297 research outputs found
Cycloheximide inhibition of peptone-induced nitrate production across a soil moisture gradient
No full textThe antibiotic block technique is used to distinguish between fungal and bacterial induced activity. In the present study, the antibiotic inhibition of peptone-induced NO3- production was tested across a soil moisture gradient. Soil was incubated at 60, 80, 90 and 100% water-filled pore space (WFPS) and as a water slurry. Peptone was used as the substrate and cycloheximide and C2H2 (0.1% v/v) were added to inhibit fungal and autotrophic nitrification, respectively, the latter being considered mainly of bacterial origin. At all moisture contents is more than 80% of NO 3- production was due to autotrophic nitrification. At increasing water contents the percentage of NO3- production inhibited by C2H2 increased, whereas the percentage inhibited by cycloheximide decreased from 26.4% at 60% WFPS to 4.6% in the water slurry, suggesting a different sensitivity of bacterial and fungal nitrification to soil moisture. Although no direct evidence of an alteration in the fungal population was produced in this experiment, data proved that water content influences the result of the test and hence care should be taken when comparing data using different test conditions. © Springer-Verlag 2005
Responses of nitrous oxide, dinitrogen and carbon dioxide production and oxygen consumption to temperature in forest and agricultural light-textured soils determined by model experiment
No full textThe experiment, carried out on a forest and arable light-textured soil, was designed to study the temperature response of autotrophic and heterotrophic N2O production and investigate how the N2O flux relates to soil respiration and O2 consumption. Although N2O production seemed to be stimulated by a temperature increase in both soils, the relationship between production rate and temperature was different in the two soils. This seemed to depend on the different contribution of nitrification and denitrification to the overall N2O flux. In the forest soil, almost all N2O was derived from nitrification, and its production rate rose linearly from 2 °C to 40 °C. A stronger effect of temperature on N2O production was observed in the arable soil, apparently as a result of an incremental contribution of denitrification to the overall N2O flux with rising temperature. The soil respiration rate increased exponentially with temperature and was significantly correlated with N2O production. O2 consumption stimulated denitrification in both soils. In the arable soil, N2O and N2 production increased exponentially with decreasing O2 concentration, though N2O was the main gas produced at any temperature. In the forest soil, only the N2 flux was related exponentially to O2 consumption and it outweighed the rate of N2O production only at >34°C. Thus, it appears that in the forest soil, where nitrification was the main source of N2O, temperature affected the N2O flux less dramatically than in the arable soil, where a temperature increase strongly stimulated N2O production by enhancing favourable conditions for denitrification
Factors influencing nitrification and denitrification variability in a natural and fire-disturbed Mediterranean shrubland
No full textThe main factors influencing the variability of nitrification and denitrification enzyme activity (DEA), in soil of a Mediterranean shrubland, were investigated in an undisturbed area and in plots treated with experimental fires of two different intensities. Soil was sampled 4 times during 1 year after burning, in periods characterised by different environmental conditions. In the control, net nitrification ranged from 0.95 to 1.32 μg NO3--N g-1 day-1 and did not show significant average differences among sampling events, probably because water content and NH4+-N availability were both limiting the process at any time. Overall, nitrification seemed associated with microsites where NH4+-N production was higher. This pattern was not evident in the burned plots, where, moreover, a partial reduction of activity immediately after burning was observed. DEA showed higher variability among sampling events, as compared with nitrification, with a peak in winter. It also presented a close spatial relationship with microsites of nitrification activity. In the burned sites, water content, organic C and NO3--N content concurred to explain DEA variability together with NH4+-N availability and nitrification activity. Plots treated with intense fire showed the lowest values of DEA, especially in the period more favourable to this activity
Methane production and consumption in an active volcanic environment of Southern Italy
No full textMethane fluxes were measured, using closed chambers, in the Crater of Solfatara volcano, Campi Flegrei (Southern Italy), along eight transects covering areas of the crater presenting different landscape physiognomies. These included open bare areas, presenting high geothermal fluxes, and areas covered by vegetation, which developed along a gradient from the central open area outwards, in the form of maquis, grassland and woodland. Methane fluxes decreased logarithmically (from 150 to -4.5 mg CH 4 m -2 day -1) going from the central part of the crater (fangaia) to the forested edges, similarly to the CO 2 fluxes (from 1500 g CO 2 m -2 day -1in the centre of the crater to almost zero flux in the woodlands). In areas characterized by high emissions, soil presented elevated temperature (up to 70°C at 0-10 cm depth) and extremely low pH (down to 1.8). Conversely, in woodland areas pH was higher (between 3.7 and 5.1) and soil temperature close to air values. Soil (0-10 cm) was sampled, in two different occasions, along the eight transects, and was tested for methane oxidation capacity in laboratory. Areas covered by vegetation mostly consumed CH 4 in the following order woodland > macchia > grassland. Methanotrophic activity was also measured in soil from the open bare area. Oxidation rates were comparable to those measured in the plant covered areas and were significantly correlated with field CH 4 emissions. The biological mechanism of uptake was demonstrated by the absence of activity in autoclaved replicates. Thus results suggest the existence of a population of micro-organisms adapted to this extreme environment, which are able to oxidize CH 4 and whose activity could be stimulated and supported by elevated concentrations of CH 4. © 2004 Elsevier Ltd. All rights reserved
In primum librum Regum expositionum libri VI
No full textThe paper traces the misunderstandings of the commentary on the first book of Regum attributed to Gregory the Great. The history of the editions is analyzed till the discovery of the only manuscript known of the work, Cava dei Tirreni, Biblioteca dell'Abbazia 9. The criteria of the last edition by Patrick Verbraken are discussed as he uncritically favored the manuscript on the constitutio textus. The problem of the authorship of the work is investigated: although recent studies date the commentary to the twelfth century and ascribe it to Peter of Venosa on the basis of the Chronicon Venusinum, it is possible that the author used texts authentically gregorian
Soil-atmosphere methane exchange in undisturbed and burned mediterranean shrubland of southern italy.
No full textSoils represent the primary biotic sink for atmospheric
methane (CH4). Uncertainty is associated,
however, with global soil CH4 consumption because
of the few data available from many areas
and, in particular, from Mediterranean-type ecosystems.
In this study, soil-atmosphere CH4 exchange
was measured for one year in a coastal
Italian shrubland (maquis), from both undisturbed
areas and areas treated with experimental fire. Although
fire represents one of the most frequent
disturbance factors in seasonally dry environments,
very few studies in these ecosystems have focused
on its effect on soil CH4 fluxes. Significant differences
in soil ammonium content, water content,
and temperature were measured between burned
and unburned plots, however, no statistical differences
were observed for CH4 fluxes. CH4 fluxes
varied between )0.39 and )16.1 mg CH4 m)2
day)1 and temporal variations were mainly driven
by variations in soil water content and temperature.
The highest CH4 oxidation rates were measured
during the driest and warmest period. Low
gravimetric soil water content in the top 10 cm, as
well as high NH4
+ concentration, did not seem to
reduce methanotrophic activity, suggesting that
maximal CH4 oxidation activity might take place
deeper in the soil profile, at least during part of the
year
Soil N2O emissions in a Mediterranean shrubland disturbed by experimental fires
No full textFire is a widespread disturbance in Mediterranean ecosystems and its frequency is expected to increase in the future due to climatic change. In the present work post burning soil N2O fluxes and several related microbial processes were investigated in a Mediterranean shrubland, where experimental fire was induced. Nine plots were selected in the study site, of which, 3 were used as control, 3 were burned with fire of low intensity (LF) and 3 with fire of higher intensity (IF). N2O fluxes, soil humidity and temperature, were measured staring 2 days after burning for one year. Soil was sampled 4 days, and 3, 5 and 8 months after burning and potential net nitrification (PNN), denitrification enzyme activity (DEA), mineral N and organic C, were measured. Cumulative data indicate a doubling of N2O production in burned plots in one year. This was mainly due to the increase of frequency of hot spots of N2O production in burned plots. A slightly detrimental effect of fire on the analysed biological activities was detected only immediately after burning. After 3 months both PNN and DEA had mostly recovered and PNN further increased, over control levels, in the following months. Fire seemed to induce a change in the main source of N2O, which in control plots was represented by heterotrophic activity (50-75%), whereas, in burned plots was mostly of authotrophic origin, and this was particularly evident in LF plots. This most probably was supported by the significant increase of soil NH4+ content following biomass burning
The effect of different N substrates on biological N2O production from forest and agricultural light textured soils
No full textN2O emissions from two slightly alkaline sandy soils, from arable land and a woodland, were determined in a laboratory experiment in which the soils were incubated with different sources of nitrogen, with or without glucose, and with 0, 1 and 100 mL C2H2 L-1. Large differences in the rate of N2O production were observed between the two soils and between the different N treatments. The arable soil showed very low N2O emissions derived from reduced forms of N as compared with the N2O which was produced when the soil was provided with NO2/- or NO3/- and a C source, suggesting a very active denitrifier population. In contrast, the woodland soil showed a very low denitrification activity and a much higher N2O production derived from the oxidation of NH4/+ and reduction of NO2/- by some processes probably mediated by autotrophic or heterotrophic nitrifiers or dissimilatory NO2/- reducers. In both soils, the highest N2O emissions were induced by NO2/- addition. Those emissions were demonstrated to have a biological origin, as no significant N2O emissions were measured when the soil was autoclaved
A GIS based application of the IPCC protocol for the estimation of N2O emissions from agricultural ecosystems of the Italian region
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