Effects Of Soil Moisture On Greenhouse Gas Fluxes Of Forest Soils At Different Elevation In Qinling Mountains

Carbon dioxide?CO₂?,methane?CH₄?and nitrous oxide?N₂O?are the three main greenhouse gase that have significant impacts on global warming.Carbon dioxide accounts for the largest proportion of greenhouse gas effects.However the global warming potential of CH4 and N2O are 28 and 300 times higher than that of carbon dioxide,respectively.Temperate forest soils are considered as major sources of CO₂ and N₂O,and also are important sinks for CH4,Soil moisture is a key factor in regulating greenhouse gas emissions from forest soils.The study was carried out to investigate the effect of soil moisture on greenhouse gas flux in forest soil by applying incubation method and acetylene inhibition denitrification methods.The main findings are as follows:?1?Carbon dioxideemitted from all the five forest soils at different soil moisture contents.The maximum amount of CO2 emitted from Picea wilsonii soil.CO2 emissions increased gradually with the increasing of the incubation time under the same moisture conditions.CO2 emissions increased with the increasing of soil moisture,and CO2 emissions decreased when the soil moisture content increased to a certain value.For all five forest soils the maximum amount of CO2 emission occurred when soil moisture content was40%.Their maximum CO₂ emissions were as follows:Betula albosinensis soil was 420.86 ug·g^-1,Picea wilsonii soil was 871.75ug·g^-1,Pinus armandii soil was 553.61 ug·g^-1,Pinus tabuli formis soil was 369.25 ug·g^-1,Quercus aliena var.acuteserrata soil was 262.69ug·g^-1.Soil moisture had a significant impact on CO2 emissionsl from soil,while soil organic carbon content was also an important factor affecting CO₂ emissions?P<0.05?.?2?CH₄ emission rates increased during the whole incubation,but were not obvious.CH4 emissions from the five forest soils were small and the emission values maintained between 20 ng·g^-1 and 50 ng·g^-1.At the early stage of incubation,there was an emission of methane.A high rate of methane emission occured after incubated for6 hours.CH4 emission rate at the initial stage of incubation e was 1-2 ng·g^-1·h^-1.The rate of CH₄ emission decreased rapidly after incubation for 6 hours until to 12 hours.?3?Soil with high water conten emitted had large N₂O emissions than that soil with low moisture content.During the early stage of incubation,N2O emission rates increased and then decreased,and finally N2O consumption occured.At the later stage ofincubation,N2O consumption occurred in high-moisture?55%?soilof Betula albosinensis,Picea wilsonii and Pinus armandii.The larges N2O emission t was found in Picea wilsonii soil.Soil moisture is a key regulator for N2O flux.N2O emission rates of acid forest soil were significantly correlated with soil denitrification potential?P<0.01?.