¹Larson, G. L., G. Lomnicky, R Hoffman, W. J. Liss, and E. A. Deimling. Accepted. Integrating physical and chemical characteristics of lakes into the glacially influenced landscape of the North Cascade Mountain Range, Washington State, USA. Environmental Management.

ABSTRACT

Physical and chemical characteristics of 58 montane lakes in alpine, subalpine, and forest vegetation zones in the North Cascades Mountain Range were assessed between 1989 and 1993. The objectives of the study were to document the time of ice-out relative to lake elevation, determine how a sharp climate gradient west and east of the hydrologic divide affected this relationship for subalpine lakes, and assess how lake water quality was associated with lake elevation, lake depth, and basin geology. As expected, lake ice-out times occurred earlier with decreasing elevation. East-slope subalpine lakes iced-out earlier than did west-slope subalpine lakes because the east slope of the study area was drier and warmer than was the west slope, On average, the lakes were relatively cold, neutral in pH, and low in dissolved substances and concentrations of nitrogen and phosphorus. Although some shallow lakes (depth <10 m) exhibited the highest alkalinities, conductivities, and concentrations of phosphorus and nitrogen, . most shallow lakes exhibited low values for these variables that were comparable to values observed in deep lakes. Geology did not play a major role in segregating the lakes based on water quality. Overall, lake temperature, pH, alkalinity, conductivity, and concentrations of total phosphorus and total Kjeldahl-N increased with decreasing elevation. These changes in water quality with decreasing elevation in this temperate mountainous region appeared to correspond with warmer air temperatures, and increased vegetation biomass, soil depth and maturity, dissolved substances, and nutrient availability.

ACKNOWLEDGMENTS

We thank the National Park Service and the USGS - Forest and Rangeland Ecosystem Science Center for the financial support of this project, and especially Mike Collopy, Jim Larson, Shirley Clark, Kathy Jope, Jon Jarvis, Bruce Freet, and Reed Glesne. Stanford Loeb, Stanley Dodson, William Neil, and John O'Brien provided recommendations for the sampling design, Stanford Loeb, Stanley Dodson, and James Petranka reviewed the manuscript, and Lisa Ganio provided recommendations for statistical analyses. Becca Berkey typed and Ruth Jacobs edited the manuscript.