• Research Professor, Institute for the Study of Earth, Oceans and Space
• Affiliate Research Professor, Natural Resources

Research

As a Research Professor, I was mainly engaged in research-oriented activities including proposal preparation, field investigation and model development for current projects, participating in meetings and conferences, paper preparation, and PostDoc training in 2001-2002.

The projects I was involved in were (1) Quantifying atmospheric impacts of paddy rice agriculture in China (granted by NASA, PI: Li, 1998-2002), (2) Wetland forest carbon biogeochemistry (granted by USDA, Forest Service, PI: Li, 1999-2002), and (3) Modeling trace gas emissions from tropical forests (LBA, PI: Crill, 2001-2003).

My tasks in the projects were (1) utilizing biogeochemical concepts to develop quantitative linkage between field observations and basic physical, chemical and biological reactions, and hence integrate the primary, ecological drivers, environmental factors, and biogeochemical processes into a mathematical framework; (2) utilizing the biogeochemical models to estimate impacts of changes in climate or management on plant productivity, ecosystem C dynamics, and trace gases (CH4, N2O, NO and NH3) emissions from agricultural or forest ecosystems; (3) establishing GIS data bases and linking them to the biogeochemical models to scale up C sequestration and/or trace gas emissions to regional or national scale; and (4) linking remote sensing analysis to biogeochemical models to improve input data acquisition at regional scale.

The major results from the above-mentioned studies were (1) accomplishment of comparison of coupled C and N biogeochemical cycles in cropland between the U.S. and China. Chinese cropland is losing C at a rate of 59 Tg C/yr, which is 5 times higher than the U.S. (loss 6 Tg C/yr). The difference is mainly caused by crop residue management. The severe loss of soil organic C in China has caused decrease in soil N mineralization rates, and hence the Chinese farmers have to use much more chemical fertilizers to compensate the degraded soils (120 kg N/ha in China vs. 60 kg N/ha in the U.S.). The overuse of fertilizers has caused eutrophication, drinking water contamination and other environmental hazards in China. The results have been incorporated in a paper submitted to Ecological Applications; (2) accomplishment of calculations of impacts of water management on methane emissions from paddy rice agriculture in China. Since 1970s, midseason drainage has been applied to gradually replace continuous flooding in most of the rice fields in China. The DNDC model was modified to precisely track impacts of alternative water management on C and N biogeochemical cycles under both aerobic and anaerobic conditions. Supported with GIS databases for entire China, DNDC predicted a reduction of 5 Tg CH4 emitted from the rice paddies in China since 1970s. The reduction is consistent to the globally observed decrease in the atmospheric CH4 increasing rates during the last three decades. The alternative water management in Asia could play an important role in mitigating global CH4 emissions. The results have been incorporated in a paper submitted to Geophysical Research Letter; (3) a forest version of DNDC was developed and modified for predicting forest productivity, water balance, C sequestration, and trace gas emissions in both upland and wetland forest ecosystems. This model has been tested against two sites at a slash pine stand in Florida and a bog in Mercall, Minnesota. The model is ready to move to tropical forest ecosystems.

Selected Publications

Li, C., J. Cui, G. Sun, and C. Trettin. 2003. Modeling Impacts of Management on Carbon Sequestration and Trace Gas Emissions in Forested Wetland Ecosystems. Environmental Management (in press).

Li, C., A. Mosier, R. Wassmann, Z. Cai, X. Zheng, Y. Huang, H. Tsuruta, J. Boonjawat, and R. Lantin, 2004. Modeling Greenhouse Gas Emissions from R ice-B ased P roduction S ystems : Sensitivity and Up scaling. Global Biogeochemical Cycles (in press).

Li, C., Y. Zhuang, S. Frolking, J. Galloway, R. Harriss, B. Moore III, D. Schimel, and X. Wang, 2003. Modeling soil organic carbon change in croplands of China. Ecological Applications 13(2)327-336.

Li, C., J Qiu, S. Frolking, X. Xiao, W. Salas, B. Moore III, S. Boles, Y. Huang, and R. Sass, 2002. Reduced methane emissions from large-scale changes in water management in China's rice paddies during 1980-2000, Geophysical Research Letters , 29(20), doi:10.1029/2002GL015370, 2002.

Li, C. 2001. Biogeochemical concepts and methodologies: Development of the DNDC model. Quaternary Sciences 21:89-99.

Li, C., 2000, Modeling trace gas emissions from agricultural ecosystems, Nutrient Cycling in Agroecosystems 58:259-276.

Li, C., Aber, J., Stange, F., Butterbach-Bahl, K., Papen, H., 2000, A process-oriented model of N2O and NO emissions from forest soils: 1, Model development, J. Geophys. Res. Vol. 105, No. 4, p. 4369-4384.

Li, C., S. Frolking, G.J. Croker, P.R. Grace, J. Klir, M. Korchens, and P.R. Poulton, 1997, Simulating trends in soil organic carbon in long-term experiments using the DNDC model, Geoderma 81:45-60.

Li, C., V. Narayanan, and R. Harriss, 1996, Model estimates of nitrous oxide emissions from agricultural lands in the United States, Global Biogeochemical Cycles 10:297-306.

Li, C., S. Frolking, and R.C. Harriss, 1994, Modeling carbon biogeochemistry in agricultural soils. Global Biogeochemical Cycles 8:237-254.

Education

Selected Service Activities

1. Conducted biogeochemical studies focusing on human-involved ecosystems since 1968. These studies have enhanced scientific understanding of impacts of trace elements on human health, urban pollution control, forest conservation, greenhouse gas emissions, and agricultural sustainability. The studies on the endemic cardiovascular disease (Keshan Disease, caused by selenium deficiency in soils), and on pollution control in Beijing were each awarded the National First Class Prize in China in 1977.
2. Distributed basic knowledge of biogeochemistry to students and the public through teaching undergraduate and graduate students, writing for textbooks, presenting lectures, and publishing papers.
3. Served government agencies - the National Environmental Protection Agency of China (1988-89) and the US EPA (1989-92)- working on scientific aspects of policies related to natural resource conservation, pollution control, and global climate change.
4. Established strong, collaborative, academic ties between the environmental research communities in China, the U.S., Germany, the U.K., Canada, Australia, and other countries through various projects.