Biogenic NO emissions from forest and pasture soils: Relating laboratory studies to field measurements

Abstract

[1] During September and October 1999, dynamic chamber measurements were carried out to determine nitric oxide (NO) fluxes from a primary forest soil and an old pasture in the Brazilian Amazon basin as part of the project ''European Studies of Trace Gases and Atmospheric Chemistry as a Contribution to the Large-Scale Biosphere-Atmosphere Experiment in Amazonia'' (LBA-EUSTACH). In addition, soil samples were collected from these two sites, and laboratory experiments were conducted to determine the NO production and consumption rate constants as functions of soil temperature and soil moisture. These laboratory results were converted into NO fluxes using a simple algorithm, which required additional information on the gas diffusion in soil, the soil bulk density, and the field conditions (soil temperature and soil moisture). Over the entire measurement period, the calculated and measured NO fluxes agreed well both for the forest (6.9 ± 2.9 and 5.0 ± 4.6 ng m À2 s À1 , respectively) and for the pasture (0.67 ± 0.09 and 0.65 ± 0.37 ng m À2 s À1 , respectively). Forest to pasture conversion decreased NO production and gas diffusion and resulted in smaller NO fluxes from pasture than forest soil.

Modelling the effect of soil moisture and organic matter degradation on biogenic NO emissions from soils in Sahel rangeland (Mali)

“…. The performance of the STEP process model in predicting herbage mass variation over time and herbage yield along a north-south bio-climatic gradient within the Sahel was tested along a 15-year period, and gave high correlation coefficients between model and measurements when the model was calibrated for each site (Tracol et al, 2006). Modifications brought to the first version of the model have been given in Jarlan et al (2008).…”

“…The quantity of nitrogen in the soil is derived from the quantity of carbon using the C / N ratio. A more detailed description of STEP can be found in Mougin et al (1995), Tracol et al (2006) and Jarlan et al (2008). Information such as the quantity of faecal and herbal masses are transferred as inputs to GENDEC, the litter decomposition model.…”

“…4 The change over time of the herbaceous standing mass is driven by mechanical and biological degradation, influenced, among other causes, by livestock grazing. Forage consumption and trampling by livestock have major effects on herbage offtake, decay and decomposition including seed dispersal (Tracol et al, 2006). The STEP model allows the drying from green to dry standing biomass, and the degradation of the dry biomass by livestock.…”

“…These results show that the coupled STEP-GENDEC-NO model gives fluxes in the order of known experimental or simulated data, while not exactly equivalent to measurements at the Agoufou site in 2004 and 2005. Several studies have shown different ranges of NO fluxes, but always with a strong link to soil moisture, especially in tropical regions where distinct dry and wet seasons exist, and where large pulses of NO emissions occur at the onset of the rainy season (Ludwig et al (2001), Otter et al (1999), Meixner et al (1997), Yang and Meixner (1997), Meixner and Yang (2006), Van Dijk et al (2002) as examples in tropical and semi-arid regions). As a comparison, Butterbach-Bahl et al (2004b) found average fluxes of 57 ng(N) m −2 s −1 in tropical forests soils at the transition between dry and wet season, where the quantity of decomposed litter is far greater than in dry savanna sites of the Sahel, and where the nutrient content of the soil is far larger, since semi-arid soils are generally nutrient poor.…”

Biogenic Nitric Oxide Emission of Mountain Soils Sampled from Different Vertical Landscape Zones in the Changbai Mountains, Northeastern China

“…Generally, forest soils may be regarded as minor sources of NO, except those forest soils in temperate regions, which receive considerable nitrogen inputs (NH 3 , HNO 3 , NH 4 + , NO 3 -) by wet and dry deposition. Recent studies found that the NO flux observed from temperate forests and rainforest soils is about 10 to 100-fold higher than that from dry arid and semiarid soils (12,15,16).…”