Mineralogical and Geochemical Controls on Nutrient Dynamics and Forest Productivity in Managed Northeastern U.S. Forests

Forests in the northeastern United States are critical for timber, firewood, and woody biofuel production, making sustainable forest management essential for balancing productivity with long-term ecosystem health. Forest productivity depends heavily on the availability of essential nutrients such as calcium (Ca), magnesium (Mg), potassium (K), and phosphorus (P), which are primarily sourced from mineral weathering. Despite the complexities of glacial soils in the northeastern United States, this dissertation investigates how soil parent material mineralogy and nutrient richness influence nutrient cycling and forest productivity across a naturally occurring Ca and Mg gradient in Vermont and New Hampshire. Using integrated mineralogical, geochemical, and isotopic analyses, I quantified nutrient concentrations and pools, rock and soil weathering rates, and nutrient fluxes. Chapter 2 evaluates the sources and weathering of parent material using the glacial till model, Ca and Mg isotopes, and immobile elements. The results indicate that glacial till composition is primarily derived from local bedrock and that soils release more nutrients than rocks when scaled to profile depth. Chapter 3 examines the influence of Ca and Mg bearing minerals on nutrient availability and highlights that mineralogy is a key control on nutrient retention and release rates in soils. Chapter 4 links soil nutrient richness to aboveground biomass, nutrient concentrations in wood and foliage, and merchantable wood value. While nutrient concentrations generally increased with soil nutrient richness, total biomass was highest at the nutrient Poor forest, and merchantable wood volume did not differ significantly across the three forests. These findings highlight the critical role of parent material mineralogy in sustaining nutrient supply and underscore the importance of considering mineralogical and geochemical context when developing adaptive, site-specific management strategies.