The response of soil organic matter decomposition and greenhouse gases emission to global warming and nitrogen addition

Abstract:

The increase of atmospheric greenhouse gases has caused noticeable climate change. The increased temperature by climate change could dramatically change in the decomposition rate and greater losses of carbon from soil organic matter. Decomposition of organic carbon regulates both the amount of organic material which is stored in soils, as well as the amount of mineralized carbon that can be released into the atmosphere as greenhouse gases (CO₂ and CH₄). In addition, the largest increase in the N-deposition was expected in Asia due to the dramatic increase in anthropogenic activities. Previous results from N-deposition experiments led to apparently contradictory hypotheses regarding the decomposition of organic carbon in soil. N-deposition has been found to decrease the decomposition of chemically complex carbon compounds, while increasing decomposition rates of labile carbon pools. Combined changes in temperature increase and N-deposition have considerable potential to affect soil carbon sequestration/loss and soil nutrient cycling. This study investigated how the combined changes of temperature increase and N-deposition influence mineralization processes and C dynamics of two soil systems (wetlands and forest). For this objective, we conducted a growth chamber experiment to examine the effects of combined changes in temperature increase and N-deposition on the decomposition of organic carbon and emission of greenhouse gases from two different soil systems. The samples were collected in wetland and forest around Gyeongan stream of South Korea. Incubator experiment was conducted under the enhanced air temperature (controlled 20 ℃, 25 ℃ and 30 ℃) and nitrogen addition (low and high condition by using ammonium nitrate). GHGs (CO₂, N₂O, and CH4) were measured gas chromatograph. Results of experiment show that CO₂ flux decrease with time at forest soil and increase at wetland. Moreover high temperature (25 ℃, 30 ℃) and high concentration of nitrogen cause emission more than 20 ℃. As time goes on, N₂O flux decrease at low concentration of nitrogen, increase at high concentration in both of the soils. But cases of N2O flux have a lot of fluctuation. While CH₄ flux was not detected at all of temperatures and soils.