02193nas a2200145   4500008004100000245011300041210006900154300001300223490000700236520161900243653002201862100001801884700001701902856012801919       1999                        eng d00aSoil air carbon dioxide and nitrous oxide concentrations in profiles under tallgrass prairie and cultivation0 aSoil air carbon dioxide and nitrous oxide concentrations in prof  a784 -7930 v283 aAssessing the dynamics of gaseous production in soils is of interest because they are important sources and sinks of greenhouse gases. Changes in soil air carbon dioxide (CO2) and nitrous oxide (N2O) concentrations were studied in a Reading silt loam (fine-silty, mixed, mesic Typic Argiudolls) under prairie and cultivation. Concentrations were measured in situ over a 17-mo period to a depth of 3 m. Multilevel samplers permitted collection of gases with subsequent measurement by gas chromatography in the laboratory. Soil air N2O concentrations were near atmospheric levels for a majority of the study period in the prairie site (0.184–2.25 µL L−1) but were significantly higher in the cultivated site (0.257–7.56 µL L−1). Annual mean N2O concentrations were 0.403 and 1.09 µL L−1 in the prairie and cultivated sites, respectively. Soil air CO2 annual mean concentrations were 1.56 × 104 and 1.10 × 104 µL L−1 and ranged from 0.096 × 104 to 6.45 × 104 µL L−1 and 0.087 × 104 to 3.59 × 104 µL L−1 in the prairie and cultivated sites, respectively. Concentrations generally increased with depth, with maximum soil air N2O and CO2 concentrations at 1.0 m in the prairie site and 0.5 m in the cultivated site. Nitrous oxide in the cultivated site and CO2 at both sites did not change markedly over winter months, but CO2 and N2O concentrations reached maximums during the summer months and decreased as the year progressed. Although soil air concentrations peaked and decreased faster at shallower depths, deeper depths exhibited relative maximum concentrations for longer time periods.10atallgrass prairie1 aSotomayor, D.1 aRice, C., W.  uhttp://lter.konza.ksu.edu/content/soil-air-carbon-dioxide-and-nitrous-oxide-concentrations-profiles-under-tallgrass-prairie02228nas a2200157   4500008004100000245009100041210006900132300001300201490000700214520165500221653002201876100001501898700001701913700001801930856012201948       1998                        eng d00aCarbon and nitrogen mineralization in tallgrass prairie and agricultural soil profiles0 aCarbon and nitrogen mineralization in tallgrass prairie and agri  a942 -9510 v623 aIn situ mineralization of N may contribute significantly to total inorganic-N pools deep in the soil profile. We conducted long-term laboratory incubation experiments to evaluate the net C and N mineralization in soils collected from various depths in tallgrass prairie and agricultural fields of the same geological materials and soil type. Samples were packed to a bulk density of 1.4 g cm-3 in 5-cm-diameter by 10-cm-long cores. The cores were incubated at 35°C for 40 wk in sealed containers. Net C mineralization was measured by evolved CO2, and N mineralized was measured by periodic leaching with NH+4 and NO-3 measured in the leachate. Carbon and N mineralization in the surface horizon were greater in the tallgrass prairie than in the agricultural soil. In both the tallgrass prairie and agricultural soil profiles, C mineralization was least at the water-table depth. Carbon mineralization was described by a first-order kinetic model, but N mineralization was described better by a consecutive (sigmoidal) reaction model. At most depths, the ratios of potentially mineralizable organic C (C0) to total organic C (C0/TOC) and potentially mineralizable organic N (N0) to total N (N0/TN) were greater in the agricultural soil profile than in the tallgrass prairie soil profile. The C0 and N0 in the surface soil (0–0.2 m) represented 11.6 and 12.2% of the total organic C and N pools for the tallgrass prairie soil profile, respectively, and 21.0 and 10.2% of the total organic C and N pools for the agricultural soil profile. Management practices affected the mineralization potentials and rates of both the surface and subsurface soils.10atallgrass prairie1 aAjwa, H.A.1 aRice, C., W.1 aSotomayor, D.  uhttp://lter.konza.ksu.edu/content/carbon-and-nitrogen-mineralization-tallgrass-prairie-and-agricultural-soil-profiles02298nas a2200193   4500008004100000245009600041210006900137300001300206490000700219520163600226100001801862700001601880700001701896700001701913700001801930700001801948700001101966856012701977       1996                        eng d00aBiological properties of soil and subsurface sediments under abandoned pasture and cropland0 aBiological properties of soil and subsurface sediments under aba  a837 -8460 v283 aLittle is known about the effects of most surface land-use practices on shallow subsurface microbial communities. We analyzed duplicate cores taken aseptically from up to 10 m depth from unconsolidated valley sediments (soils) beneath an abandoned pasture reverting to tall grass prairie and cropland. Both profiles had similar soil texture, with moderately higher silt under cropland and a slight decrease in clay with depth. Soluble organic C was about two times higher in the grassland site and dissolved O2 was about 8% lower compared with the cropland site. Water content and C-to-N ratios were greatest at the grassland surface but were less in the grassland than the cropland site within 2 m depth. In general, numbers of aerobic heterotrophic bacteria and protozoa decreased with depth until the saturated zone (4.3 m in grassland and 5.3 m in the cropland site). Bacterial numbers as determined by plate counts were about 10-fold less at the groundwater interface than in the surface soils at both sites. Direct microscopic counts of total bacteria were approximately the same in the surface soil and the sediments at the top of the water table at both sites. The top of the water table generally did not exhibit elevated microbial biomass or activity relative to deeper sediments. There was no significant relationship between protozoan numbers and microbial thymidine uptake at the cropland site, but a negative relationship was observed at the grassland site. The data suggest that cultivation may affect microbial biomass and activity in the subsurface, as well as community interactions between protozoa and bacteria.1 aDodds, W., K.1 aBanks, M.K.1 aClenan, C.S.1 aRice, C., W.1 aSotomayor, D.1 aStrauss, E.A.1 aYu, W.  uhttp://lter.konza.ksu.edu/content/biological-properties-soil-and-subsurface-sediments-under-abandoned-pasture-and-cropland01749nas a2200133   4500008004100000245007600041210006900117300001500186490000700201520126500208100001801473700001701491856010701508       1996                        eng d00aDenitrification in soil profiles beneath grassland and cultivated soils0 aDenitrification in soil profiles beneath grassland and cultivate  a1822 -18280 v603 aThe denitrification potential of subsoils and aquifers must be characterized to assess the ultimate fate of soil N. This experiment was conducted to study changes in the subsurface distribution and activity of denitrifying bacteria as a result of cultivation. We examined soil profiles for their capacity (N addition) and potential (N + C addition) to denitrify as well as for denitrifying bacterial numbers in a Reading silt loam (fine, mixed, mesic Typic Argiudoll) soil under grassland and cultivation. Denitrifying enzyme activity was undetectable throughout the subsurface of soil profiles at both sites. Overall, the cultivated site had significantly higher NO−3 concentrations, denitrifier populations, and denitrification potential. Denitrifying bacteria were stratified in the vadose zone at the prairie site, with lowest numbers and lowest denitrification potential occurring at the interface of the water table. Although C addition enhanced denitrification at this site, the profile was not nearly as limited by C as that of the cultivated site. The results demonstrated that increased N inputs and cultivation during approximately 50 yr changed the denitrifying population and denitrification potential in the vadose and saturated zones of soils.1 aSotomayor, D.1 aRice, C., W.  uhttp://lter.konza.ksu.edu/content/denitrification-soil-profiles-beneath-grassland-and-cultivated-soils00558nas a2200133   4500008004100000245008400041210006900125260004300194300001100237490002100248653002200269100001800291856011500309       1996                        eng d00aMicrobial ecology and denitrification in tallgrass prairie and cultivated soils0 aMicrobial ecology and denitrification in tallgrass prairie and c  aManhattan, KSbKansas State University  a1 -3100 vPhD Dissertation10atallgrass prairie1 aSotomayor, D.  uhttp://lter.konza.ksu.edu/content/microbial-ecology-and-denitrification-tallgrass-prairie-and-cultivated-soils