Spatial Variability And The Factors Controlling Nitrous Oxide And Carbon Dioxide Production From Temperate Forest Soils In Changbai Mountain, China

Human activities has result in the increase of atmospheric concentration of greenhouse gases,which is concerned as a main cause of the global climate change.Forest is one of the most widely distributed vegetation types at an areal proportion of one third of the globe. Hower,forest soils are important sources of greenhouse gas production of the earth surface. It is important to study the soil spatial variability of N₂O,CO₂ production and the influencing factors for evaluating the role of forest ecosystems on the impact of the greenhouse effect.In this thesis,production of N₂O,CO₂ from forest soil from the Changbai Mountain was studied with tree species(Korean pine forest,cloud fir,linden tree,Mongolian oak, etc.),seasons(July,September and Novermber),fertilizer treatments(NH₄)₂SO₄,NH₄Cl,KNO₃),soil layers(humus layer,minerial layer,whole layer).In addition,soil nitrification and N₂O production in the forest soil was traced by AIM inhibitor under oxygen presence.Acetylene effectively blocked the soil autotrophic nitrification when it is added at 10Pa,50Pa,100Pa,respectively;there was no significant difference among different concentrations of acetylene;soil heterotrophic nitrification at vary distances from the trunk accounts for the range from 20%to 48%of total N₂O production.For the conierferous soil the further the distance from the trunk,the higher the heterotrophic nitrification proportion, while no such trend for broadleaf soil.The further the distance from the trunk,the lower the N₂O,CO₂ production for the same tree species;at the same distance from the trunk,soil of broadleaved forests has higher N₂O,CO₂ production than coniferous forests'.Acetylene did not influence the soil nitrification,soil mineralization and soil respiration when it is added as 10Pa,50Pa,100Pa,respectively;but we found 100Pa acetylene treatment lead to the decrease of soil respiration appreciably;10Pa acetylene treatment has the effect of incompletely inhibition,50Pa acetylene has the best inhibiting effect on N₂O production in autotrophic nitrification.N₂O production is significantly reduced at different layers and different fertilization treatment soils when it is added with 50Pa acetylene;soil heterotrophic nitrification accounts for 14%-55%of nitrification;the ratio of the mineral layer was significantly higher than that of the organic layer.The inhibition of acetylene on soil N₂O release weakened at the lower layer with less mineral nutrients.The proportion of soil heterotrophic nitrification in November(17%-55%) when the temperature is lower is higher than that in September(17%-36%).Ammonium-nitrogen fertilizer addition can erthence the heterotrophic soil nitrification.Factor analysis showed that the main factors influencing the N₂O,CO₂ production in the soils were soil total carbon and nitrogen,soil extracted organic nitrogen and soil microbial biomass.Soil microbial biomass nitrogen can explain 25%of changes heterotrophic nitrification.Regression analysis showed that the N₂O and CO₂ production of forest soil under the influence of acetylene fits well with soil net nitrification in linear regression.N₂O,CO₂ production in the organic layer soils are obviously higher than the mineral layer.N₂O,CO₂ production in forest soil are mainly from organic soil layers.N feitilizer have no significant influence on CO₂ production and KNO₃ can promote soil N₂O release, while NH₄Cl soil showed a inhibitory effect.After applying(NH₄)₂SO₄ and NH₄Cl fertilizer,soil q-CO₂ and q-N₂O dropped,which may be explained partly by the addition of SO₄^2- or Cl^-.