AtmosphericEnvironment39(2005)4479–4487 Seasonalanddiurnalvariationsinmethaneemissionsfrom WuliangsuLakeinaridregionsofChina XiaonanDuan,XiaokeWang à ,YujingMu,ZhiyunOuyang Key Laboratory of System Ecology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China Received9September2004;accepted21March2005 Abstract CH 4 emissions have been widely studied in various wetlands, such as boreal peatlands, rice paddies, and tropical swamps.However,littleinvestigationhasbeencarriedoutforCH 4 emissionsfromlakesorwetlandsinaridregions wherethesefreshwatersplayavitalroleinprovidingecosystemservicesforlocalpeople.Toquantifythespatialand temporalvariationsofCH 4 fluxandunderstanditskeycontrollingfactorsinshallowlakesinaridregionsofWestern China,CH 4 fluxesfromWuliangsuLakeweremeasuredatdifferentvegetationzonesandwaterdepthswithastatic chambertechniqueduringagrowingseasonfromApriltoOctoberin2003.Resultsshowedthattheaverageemission flux of CH 4 from submerged plant (Potamogeton pectinatus) growing zones was 2.16mg CH 4 m 2 h 1 , which was 85.8%lowerthanthatfromemergentmacrophyte(Phragmites australis)growingzones.CH 4 emissionsincreasedwith increasing water depth in Phragmites Community. Significant seasonal and diurnal variations of CH 4 emission were observedfor P. australis duringtheplantgrowthstage,for P. pectinatus growingzones,however,thevariationswere minor.Inadditiontovegetationcoverandwaterdepth,bottomsilttemperatureandlightintensitywerealsoimportant factorsinfluencingseasonalanddiurnalvariationsofCH 4 fluxfrom Phargmites growingzone. r 2005ElsevierLtd.Allrightsreserved. Keywords: Methane;Emissionflux;Emergentplants;Submergedmacrophyte 1. Introduction Methane (CH 4 ), a radiative gas, plays an important role in the greenhouse effect and in the chemistry of ozone destruction (Etiope and Klusman, 2002). Methaneemissionshavebeenwidelystudiedinvarious wetlands, such as peat soils, paddy fields, and tropical swamps, where freshwater ecosystems have been esti- matedtocontributeover70%ofthenaturalsourceof CH 4 (Khalil, 2000) and over 20% of the total CH 4 sourcetotheatmosphere(IPCC,2001).InChina,great efforts have recently been undertaken to quantify methane emissions from rice paddies and natural wet- lands(Cui,1997; Yeetal.,2000; Jinetal.,1999; Huang etal.,2001; Dingetal.,2004; Hirotaetal.,2004).Most oftheCH 4 emissionsfromthenaturalwetlandsinChina are suggested to be released from the northern fresh- watermarshes(Dingetal.,2004).However,thereisstill no investigation for CH 4 emissions from lakes and wetlands in arid regions of China, where these aquatic ecosystems play a vital role in providing ecosystem servicesforlocalpeople. The arid regions in northwestern China with the annual precipitation below 400mm include Gansu, Qinghai, Ningxia, Xizhang and Xinjiang Provinces ARTICLE IN PRESS www.elsevier.com/locate/atmosenv 1352-2310/$-seefrontmatter r 2005ElsevierLtd.Allrightsreserved. doi:10.1016/j.atmosenv.2005.03.045 à Correspondingauthor.Tel./fax:+861062943822. E-mail address: wangxk@mail.rcees.ac.cn(X.Wang).