Electronic Thesis and Dissertation Repository


Master of Science




Yates, Adam G.


The cotton strip assay (CSA) has been promoted as a method of incorporating functional indicators into standardized river assessments by study of organic-matter decomposition. However, operationalization of the CSA as an indicator requires testing the spatial and temporal controls of variance associated with decomposition of cotton strips at regional reference sites. I conducted a hierarchically structured study of decomposition rates in Ontario, Canada. Cotton strips were deployed during the spring, summer and fall in pool and riffle habitats of 22 streams located in three distinct physiographic regions. Partitioning of variation among hierarchical scales associated with rates of decomposition were examined using nested ANOVAs, and comparisons of regional, habitat and seasonal differences were studied using a linear mixed effects model (LMEM). A partial least squares (PLS) regression analysis was performed to identify environmental variables associated with decomposition patterns. I found that variance associated with each successive spatial scale was seasonally dependent, and that temperature was the source of the majority of seasonal distribution of variance. I also found that temperature was be the primary environmental controls of decomposition. By quantifying the natural heterogeneity in decomposition rates, this study will inform biomonitoring practices, enabling progress towards inclusion of the CSA in regional monitoring programs.