Fluxes and production pathways of nitrous oxide in different types of tropical forest soils in Thailand

Abstract

Nitrous oxide (N 2 O) emissions from the soil surface of five different forest types in Thailand were measured using the closed chamber method. Soil samples were also taken to study the N 2 O production pathways. The monthly average emissions (AESD, n ¼ 12) of N 2 O from dry evergreen forest (DEF), hill evergreen forest (HEF), moist evergreen forest (MEF), mixed deciduous forest (MDF) and acacia reforestation (ARF) were 13.0 AE 8.2, 5.7 AE 7.1, 1.2 AE 12.1, 7.3 AE 8.5 and 16.7 AE 9.2 mg N m À2 h À1, respectively. Large seasonal variations in fluxes were observed. Emission was relatively higher during the wet season than during the dry season, indicating that soil moisture and denitrification were probably the main controlling factors. Net N 2 O uptake was also observed occasionally. Laboratory studies were conducted to further investigate the influence of moisture and the N 2 O production pathways. Production rates at 30% water holding capacity (WHC) were 3.9 AE 0.2, 0.5 AE 0.06 and 0.87 AE 0.01 ng N 2 O-nitrogen (N) g-dw À1 day À1 in DEF, HEF and MEF respectively. At 60% WHC, N 2 O production rates in DEF, HEF and MEF soils increased by factors of 68, 9 and 502, respectively. Denitrification was found to be the main N 2 O production pathway in these soils except in MEF.

Management zone‐based estimation of positive and negative nitrous oxide flux in organic corn fields

“…Rain event-based sampling would need to be repeated over time to capture seasonality dynamics as the occurrence and magnitude of N 2 O pulses are expected to change with the availability of C and N sources that vary in time due to fertilizer N inputs and crop growth. Soil fluxes might actually shift from positive to negative sources for N 2 O late in the season if soil N 2 O consumption (i.e., conversion to N 2 ) increases due to consumption favored by high labile C abundances when nitrate availability is low (Davidsson & Leonardson, 1997;van Groenigen et al, 2015;Vanitchung et al, 2011). Both the consumption of soil-produced N 2 O before it reaches the atmosphere, and the conversion of atmospheric N 2 O, which diffuses into soils that have lower N 2 O concentrations (Clough et al, 2005;Wu et al, 2013), can result in reduced net N 2 O fluxes or even negative fluxes.…”

Seasonal Variation in Soil Greenhouse Gas Emissions at Three Age-Stages of Dawn Redwood (Metasequoia glyptostroboides) Stands in an Alluvial Island, Eastern China

“…According to the reported study, soil N 2 O production and consumption were mainly influenced by the amount of mineral N in soils, and low N availability was linked with N 2 O emissions [2]. Highly dynamic emissions of N 2 O were found among different forest soil types [68]. The primary controlling factors of N 2 O production were found to be soil pH and C/N ratio, and these soil properties could explain most of the variability of N 2 O emissions [9,69].…”