Permalink : http://hdl.handle.net/2115/53369

KEYWORDS : Greenhouse gases;elevated CO2 concentration;nitrogen deposition;forest fire;forest ecosystems

Global environmental change and its causes and effects in relation to natural and anthropogenic activity have been the recent focus of concern. An important component of this issue is the role management of soils plays in contributing as a source or sink of greenhouse gases (GHGs), e.g. carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), etc. In forest ecosystems, especially, the production and consumption of these three GHGs are biologically mediated, but also strongly controlled by natural or man-made disturbances and other climate changes influenced environmental variables, e.g. elevated atmospheric CO2 concentrations (Chapter 2), nitrogen (N) deposition (Chapter 3) and fire (Chapter 4). In this study, such environmental changes in forest ecosystems had the potential impacts to change the soil-atmosphere exchange of GHGs. Changes in soil GHG fluxes, furthermore, is that it varied with the environmental changes. Firstly, reduced CH4 consumption with CO2 enrichment was observed with increased levels of soil moisture as a result of increased leaf stomatal closure and evaporative water loss from the forest floor. Secondly, simulated N addition, which was conducted to evaluate the effects of elevated atmospheric N deposition on soil GHG fluxes, inhibited soil CH4 uptake and stimulated soil N2O emission in response to increased inorganic-N concentration. Finally, our low-intensity surface fire reduced soil CO2 flux by the combustion of understory vegetation and litter layer. Especially, soil N2O flux was represented different seasonal pattern, depending on the existence of charcoal. We considered that although increased inorganic-N levels in the burned area as a result of the fire influence preferentially the soil N2O emission, it might be suppressed through net immobilization of NH4 + or interfere with nitrification by fire-produced charcoal.