Carbon and Nitrogen Dynamics Following American Chestnut Restoration in Mixed Hardwood Forests.

The once dominant American chestnut tree (Castenea dentata) was essentially extirpated from the US eastern hardwood forest as a result of the infestation by the chestnut blight-fungus (Cryphonectria parasitica) in the early 1900’s, in what is considered the largest disturbance event since glaciation. However, back-cross breeding and transgenic approaches have resulted in the production of blight resistant trees, and the reintroduction of the American chestnut is considered imminent. In the event of a successful reintroduction, significant ecosystem changes in carbon (C) and nutrient cycling are expected, but have yet to be understood or quantified at a landscape level. This study aims to quantify changes in ecosystem nutrient cycling between chestnut and two contemporary species, northern red oak and black cherry, at a plantation at Purdue University’s Martell Forest. Measured pools of C and nitrogen (N) include mineral soil, leaf litter and forest floor, and standing biomass. Measured fluxes include N mineralization, CO₂ respiration, dissolved organic carbon (DOC) leachate from soils, and litter decomposition rates, which are being measured via a laboratory incubation study. Explanatory variables from the incubation units include soil pH, oxidizable C content, and extracellular enzyme activity to assess differences in organic matter chemistry and microbial function related to C cycling. Early results indicate soils beneath chestnut have lower extractable inorganic N, N mineralization, and peroxidase enzyme activity associated with lignin degradation relative to soils beneath red oak and black cherry.