Document Type

Honors Thesis

Publication Date

Spring 5-9-2026

Abstract

Low-molecular-weight organic acids (LMWOAs) play important roles in nutrient mobilization, microbial activity, and carbon cycling in forest soils, yet their response to prescribed fire and thinning remains poorly understood. This thesis examined whether thinning and prescribed burning altered extractable LMWOA in O-horizon soils from the Lubrecht Experimental Forest. The study focused on lactic, propionic, glycolic, acetic, and formic acids measured in soils collected immediately before and approximately two weeks after the 2024 prescribed burn across four treatment categories: control, burn, thin, and thin+burn. The managed plots belong to a long-term experiment first treated in 2001-2002, whereas the control remained unmanaged for more than 100 years. Across analytes, the clearest signal was temporal rather than treatment-specific. Acetate, propionate, and lactate overall increased from PRE to POS, whereas formate and glycolate displayed weaker and more heterogeneous responses. Contrasts comparing disturbed treatments with the control, burned with unburned plots, thinned with unthinned plots, and the burn-by-thin interaction yielded uncertain estimates. These results indicate that the 2024 prescriptions did not produce strongly separable treatment effects at the sampling scale used. Instead, analyte behavior was better explained by microsite conditions, including roots, soil water content, decomposed wood, pH, and muddy/plastic wet consistency. The findings suggest that post-treatment organic acid dynamics reflected a short-lived pulse of decomposition, combustion-derived soluble carbon, and spatially variable microbial activity. Ecologically, acetate emerged as the analyte most responsive to disturbance; formate and propionate reflected wetter or diffusion-limited microsites; lactate marked moist, carbon-rich microsites; and glycolate appeared to be shaped more by background spatial heterogeneity than by treatment.

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