Publication Date

Summer 2025

Degree Type

Thesis

Degree Name

Master of Science (MS)

Department

Environmental Studies

Advisor

Rachel O’Malley; Will Russell; Kristen Dybala

Abstract

Land use change has caused the degradation of 70% of the Earth’s soils, directly altering soil microbial communities and carbon cycling. Interest in carbon farming practices is growing, but studies that document the nuances of soil carbon flux in specific bioregions are still too few. In this study, I examined how one practice, riparian restoration, alters soil carbon stock and microbial community structure over time. Using a paired sampling time series design, I collected soil samples from twelve riparian forests and adjacent rangelands near Marin County, California. Young and mature sites ranged from five to 29 years since restoration, and remnant sites had been undisturbed for at least 70 years. Soil bulk density decreased over time while microbial biomass, represented by phospholipid fatty acid abundances, increased over time. Remnant forests supported less dense soils with a larger mass of microbes per unit of volume. The following four functional groups increased with age of restoration: gram (+/-) and (-) bacteria, arbuscular mycorrhizal fungi and saprophytic fungi, however neither soil organic carbon stock nor carbon:nitrogen nor fungal:bacterial ratios changed with restoration age. The microbial biomass pattern I saw in Marin County’s restored riparian soils echoes microbial community development patterns described by authors in other restored systems and provides promising evidence of the value of restoration as a carbon farming strategy, but the short- and long-term effects of restoration on soil organic carbon serve as a caution against assuming benefits without measuring carefully.

Download

Available for download on Sunday, September 20, 2026

Share

COinS