Abstract
Assessment of stream ecosystem 'health' traditionally uses structural indicators (e.g., invertebrate community composition) but often neglects indicators of ecosystem processes (e.g., decomposition rates), providing an incomplete picture of overall ecosystem condition. Given a lack of standardized process-based indicators, we present a protocol for measuring organic-matter decomposition, represented by the breakdown of cellulose in the form of woven cotton fabric. The material, used more conventionally as artists' fabric, has been suggested as a replacement for a standard cotton material (Shirley Burial Test Fabric) that had been widely used in decomposition studies for decades but is no longer manufactured. In field trials, we incubated cotton strips made of artists' fabric in 49 streams in the Midwest (USA), northern Michigan (USA), and in New Zealand to: (1) test the assay under field conditions, (2) provide an initial population of data to which future studies can be compared, and (3) assess some environmental conditions that might influence cotton-strip decay. Decomposition of the strips, as loss of tensile strength, differed among regions and, in some cases, among streams within regions, suggesting that the assay is sensitive to differences in environmental conditions at regional and watershed scales. Mean rates (and standard deviation) of tensile-strength loss across streams of tensile-strength loss were 2.3%/d (0.4), 1.8%/d (0.7), and 1.5%/d (1.0) for the midwestern, Michigan, and New Zealand streams, and 1.7%/d (0.8) overall. Principal components analysis indicated that stream water ammonium and soluble reactive phosphorus explained a small but significant amount of variation (R2 = 0.12) in tensile-strength loss among streams. Rates of respiration of cotton strips incubated in Michigan streams were positively related to tensile-strength loss (R2 = 0.70). When streams were classified by substrate size, cotton-strip tensile strength (but not respiration) differed among substrate size classes. We conclude that a cotton-strip assay based on the artists' fabric holds promise for replacing the assay based on the Shirley material, and as a process-based indicator for assessing the condition of stream ecosystems.
| Original language | English |
|---|---|
| Pages (from-to) | 131-139 |
| Number of pages | 9 |
| Journal | Ecological Indicators |
| Volume | 32 |
| DOIs | |
| State | Published - 2013 |
Funding
We thank Ashley Burtner, Kati Doehring, Jessica Dunn, Crystal Moon, Anita Baxter, Emily Campbell, Donna Kashian, and Joshua Martin for help in the field and lab, and we thank Mark Gessner for discussion related to cotton strips. We also thank Cathy Starnes, Jan Bills, Sheryl Hugger, and Rita Perris in the Oakland University Department of Biological Sciences for administrative support. Nick Bongers, Oakland University eLearning and Instructional Support, created the line drawings based on photographs taken by Kelly Garnett. Jordan Hoffman and Mariana Burchi provided the photograph of the cotton strip. This research was supported by an Oakland University Research Council award to ST, an award by the Huron Mountain Wildlife Foundation to ST and DK, a Cawthron Trust award to JC, and a Sigma Xi Grant-in-Aid of Research and Post-Graduate Scholarship (PGS-D) from the Natural Sciences and Engineering Research Council of Canada to NG. Partial support to NG during manuscript preparation was provided by the U.S. Department of Energy, Office of Science, Biological and Environmental Research.
Keywords
- Cellulose decomposition
- Litter decomposition
- Process-based indicators
- Shirley soil-burial test fabric
- Stream assessment
- Stream health