DISSERTATION RESEARCH: Limits to proteolytic enzyme production and activity in temperate forest soils

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The ability of temperate forest trees to take up carbon dioxide from the atmosphere and incorporate it in their living tissues is limited by the availability of nitrogen (N) in soils. There remain significant uncertainties in the processes that control N availability in soils. Soil microorganisms release N from organic material in the soil through the release of enzymes. This study will focus on one class of enzymes, proteolytic enzymes, which break down proteins into amino acids that can be used by plants and microbes as a source of N. The goal of this research is to test a new conceptual model for proteolytic enzyme production and activity. This model applies economic theory to proteolytic enzyme activity in that it tests the hypothesis that (1) tree roots provide energy in the form of carbon to subsidize the production of proteolytic enzymes by soil microbes, and (2) microbial investment in the production of proteolytic enzymes depends on the availability of N in the soil. These hypotheses will be tested through the growing season and therefore in response to seasonal variations in temperature and protein-substrate availability. These analyses will be conducted in a series of integrated field and laboratory experiments.This research will advance fundamental understanding of the processes that regulate N availability in the soil and hence the productivity of forests as well as their ability to sequester rising concentrations of atmospheric carbon dioxide. This is potentially transformative research through its detailed analysis of the processes controlling the production of proteolytic enzymes and the response of this large class of enzymes to global changes, including rising temperatures and changes in belowground plant carbon allocation. The doctoral candidate and his advisor will continue their substantial educational and outreach activities targeting K-12 schools in the greater Boston MA area, many of which serve underrepresented groups.