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Soil Nutrient Cycling and Control Mechanisms

Research Accomplishments and Their Significance

Soil is a key resource for food and fiber production and other ecosystem services. Properly maintaining and enhancing the sustainability of soil functions has been given the highest priority in our national agenda. In order to address this need, our Center has focused on the key research area of soil nutrient cycling and control mechanisms. In this report, we highlight some of our research findings in two crucial areas: (1) biogeochemical cycling and underlying mechanisms for soil carbon and nitrogen; and (2) transformation processes of soil organic matter and their physico-chemical and biological mechanisms.

       We have set our research agenda for the first focal area based on the fundamental understanding that biogeochemical cycles of soil carbon and nitrogen form the scientific basis for optimally managing terrestrial ecosystems for regional sustainable development in a rapidly changing global environment. Specific research questions in the first focal area include (a) What are the key mechanisms responsible for soil carbon and nitrogen retention and storage? (b) What mechanisms significantly control and influence soil N dynamics and N use efficiency? (c) How important are soil biological interactions in regulating C-N cycling? and (d) What are the ecological stoichiometric mechanisms in C-N cycling processes?

Our second focal area of research stems from the understanding that soil organic matter (SOM) controls and influences physical, chemical and biological properties of most soils. Thus it also to a large extent determines the overall function of soil systems. However, which key microbiological mechanisms are responsible for SOM transformation remain largely unknown, even though soil microorganisms are generally believed to largely control SOM degradation and accumulation. The lack of understanding regarding the fate and transformation of microbial residues and metabolites constitutes a major gap in our knowledge of these processes.

Soil organic matter represents the largest dynamic carbon pool, the size of which is greater than that of vegetation and atmosphere combined. The presence of soil organic matter directly influences soil physical and chemical properties, and indirectly influences the microbial activities through control of below-ground nutrients. Therefore, under a scenario of global climate change and land degradation, the study of soil carbon and nitrogen has become a major focus of international research. A key objective in carbon management research is to enhance the natural capacity of soils to sequester carbon, and substantial gains in improving the sequestration potential of terrestrial ecosystems will require major scientific advances in understanding the fundamental biological processes that control the initial addition, ultimate chemical forms, and subsequent carbon transfer and turnover in soils. To this end, the role and functions of microorganisms associated with soil organic matter (carbon and nitrogen) turnover is the most important frontier issue for global research.

We will address three key research issues in this second focal area: (a) Developing new approaches for tracking soil microbial residues and metabolites through time; (b) The role of newly produced microbial residues from plant litter and other added substrates in regulating SOM storage; and (c) Soil microbial metabolism and residue production in response to external additions of nitrogen sources. A thorough understanding of carbon transformation and sequestration driven by microbial communities cannot be obtained by analysis of bulk microbial biomass alone, since incorporation of microbial biomass carbon into soil organic carbon does not significantly increase the total carbon in the soil. Alternatively, microbial residues can be a significant component of soil organic matter and can serve as biologically relevant ecosystem properties. However, measurement of total microbial residues is difficult since reliable differentiation between the carbon bound in microbial residues and soil extant organic carbon is still lacking to date. It is well recognized that biomarker molecules can be used to trace the microbial origin of soil organic carbon and assess the mechanism of soil organic matter dynamics. We believe that effective management can only be obtained when we have a thorough understanding of the underlying microbial controls on soil carbon and nitrogen turnover.

Research Team

       The Center for Agricultural and Soil Ecology consists of 12 research groups  ¾ Soil Ecology, Soil Chemistry, Applied Soil Chemistry and Ecology, Plant Nutrition and Fertilizers, Nutrient Cycles, Biogeochemistry, Ecological Stoichiometry, Rhizosphere Ecology, Agricultural Water Conservation, and Ecological Engineering for Agriculture. The Center has 15 senior scientists (full professors), 18 associated scientists, 18 assistant scientists, and 5 assistant researchers. Among the 15 senior scientists, six are research leaders in the Center (Drs. X. Han, W. Cheng, X. Zhang, Z. Wu, E. Bai and C. Liang), who have held nationally influential positions such as the Chief Scientist for a National “973” Project, two nationally endowed “1000 Plan” Scientists, two CAS-endowed “100 Plan” Scientists, and a Chief Scientist for the “863” Agricultural Project. A detailed biography of each leader is provided in the appendix. A brief summary is provided as follows.

Han Xingguo, born in 1959, senior scientist, PhD. Professor Han is an expert in ecosystem ecology. His research interests encompass biogeochemical cycling, supporting mechanisms for net primary production, and biodiversity-function relationships in terrestrial ecosystems. His pioneering work has demonstrated that functional compensatory relationships between different species and functional groups play a major role in maintaining and enhancing ecosystem stability, and that nutrient stoichiometric homeostasis is a key mechanism for maintaining the structure, function and stability of terrestrial ecosystems across large spatial and temporal scales. He has successfully led a National “973” Project entitled “Scientific basis for understanding and sustainably managing Northern grasslands and agro-pastoral transition zones” and a Creative Research Group Project supported by the Chinese Natural Science Foundation. He is the Director of the Institute of Applied Ecology, Chinese Academy of Sciences, and the Director of the State Key Laboratory of Forest and Soil Ecology. He holds or has held the following academic positions: president of Chinese Society of Botany; vice president of Chinese Ecological Society; editor-in-chief of Ecological Processes and Journal of Integrative Plant Biology; associate editor of Plant and Soil, Journal of Plant Biology, Ecological Research, and other research journals. He participated in “Establishment, observation and demonstration of Chinese Ecosystem Research Network (CERN)”, for which he received the 1st class National Scientific and Technological Progress award in 2012. He has published more than 140 scientific research articles in journals such as Nature, Science, Ecology Letters, Global Change Biology and Ecology. His articles have been cited more than 2500 times.

Cheng Weixin, senior scientist. Cheng’s research interests include soil ecology (C and N biogeochemistry and rhizosphere processes), agricultural ecology, and global environmental change. He holds or has held the following academic positions: Secretary-general of the International Society of Soil Ecology; president of the Ecological Society of America Asia Branch; a review committee member of the National Science Foundation of the United States of America ecological system project; Nationally endowed “1000 Plan” Scientist ; Associate Editor of the Journal of Integrative Plant Biology, Journal of Plant Ecology, Journal of Soils and Sediments, Plant and Soil, Ecological Processes, and other research journals. He is widely known for his contributions for advancing the understanding of the rhizosphere priming effect and his innovative isotope approaches. He has published more than 80 scientific research articles.

Zhang Xudong, born in 1957, senior scientist. He is the Director of the Shenyang Agricultural Ecosystem Research Station. He holds or has held the following academic positions: vice president of the Chinese Society of Soil Sciences; president of the Liaoning Society of Soil Sciences; vice chairman of the Scientific Committee of the Institute of Applied Ecology, Chinese Academy of Sciences (CAS); CAS-endowed “100 Plan” Scientist; Associate Editor of Ecotoxicology, and Ecological Processes. His research interests include the processes, mechanisms and regulation of soil C and N transformations driven by microbiological processes. His pioneering work has demonstrated the regulatory mechanisms through which carbon plays a major role in the microbial process of nitrogen cycles. He has defined a concept of transitional nitrogen pools in the soil and developed a set of new methods to distinguish between microbial residues from exogenous substrate and natural components of soils. He has published more than 200 scientific research articles, and his work won the Scientific and Technological Progress Award from the Ministry of Agriculture, the Liaoning Province Science and Technology Progress Award, and the National Scientific and Technological Progress Award from the Ministry of Science and Technology.

Wu Zhijie, born in 1962, senior scientist. He is Director of the Center for Agriculture in the Institute of Applied Ecology. He holds or has held the following academic positions: Chief Scientist for the “863” Agricultural Project; vice chairman of the Academic Committee of China Fertilizer and Soil Conditioner Standardization; vice Director of the Liaoning Province Fertilizer Registration Review Committee; associate chief editor of the Chinese Journal of Ecology; and president of the Technology Innovation Strategy Alliance of Stable Fertilizers. His research interests include slow-release and stable fertilizers. His pioneering work has resulted in the development of efficient and greener inhibitors of urease and nitrification. His findings helped reduce N losses to the environment in the application of inorganic fertilizers. He has developed a series of long-lasting urea products, slow-release urea and compound fertilizers. He has received the National Scientific and Technological Progress Award from the Ministry of Science and Technology, and the Liaoning Province Science and Technology Progress Award. His team has applied for 64 national invention patents, of which 19 have been authorized. He has successfully guided the development of China's first stable fertilizer industry standards. He has published a book entitled “The principles and applications of slow-release fertilizer” as well as 46 scientific research articles.

Bai Edith, senior scientist. She became a CAS-endowed “100 Plan” Scientist in 2010. She obtained her B.S. degree in Environmental Sciences in 2000 from Nankai University, China, and her Ph.D. degree in the Department of Ecosystem Science in 2007 from Texas A&M University, USA. She has been a postdoctoral research fellow at Texas A&M University and the University of California, Davis. Her research interests include forest ecosystem biogeochemistry and isotope geochemistry. Her pioneering work has focused on the natural abundance of stable isotopes, and she has developed a nitrogen stable isotope model which is used to explore soil denitrification. Since 2005 she has published 11 scientific research articles in journals such as PNAS, Oecologia, Global Biogeochemical Cycles, Global Change Biology and Journal of Geophysical Research-Biogeoscience. Her articles have been cited on more than 100 occasions during the last 5 years. She is currently serving as an associate editor for the journal Ecological Processes, and as a reviewer for more than 20 international journals. Her research results have been presented at more than 20 international conferences.

Liang Chao, born in 1977, senior scientist. He became a nationally endowed “Young 1000 Plan” Scientist in 2012. He obtained his Ph.D. degree in 2008 from the University of Wisconsin at Madison, USA. His research interests include microbial ecology and biogeochemistry. His recent research focuses on soil microbial communities and their functional responses to global warming and human disturbance. He aims to reveal the regulatory mechanisms of soil C and N microbial transformations from a micro perspective. He also strives to provide a theoretical basis and practical guidance for maintaining or optimizing ecosystem functions and their sustainability from a macro perspective. He has developed a Markov Chain model to study the dynamics of soil C transformations. He found that some amino glycoside antibiotics interfere with amino sugar quantification in vitro, and isolated microbial cells in the process of standardizing a method for the determination of microbial cell residues. He has published 30 scientific research articles.







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