Landscape Controls Over Seasonal Dissolved Organic Matter Concentrations in a Northern Michigan, USA Watershed
Abstract
We examined dissolved organic matter (DOM) concentrations seasonally over two years in 35 sub-watersheds of the 3600 km2 Ontonagon River watershed in the Upper Peninsula of Michigan, USA. A comprehensive set of landscape predictors were examined, including overall wetland area, area of different wetland types, watershed topography, stream geomorphology, upland vegetation type, land use, soil carbon and nitrogen content, and surficial geology. Classification and regression trees (CART) and Akaike Information Criterion (AIC) were used to examined multivariate relationships among the variables. DOM concentrations within this watershed were explained by a complex set of landscape variables. Despite the substantial area of wetlands in this watershed, the percentage of wetlands in a sub-watershed explained only about 25% of the variation in DOM concentration, much less than many previous studies. Using CART, we explained ~ 70% of the variation in DOM concentration, with particularly important variables being wetland area, slope and elevation, percent agriculture, and soil C:N ratios. Total wetland area was as effective as using the area of different wetland types in predicting DOM concentrations, although individual wetland types had very different individual correlation coefficients (and even different signs). Discharge was not an overall effective predictor of DOM concentration, as the slope of this relationship varied from positive, to non-significant, to negative depending on the sub-watershed. However, using AIC we could explain over 90% of the variation in the discharge-DOM concentration relationship, with the most important landscape predictors being % development, soil C:N ratio, stream density, and elevation, with a number of surficial geology variable also entering the models but being of lesser importance.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2006
- Bibcode:
- 2006AGUFM.B31E..07L
- Keywords:
-
- 0414 Biogeochemical cycles;
- processes;
- and modeling (0412;
- 0793;
- 1615;
- 4805;
- 0428 Carbon cycling (4806);
- 0458 Limnology (1845;
- 4239;
- 4942);
- 0497 Wetlands (1890)