NSF Award
2307254
Organic matter is a component of most soil that provides disproportionate and critical services to society. Soil organic matter influences fertility and plant growth, water quality and quantity, and global climate, due to its roles in storing carbon and nutrients and releasing them during decomposition. Predicting the distribution and functions of soil organic matter remains challenging despite more than a century of research on this topic. The ecosystem properties that influence soil organic matter vary tremendously over small and large spatial scales, and many previous studies have focused on a single soil type or geographic region. Scientists continue to debate the nature of soil organic matter and why it persists, given that microorganisms can inevitably decompose it over timescales of days to millennia. This project aims to reconcile previous debates regarding what soil organic matter consists of, and the physical, chemical, and biological factors that control its decomposition and capacity to supply nitrogen to plants. The study will combine a wealth of existing data with new samples and measurements from the National Ecological Observatory Network (NEON), a monitoring network including diverse sites across the U.S. Researchers will test a new quantitative framework to predict soil carbon and nitrogen cycling by incorporating multiple trade-offs in environmental characteristics at local to continental scales. The project will train graduate and undergraduate students, including those from underrepresented groups in science, and will develop soil-related curricula for a general educational audience.<br/> <br/>Many influential scientific concepts related to soil organic matter were developed within single ecosystem types and struggle to predict its distribution and dynamics at continental scale. The leaf economics spectrum showed that numerous aspects of plant diversity collapse along a fundamental axis of trait variation corresponding to fast vs. slow return on investment. However, the tremendous heterogeneity of soil and the lack of comprehensive and standardized data has stymied efforts to develop a similarly simple framework for predicting soil biogeochemical processes. This project will test whether variation in soil organic matter properties and cycling can be explained by three fundamental axes of ecosystem variation corresponding to fast and slow biogeochemical rates, each linked to interactions among climate, minerals, plants, microbes, and organic molecules, as supported by theory and preliminary data. Consideration of the composition of individual soil samples along each axis, and their joint influence on process rates, may help reconcile the importance of distinct mechanisms of organic matter persistence demonstrated in previous work, and thereby improve prediction of critical ecosystem functions that soil organic matter provides. To test this model, the researchers will collect new measurements of organic matter molecular composition, geochemistry and mineralogy, short- and long-term biogeochemical process rates, and microbial functional genes that leverage existing and ongoing data and sample collection from NEON sites. The project will include recruitment, education, and training of the future scientific, engineering, technical, and policy workforce and leadership needed to pursue basic research on regional to continental scale biology, as well as opportunities to engage a diverse community of learners and educators in regional to continental scale research and the use of NEON.<br/><br/>This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.
