Comparison of manual and automated chambers for field measurements of N2O,CH4, CO2 fluxes from cultivated land |
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| Authors: | Zhisheng Yao Xunhua Zheng Baohua Xie Chunyan Liu Baoling Mei Haibo Dong Klaus Butterbach-Bahl Jianguo Zhu |
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| Institution: | 1. State Key Laboratory of Atmospheric Boundary Layer Physics and Atmospheric Chemistry, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, China;2. Institute for Meteorology and Climate Research, Atmospheric Environmental Research, Karlsruhe Research Center, D-82467 Garmisch-Partenkirchen, Germany;3. State Key Laboratory of Soil and Sustainable Agriculture, Nanjing Institute of Soil Sciences, Chinese Academy of Sciences, Nanjing 21008, China;1. Department of Forest and Conservation Sciences, Faculty of Forestry, University of British Columbia, 2424 Main Mall, Vancouver, British Columbia V6T 1Z4, Canada;2. Faculty of Land and Food Systems, University of British Columbia, 2357 Main Mall, Vancouver, British Columbia V6T 1Z4, Canada;1. Institute for Soil Landscape Research, Leibniz Centre for Agricultural Landscape Research (ZALF), Eberswalder Str. 84, 15374 Müncheberg, Germany;2. Institute of Landscape Biogeochemistry, Leibniz Centre for Agricultural Landscape Research (ZALF), Eberswalder Str. 84, 15374 Müncheberg, Germany;3. Vegetation Ecology, Weihenstephan University of Applied Sciences, Weihenstephaner Berg 4, 85354 Freising, Germany;1. Department of Science, Information Technology and Innovation, Dutton Park, Qld 4102, Australia;2. Environmental Futures Research Institute, Griffith University, Nathan, Qld 4111, Australia;3. Sugar Research Australia, Te Kowai, Qld 4740, Australia;4. Department of Agriculture and Fisheries, Bundaberg, Qld 4670, Australia;1. Exchanges Ecosystems—Atmosphere, TERRA, Gembloux Agro-Bio Tech, University of Liège, Belgium;2. AgroBioChem Dept., Gembloux Agro-Bio Tech, University of Liège, Belgium;1. Centre d’Etudes Spatiales de la BIOsphère, UMR 5126 CNES/CNRS/IRD/UPS, 18 avenue Edouard Belin, 31401, Toulouse, France;2. Groupe de Spectrométrie Moléculaire et Atmosphérique GSMA, Université de Reims-Champagne Ardenne, UMR 7331 URCA/CNRS, Moulin de la Housse, BP 1039, 51687, Reims, France;3. Laboratoire d''Aérologie, OMP, UMR 5560 UPS/CNRS, 14 avenue Edouard Belin, 31400, Toulouse, France;4. Groupe d’étude de l’Atmosphère Météorologique, Centre National de Recherches Météorologiques, UMR 3589, Météo, France;5. Geosciences Environnement Toulouse UMR 5563 & UR 234 IRD, Université Paul Sabatier, Avenue Edouard Belin 14, Toulouse, 31400, France |
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| Abstract: | Chamber techniques can easily be applied to field trials with multiple small plots measuring carbon- and nitrogen-trace gas fluxes. Nevertheless, such chamber measurements are usually made weekly and rarely more frequently than once daily. However, automatic chambers do allow flux measurements on sub-daily time scales. It has been hypothesized that sub-daily measurements provide more reliable results, as diurnal variations are captured better compared to manual measurements. To test this hypothesis we compared automatic and manual measurements of N2O, CO2 and CH4 fluxes from tilled and non-tilled plots of a rice–wheat rotation ecosystem over a non-waterlogged period. Our results suggest that both techniques, i.e., either manual or automatic chambers of N2O and CO2 emissions resulted in biased fluxes. The manual measurements were adequate to capture either day-to-day or seasonal dynamics of N2O, CO2 and CH4 exchanges, but overestimated the cumulative N2O and CO2 emissions by 18% and 31%, respectively. This was due to neglecting temperature-dependent diurnal variations of C and N trace gas fluxes. However, the automatic measurements underestimated the cumulative emissions of N2O and CO2 by 22% and 17%, respectively. This underestimation resulted from chamber effects upon soil moisture during rainfall processes. No significant difference was detected between the two methods in CH4 exchanges over the non-waterlogged soils. The bias of manual chambers may be significant when pronounced diurnal variations occur. The bias of automatic measurements can only be avoided/minimized if chamber positions are frequently changed and/or if chambers are automatically opened during rainfall events. We therefore recommend using automatic chambers together with continuous measurements of soil chamber moisture to allow for soil moisture correction of fluxes or to correct flux estimates as derived by manual chambers for possible diurnal variations. |
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