Comparisons of N2O and CH4 fluxes as affected by land use systems and climate in small catchments in Korea

Funding: IRTG 1565 WP 3-04 "TERRECO -Complex Terrain and Ecological Heterogeneity - Evaluating ecosystem services in production versus water yield and water quality in mountainous landscapes"

From 10/2009 to 09/2012

Principal Investigator: Gerhard Gebauer, Hojeong Kang
Staff: Sina Berger

Goal within the TERRECO Assessments:

• Comparison of trace gas emissions from the Haean-myun and Eger Basins and in Joellanam-do Province, Korea
• Examination of the influences of land use, of agricultural practices, and of change in the seasonal course for temperature and precipitation
• Evaluation of contrasting regulation of hotspot emissions from high elevation summer agricultural fields in Korean mountain locations

Abstract 2011: Global change is a challenge for mankind, especially to mitigate the negative effects. One important aspect of global change is the increasing release of infrared absorbing trace gases into the atmosphere, since they contribute significantly to global warming.  Agricultural land covers a large part of the earths’ surface, and agricultural management is becoming more intensive in order to meet food demands of the continuously growing population on earth. In addition to intensified nitrogen fertilization of crops, plastic mulching is an often used weed control method in East Asia. Until now, little information exists about the effect of plastic mulching on N₂O emissions. This work aims to elucidate such soil processes behind the trace gas emissions in dry land fields. Besides the work in agricultural ecosystems we also focus on natural ecosystems. We investigate the effect of the South Korean early summer drought followed by heavy monsoon rains on N₂O fluxes of deciduous forests. All of the research was conducted in the Haean Basin, South Korea, which as a super study site has both natural forest and intensively used agricultural land use systems.       

Keywords: N₂O emission, N₂O consumption, plastic mulching, nitrogen fertilization, soil moisture 

project description in detail from proceedings of 2011 TERRECO Science Conference GAP

Abstract 2013: N₂O is one of the most important greenhouse gases. To achieve a better understanding of its flux dynamics and of underlying soil processes is currently of great interest. The overall-aim of this study, on the one hand, was to obtain an overview of the amounts of N₂O being emitted from typical land use systems of the study region in South Korea and, on the other hand, to identify those soil processes which are driving the N₂O fluxes. The land use systems investigated were deciduous forests (experiencing long early summer drought periods followed by heavy monsoon rains), dry crop fields (which were subjected to PE-mulching) and rice fields (undergoing different water management practices). Additional specific research questions were addressed for each land use system.

To tackle these questions, a variety of methods were applied, such as closed-chamber-measurements in conjunction with a photoacoustic infrared trace gas analyzer to measure the N₂O exchange between soil and atmosphere as well as several methods investigating soil processes in order to identify N₂O producing and consuming areas along the soil profiles. As an overall-result, it is suggested that the N₂O emissions of the entire study region are quite low and not much N₂O is being produced along the soil profiles. At three different forest sites, even negative N₂O fluxes (from the atmosphere into the soil) could be detected, which were driven by soil moisture and temperature as well as an apparent effect of soil texture. At the dry crop fields, we observed a positive effect of plastic mulching on N₂O emissions, meaning that the use of plastic mulch slightly reduced the amounts of N₂O degassing from the investigated fields. Regarding the rice paddies, it can be concluded that water management with the shortest flooding-period showed the least N₂O emissions, whereas moister paddies emitted more N₂O. The N₂O fluxes between rice paddies’ soils and atmosphere appeared to be driven by processes occurring in 40-50 cm soil depth. The result of having low emissions of N₂O and little amounts of N₂O being produced in the soils, is on the one hand pleasing, but on the other hand suggests that more research should be done to determine what happens to the NO₃^- (terminal electron acceptor for denitrification – the main process which produces N₂O) being washed out of the soils.

Keywords: nitrous oxide, soil profiles, drought period, heavy rainfall, PE-mulching, rice paddy water management

Poster January 2013

List of publications of this Project

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