College Park, MD 20740
ABSTRACT:
Carbon (C), fixed photosynthetically by plants, is cycled through plant, microbial biomass, soil, and atmospheric carbon pools. The effects of global change on this cycling are poorly understood, but are likely to have important impacts on future levels of atmospheric carbon dioxide. My research and education have been focused on finding new approaches to study the effects of global changes.
My most recent project was to design and conduct an observational study of soil carbon in minimally managed, long-undisturbed soils. In 62 golf courses located at varying distances from urban areas, where similar communities of grasses grew in undisturbed soil for at least 25 years, I measured total and active soil C as well as many potential explanatory factors. I used these measurements to explore correlations using multiple regression. Contrary to expectations, soil C increased with warmer wintertime daily minimum soil temperatures and did not decrease with warmer overall mean temperatures. This result suggests that winter freeze/thaw events may be more important for soil C storage than mean annual temperature in temperate grassland soils. Other correlations were also detected in this dataset: total and/or active soil C were positively correlated with soil cation exchange capacity, soil lead levels, and tropospheric ozone exposure during the peak ozone season. While some of these responses go against expectations, I have explored potential mechanisms that make sense in this system. These findings generate new hypotheses to examine and may help refine expectations and modeling of soil C dynamics.
Prior to this observational study, I looked at the impacts of elevated carbon dioxide ([CO2]) on arbuscular mycorrhizal fungi and on allergenic, plant-pathogenic fungi in controlled experiments. I also explored proper statistical analysis of experiments utilizing chambers or Free-Air CO2 Enrichment (FACE) rings to apply CO2, which tend to be imbalanced or incomplete block designs.
Commonly-held expectations of the impacts of future climate change, based on single-factor global change experiments and/or simple models, are not always borne out in complex natural systems. My research goals are to improve statistical analysis and modeling to better represent these impacts.
