Soil Solution Properties And The Relevance With Soil Surface CO₂ And N₂O Flux Under Exogenous Carbon And Nitrogen Input In A Temperate Old-Growth Forest

In the past several decades, atmospheric nitrogen deposition due to fossil fuel combusition and agricultural intensification has more than doubled in many aeras throughout of the world, resulting in the growing deposition of nitrogen from atmosphere to the forest ecosystem. Incremental nitrogen deposition onto the forest soil can have numerous and variable impacts on the biogeochemical cycling of soil carbon and nitrogen thus affecting the health of forest ecosystems "carbon sinks" feature. Soil solution chemisty is often a sensitive indicator of biogeochemical processes in forest ecosystem, responsing quickly to various disturbances or stresses. Examining soil solution chemisty is of great importance to better understanding the response of forest ecosystems to atmospheric nitrogen deposition on forest soil carbon and nitrogen cycling during the early level of interference.To study the early effects of in situ carbon and nitrogen amendment on temperate forest ecosystem, soil solution chemistry, flux of carbon dioxide and nitrogen oxide in a temperate broad-leaved Korean pine forest in Changbai Mountain were measured for 2 years during the growing season (May to September in 2006-2007). The main objects of this paper are to evaluate the effects of carbon and nitrogen amendment on soil solution properties and the response of these properties on fluxs of carbon dioxide and nitrogen oxide, and analysising the main factors attributed to the seasonal change of dissolved gas concentrations in the soil solution.After two consecutive years of field observations, our results showed that: effects of carbon and nitrogen amendment on soil solution chemistry were different. Addition of glucose had increased the concentration of DON and NH₄⁺-N in surface and deep soil solution; Nitrogen fertilizer addition inhibited the concentration of DOC but improved the formation of DON and NO₃^--N in soil solution, the concentrations of NH₄⁺-N in soil solution was less affected. The concentration of dissolved CO₂ was decrease in surface soil solution but increased at 60cm depth due to nitrogen fertilizer additioned. The concentration of dissolved N₂O in soil solution was improved at 15 and 60 cm depths.Both factor analysis and regressuin analysis showed that there was a significant liner relationship between dissolved CO₂ concentration and DOC in surface soil solution (15cm), and a significant liner relationship between dissolved N₂O concentration and DON in bottom soil solution (60cm). These relationships were the same in the carbon and nitrogen amendments.There were good relationships between surface soil gas emissions and soil solution chemistry, but the attribute of carbon and nitrogen fertilizer addition to these relationships were large different. At carbon addition treatments, a significant positive correlation relation between fluxes of CO₂ emissions and DOC and NH₄⁺-N concentration in soil solution was found at 15 cm depth, and the cumulative monthly emissions of CO₂ was significant positive correlated with NH₄⁺-N flux in soil solution at 60cm depth. At nitrogen fertilizer addition treatments, however, there was a significant negative correlation relation between fluxes of CO₂ emissions and dissolved N₂O concentration in soil solution at 60cm depth, the cumulative monthly emissions of CO₂ was significant positive correlated with DON flux in soil solution at 15cm depth. There was a significant positive correlation relation between flux of N₂O emissions and DON concentration in soil solution at 15cm depth. And the cumulative monthly emissions of N₂O were significant positive correlated with DON flux at 15 cm and 60cm depths, respectively.