Can short-term pasture management increase C balance in the Atlantic Rainforest?

Few studies have shown the importance of different pasture management practices on C storage and the reduction of CO2-C emissions in tropical conditions. The objective of the present study was to determine short-term changes in C pools and C balance from different pasture management practices established in the Atlantic Rainforest. A field study was carried out in Alegre, ES, Brazil from September 2013 to August 2014 to investigate the first-year effect of pasture management practices on a Udult clayey soil. The different pasture management practices studied included the following: control (CON), chiseled (CHI), fertilized (FER), burned (BUR), integrated with crop-livestock (iCL) systems, and plowed and harrowed (PH). Monthly disturbed and undisturbed soil samples were taken at two different layers (0.00-0.05 and 0.05-0.20 m) for chemical, physical, and organic matter characterization. C inputs monitored in aboveground pools included plant aerial parts and litter, and belowground pools included roots and soil C stocks. C outputs monitored were CO2-C emissions, erosion water, and sediment. C balance was considered the difference between inputs and outputs in each treatment during four seasons. The spring and summer seasons had a strong influence on C inputs and outputs where there is significant difference between spring and summer, while the autumn and winter seasons had less influence. All pasture management practices exhibited positive C balance after 1 year. High values of C balance were verified in pastures fertilized (FER) (53.04 Mg ha-1 year-1. Intermediate C balance was found in the burned (BUR) (40.84 Mg ha-1 year-1), traditional control (CON) (40.31 Mg ha-1 year-1), and in the plowing and harrowing (PH) (40.02 Mg ha-1 year-1) management practices. The practices of chiseled (40.00 Mg ha-1 year-1) and integrated crop-livestock systems (iCL) (59.06 Mg ha-1 year-1) resulted in low C balance.

Fluxes of CO2, CH4, and N2O in tundra-covered and Nothofagus forest soils in the Argentinian Patagonia.

While most soils in periglacial environments present high fluxes of CO2 (FCO2), CH4 (FCH4), and N2O (FN2O), few of them have a tendency to drain greenhouse gases from the atmosphere. This study aimed to assess greenhouse gas fluxes at different sub-Antarctic sites and time periods (at the beginning of thaw and height of summer). To investigate the time of year effect on greenhouse gas emissions, FCO2, FCH4, and FN2O were measured at two sites tundra-covered (Ti and Th) and Nothofagus forest soil (Nf) on Monte Martial, at the southernmost tip of South America, Tierra del Fuego, Argentina. FCO2 ranged from 96.33 to 225.72 µg CO2 m-2 s-1 across all sites and periods, showing a positive correlation with soil temperature (Ts) (4.1 and 8.2 °C, respectively) (r2 > 0.7; p < 0.05). The highest values of FCO2 were found at Ti and Th (728.2 and 662.64 µg CO2 m-2 s-1, respectively), which were related to higher temperatures (8.2 and 8.6 °C, respectively) when compared to those of Nf. For FCH4, the capture (drain) occurred during both periods at Nf (-26 and -79 µg C-CH4 m-2 h-1) as well as Ti and Th (-21 and 12 µg C-CH4 m-2 h-1, respectively). FN2O also presented low values during both periods and showed a tendency to drain N2O from the atmosphere, especially at Nf (-2 µg N-N2O m-2 h-1). In addition, FN2O was slightly positive for Ti and Th (0.3 and 0.55 µg N-N2O m-2 h-1, respectively). Soil moisture did not show a correlation (p > 0.05) with the measured greenhouse gas fluxes. A scenario of increased temperatures might result in changes in the balance between the emissions and drains of these gases from soils, leading to higher emission values of CH4 and N2O, especially for tundra covered soils (Ti and Th), where the highest average fluxes and thermohydric variations were observed over the year.