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Effects Of Harvest On Greenhouse Gas Emission From Forested Wetlands During Non-Growing Season In Northeast China

Posted on:2020-03-18Degree:MasterType:Thesis
Country:ChinaCandidate:L HaoFull Text:PDF
GTID:2370330578976100Subject:Ecology
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Emission of greenhouse gas during non-growing season from soil may play an important role on ecosystem carbon and nitrogen cycle in mid and high latitude regions,yet,it is not clear that how harvest disturbance affect them during this season.The fluxes of CO2,CH4 and N2O emissions and related environmental factors(temperature,moisture,soil organic carbon and total nitrogen etc.)were observed simultaneously from four kinds of forested wetland(Alnus sibirica-C.schmidtii swamp-M,B.platyphylla-C.schmidtii swamp-B,Larix gmelinii-C.schmidtii swamp-LT,Larix gmelinii-Moss swamp-LX)under different harvest disturbances(control-no cutting,selective cutting-45%(volume),clear cutting;harvesting operation has been done for 10 years)by using static chamber technique and gas chromatography during non-growing season in temperate Xiaoxing'an Mountains,northeast China,so as to reveal effects of harvest disturbances on greenhouse gases emission from temperate forested wetlands during non-growing season and their main controlling factors.The results showed that:(1)The harvest disturbances significantly increased soil temperature of 0?40 cm by 0.44?1.47?;selective cutting significantly decreased the soil water content by 14.9%?38.0%(except B),the clear cutting significantly decreased of LT,LX by 28.9%?46.4%;harvesting significantly decreased the 0-40 cm total nitrogen content of M and LX by 4.8%-9.4%and C/N of B and LT by 0.87-4.87,only clear cutting decreased the 0?40 cm soil organic carbon and total nitrogen content of LT by 50.0%and 25.7%.(2)The average fluxes of CO2 during non-growing season from four kinds of forested wetlands distributed in 53.08?81.31 mg·m-2·h-1,clear cutting significantly increased the fluxes of CO2by 6.8%?30.3%,the effect of selective cutting on its soil CO2 fluxes was related to the type of wetland(B and LX significantly increased by 12.0%-25.3%,M significantly decreased by 14.5%and LT did not change significantly).(3)The average fluxes of CH4 during non-growing season from four kinds of forested wetlands distributed in 0.09-3.07 mg m-2·h-1,the effect of clear cutting on its soil CH4 fluxes was related to the type of wetland(M and LX significantly increased by 42.1%-300.0%,LT significantly decreased by 72.2%and B did not change significantly),selective cutting significantly decreased soil fluxes of CH4 by 19.7%?38.9%.(4)The average fluxes of N2O during non-growing season from four kinds of forested wetland distributed in 4.07?8.83 ug·m-2·h-1,clear cutting significantly increased the fluxes of N2Oby 23.5%-55.2%,yet selective cutting significantly decreased the fluxes of N2O from LT by 31.8%.(5)The CO2 fluxes from natural forested wetlands were strongly influenced by soil temperature,soil organic carbon and C/N;CH4 fluxes were influenced by soil temperature,soil organic carbon;N2O fluxes were affected by air temperature and soil pH value.Harvesting increased the correlation between soil CO2 fluxes and air temperature,soil water content and snow depth,the correlation between soil CH4 fluxes and air temperature,soil water content and C/N,as well as the correlation between soil N2O fluxes and soil total nitrogen and C/N.(6)The annual cumulative contribution of CO2,CH4 and N2O emission from natural forested wetlands during non-growing season were 33.2%?46.5%,6.3%-9.1%and 61.5%?68.3%,respectively.The clear cutting increased the annual cumulative contribution of CO2 by 4.2%?7.3%(B and LX)and that of N2O by 4.2%?7.5%(except LX).The selective cutting increased the annual cumulative contribution of CO2,CH4 and N2O by 1.6%?3.2%,11.3%-13.2%,and 1.7%-5.2%(LT and LX),but decreased that from B by 2.0?4.6%.Therefore,the annual cumulative contribution of N2O and CO2 during non-growing season were relatively high from temperate natural forested wetlands,and the clear cutting further increased their contribution,while the selective cutting just increased that of CH4 during non-growing season.
Keywords/Search Tags:Xiaoxing'an Mountains, forested wetlands, greenhouse gas, non-growing season, harvesting
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