Date of Award

Fall 2021

Project Type

Thesis

Program or Major

Natural Resources

Degree Name

Master of Science

First Advisor

A Stuart Grandy

Second Advisor

Andrea Jilling

Third Advisor

William H McDowell

Abstract

Enzymes are the drivers of organic matter degradation and biogeochemical cycling. Extracellular enzyme activity is often examined on a bulk soil level though some studies explore their activity within soil fractions. Across soil size fractions, organic matter turnover differs greatly suggesting that enzymes are either unevenly distributed across fractions or their activity or efficacy is concentrated in certain fractions, likely those with the greatest quantities of organic matter. By examining the distribution of soil enzyme activity across different size fractions, we can better understand the relative role individual particles and aggregate building blocks have on enzyme activity, and also the soil hotspots of organic matter degradation and accumulation. Though studies have examined the distribution of enzyme activity across fractions, to date there has been no effort to synthesize existing work on enzyme activities across soil fractions in relation to edaphic soil properties and land management practices. This meta-analysis examines differences in enzyme activity across soil size fractions looking specifically at activity of enzymes across soil particle and aggregate size fractions and the influence of land us on soil enzyme activity. My results show combined enzyme activity is generally elevated in the finest soil fractions, regardless of fractionation method. Additionally, individual enzymes respond differently, even those involved with mobilizing the same nutrient, highlighting the importance of enzyme characteristics on enzyme activity and supporting future research on enzyme-surface interactions. Enzyme activity is influenced by both land use and land management with natural sites having the greatest enzyme activity while activity is reduced under agricultural tillage and fertilizer regimes. These results highlight the importance of continued research on enzyme-soil interactions, particularly within the fine fractions, to improve our understanding of organic matter dynamics.

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