Diurnal and Seasonal Variations in Carbon Dioxide Exchange in Ecosystems in the Zhangye Oasis Area, Northwest China

Quantifying carbon dioxide exchange and understanding the response of key environmental factors in various ecosystems are critical to understanding regional carbon budgets and ecosystem behaviors. For this study, CO2 fluxes were measured in a variety of ecosystems with an eddy covariance observation matrix between June 2012 and September 2012 in the Zhangye oasis area of Northwest China. The results show distinct diurnal variations in the CO2 fluxes in vegetable field, orchard, wetland, and maize cropland. Diurnal variations of CO2 fluxes were not obvious, and their values approached zero in the sandy desert, desert steppe, and Gobi ecosystems. Additionally, daily variations in the Gross Primary Production (GPP), Ecosystem Respiration (Reco) and Net Ecosystem Exchange (NEE) were not obvious in the sandy desert, desert steppe, and Gobi ecosystems. In contrast, the distributions of the GPP, Reco, and NEE show significant daily variations, that are closely related to the development of vegetation in the maize, wetland, orchard, and vegetable field ecosystems. All of the ecosystems are characterized by their carbon absorption during the observation period. The ability to absorb CO2 differed significantly among the tested ecosystems. We also used the Michaelis-Menten equation and exponential curve fitting methods to analyze the impact of Photosynthetically Active Radiation (PAR) on the daytime CO2 flux and impact of air temperature on Reco at night. The results show that PAR is the dominant factor in controlling photosynthesis with limited solar radiation, and daytime CO2 assimilation increases rapidly with PAR. Additionally, the carbon assimilation rate was found to increase slowly with high solar radiation. The light response parameters changed with each growth stage for all of the vegetation types, and higher light response values were observed during months or stages when the plants grew quickly. Light saturation points are different for different species. Nighttime Reco increases exponentially with air temperature. High Q10 values were observed when the vegetation coverage was relatively low, and low Q10 values occurred when the vegetables grew vigorously.

[1]  Zhilin Zhu,et al.  Carbon dioxide exchange and the mechanism of environmental control in a farmland ecosystem in North China Plain , 2006 .

[2]  S. T. Gower,et al.  A global relationship between the heterotrophic and autotrophic components of soil respiration? , 2004 .

[3]  William H. Schlesinger,et al.  Desertification alters patterns of aboveground net primary production in Chihuahuan ecosystems , 2002 .

[4]  Lin Zhao,et al.  Seasonal variations in carbon dioxide exchange in an alpine wetland meadow on the Qinghai-Tibetan Plateau. , 2009 .

[5]  Andrew D. Friend,et al.  A process-based, terrestrial biosphere model of ecosystem dynamics (Hybrid v3.0) , 1997 .

[6]  Y. Goto,et al.  Automated foliage chamber method for long-term measurement of CO2 flux in the uppermost canopy , 2003 .

[7]  Andrew E. Suyker,et al.  Growing season carbon dioxide exchange in irrigated and rainfed maize , 2004 .

[8]  Xiangming Xiao,et al.  Modeling gross primary production of maize cropland and degraded grassland in northeastern China , 2010 .

[9]  T. Hirano,et al.  Contribution of litter CO2 production to total soil respiration in two different deciduous forests , 2005 .

[10]  W. Oechel,et al.  FLUXNET: A New Tool to Study the Temporal and Spatial Variability of Ecosystem-Scale Carbon Dioxide, Water Vapor, and Energy Flux Densities , 2001 .

[11]  Zhilin Zhu,et al.  Study on the processing method of nighttime CO2 eddy covariance flux data in ChinaFLUX , 2006 .

[12]  C. Fu,et al.  Three-year variations of water, energy and CO2 fluxes of cropland and degraded grassland surfaces in a semi-arid area of Northeastern China , 2008 .

[13]  Eric A. Davidson,et al.  Seasonal patterns and environmental control of carbon dioxide and water vapour exchange in an ecotonal boreal forest , 1999 .

[14]  Olaf Kolle,et al.  Seasonal variation in energy fluxes and carbon dioxide exchange for a broad‐leaved semi‐arid savanna (Mopane woodland) in Southern Africa , 2004 .

[15]  J. Wilczak,et al.  Sonic Anemometer Tilt Correction Algorithms , 2001 .

[16]  S. Regional.  Several Issues on Aridification in the Northern China , 2002 .

[17]  T. Hirano,et al.  Seasonal variation in CO_2 production of leaf litter from different deciduous forests at the early decomposition stage , 2005 .

[18]  Qing Xiao,et al.  Heihe Watershed Allied Telemetry Experimental Research (HiWATER): Scientific Objectives and Experimental Design , 2013 .

[19]  Shaomin Liu,et al.  A comparison of eddy-covariance and large aperture scintillometer measurements with respect to the energy balance closure problem , 2011 .

[20]  H. Odum,et al.  Primary Productivity of the Biosphere , 1978, Ecological Studies.

[21]  Yiqi Luo,et al.  Invasion of Spartina alterniflora Enhanced Ecosystem Carbon and Nitrogen Stocks in the Yangtze Estuary, China , 2007, Ecosystems.

[22]  Charlotte Bay Hasager,et al.  Carbon dioxide exchange over agricultural landscape using eddy correlation and footprint modelling , 2003 .

[23]  H. Koizumi,et al.  Microbial activity and litter decomposition under snow cover in a cool-temperate broad-leaved deciduous forest , 2005 .

[24]  A. Nik,et al.  CO2 exchange of a tropical rainforest at Pasoh in Peninsular Malaysia , 2008 .

[25]  Andrew E. Suyker,et al.  Gross primary production and light response parameters of four Southern Plains ecosystems estimated using long‐term CO2‐flux tower measurements , 2003 .

[26]  W. Oechel,et al.  Environmental controls over carbon dioxide and water vapor exchange of terrestrial vegetation , 2002 .

[27]  T. Kawahara,et al.  Components and seasonal variation of night-time total ecosystem respiration in a Japanese broad-leaved secondary forest , 2006 .

[28]  Xiangming Xiao,et al.  Modeling gross primary production of alpine ecosystems in the Tibetan Plateau using MODIS images and climate data , 2007 .

[29]  John M. Baker,et al.  Examining strategies to improve the carbon balance of corn/soybean agriculture using eddy covariance and mass balance techniques , 2005 .

[30]  G. Inoue,et al.  Measurement of wood CO2 efflux using a multichannel automated chamber system , 2005 .

[31]  Ü. Rannik,et al.  Gap filling strategies for defensible annual sums of net ecosystem exchange , 2001 .

[32]  Shaomin Liu,et al.  Measurements of evapotranspiration from eddy-covariance systems and large aperture scintillometers in the Hai River Basin, China , 2013 .

[33]  Dennis D. Baldocchi,et al.  Seasonal variation in carbon dioxide exchange over a Mediterranean annual grassland in California , 2004 .

[34]  Carl J. Bernacchi,et al.  Carbon budget of mature no-till ecosystem in North Central Region of the United States , 2005 .

[35]  David C. Goodrich,et al.  Preface paper to the Semi-Arid Land-Surface-Atmosphere (SALSA) Program special issue , 2000 .

[36]  M. Dannoura,et al.  The carbon budget of coarse woody debris in a temperate broad-leaved secondary forest in Japan , 2007 .

[37]  J. Lloyd,et al.  On the temperature dependence of soil respiration , 1994 .

[38]  M. Dannoura,et al.  Development of an automatic chamber system for long-term measurements of CO2 flux from roots , 2006 .

[39]  T. Vesala,et al.  Towards a standardized processing of Net Ecosystem Exchange measured with eddy covariance technique: algorithms and uncertainty estimation , 2006 .

[40]  S. Trumbore.  Carbon respired by terrestrial ecosystems – recent progress and challenges , 2006 .

[41]  Jiemin Wang,et al.  Intercomparison of surface energy flux measurement systems used during the HiWATER‐MUSOEXE , 2013 .

[42]  Dawen Yang,et al.  Seasonal and interannual variations in carbon dioxide exchange over a cropland in the North China Plain , 2009 .

[43]  G E O R G W O H L Fa,et al.  Large annual net ecosystem CO 2 uptake of a Mojave Desert ecosystem , 2008 .

[44]  L. Fenstermaker,et al.  Large annual net ecosystem CO2 uptake of a Mojave Desert ecosystem , 2008 .

[45]  N. Jensen,et al.  Two years of continuous CO2 eddy-flux measurements over a Danish beech forest , 2001 .

[46]  Lawrence B. Flanagan,et al.  Seasonal and interannual variation in carbon dioxide exchange and carbon balance in a northern temperate grassland , 2002 .

[47]  Andrew E. Suyker,et al.  Year‐round observations of the net ecosystem exchange of carbon dioxide in a native tallgrass prairie , 2001 .