Effects Of Drained Mires For Forestry On CO₂, CH₄ And N₂O Emissions In Xiaoxing'an Mountain Northeast China

The seasonal and spatial variation,influence factors and sources/ sinks of emission of CO₂,CH₄ and N₂O from marshes and 10-20 year artificial larch forests swamp soils were studied during the growing season by static opaque chamber-GC technique in Xiaoxing'an Mountains of China,the effects of afforestation by marsh drained on greenhouse emission were assessed quantitatively.The results showed that:â‘ Nature mires drained for forestry greatly changed the greenhouse fluxes from soil both in spatial and temporal.The emission fluxes of CO_,CH₄ and N₂O from marsh soils (distribution:76.07～809.25,-0.034～7.230,-0.019～0.029 mg.m^-2.h^-1;average values: 487.89,1.876,0.004mg.m^-2.h^-1)took on summer>spring>autumn,summer>autumn >spring,absorbing N₂O in spring and emitting it in summer and autumn during growing season respectively;The emission fluxes of CO₂ from 10-20 year ridge and ditch soils (121.34～1688.51,4.10～1441.10,42.62～384.27,59.15～588.83;885.21,684.07, 166.47,245.33mg.m^-2.h^-1) increased by 40.2%～81.4%on ridge,and decreased by 49.7%～65.9%in ditch comparing to marsh soils,but their seasonal variation all were similar to marsh soils;The emission fluxes of CH₄(-0.105～0.242,-0.141～0.022,-0.152～0.848, -0.061～0.366;-0.004,-0.073,0.118,0.054 mg.m^-2.h^-1) only were 0.2%～6.3%of marsh soil,and taking on absorbing CH₄ in spring and summer and emitting it in autumn, absorbing CH₄ in all growing season,absorbing CH₄ in spring and emitting it in summer and autumn,emitting CH₄ in all growing season respectively;The emission fluxes of N₂O (0.005～0.123,-0.002～0.071,-0.006～0.015,-0.001～0.158;0.029,0.027,0.004, 0.033 mg.m^-2.h^-1) were 6.8～8.3 times of marsh soil,and taking on summer>spring> autumn,spring>summer>autumn,spring>autumn>summer,summer>spring>autumn respectively.â‘¡drainage also changed the main affecting factors of CO₂,CH₄and N₂O emission fluxes from marshes soils.The soil temperature(<20 cm),the soil temperature (30cm～40cm ),and water table were the main affecting factors of CO₂,CH₄,andN₂O emission fluxes from marshes soils in growing season separately;but the soil temperature(≤40cm) and water table,the soil temperature or it with water table were the main affecting factors of CO₂,N₂O emission fluxes from artificial larch forest swamp soils in growing season separately,however,its CH₄ emission fluxes did not correlate with soil temperature or water table.â‘¢Meanwhile drainage also changed the character of mires whatever it act as a source or a sink of greenhouse gases in the atmosphere.In the growing season,the marsh soil and 10- 20 year artificial larch forest swamp soils(17.56±3.79,23.24±4.45,19.36±2.76 t.hm^-2yr^-1) all were the sources of CO₂,but the later was higher 10.3%～32.4%than the former;The three kinds of soils were different in the sources or sinks of CH4(67.54±31.72,1.33±0.24,-1.11±0.15 kg.hm^-2.yr^-1),the marsh soil was the strong source of CH₄,10 year artificial larch forest swamp soil was its weak source,and 20 year artificial larch forest swamp soil was its weak sink;The three kinds of soils all were the sources of N₂O(0.133±0.093,0.753±0.03,1.047±0.043 kg.hm^-2.yr^-1),but the marsh soil was the weak source of N₂O, the artificial larch forest swamp soil was its strong source.