon (SOC), total nitrogen (TN), and microbial communities. The three treatments studied (no grazing, EX; continuously, lightly grazed [10% utilization], CL; and continuously, heavily grazed [50% utilization], CH) have been imposed on a northern mixed‐grass prairie near Cheyenne, WY, for 21 yr. In the 10 yr since treatments were last sampled in 1993, the study area has been subject to several years of drought. In the 0 to 60 cm depth there was little change in SOC in the EX or CL treatments between 1993 and 2003, whereas there was a 30% loss of SOC in the CH treatment. This loss is attributed to plant community changes (from a cool‐season [C3] to a warm‐season [C4] plant dominated community) resulting in organic C accumulating nearer the soil surface, making it more vulnerable to loss. Soil TN increased in the EX and CL treatments between 1993 and 2003, but declined in the CH treatment. Differences in plant community composition and subsequent changes in SOC and TN may have contributed to microbial biomass, respiration, and N‐mineralization rates generally being greatest in CL and least in the CH treatment. Although no significant differences were observed in any specific microbial group based on concentrations of phospholipid fatty acid (PLFA) biomarkers, multivariate analysis of PLFA data revealed that microbial community structure differed among treatments. The CH grazing rate during a drought period altered plant community and microbial composition which subsequently impacted biogeochemical C and N cycles.

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Layered double hydroxides (LDHs) are anionic clays that can be synthesized under laboratory conditions. In this study, different LDHs were synthesized by a coprecipitation method, with the parent products and calcined derivatives evaluated for their ability to adsorb the anionic surfactant, dodecylbenzenesulfonate (DBS). Adsorption isotherms for DBS retention on LDHs were typical L-type curves, with adsorption data conforming to a simple Langmuir equation. Langmuir maximum adsorption of DBS on calcined-LDH was significantly higher than that on uncalcined-LDHs. Organo-LDHs were also synthesized by incorporating DBS into LDHs via ion-exchange, reconstruction of calcined-LDH and in-situ synthesis methods. X-ray diffraction analysis of organo-LDHs revealed that DBS was intercalated into LDHs with the mono-layer DBS molecules oriented perpendicularly to LDH surfaces. Intercalation of DBS into LDHs decreased surface area according to BET analysis. The adsorption capacities of organo-LDHs for trichloroethylene (TCE) and tetrachloroethylene (PCE) were substantially greater than the original LDH materials. Adsorption of organic compounds by organo-LDHs was due to a partitioning mechanism.Reagent grade metal salts were obtained from Spectrum Quality Products (Gardena, CA, USA). Sodium dodecylbenzenesulfonate and the organic compounds, trichloroethylene