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Turbulence data measured with fast response instruments at two sites with distinct conditions were available. The ability of a mesoscale model in the simulation of turbulent fluxes and boundary layer height was assessed in case studies covering periods in the Southern Hemisphere summer and winter. The energy apportionment at both locations was properly reproduced. In summer, at the site with native forest, the sensible heat flux was well estimated and the latent heat flux was underestimated. At the other site (commercial plantation) the sensible heat flux was properly represented and the latent heat flux was slightly overestimated. In winter, the best results were obtained at the implanted forest site. The performance of the model at the native forest site was very satisfactory when homogeneous initial soil moisture was considered. A model intercomparison between the boundary layer height obtained with an analytical model and the mesoscale model showed the influence of data and methodologies used in the two approaches. [ABSTRACT FROM AUTHOR]

Nitrous oxide (N 2 O) is the main greenhouse gas emitted from farming systems and is associated with nitrogen (N) fertilizer application as well as decomposition of organic matter present in the environment. The objective of this study was to determine the effect of post-harvest straw burning and synthetic N fertilization on the dynamics of N 2 O emissions in the sugarcane-soil system in Tucuman, Argentina, compared with a native forest. Close-vented chambers were used to capture N 2 O during three consecutive growing seasons. The highest N 2 O emissions from the sugarcane-soil system coincided with the period of high soil and air temperatures, rainfall and soil N content. The effect of synthetic N fertilization on annual cumulative N 2 O emission was 7.4–61.5% higher in straw burned than in unburned treatments, especially during a wet growing season. There was a significant effect of treatments on N 2 O emission factors among growing seasons: 0.58–1.67% and 0.94–3.34% in the unburnt and burnt treatments, respectively. The emission factors for sugarcane are highly dependent on rainfall, temperature and crop management practices; regarding the latter, avoiding straw burning and reducing N soil availability, assessing alternative N fertilizers or new application modes such as split rates, seem to be the key for mitigating N 2 O emissions from the sugarcane-soil system in Tucumán, Argentina. [ABSTRACT FROM AUTHOR]

Eucalyptus species are strong source of isoprenoid emission. The objective of the present study was to estimate isoprenoid emissions from Eucalyptus grandis forest crops in the Entre Rios province in the Mesopotamia region of Argentina. The emission rates of isoprene and monoterpenes were measured on individual leaves under; controlled environmental conditions. At 30°C and with a PPFD of 1000 μM m-2 s-1 the emission rate of isoprene emission was 12.5 ± 1.9 nM m-2 s-1 and monoterpenes 15.1 ± 3.1 nM m-2 s-1. Emission was significantly affected by leaf position and decreased significantly from East to West. The most abundant compound emitted was limonene, accounting for between 50 and 68% of the total monoterpene emission. The time course of the isoprene emission course showed its strong dependence on light. On sunny days 42% of the isoprene emission comes from top of the canopy and only 2% from bottom of the canopy. But on overcast days, the relative contribution of diffuse radiation may be larger and can exceed the contribution of direct radiation. A model procedure in a Geographic Information System was implemented to estimate isoprene emissions at a regional scale. A forest inventory, data from a meteorological station and leaf area indices derived from satellite data served as inputs for the model. For the Entre Rios province (78781 km²), the isoprene emission totals up to 39.5 t d-1 on a clear summer day. The methodology applied to estimate isoprenoid emissions on a regional scale contributes to the understanding of carbon exchange between biosphere and atmosphere. [ABSTRACT FROM AUTHOR]