The vast majority of theses in this collection are open access and freely available. There are a small number of theses that have access restricted to the WWU campus. For off-campus access to a thesis labeled "Campus Only Access," please log in here with your WWU universal ID, or talk to your librarian about requesting the restricted thesis through interlibrary loan.

Date Permissions Signed


Date of Award

Summer 2022

Document Type

Masters Thesis

Department or Program Affiliation

Environmental Studies

Degree Name

Master of Arts (MA)


Environmental Studies

First Advisor

Bach, Andrew J.

Second Advisor

Bunn, Rebecca

Third Advisor

LaHue, Deirdre Griffin


I sampled Skagit silt loam soils from a field trial at the WSU NWREC where biochar and compost were added to potato crops in late spring pre-planting. Soil mesofauna were sampled at mid and late-summer, while soil microbes were sampled at late summer exclusively. Soil treatments included mixed biochar and compost, compost-only, and an unamended control. Mesofauna were extracted with Berlese funnels and sorted to functional groups. F:B ratios and total microbial C were determined using microbiometer test kits. To test whether biochar and compost induced changes to soil mesofauna communities, I used permutational ANOVA. Differences in F:B ratios and total microbial C were tested using a linear mixed effects model with ANOVA. Mesofauna communities differed markedly between mid and late-summer sampling (p=0.001) with a shift from Rhyzoglyphus, and Collembola dominance to a more even mix of functional groups including Formicidae, Psocodea, Symphyla, Apocrita, and Diptera with a diminished overall population. However, neither compost nor biochar treatments had a significant effect on soil mesofauna communities (p=0.291) nor did they alter F:B ratios and total microbial C (p=0.246 and 0.787 respectively). The microbial community favored bacterial dominance with an average F:B ratio of 0.60±0.21 across treatments and total microbial C was 272.50 µg C/g±115.82. The decrease in mesofauna abundance between mid and late summer likely reflects seasonal changes in mesofauna activity due to differences in soil temperature and moisture levels. The F:B ratio favoring bacterial dominance is indicative of chemical fertilizer use and heavy tillage which favors fast growing bacterial groups.




Biochar, compost, microbes, mesofauna, Skagit, F:B ratio, mites


Western Washington University

OCLC Number


Subject – LCSH

Silt loam--Skagit River Valley (B.C. and Wash.); Soil invertebrates--Skagit River Valley (B.C. and Wash.); Biochar--Skagit River Valley (B.C. and Wash.); Compost--Skagit River Valley (B.C. and Wash.)

Geographic Coverage

Skagit River Valley (B.C. and Wash.)




masters theses




Copying of this document in whole or in part is allowable only for scholarly purposes. It is understood, however, that any copying or publication of this document for commercial purposes, or for financial gain, shall not be allowed without the author’s written permission.