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Prof. Dr. Derrick Y.F. Lai
The Chinese University of Hong Kong, China

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0 Biogeochemistry
0 Soil Management
0 Wetlands
0 carbon cycling
0 Greenhouse gas flux

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carbon cycling

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Data description paper
Published: 29 July 2021 in Earth System Science Data
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Methane (CH4) emissions from natural landscapes constitute roughly half of global CH4 contributions to the atmosphere, yet large uncertainties remain in the absolute magnitude and the seasonality of emission quantities and drivers. Eddy covariance (EC) measurements of CH4 flux are ideal for constraining ecosystem-scale CH4 emissions due to quasi-continuous and high-temporal-resolution CH4 flux measurements, coincident carbon dioxide, water, and energy flux measurements, lack of ecosystem disturbance, and increased availability of datasets over the last decade. Here, we (1) describe the newly published dataset, FLUXNET-CH4 Version 1.0, the first open-source global dataset of CH4 EC measurements (available at https://fluxnet.org/data/fluxnet-ch4-community-product/, last access: 7 April 2021). FLUXNET-CH4 includes half-hourly and daily gap-filled and non-gap-filled aggregated CH4 fluxes and meteorological data from 79 sites globally: 42 freshwater wetlands, 6 brackish and saline wetlands, 7 formerly drained ecosystems, 7 rice paddy sites, 2 lakes, and 15 uplands. Then, we (2) evaluate FLUXNET-CH4 representativeness for freshwater wetland coverage globally because the majority of sites in FLUXNET-CH4 Version 1.0 are freshwater wetlands which are a substantial source of total atmospheric CH4 emissions; and (3) we provide the first global estimates of the seasonal variability and seasonality predictors of freshwater wetland CH4 fluxes. Our representativeness analysis suggests that the freshwater wetland sites in the dataset cover global wetland bioclimatic attributes (encompassing energy, moisture, and vegetation-related parameters) in arctic, boreal, and temperate regions but only sparsely cover humid tropical regions. Seasonality metrics of wetland CH4 emissions vary considerably across latitudinal bands. In freshwater wetlands (except those between 20∘ S to 20∘ N) the spring onset of elevated CH4 emissions starts 3 d earlier, and the CH4 emission season lasts 4 d longer, for each degree Celsius increase in mean annual air temperature. On average, the spring onset of increasing CH4 emissions lags behind soil warming by 1 month, with very few sites experiencing increased CH4 emissions prior to the onset of soil warming. In contrast, roughly half of these sites experience the spring onset of rising CH4 emissions prior to the spring increase in gross primary productivity (GPP). The timing of peak summer CH4 emissions does not correlate with the timing for either peak summer temperature or peak GPP. Our results provide seasonality parameters for CH4 modeling and highlight seasonality metrics that cannot be predicted by temperature or GPP (i.e., seasonality of CH4 peak). FLUXNET-CH4 is a powerful new resource for diagnosing and understanding the role of terrestrial ecosystems and climate drivers in the global CH4 cycle, and future additions of sites in tropical ecosystems and site years of data collection will provide added value to this database. All seasonality parameters are available at https://doi.org/10.5281/zenodo.4672601 (Delwiche et al., 2021). Additionally, raw FLUXNET-CH4 data used to extract seasonality parameters can be downloaded from https://fluxnet.org/data/fluxnet-ch4-community-product/ (last access: 7 April 2021), and a complete list of the 79 individual site data DOIs is provided in Table 2 of this paper.

ACS Style

Kyle B. Delwiche; Sara Helen Knox; Avni Malhotra; Etienne Fluet-Chouinard; Gavin McNicol; Sarah Feron; Zutao Ouyang; Dario Papale; Carlo Trotta; Eleonora Canfora; You-Wei Cheah; Danielle Christianson; Ma. Carmelita R. Alberto; Pavel Alekseychik; Mika Aurela; Dennis Baldocchi; Sheel Bansal; David P. Billesbach; Gil Bohrer; Rosvel Bracho; Nina Buchmann; David I. Campbell; Gerardo Celis; Jiquan Chen; Weinan Chen; Housen Chu; Higo J. Dalmagro; Sigrid Dengel; Ankur R. Desai; Matteo Detto; Han Dolman; Elke Eichelmann; Eugenie Euskirchen; Daniela Famulari; Kathrin Fuchs; Mathias Goeckede; Sébastien Gogo; Mangaliso J. Gondwe; Jordan P. Goodrich; Pia Gottschalk; Scott L. Graham; Martin Heimann; Manuel Helbig; Carole Helfter; Kyle S. Hemes; Takashi Hirano; David Hollinger; Lukas Hörtnagl; Hiroki Iwata; Adrien Jacotot; Gerald Jurasinski; Minseok Kang; Kuno Kasak; John King; Janina Klatt; Franziska Koebsch; Ken W. Krauss; Derrick Y. F. Lai; Annalea Lohila; Ivan Mammarella; Luca Belelli Marchesini; Giovanni Manca; Jaclyn Hatala Matthes; Trofim Maximov; Lutz Merbold; Bhaskar Mitra; Timothy H. Morin; Eiko Nemitz; Mats B. Nilsson; Shuli Niu; Walter C. Oechel; Patricia Y. Oikawa; Keisuke Ono; Matthias Peichl; Olli Peltola; Michele L. Reba; Andrew D. Richardson; William Riley; Benjamin R. K. Runkle; Youngryel Ryu; Torsten Sachs; Ayaka Sakabe; Camilo Rey Sanchez; Edward A. Schuur; Karina V. R. Schäfer; Oliver Sonnentag; Jed P. Sparks; Ellen Stuart-Haëntjens; Cove Sturtevant; Ryan C. Sullivan; Daphne J. Szutu; Jonathan E. Thom; Margaret S. Torn; Eeva-Stiina Tuittila; Jessica Turner; Masahito Ueyama; Alex C. Valach; Rodrigo Vargas; Andrej Varlagin; Alma Vazquez-Lule; Joseph G. Verfaillie; Timo Vesala; George L. Vourlitis; Eric J. Ward; Christian Wille; Georg Wohlfahrt; Guan Xhuan Wong; Zhen Zhang; Donatella Zona; Lisamarie Windham-Myers; Benjamin Poulter; Robert B. Jackson. FLUXNET-CH4: a global, multi-ecosystem dataset and analysis of methane seasonality from freshwater wetlands. Earth System Science Data 2021, 13, 3607 -3689.

AMA Style

Kyle B. Delwiche, Sara Helen Knox, Avni Malhotra, Etienne Fluet-Chouinard, Gavin McNicol, Sarah Feron, Zutao Ouyang, Dario Papale, Carlo Trotta, Eleonora Canfora, You-Wei Cheah, Danielle Christianson, Ma. Carmelita R. Alberto, Pavel Alekseychik, Mika Aurela, Dennis Baldocchi, Sheel Bansal, David P. Billesbach, Gil Bohrer, Rosvel Bracho, Nina Buchmann, David I. Campbell, Gerardo Celis, Jiquan Chen, Weinan Chen, Housen Chu, Higo J. Dalmagro, Sigrid Dengel, Ankur R. Desai, Matteo Detto, Han Dolman, Elke Eichelmann, Eugenie Euskirchen, Daniela Famulari, Kathrin Fuchs, Mathias Goeckede, Sébastien Gogo, Mangaliso J. Gondwe, Jordan P. Goodrich, Pia Gottschalk, Scott L. Graham, Martin Heimann, Manuel Helbig, Carole Helfter, Kyle S. Hemes, Takashi Hirano, David Hollinger, Lukas Hörtnagl, Hiroki Iwata, Adrien Jacotot, Gerald Jurasinski, Minseok Kang, Kuno Kasak, John King, Janina Klatt, Franziska Koebsch, Ken W. Krauss, Derrick Y. F. Lai, Annalea Lohila, Ivan Mammarella, Luca Belelli Marchesini, Giovanni Manca, Jaclyn Hatala Matthes, Trofim Maximov, Lutz Merbold, Bhaskar Mitra, Timothy H. Morin, Eiko Nemitz, Mats B. Nilsson, Shuli Niu, Walter C. Oechel, Patricia Y. Oikawa, Keisuke Ono, Matthias Peichl, Olli Peltola, Michele L. Reba, Andrew D. Richardson, William Riley, Benjamin R. K. Runkle, Youngryel Ryu, Torsten Sachs, Ayaka Sakabe, Camilo Rey Sanchez, Edward A. Schuur, Karina V. R. Schäfer, Oliver Sonnentag, Jed P. Sparks, Ellen Stuart-Haëntjens, Cove Sturtevant, Ryan C. Sullivan, Daphne J. Szutu, Jonathan E. Thom, Margaret S. Torn, Eeva-Stiina Tuittila, Jessica Turner, Masahito Ueyama, Alex C. Valach, Rodrigo Vargas, Andrej Varlagin, Alma Vazquez-Lule, Joseph G. Verfaillie, Timo Vesala, George L. Vourlitis, Eric J. Ward, Christian Wille, Georg Wohlfahrt, Guan Xhuan Wong, Zhen Zhang, Donatella Zona, Lisamarie Windham-Myers, Benjamin Poulter, Robert B. Jackson. FLUXNET-CH4: a global, multi-ecosystem dataset and analysis of methane seasonality from freshwater wetlands. Earth System Science Data. 2021; 13 (7):3607-3689.

Chicago/Turabian Style

Kyle B. Delwiche; Sara Helen Knox; Avni Malhotra; Etienne Fluet-Chouinard; Gavin McNicol; Sarah Feron; Zutao Ouyang; Dario Papale; Carlo Trotta; Eleonora Canfora; You-Wei Cheah; Danielle Christianson; Ma. Carmelita R. Alberto; Pavel Alekseychik; Mika Aurela; Dennis Baldocchi; Sheel Bansal; David P. Billesbach; Gil Bohrer; Rosvel Bracho; Nina Buchmann; David I. Campbell; Gerardo Celis; Jiquan Chen; Weinan Chen; Housen Chu; Higo J. Dalmagro; Sigrid Dengel; Ankur R. Desai; Matteo Detto; Han Dolman; Elke Eichelmann; Eugenie Euskirchen; Daniela Famulari; Kathrin Fuchs; Mathias Goeckede; Sébastien Gogo; Mangaliso J. Gondwe; Jordan P. Goodrich; Pia Gottschalk; Scott L. Graham; Martin Heimann; Manuel Helbig; Carole Helfter; Kyle S. Hemes; Takashi Hirano; David Hollinger; Lukas Hörtnagl; Hiroki Iwata; Adrien Jacotot; Gerald Jurasinski; Minseok Kang; Kuno Kasak; John King; Janina Klatt; Franziska Koebsch; Ken W. Krauss; Derrick Y. F. Lai; Annalea Lohila; Ivan Mammarella; Luca Belelli Marchesini; Giovanni Manca; Jaclyn Hatala Matthes; Trofim Maximov; Lutz Merbold; Bhaskar Mitra; Timothy H. Morin; Eiko Nemitz; Mats B. Nilsson; Shuli Niu; Walter C. Oechel; Patricia Y. Oikawa; Keisuke Ono; Matthias Peichl; Olli Peltola; Michele L. Reba; Andrew D. Richardson; William Riley; Benjamin R. K. Runkle; Youngryel Ryu; Torsten Sachs; Ayaka Sakabe; Camilo Rey Sanchez; Edward A. Schuur; Karina V. R. Schäfer; Oliver Sonnentag; Jed P. Sparks; Ellen Stuart-Haëntjens; Cove Sturtevant; Ryan C. Sullivan; Daphne J. Szutu; Jonathan E. Thom; Margaret S. Torn; Eeva-Stiina Tuittila; Jessica Turner; Masahito Ueyama; Alex C. Valach; Rodrigo Vargas; Andrej Varlagin; Alma Vazquez-Lule; Joseph G. Verfaillie; Timo Vesala; George L. Vourlitis; Eric J. Ward; Christian Wille; Georg Wohlfahrt; Guan Xhuan Wong; Zhen Zhang; Donatella Zona; Lisamarie Windham-Myers; Benjamin Poulter; Robert B. Jackson. 2021. "FLUXNET-CH4: a global, multi-ecosystem dataset and analysis of methane seasonality from freshwater wetlands." Earth System Science Data 13, no. 7: 3607-3689.

Journal article
Published: 24 July 2021 in Aquaculture
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Small-scale aquaculture operation is increasing rapidly in the world, particularly in developing countries, but the greenhouse gas (GHG) dynamics and fluxes from small aquaculture ponds are still poorly assessed. In this study, dissolved concentrations and fluxes of CO2 and CH4 were determined in three coastal earthen shrimp ponds over one whole year, including both farming and non-farming periods, in the Min River Estuary, southeastern China. Different from many previous studies, both ebullitive and diffusive CH4 fluxes were measured. The average concentrations of dissolved CO2 and CH4 in water column in the farming period varied between 18.1 ± 0.1 and 79.6 ± 1.1 μmol L−1, and 1.3 ± 0.1 and 55.9 ± 3.2 μmol L−1, respectively. Averaged across the whole year, the mean CO2 and CH4 fluxes from the ponds were − 18.4 ± 7.4 and 22.6 ± 6.9 mg m−2 h−1, respectively, suggesting that the shrimp ponds worked as a CO2 sink and a CH4 source. Based on the sustained-flux global warming potential (SGWP) and sustained-flux global cooling potential (SGCP) models, the annual warming potential was estimated to be 7.1 × 103 g CO2-eq m−2 yr−1, with approximately 90% from the farming period. Ebullition was the dominant emission pathway for CH4, accounting for over 90% of the total CH4 emission during the farming period. The full-year study improves the understanding of carbon cycling in coastal aquaculture ponds and provides scientific basis for updating GHG inventories.

ACS Style

Chuan Tong; David Bastviken; Kam W. Tang; Ping Yang; Hong Yang; Yifei Zhang; Qianqian Guo; Derrick Y.F. Lai. Annual CO2 and CH4 fluxes in coastal earthen ponds with Litopenaeus vannamei in southeastern China. Aquaculture 2021, 545, 737229 .

AMA Style

Chuan Tong, David Bastviken, Kam W. Tang, Ping Yang, Hong Yang, Yifei Zhang, Qianqian Guo, Derrick Y.F. Lai. Annual CO2 and CH4 fluxes in coastal earthen ponds with Litopenaeus vannamei in southeastern China. Aquaculture. 2021; 545 ():737229.

Chicago/Turabian Style

Chuan Tong; David Bastviken; Kam W. Tang; Ping Yang; Hong Yang; Yifei Zhang; Qianqian Guo; Derrick Y.F. Lai. 2021. "Annual CO2 and CH4 fluxes in coastal earthen ponds with Litopenaeus vannamei in southeastern China." Aquaculture 545, no. : 737229.

Journal article
Published: 10 July 2021 in Agricultural and Forest Meteorology
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Time series of wetland methane fluxes measured by eddy covariance require gap-filling to estimate daily, seasonal, and annual emissions. Gap-filling methane fluxes is challenging because of high variability and complex responses to multiple drivers. To date, there is no widely established gap-filling standard for wetland methane fluxes, with regards both to the best model algorithms and predictors. This study synthesizes results of different gap-filling methods systematically applied at 17 wetland sites spanning boreal to tropical regions and including all major wetland classes and two rice paddies. Procedures are proposed for: 1) creating realistic artificial gap scenarios, 2) training and evaluating gap-filling models without overstating performance, and 3) predicting half-hourly methane fluxes and annual emissions with realistic uncertainty estimates. Performance is compared between a conventional method (marginal distribution sampling) and four machine learning algorithms. The conventional method achieved similar median performance as the machine learning models but was worse than the best machine learning models and relatively insensitive to predictor choices. Of the machine learning models, decision tree algorithms performed the best in cross-validation experiments, even with a baseline predictor set, and artificial neural networks showed comparable performance when using all predictors. Soil temperature was frequently the most important predictor whilst water table depth was important at sites with substantial water table fluctuations, highlighting the value of data on wetland soil conditions. Raw gap-filling uncertainties from the machine learning models were underestimated and we propose a method to calibrate uncertainties to observations. The python code for model development, evaluation, and uncertainty estimation is publicly available. This study outlines a modular and robust machine learning workflow and makes recommendations for, and evaluates an improved baseline of, methane gap-filling models that can be implemented in multi-site syntheses or standardized products from regional and global flux networks (e.g., FLUXNET).

ACS Style

Jeremy Irvin; Sharon Zhou; Gavin McNicol; Fred Lu; Vincent Liu; Etienne Fluet-Chouinard; Zutao Ouyang; Sara Helen Knox; Antje Lucas-Moffat; Carlo Trotta; Dario Papale; Domenico Vitale; Ivan Mammarella; Pavel Alekseychik; Mika Aurela; Anand Avati; Dennis Baldocchi; Sheel Bansal; Gil Bohrer; David I Campbell; Jiquan Chen; Housen Chu; Higo J Dalmagro; Kyle B Delwiche; Ankur R Desai; Eugenie Euskirchen; Sarah Feron; Mathias Goeckede; Martin Heimann; Manuel Helbig; Carole Helfter; Kyle S Hemes; Takashi Hirano; Hiroki Iwata; Gerald Jurasinski; Aram Kalhori; Andrew Kondrich; Derrick Yf Lai; Annalea Lohila; Avni Malhotra; Lutz Merbold; Bhaskar Mitra; Andrew Ng; Mats B Nilsson; Asko Noormets; Matthias Peichl; A. Camilo Rey-Sanchez; Andrew D Richardson; Benjamin Rk Runkle; Karina Vr Schäfer; Oliver Sonnentag; Ellen Stuart-Haëntjens; Cove Sturtevant; Masahito Ueyama; Alex C Valach; Rodrigo Vargas; George L Vourlitis; Eric J Ward; Guan Xhuan Wong; Donatella Zona; Ma. Carmelita R Alberto; David P Billesbach; Gerardo Celis; Han Dolman; Thomas Friborg; Kathrin Fuchs; Sébastien Gogo; Mangaliso J Gondwe; Jordan P Goodrich; Pia Gottschalk; Lukas Hörtnagl; Adrien Jacotot; Franziska Koebsch; Kuno Kasak; Regine Maier; Timothy H Morin; Eiko Nemitz; Walter C Oechel; Patricia Y Oikawa; Keisuke Ono; Torsten Sachs; Ayaka Sakabe; Edward A Schuur; Robert Shortt; Ryan C Sullivan; Daphne J Szutu; Eeva-Stiina Tuittila; Andrej Varlagin; Joeseph G Verfaillie; Christian Wille; Lisamarie Windham-Myers; Benjamin Poulter; Robert B Jackson. Gap-filling eddy covariance methane fluxes: Comparison of machine learning model predictions and uncertainties at FLUXNET-CH4 wetlands. Agricultural and Forest Meteorology 2021, 308-309, 108528 .

AMA Style

Jeremy Irvin, Sharon Zhou, Gavin McNicol, Fred Lu, Vincent Liu, Etienne Fluet-Chouinard, Zutao Ouyang, Sara Helen Knox, Antje Lucas-Moffat, Carlo Trotta, Dario Papale, Domenico Vitale, Ivan Mammarella, Pavel Alekseychik, Mika Aurela, Anand Avati, Dennis Baldocchi, Sheel Bansal, Gil Bohrer, David I Campbell, Jiquan Chen, Housen Chu, Higo J Dalmagro, Kyle B Delwiche, Ankur R Desai, Eugenie Euskirchen, Sarah Feron, Mathias Goeckede, Martin Heimann, Manuel Helbig, Carole Helfter, Kyle S Hemes, Takashi Hirano, Hiroki Iwata, Gerald Jurasinski, Aram Kalhori, Andrew Kondrich, Derrick Yf Lai, Annalea Lohila, Avni Malhotra, Lutz Merbold, Bhaskar Mitra, Andrew Ng, Mats B Nilsson, Asko Noormets, Matthias Peichl, A. Camilo Rey-Sanchez, Andrew D Richardson, Benjamin Rk Runkle, Karina Vr Schäfer, Oliver Sonnentag, Ellen Stuart-Haëntjens, Cove Sturtevant, Masahito Ueyama, Alex C Valach, Rodrigo Vargas, George L Vourlitis, Eric J Ward, Guan Xhuan Wong, Donatella Zona, Ma. Carmelita R Alberto, David P Billesbach, Gerardo Celis, Han Dolman, Thomas Friborg, Kathrin Fuchs, Sébastien Gogo, Mangaliso J Gondwe, Jordan P Goodrich, Pia Gottschalk, Lukas Hörtnagl, Adrien Jacotot, Franziska Koebsch, Kuno Kasak, Regine Maier, Timothy H Morin, Eiko Nemitz, Walter C Oechel, Patricia Y Oikawa, Keisuke Ono, Torsten Sachs, Ayaka Sakabe, Edward A Schuur, Robert Shortt, Ryan C Sullivan, Daphne J Szutu, Eeva-Stiina Tuittila, Andrej Varlagin, Joeseph G Verfaillie, Christian Wille, Lisamarie Windham-Myers, Benjamin Poulter, Robert B Jackson. Gap-filling eddy covariance methane fluxes: Comparison of machine learning model predictions and uncertainties at FLUXNET-CH4 wetlands. Agricultural and Forest Meteorology. 2021; 308-309 ():108528.

Chicago/Turabian Style

Jeremy Irvin; Sharon Zhou; Gavin McNicol; Fred Lu; Vincent Liu; Etienne Fluet-Chouinard; Zutao Ouyang; Sara Helen Knox; Antje Lucas-Moffat; Carlo Trotta; Dario Papale; Domenico Vitale; Ivan Mammarella; Pavel Alekseychik; Mika Aurela; Anand Avati; Dennis Baldocchi; Sheel Bansal; Gil Bohrer; David I Campbell; Jiquan Chen; Housen Chu; Higo J Dalmagro; Kyle B Delwiche; Ankur R Desai; Eugenie Euskirchen; Sarah Feron; Mathias Goeckede; Martin Heimann; Manuel Helbig; Carole Helfter; Kyle S Hemes; Takashi Hirano; Hiroki Iwata; Gerald Jurasinski; Aram Kalhori; Andrew Kondrich; Derrick Yf Lai; Annalea Lohila; Avni Malhotra; Lutz Merbold; Bhaskar Mitra; Andrew Ng; Mats B Nilsson; Asko Noormets; Matthias Peichl; A. Camilo Rey-Sanchez; Andrew D Richardson; Benjamin Rk Runkle; Karina Vr Schäfer; Oliver Sonnentag; Ellen Stuart-Haëntjens; Cove Sturtevant; Masahito Ueyama; Alex C Valach; Rodrigo Vargas; George L Vourlitis; Eric J Ward; Guan Xhuan Wong; Donatella Zona; Ma. Carmelita R Alberto; David P Billesbach; Gerardo Celis; Han Dolman; Thomas Friborg; Kathrin Fuchs; Sébastien Gogo; Mangaliso J Gondwe; Jordan P Goodrich; Pia Gottschalk; Lukas Hörtnagl; Adrien Jacotot; Franziska Koebsch; Kuno Kasak; Regine Maier; Timothy H Morin; Eiko Nemitz; Walter C Oechel; Patricia Y Oikawa; Keisuke Ono; Torsten Sachs; Ayaka Sakabe; Edward A Schuur; Robert Shortt; Ryan C Sullivan; Daphne J Szutu; Eeva-Stiina Tuittila; Andrej Varlagin; Joeseph G Verfaillie; Christian Wille; Lisamarie Windham-Myers; Benjamin Poulter; Robert B Jackson. 2021. "Gap-filling eddy covariance methane fluxes: Comparison of machine learning model predictions and uncertainties at FLUXNET-CH4 wetlands." Agricultural and Forest Meteorology 308-309, no. : 108528.

Journal article
Published: 05 May 2021 in Water Research
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Aquaculture ponds are important anthropogenic sources of nitrous oxide (N2O). Direct N2O emissions arising from feed application to ponds have been widely investigated, but indirect emissions from N2O production from residual feeds in pond water are much less understood and characterized to refine the IPCC emission factor. In this study, we determined the concentrations and spatiotemporal variations of dissolved N2O and NO3––N in situ in three aquaculture ponds at the Min River Estuary in southeastern China during the culture period over two years, and calculated the indirect N2O emission factor (EF5) for aquaculture ponds using the N2O–N/NO3––N mass ratio methodology. Our results indicated that the EF5 values in the ponds over the culture period ranged between 0.0007 and 0.0543, with a clear seasonal pattern which closely followed that of the DOC:NO3—N ratio. We also observed significant spatial variations in EF5 among the three ponds, which could be attributed to the difference in feed conversion rate. In addition, we assessed the EF5 values from aquaculture ponds in five regions of the Chinese coastline across the latitudinal gradient from the tropical to the temperate zones. The average EF5 value from aquaculture ponds across the five coastal regions was 0.0093±0.0024, which was approximately 3.7 times of the IPCC default value for rivers and estuaries (0.0025). Moreover, the EF5 values demonstrated considerable spatial variations across these coastal regions with a coefficient of variation of 59%, which were largely related to the difference in water salinity. Our findings filled a key knowledge gap about the indirect N2O emission factor from aquaculture ponds, and provided field evidence for the refinement of EF5 value currently adopted by IPCC in the national greenhouse gas inventory.

ACS Style

Ping Yang; Jiafang Huang; Lishan Tan; Chuan Tong; Baoshi Jin; Beibei Hu; Changjun Gao; Junji Yuan; Derrick Y.F. Lai; Hong Yang. Large variations in indirect N2O emission factors (EF5) from coastal aquaculture systems in China from plot to regional scales. Water Research 2021, 200, 117208 .

AMA Style

Ping Yang, Jiafang Huang, Lishan Tan, Chuan Tong, Baoshi Jin, Beibei Hu, Changjun Gao, Junji Yuan, Derrick Y.F. Lai, Hong Yang. Large variations in indirect N2O emission factors (EF5) from coastal aquaculture systems in China from plot to regional scales. Water Research. 2021; 200 ():117208.

Chicago/Turabian Style

Ping Yang; Jiafang Huang; Lishan Tan; Chuan Tong; Baoshi Jin; Beibei Hu; Changjun Gao; Junji Yuan; Derrick Y.F. Lai; Hong Yang. 2021. "Large variations in indirect N2O emission factors (EF5) from coastal aquaculture systems in China from plot to regional scales." Water Research 200, no. : 117208.

Journal article
Published: 02 April 2021 in Atmospheric Environment
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Static floating chambers (FCs) are the conventional method to measure CH4 fluxes across the water-air interface in ponds, while thin boundary layer (TBL) modelling is increasingly used to estimate CH4 fluxes. In this study, both FCs measurements and TBL models of gas transfer velocity were used to determine CH4 evasion from aquaculture ponds in southeastern China. The surface water CH4 concentrations ranged from 0.4 to 9.1 μmol L-1 with an average of 4.8 ± 0.8 μmol L-1. CH4 flux was always positive, indicating the ponds as a persistent CH4 source to air. Mean CH4 flux based on different TBL models showed large variations, ranging between 19 and 316 μmol m−2 h−1. Compared against the direct measurement FCs, three TBL models developed for the open sea, flowing estuarine system and lentic ecosystem (TBLW92a, TBLRC01, and TBLCL98, respectively) overestimated CH4 emission by 40–200%, while the wind tunnel-based TBL model (TBLLM86) underestimated CH4 emission. Two TBL models developed for lakes (TBLW92b and TBLCW03) gave estimates similar to FCs.

ACS Style

Ping Yang; Jiafang Huang; Hong Yang; Josep Peñuelas; Kam W. Tang; Derrick Y.F. Lai; Dongqi Wang; Qitao Xiao; Jordi Sardans; Yifei Zhang; Chuan Tong. Diffusive CH4 fluxes from aquaculture ponds using floating chambers and thin boundary layer equations. Atmospheric Environment 2021, 253, 118384 .

AMA Style

Ping Yang, Jiafang Huang, Hong Yang, Josep Peñuelas, Kam W. Tang, Derrick Y.F. Lai, Dongqi Wang, Qitao Xiao, Jordi Sardans, Yifei Zhang, Chuan Tong. Diffusive CH4 fluxes from aquaculture ponds using floating chambers and thin boundary layer equations. Atmospheric Environment. 2021; 253 ():118384.

Chicago/Turabian Style

Ping Yang; Jiafang Huang; Hong Yang; Josep Peñuelas; Kam W. Tang; Derrick Y.F. Lai; Dongqi Wang; Qitao Xiao; Jordi Sardans; Yifei Zhang; Chuan Tong. 2021. "Diffusive CH4 fluxes from aquaculture ponds using floating chambers and thin boundary layer equations." Atmospheric Environment 253, no. : 118384.

Journal article
Published: 10 March 2021 in Forests
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Acacia spp. are exotic tree species that have been widely planted on man-made slopes in Hong Kong since the 1960s. However, as they become mature and senescent, they may become a concern and cause various problems, including soil constraints for plant growth, decreasing provision of intended ecosystem services, declining syndromes, arrested succession, and high risk of failure. In this perspective paper, we present and discuss these problems using practical examples of Acacia-dominated urban forests on man-made roadside slopes in Hong Kong, based on a cross-disciplinary survey and a literature review. To conclude, we suggest that selective cutting, specific silvicultural operations of Acacia plantations, and the management of plantation edge and soils can be exercised, along with the planting of native species, to potentially alleviate these problems associated with mature Acacia plantations, by promoting the establishment of native forests, enhancing biodiversity, expediting succession, and providing better ecosystem services.

ACS Style

Cody Lee; Alvin Tang; Derrick Lai; Amos Tai; Alan Leung; Donald Tao; Felix Leung; Simon Leung; Charis Wu; Sandy Tong; Kathy Ng. Problems and Management of Acacia-Dominated Urban Forests on Man-Made Slopes in a Subtropical, High-Density City. Forests 2021, 12, 323 .

AMA Style

Cody Lee, Alvin Tang, Derrick Lai, Amos Tai, Alan Leung, Donald Tao, Felix Leung, Simon Leung, Charis Wu, Sandy Tong, Kathy Ng. Problems and Management of Acacia-Dominated Urban Forests on Man-Made Slopes in a Subtropical, High-Density City. Forests. 2021; 12 (3):323.

Chicago/Turabian Style

Cody Lee; Alvin Tang; Derrick Lai; Amos Tai; Alan Leung; Donald Tao; Felix Leung; Simon Leung; Charis Wu; Sandy Tong; Kathy Ng. 2021. "Problems and Management of Acacia-Dominated Urban Forests on Man-Made Slopes in a Subtropical, High-Density City." Forests 12, no. 3: 323.

Journal article
Published: 29 January 2021 in Science of The Total Environment
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Biochar management has been proposed as a promising strategy to mitigate climate change. However, the long-term effects of biochar amendment on soil greenhouse gas (GHG) production and microbial community in forest ecosystems under projected warming remain highly uncertain. In this study, we conducted a 49-day incubation experiment to investigate the impact of biochar application on soil physico-chemical properties, GHG production rates, and microbial community at three temperature levels using a temperate forest soil amended with spruce biochar four years ago. Our results showed that temperature exerted a positive effect on soil CO2, CH4 and N2O production, leading to an increase in total global warming potential by 169% and 87% as temperature rose from 5 to 15 °C and from 15 to 25 °C, respectively, and thus a positive feedback to warming. Moreover, warming was found to reduce soil microbial biomass significantly, but at the same time promote the selection of an activated microbial community towards some phyla, e.g. Acidobacteria and Actinobacteria. We observed that biochar amendment reduced soil CH4 consumption and N2O production in the absence of litter by 106% and 94%, respectively, but did not affect soil CO2 production. While biochar had no significant influence of total global warming potential of forest soil, it could promote climate change mitigation by increasing the total soil carbon content by 26% in the presence of litter. In addition, biochar application was shown to enhance soil available phosphorus and dissolved organic carbon concentrations, as well as soil microbial biomass under a warmer environment. Our findings highlighted the potential of spruce biochar as a soil amendment in improving soil fertility and carbon sequestration in temperate forest over the long term, without creating any adverse climatic impacts associated with soil GHG production.

ACS Style

Jinglan Cui; Stephan Glatzel; Viktor J. Bruckman; Baozhan Wang; Derrick Y.F. Lai. Long-term effects of biochar application on greenhouse gas production and microbial community in temperate forest soils under increasing temperature. Science of The Total Environment 2021, 767, 145021 .

AMA Style

Jinglan Cui, Stephan Glatzel, Viktor J. Bruckman, Baozhan Wang, Derrick Y.F. Lai. Long-term effects of biochar application on greenhouse gas production and microbial community in temperate forest soils under increasing temperature. Science of The Total Environment. 2021; 767 ():145021.

Chicago/Turabian Style

Jinglan Cui; Stephan Glatzel; Viktor J. Bruckman; Baozhan Wang; Derrick Y.F. Lai. 2021. "Long-term effects of biochar application on greenhouse gas production and microbial community in temperate forest soils under increasing temperature." Science of The Total Environment 767, no. : 145021.

Preprint content
Published: 18 January 2021
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Methane (CH4) emissions from natural landscapes constitute roughly half of global CH4 contributions to the atmosphere, yet large uncertainties remain in the absolute magnitude and the seasonality of emission quantities and drivers. Eddy covariance (EC) measurements of CH4 flux are ideal for constraining ecosystem-scale CH4 emissions, including their seasonality, due to quasi-continuous and high temporal resolution of flux measurements, coincident measurements of carbon, water, and energy fluxes, lack of ecosystem disturbance, and increased availability of datasets over the last decade. Here, we 1) describe the newly published dataset, FLUXNET-CH4 Version 1.0, the first global dataset of CH4 EC measurements (available at https://fluxnet.org/data/fluxnet-ch4- community-product/). FLUXNET-CH4 includes half-hourly and daily gap-filled and non gap-filled aggregated CH4 fluxes and meteorological data from 79 sites globally: 42 freshwater wetlands, 6 brackish and saline wetlands, 7 formerly drained ecosystems, 7 rice paddy sites, 2 lakes, and 15 uplands. Then, we 2) evaluate FLUXNET-CH4 representativeness for freshwater wetland coverage globally, because the majority of sites in FLUXNET-CH4 Version 1.0 are freshwater wetlands and because freshwater wetlands are a substantial source of total atmospheric CH4 emissions; and 3) provide the first global estimates of the seasonal variability and seasonality predictors of freshwater wetland CH4 fluxes. Our representativeness analysis suggests that the freshwater wetland sites in the dataset cover global wetland bioclimatic attributes (encompassing energy, moisture, and vegetation-related parameters) in arctic, boreal, and temperate regions, but only sparsely cover humid tropical regions. Seasonality metrics of wetland CH4 emissions vary considerably across latitudinal bands. In freshwater wetlands (except those between 20° S to 20° N) the spring onset of elevated CH4 emissions starts three days earlier, and the CH4 emission season lasts 4 days longer, for each degree C increase in mean annual air temperature. On average, the onset of increasing CH4 emissions lags soil warming by one month, with very few sites experiencing increased CH4 emissions prior to the onset of soil warming. In contrast, roughly half of these sites experience the spring onset of rising CH4 emissions prior to the spring increase in gross primary productivity (GPP). The timing of peak summer CH4 emissions does not correlate with the timing for either peak summer temperature or peak GPP. Our results provide seasonality parameters for CH4 modeling, and highlight seasonality metrics that cannot be predicted by temperature or GPP (i.e., seasonality of CH4 peak). The FLUXNET-CH4 dataset provides an open-access resource for CH4 flux synthesis, has a range of applications, and is unique in that it includes coupled measurements of important CH4 drivers such as GPP and temperature. Although FLUXNET-CH4 could certainly be improved by adding more sites in tropical ecosystems and by increasing the number of site-years at existing sites, it is a powerful new resource for diagnosing and understanding the role of terrestrial ecosystems and climate drivers in the global CH4 cycle. All seasonality parameters are available at https://doi.org/10.5281/zenodo.4408468. Additionally, raw FLUXNET-CH4 data used to extract seasonality parameters can be downloaded from https://fluxnet.org/data/fluxnet-ch4-community-product/, and a complete list of the 79 individual site data DOIs is provided in Table 2 in the Data Availability section of this document.

ACS Style

Kyle B. Delwiche; Sara Helen Knox; Avni Malhotra; Etienne Fluet-Chouinard; Gavin McNicol; Sarah Feron; Zutao Ouyang; Dario Papale; Carlo Trotta; Eleonora Canfora; You-Wei Cheah; Danielle Christianson; M. Carmelita R. Alberto; Pavel Alekseychik; Mika Aurela; Dennis Baldocchi; Sheel Bansal; David P. Billesbach; Gil Bohrer; Rosvel Bracho; Nina Buchmann; David I. Campbell; Gerardo Celis; Jiquan Chen; Weinan Chen; Housen Chu; Higo J. Dalmagro; Sigrid Dengel; Ankur R. Desai; Matteo Detto; Han Dolman; Elke Eichelmann; Eugenie Euskirchen; Daniela Famulari; Thomas Friborg; Kathrin Fuchs; Mathias Goeckede; Sébastien Gogo; Mangaliso J. Gondwe; Jordan P. Goodrich; Pia Gottschalk; Scott L. Graham; Martin Heimann; Manuel Helbig; Carole Helfter; Kyle S. Hemes; Takashi Hirano; David Hollinger; Lukas Hörtnagl; Hiroki Iwata; Adrien Jacotot; Joachim Jansen; Gerald Jurasinski; Minseok Kang; Kuno Kasak; John King; Janina Klatt; Franziska Koebsch; Ken W. Krauss; Derrick Y. F. Lai; Ivan Mammarella; Giovanni Manca; Luca Belelli Marchesini; Jaclyn Hatala Matthes; Trofim Maximon; Lutz Merbold; Bhaskar Mitra; Timothy H. Morin; Eiko Nemitz; Mats B. Nilsson; Shuli Niu; Walter C. Oechel; Patricia Y. Oikawa; Keisuke Ono; Matthias Peichl; Olli Peltola; Michele L. Reba; Andrew D. Richardson; William Riley; Benjamin R. K. Runkle; Youngryel Ryu; Torsten Sachs; Ayaka Sakabe; Camilo Rey Sanchez; Edward A. Schuur; Karina V. R. Schäfer; Oliver Sonnentag; Jed P. Sparks; Ellen Stuart-Haëntjens; Cove Sturtevant; Ryan C. Sullivan; Daphne J. Szutu; Jonathan E. Thom; Margaret S. Torn; Eeva-Stiina Tuittila; Jessica Turner; Masahito Ueyama; Alex C. Valach; Rodrigo Vargas; Andrej Varlagin; Alma Vazquez-Lule; Joseph G. Verfaillie; Timo Vesala; George L. Vourlitis; Eric J. Ward; Christian Wille; Georg Wohlfahrt; Guan Xhuan Wong; Zhen Zhang; Donatella Zona; Lisamarie Windham-Myers; Benjamin Poulter; Robert B. Jackson. FLUXNET-CH4: A global, multi-ecosystem dataset and analysis of methane seasonality from freshwater wetlands. 2021, 2021, 1 -111.

AMA Style

Kyle B. Delwiche, Sara Helen Knox, Avni Malhotra, Etienne Fluet-Chouinard, Gavin McNicol, Sarah Feron, Zutao Ouyang, Dario Papale, Carlo Trotta, Eleonora Canfora, You-Wei Cheah, Danielle Christianson, M. Carmelita R. Alberto, Pavel Alekseychik, Mika Aurela, Dennis Baldocchi, Sheel Bansal, David P. Billesbach, Gil Bohrer, Rosvel Bracho, Nina Buchmann, David I. Campbell, Gerardo Celis, Jiquan Chen, Weinan Chen, Housen Chu, Higo J. Dalmagro, Sigrid Dengel, Ankur R. Desai, Matteo Detto, Han Dolman, Elke Eichelmann, Eugenie Euskirchen, Daniela Famulari, Thomas Friborg, Kathrin Fuchs, Mathias Goeckede, Sébastien Gogo, Mangaliso J. Gondwe, Jordan P. Goodrich, Pia Gottschalk, Scott L. Graham, Martin Heimann, Manuel Helbig, Carole Helfter, Kyle S. Hemes, Takashi Hirano, David Hollinger, Lukas Hörtnagl, Hiroki Iwata, Adrien Jacotot, Joachim Jansen, Gerald Jurasinski, Minseok Kang, Kuno Kasak, John King, Janina Klatt, Franziska Koebsch, Ken W. Krauss, Derrick Y. F. Lai, Ivan Mammarella, Giovanni Manca, Luca Belelli Marchesini, Jaclyn Hatala Matthes, Trofim Maximon, Lutz Merbold, Bhaskar Mitra, Timothy H. Morin, Eiko Nemitz, Mats B. Nilsson, Shuli Niu, Walter C. Oechel, Patricia Y. Oikawa, Keisuke Ono, Matthias Peichl, Olli Peltola, Michele L. Reba, Andrew D. Richardson, William Riley, Benjamin R. K. Runkle, Youngryel Ryu, Torsten Sachs, Ayaka Sakabe, Camilo Rey Sanchez, Edward A. Schuur, Karina V. R. Schäfer, Oliver Sonnentag, Jed P. Sparks, Ellen Stuart-Haëntjens, Cove Sturtevant, Ryan C. Sullivan, Daphne J. Szutu, Jonathan E. Thom, Margaret S. Torn, Eeva-Stiina Tuittila, Jessica Turner, Masahito Ueyama, Alex C. Valach, Rodrigo Vargas, Andrej Varlagin, Alma Vazquez-Lule, Joseph G. Verfaillie, Timo Vesala, George L. Vourlitis, Eric J. Ward, Christian Wille, Georg Wohlfahrt, Guan Xhuan Wong, Zhen Zhang, Donatella Zona, Lisamarie Windham-Myers, Benjamin Poulter, Robert B. Jackson. FLUXNET-CH4: A global, multi-ecosystem dataset and analysis of methane seasonality from freshwater wetlands. . 2021; 2021 ():1-111.

Chicago/Turabian Style

Kyle B. Delwiche; Sara Helen Knox; Avni Malhotra; Etienne Fluet-Chouinard; Gavin McNicol; Sarah Feron; Zutao Ouyang; Dario Papale; Carlo Trotta; Eleonora Canfora; You-Wei Cheah; Danielle Christianson; M. Carmelita R. Alberto; Pavel Alekseychik; Mika Aurela; Dennis Baldocchi; Sheel Bansal; David P. Billesbach; Gil Bohrer; Rosvel Bracho; Nina Buchmann; David I. Campbell; Gerardo Celis; Jiquan Chen; Weinan Chen; Housen Chu; Higo J. Dalmagro; Sigrid Dengel; Ankur R. Desai; Matteo Detto; Han Dolman; Elke Eichelmann; Eugenie Euskirchen; Daniela Famulari; Thomas Friborg; Kathrin Fuchs; Mathias Goeckede; Sébastien Gogo; Mangaliso J. Gondwe; Jordan P. Goodrich; Pia Gottschalk; Scott L. Graham; Martin Heimann; Manuel Helbig; Carole Helfter; Kyle S. Hemes; Takashi Hirano; David Hollinger; Lukas Hörtnagl; Hiroki Iwata; Adrien Jacotot; Joachim Jansen; Gerald Jurasinski; Minseok Kang; Kuno Kasak; John King; Janina Klatt; Franziska Koebsch; Ken W. Krauss; Derrick Y. F. Lai; Ivan Mammarella; Giovanni Manca; Luca Belelli Marchesini; Jaclyn Hatala Matthes; Trofim Maximon; Lutz Merbold; Bhaskar Mitra; Timothy H. Morin; Eiko Nemitz; Mats B. Nilsson; Shuli Niu; Walter C. Oechel; Patricia Y. Oikawa; Keisuke Ono; Matthias Peichl; Olli Peltola; Michele L. Reba; Andrew D. Richardson; William Riley; Benjamin R. K. Runkle; Youngryel Ryu; Torsten Sachs; Ayaka Sakabe; Camilo Rey Sanchez; Edward A. Schuur; Karina V. R. Schäfer; Oliver Sonnentag; Jed P. Sparks; Ellen Stuart-Haëntjens; Cove Sturtevant; Ryan C. Sullivan; Daphne J. Szutu; Jonathan E. Thom; Margaret S. Torn; Eeva-Stiina Tuittila; Jessica Turner; Masahito Ueyama; Alex C. Valach; Rodrigo Vargas; Andrej Varlagin; Alma Vazquez-Lule; Joseph G. Verfaillie; Timo Vesala; George L. Vourlitis; Eric J. Ward; Christian Wille; Georg Wohlfahrt; Guan Xhuan Wong; Zhen Zhang; Donatella Zona; Lisamarie Windham-Myers; Benjamin Poulter; Robert B. Jackson. 2021. "FLUXNET-CH4: A global, multi-ecosystem dataset and analysis of methane seasonality from freshwater wetlands." 2021, no. : 1-111.

Journal article
Published: 05 January 2021 in Pedosphere
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Effects of earthworm casts on soil nutrient dynamics and their responses to changing moisture availability in subtropical ecosystems remain poorly understood. This study aimed to examine short-term carbon (C) and nitrogen (N) dynamics and their interactions with wetting-drying cycles in three different structural forms (i.e., granular, globular, and heap-like) of Amynthas earthworm casts. The rates of C and N mineralization in the earthworm casts were examined under two different wetting-drying cycles (i.e., 2-d and 4-d wetting intervals) using a rainfall simulation experiment. After three simulated rainfall events, subsamples of the earthworm casts were further incubated for 4 d for the determination of CO2 and N2O fluxes. The results of this study indicated that the impacts of wetting-drying cycles on the short-term C and N dynamics were highly variable among the three cast forms, but wetting-drying cycles significantly reduced the cumulative CO2 and N2O fluxes by 62%–83% and 57%–85%, respectively, when compared to the control without being subjected to any rainfall events. The C mineralization rates in different cast forms were affected by the amount of organic substrates and N content in casts, which were associated with the food preference and selection of earthworms. Meanwhile, the cumulative N2O fluxes did not differ among the three cast forms. Repeated wetting and drying of casts not only enhanced aggregate stability by promoting bonds between the cast particles, but also inhibited microbial survival and growth during the prolonged drying period, which together hindered decomposition and denitrification. Our findings demonstrated that the interactions between the structural forms, aggregate dynamics, and C and N cycling in the earthworm casts were highly complex.

ACS Style

Michelle Man Suet Law; Derrick Yuk Fo Lai. Impacts of wetting-drying cycles on short-term carbon and nitrogen dynamics in Amynthas earthworm casts. Pedosphere 2021, 31, 423 -432.

AMA Style

Michelle Man Suet Law, Derrick Yuk Fo Lai. Impacts of wetting-drying cycles on short-term carbon and nitrogen dynamics in Amynthas earthworm casts. Pedosphere. 2021; 31 (3):423-432.

Chicago/Turabian Style

Michelle Man Suet Law; Derrick Yuk Fo Lai. 2021. "Impacts of wetting-drying cycles on short-term carbon and nitrogen dynamics in Amynthas earthworm casts." Pedosphere 31, no. 3: 423-432.

Journal article
Published: 04 October 2020 in Global Change Biology
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ACS Style

Zhi‐Yun Jiang; Zhong‐Min Hu; Derrick Y. F. Lai; Dao‐Rui Han; Mei Wang; Min Liu; Meng Zhang; Ming‐Yan Guo. Light grazing facilitates carbon accumulation in subsoil in Chinese grasslands: A meta‐analysis. Global Change Biology 2020, 26, 7186 -7197.

AMA Style

Zhi‐Yun Jiang, Zhong‐Min Hu, Derrick Y. F. Lai, Dao‐Rui Han, Mei Wang, Min Liu, Meng Zhang, Ming‐Yan Guo. Light grazing facilitates carbon accumulation in subsoil in Chinese grasslands: A meta‐analysis. Global Change Biology. 2020; 26 (12):7186-7197.

Chicago/Turabian Style

Zhi‐Yun Jiang; Zhong‐Min Hu; Derrick Y. F. Lai; Dao‐Rui Han; Mei Wang; Min Liu; Meng Zhang; Ming‐Yan Guo. 2020. "Light grazing facilitates carbon accumulation in subsoil in Chinese grasslands: A meta‐analysis." Global Change Biology 26, no. 12: 7186-7197.

Journal article
Published: 07 September 2020 in Journal of Geophysical Research: Biogeosciences
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While aquaculture ponds are potentially important sources of atmospheric N2O, the magnitude and variability of N2O concentrations and fluxes both within and across the ponds remain poorly understood. In this study, we examined the small‐scale spatial variations of dissolved N2O concentrations in water and N2O fluxes across the water‐air interface from three mariculture ponds in a subtropical estuary in southeast China. Our results showed that the dissolved concentrations and diffusive fluxes of N2O in the shrimp ponds ranged between 2.3‐19.2 nM and 16.4‐589.7 nmol m‐2 h‐1, respectively, over the culture period. Significant variations of N2O concentrations and fluxes were observed within the ponds, with higher values being observed in the aeration area that could be attributed to the high rates of nitrification in the water column, as well as sediment N2O production and diffusive flux into the overlying water. Also, N2O concentrations and fluxes varied significantly among the three ponds as a result of the difference in N‐NO3‐ and N‐NH4+ concentrations in the water column. The large fine‐scale spatial variations of N2O concentrations and fluxes observed in our aquaculture ponds suggested that management practices such as aeration and bait feeding could greatly affect the extent that aquaculture activities have on N2O emissions and climate change through their influence on the physico‐chemical environment (e.g. oxygen and N‐NH4+ concentrations) of the ponds.

ACS Style

Ping Yang; Dongqi Wang; Derrick Y. F. Lai; Yifei Zhang; Qianqian Guo; Lishan Tan; Hong Yang; Chuan Tong; Xiaofei Li. Spatial Variations of N 2 O Fluxes Across the Water‐Air Interface of Mariculture Ponds in a Subtropical Estuary in Southeast China. Journal of Geophysical Research: Biogeosciences 2020, 125, 1 .

AMA Style

Ping Yang, Dongqi Wang, Derrick Y. F. Lai, Yifei Zhang, Qianqian Guo, Lishan Tan, Hong Yang, Chuan Tong, Xiaofei Li. Spatial Variations of N 2 O Fluxes Across the Water‐Air Interface of Mariculture Ponds in a Subtropical Estuary in Southeast China. Journal of Geophysical Research: Biogeosciences. 2020; 125 (9):1.

Chicago/Turabian Style

Ping Yang; Dongqi Wang; Derrick Y. F. Lai; Yifei Zhang; Qianqian Guo; Lishan Tan; Hong Yang; Chuan Tong; Xiaofei Li. 2020. "Spatial Variations of N 2 O Fluxes Across the Water‐Air Interface of Mariculture Ponds in a Subtropical Estuary in Southeast China." Journal of Geophysical Research: Biogeosciences 125, no. 9: 1.

Journal article
Published: 13 July 2020 in Water Research
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Aquaculture ponds are hotspots of carbon cycling and important anthropogenic sources of the potent greenhouse gas methane (CH4). Despite the importance of CH4 ebullition in aquatic ecosystems, its magnitude and spatiotemporal variations in aquaculture ponds remain poorly understood. In this study, we determined the rates and spatiotemporal variations of ebullitive CH4 emissions from three mariculture ponds during the aquaculture period of two years at a subtropical estuary in southeast China. Our results showed that the mean ebullitive CH4 flux from the studied ponds was 14.9 mg CH4 m−2 h−1 during the aquaculture period and accounted for over 90% of the total CH4 emission, indicating the importance of ebullition as a major CH4 transport mechanism. Ebullitive CH4 emission demonstrated a clear seasonal pattern, with a peak value during the middle stage of aquaculture. Sediment temperature was found to be an important factor influencing the seasonal variations in CH4 ebullition. Ebullitive CH4 fluxes also exhibited considerable spatial variations within the ponds, with 49.7–71.8% of the whole pond CH4 ebullition being detected in the feeding zone where the large loading of sediment organic matter fueled CH4 production. Aquaculture ponds have much higher ebullitive CH4 effluxes than other aquatic ecosystems, which indicated the urgency to mitigate CH4 emission from aquaculture activities. Our findings highlighted that the importance of considering the large spatiotemporal variations in ebullitive CH4 flux in improving the accuracy of large-scale estimation of CH4 fluxes in aquatic ecosystems. Future studies should be conducted to characterize CH4 ebullitive fluxes over a greater number and diversity of aquaculture ponds and examine the mechanisms controlling CH4 ebullition in aquatic ecosystems.

ACS Style

Ping Yang; Yifei Zhang; Hong Yang; Qianqian Guo; Derrick Y.F. Lai; Guanghui Zhao; Ling Li; Chuan Tong. Ebullition was a major pathway of methane emissions from the aquaculture ponds in southeast China. Water Research 2020, 184, 116176 .

AMA Style

Ping Yang, Yifei Zhang, Hong Yang, Qianqian Guo, Derrick Y.F. Lai, Guanghui Zhao, Ling Li, Chuan Tong. Ebullition was a major pathway of methane emissions from the aquaculture ponds in southeast China. Water Research. 2020; 184 ():116176.

Chicago/Turabian Style

Ping Yang; Yifei Zhang; Hong Yang; Qianqian Guo; Derrick Y.F. Lai; Guanghui Zhao; Ling Li; Chuan Tong. 2020. "Ebullition was a major pathway of methane emissions from the aquaculture ponds in southeast China." Water Research 184, no. : 116176.

Journal article
Published: 28 June 2020 in Water
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Changes in land use types can alter the soil and environmental characteristics of wetlands, which in turn influence the magnitude of greenhouse gas production by soil microbes. However, the effects of land use change on the production potential of methane (CH4) and carbon dioxide (CO2) in subtropical wetland soils and the underlying controls are still largely unknown. In this study, we examined the soil CH4 and CO2 production potentials under five different land use types (natural mangrove, Gei Wai water channel, Gei Wai forest, reedbed, and freshwater pond) and their relationships with soil physico-chemical properties in a subtropical wetland in Hong Kong using aerobic and anaerobic laboratory incubation experiments. Our results showed an overall decreasing trend of CH4 and CO2 production potentials down the soil profile at all sites, which could be attributed to a reduction in the concentrations of soil organic matter (SOM), total Kjeldahl nitrogen (TKN) and ammonium nitrogen (NH4+-N). Moreover, the soil CH4 and CO2 production potentials varied significantly in the surface soils among land use types, but were more similar across the sites in the deeper soils. The conversion of natural mangrove to other land use types significantly reduced both the aerobic and anaerobic CO2 production potentials in the top 10 cm soils, except for Gei Wai forest, which demonstrated significantly higher CO2 production rates (61.15–97.91 µg g−1 day−1). Meanwhile, the mean CH4 production potential in the surface soils of natural mangrove (0.05 µg g−1 d−1) was significantly lower than that in the Gei Wai forest and Gei Wai channel (0.26–0.27 µg g−1 day−1) but slightly higher than that in the freshwater pond and reedbed (0.00–0.02 µg g−1 day−1). The high soil CH4 and CO2 production potentials observed in the Gei Wai forest could be explained by the high soil concentrations of SOM, TKN and NH4+-N. On the other hand, the lower anaerobic CH4 and aerobic CO2 productions observed in the reedbed could be attributed to the lower concentrations of NH4+-N and available phosphorus. Our findings highlighted the significant impacts of land use types on the CH4 and CO2 production potentials of subtropical wetland soils, which had practical implications for wetland management for climate change mitigation.

ACS Style

Jiaxing Xu; Derrick Y. F. Lai; Suvadip Neogi. Effects of Land Use Types on CH4 and CO2 Production Potentials in Subtropical Wetland Soils. Water 2020, 12, 1856 .

AMA Style

Jiaxing Xu, Derrick Y. F. Lai, Suvadip Neogi. Effects of Land Use Types on CH4 and CO2 Production Potentials in Subtropical Wetland Soils. Water. 2020; 12 (7):1856.

Chicago/Turabian Style

Jiaxing Xu; Derrick Y. F. Lai; Suvadip Neogi. 2020. "Effects of Land Use Types on CH4 and CO2 Production Potentials in Subtropical Wetland Soils." Water 12, no. 7: 1856.

Primary research article
Published: 23 June 2020 in Global Change Biology
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The role of coastal mangrove wetlands in sequestering atmospheric carbon dioxide (CO2) and mitigating climate change has received increasing attention in recent years. While recent studies have shown that methane (CH4) emissions can potentially offset the carbon burial rates in low‐salinity coastal wetlands, there is hitherto a paucity of direct and year‐round measurements of ecosystem‐scale CH4 flux (FCH4) from mangrove ecosystems. In this study, we examined the temporal variations and biophysical drivers of ecosystem‐scale FCH4 in a subtropical estuarine mangrove wetland based on 3 years of eddy covariance measurements. Our results showed that daily mangrove FCH4 reached a peak of over 0.1 g CH4‐C m−2 day−1 during the summertime owing to a combination of high temperature and low salinity, while the wintertime FCH4 was negligible. In this mangrove, the mean annual CH4 emission was 11.7 ± 0.4 g CH4‐C m–2 year−1 while the annual net ecosystem CO2 exchange ranged between −891 and −690 g CO2‐C m−2 year−1, indicating a net cooling effect on climate over decadal to centurial timescales. Meanwhile, we showed that mangrove FCH4 could offset the negative radiative forcing caused by CO2 uptake by 52% and 24% over a time horizon of 20 and 100 years, respectively, based on the corresponding sustained‐flux global warming potentials. Moreover, we found that 87% and 69% of the total variance of daily FCH4 could be explained by the random forest machine learning algorithm and traditional linear regression model, respectively, with soil temperature and salinity being the most dominant controls. This study was the first of its kind to characterize ecosystem‐scale FCH4 in a mangrove wetland with long‐term eddy covariance measurements. Our findings implied that future environmental changes such as climate warming and increasing river discharge might increase CH4 emissions and hence reduce the net radiative cooling effect of estuarine mangrove forests.

ACS Style

Jiangong Liu; Yulun Zhou; Alex Valach; Robert Shortt; Kuno Kasak; Camilo Rey‐Sanchez; Kyle S. Hemes; Dennis Baldocchi; Derrick Y. F. Lai. Methane emissions reduce the radiative cooling effect of a subtropical estuarine mangrove wetland by half. Global Change Biology 2020, 26, 4998 -5016.

AMA Style

Jiangong Liu, Yulun Zhou, Alex Valach, Robert Shortt, Kuno Kasak, Camilo Rey‐Sanchez, Kyle S. Hemes, Dennis Baldocchi, Derrick Y. F. Lai. Methane emissions reduce the radiative cooling effect of a subtropical estuarine mangrove wetland by half. Global Change Biology. 2020; 26 (9):4998-5016.

Chicago/Turabian Style

Jiangong Liu; Yulun Zhou; Alex Valach; Robert Shortt; Kuno Kasak; Camilo Rey‐Sanchez; Kyle S. Hemes; Dennis Baldocchi; Derrick Y. F. Lai. 2020. "Methane emissions reduce the radiative cooling effect of a subtropical estuarine mangrove wetland by half." Global Change Biology 26, no. 9: 4998-5016.

Journal article
Published: 01 December 2019 in Ecological Indicators
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ACS Style

Weifang Hu; Wenlong Zhang; Linhai Zhang; Xianbiao Lin; Chuan Tong; Derrick Y.F. Lai; Yuehmin Chen; Congsheng Zeng. Short-term changes in simulated inundation frequency differentially affect inorganic nitrogen, nitrification, and denitrification in estuarine marshes. Ecological Indicators 2019, 107, 1 .

AMA Style

Weifang Hu, Wenlong Zhang, Linhai Zhang, Xianbiao Lin, Chuan Tong, Derrick Y.F. Lai, Yuehmin Chen, Congsheng Zeng. Short-term changes in simulated inundation frequency differentially affect inorganic nitrogen, nitrification, and denitrification in estuarine marshes. Ecological Indicators. 2019; 107 ():1.

Chicago/Turabian Style

Weifang Hu; Wenlong Zhang; Linhai Zhang; Xianbiao Lin; Chuan Tong; Derrick Y.F. Lai; Yuehmin Chen; Congsheng Zeng. 2019. "Short-term changes in simulated inundation frequency differentially affect inorganic nitrogen, nitrification, and denitrification in estuarine marshes." Ecological Indicators 107, no. : 1.

Journal article
Published: 01 November 2019 in Agricultural and Forest Meteorology
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ACS Style

Jiangong Liu; Derrick Y.F. Lai. Subtropical mangrove wetland is a stronger carbon dioxide sink in the dry than wet seasons. Agricultural and Forest Meteorology 2019, 278, 1 .

AMA Style

Jiangong Liu, Derrick Y.F. Lai. Subtropical mangrove wetland is a stronger carbon dioxide sink in the dry than wet seasons. Agricultural and Forest Meteorology. 2019; 278 ():1.

Chicago/Turabian Style

Jiangong Liu; Derrick Y.F. Lai. 2019. "Subtropical mangrove wetland is a stronger carbon dioxide sink in the dry than wet seasons." Agricultural and Forest Meteorology 278, no. : 1.

Research article
Published: 10 July 2019 in Journal of Geophysical Research: Biogeosciences
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Soils exert considerable influence on the global biogeochemical cycles, but their role in the abiotic production of volatile compounds remains poorly understood. In this study, we demonstrated evidence for the abiotic production of three major greenhouse gases (GHGs), i.e. carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O), simultaneously in six different subtropical surface soils under thermal treatment at 30 to 90°C, wetting, and the addition of hydrogen peroxide. This study identified soils as a novel source of N2O through abiotic processes such as thermal treatment and the oxidation of reactive oxygen species. Our results showed that the abiotic production rate of all three GHGs increased exponentially with temperature, while that of CO2 and CH4 increased linearly with hydrogen peroxide concentrations. Wetting of soil samples could further enhance the rate of abiotic CO2 and N2O production in soils. These findings highlight the potential contribution of abiotic processes in the production of GHGs in subtropical soils and help constrain the uncertainties of the global GHG budgets.

ACS Style

Jiangong Liu; Simon Christoph Hartmann; Frank Keppler; Derrick Y.F. Lai. Simultaneous Abiotic Production of Greenhouse Gases (CO 2 , CH 4 , and N 2 O) in Subtropical Soils. Journal of Geophysical Research: Biogeosciences 2019, 124, 1977 -1987.

AMA Style

Jiangong Liu, Simon Christoph Hartmann, Frank Keppler, Derrick Y.F. Lai. Simultaneous Abiotic Production of Greenhouse Gases (CO 2 , CH 4 , and N 2 O) in Subtropical Soils. Journal of Geophysical Research: Biogeosciences. 2019; 124 (7):1977-1987.

Chicago/Turabian Style

Jiangong Liu; Simon Christoph Hartmann; Frank Keppler; Derrick Y.F. Lai. 2019. "Simultaneous Abiotic Production of Greenhouse Gases (CO 2 , CH 4 , and N 2 O) in Subtropical Soils." Journal of Geophysical Research: Biogeosciences 124, no. 7: 1977-1987.

Journal article
Published: 17 June 2019 in Journal of Geophysical Research: Biogeosciences
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Aquaculture ponds are potentially large sources of atmospheric methane (CH4) that can exacerbate climate change. A thorough understanding of various CH4 biogeochemical processes occurring in the ponds is essential for the prediction and management of CH4 emissions arising from aquaculture. However, the variations in pond CH4 biogeochemical processes among estuaries and aquaculture stages remain poorly understood. In this study, we assessed the net sediment release, oxidation, and dissolved concentrations of CH4 in aquaculture ponds in two subtropical estuaries among three shrimp growth stages. Overall, porewater CH4 concentrations and sediment CH4 release rates varied greatly among different stages in the order: middle stage > final stage > initial stage. Water column CH4 concentrations and overlying water CH4 oxidation rates showed an increasing trend over the study period. Sediment CH4 release rates and dissolved CH4 concentrations also varied considerably between the two estuaries. In the more saline Jiulong River Estuary, sediment CH4 release rate was lower while the shrimp survival rate and yield were higher as compared to the Min River Estuary with a lower water salinity. Our results suggest that both high water salinity and feed utilization efficiency can effectively mitigate CH4 emissions from the coastal shrimp ponds. Overall, the large magnitude of net CH4 emissions observed in our shrimp ponds highlights the urgency of formulating appropriate policies and building sustainable institutions that can strike a balance between land‐based aquaculture development and greenhouse gas mitigation in the subtropical coastal regions.

ACS Style

Ping Yang; Derrick Y. F. Lai; Hong Yang; Chuan Tong; Louis Lebel; Jiafang Huang; Jin Xu. Methane Dynamics of Aquaculture Shrimp Ponds in Two Subtropical Estuaries, Southeast China: Dissolved Concentration, Net Sediment Release, and Water Oxidation. Journal of Geophysical Research: Biogeosciences 2019, 124, 1430 -1445.

AMA Style

Ping Yang, Derrick Y. F. Lai, Hong Yang, Chuan Tong, Louis Lebel, Jiafang Huang, Jin Xu. Methane Dynamics of Aquaculture Shrimp Ponds in Two Subtropical Estuaries, Southeast China: Dissolved Concentration, Net Sediment Release, and Water Oxidation. Journal of Geophysical Research: Biogeosciences. 2019; 124 (6):1430-1445.

Chicago/Turabian Style

Ping Yang; Derrick Y. F. Lai; Hong Yang; Chuan Tong; Louis Lebel; Jiafang Huang; Jin Xu. 2019. "Methane Dynamics of Aquaculture Shrimp Ponds in Two Subtropical Estuaries, Southeast China: Dissolved Concentration, Net Sediment Release, and Water Oxidation." Journal of Geophysical Research: Biogeosciences 124, no. 6: 1430-1445.

Research article
Published: 24 May 2019 in Environmental Science and Pollution Research
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Water quality deterioration can adversely affect the long-term sustainability of aquaculture industry. Understanding the processes of nutrient regeneration and uptake is important for improving water quality and the overall ecosystem health of aquaculture system. In spite of the importance of dissolved nutrients (DOC, DIC, N-NOx-, N-NH4+, and P-PO43-) in governing water quality and ecosystem functioning, the spatiotemporal variations in the production and uptake of dissolved nutrients in aquaculture ponds is still poorly understood. In this study, the nutrient production and uptake rates in the overlying water were quantified among different shrimp growth stages in the aquaculture ponds in the Min River Estuary (MRE) and Jiulong River Estuary (JRE), southeast China. Significant differences in the nutrient production and uptake rates in the overlying water were observed among the three growth stages and two estuaries. The temporal variations of DOC and DIC production rates in both estuarine ponds closely followed the seasonal cycle of temperature, while the difference in DOC and DIC production rates between the two estuaries was likely caused by differences in water salinity. The changes in the production and uptake rates of dissolved inorganic nitrogen (N-NOx- and N-NH4+) and P-PO43- in the water column over time were partly related to the interactions between thermal conditions and phytoplankton biomass (e.g., chlorophyll a concentrations) in the ponds. Our results demonstrate the complex dynamics and environmental risk of dissolved nutrients in subtropical shrimp ponds, and call for a more effective management of nutrient-laden wastewater in safeguarding the long-term sustainability of aquaculture production.

ACS Style

Ping Yang; Hong Yang; Derrick Y. F. Lai; Baoshi Jin; Chuan Tong. Production and uptake of dissolved carbon, nitrogen, and phosphorus in overlying water of aquaculture shrimp ponds in subtropical estuaries, China. Environmental Science and Pollution Research 2019, 26, 21565 -21578.

AMA Style

Ping Yang, Hong Yang, Derrick Y. F. Lai, Baoshi Jin, Chuan Tong. Production and uptake of dissolved carbon, nitrogen, and phosphorus in overlying water of aquaculture shrimp ponds in subtropical estuaries, China. Environmental Science and Pollution Research. 2019; 26 (21):21565-21578.

Chicago/Turabian Style

Ping Yang; Hong Yang; Derrick Y. F. Lai; Baoshi Jin; Chuan Tong. 2019. "Production and uptake of dissolved carbon, nitrogen, and phosphorus in overlying water of aquaculture shrimp ponds in subtropical estuaries, China." Environmental Science and Pollution Research 26, no. 21: 21565-21578.

Article
Published: 20 May 2019 in Estuaries and Coasts
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While an increase in saltwater intrusion into historically freshwater environments will undoubtedly affect ecosystem functioning, the resultant impacts on litter decay and hydrolytic enzyme activities remain poorly understood. Here, we examined the decay of shichito matgrass stem litter, the associated loss of total carbon (TC) and total nitrogen (TN), and the activity of litter- and sediment-associated hydrolytic enzymes in two subtropical tidal marshes (one brackish and one freshwater) in southeastern China. Results obtained after 202 days of incubation revealed that there was no significant difference in litter mass loss between the brackish and freshwater marshes during both the standing phase (aerially decomposing litter) and the late phase of sediment-surface decomposition (slow decomposition of relatively refractory materials) (p > 0.05). The loss of TC and TN from litter was most rapid during the first month of the sediment-surface phase, and the loss rates were significantly greater in the brackish marsh (mass loss 61.63%, TC released 50.55%, and TN released 36.40%) than in the freshwater marsh (mass loss 43.28%, TC released 46.31%, and TN released 41.31%). Moreover, we found significantly higher sediment-associated β-glucosidase activities in brackish marsh sediments during the sediment-surface phase, and it correlated significantly with litter mass loss. The enhanced β-glucosidase activities stimulated decomposition in the early sediment-surface phase in brackish marsh sediments; however, a decrease in decomposition caused by salinity and tidal SO42− levels at the last phase ultimately offset the previous difference. Our findings provide insight into the potential consequences of modest saltwater intrusion; these may not alter the rates of litter decomposition, but could change the dominant pathway.

ACS Style

Weifang Hu; Linhai Zhang; Derrick Y. F. Lai; Jintao Gao; Zhigao Sun; Chuan Tong; Yuehmin Chen; Congsheng Zeng. The Difference of Litter Decay, Litter- and Sediment-Associated Hydrolytic Enzymes between Brackish and Freshwater Tidal Marshes. Estuaries and Coasts 2019, 42, 1328 -1341.

AMA Style

Weifang Hu, Linhai Zhang, Derrick Y. F. Lai, Jintao Gao, Zhigao Sun, Chuan Tong, Yuehmin Chen, Congsheng Zeng. The Difference of Litter Decay, Litter- and Sediment-Associated Hydrolytic Enzymes between Brackish and Freshwater Tidal Marshes. Estuaries and Coasts. 2019; 42 (5):1328-1341.

Chicago/Turabian Style

Weifang Hu; Linhai Zhang; Derrick Y. F. Lai; Jintao Gao; Zhigao Sun; Chuan Tong; Yuehmin Chen; Congsheng Zeng. 2019. "The Difference of Litter Decay, Litter- and Sediment-Associated Hydrolytic Enzymes between Brackish and Freshwater Tidal Marshes." Estuaries and Coasts 42, no. 5: 1328-1341.