| Summary: | In a four-month comparison of hourly littoral water temperatures in four small boreal lakes, recent shoreline deforestation was associated with an altered temperature regime at only one lake, on a southern shoreline. There, daytime hourly median water temperatures were increased by 0.3deg.C, with frequent increases of 0.5deg.C and occasional increases of up to 1.2deg.C, relative to a nearby forested shoreline; nighttime temperatures were reduced by about 0.2deg.C. Over about three months, the littoral zone of the deforested southern shoreline accumulated only about one-half of a degree day more than the forested shoreline. Time-series analyses of hourly climate data and water temperature patterns from two nearby undisturbed lakes suggest that hourly littoral water temperature patterns were primarily associated with hourly patterns of solar energy, while day-to-day water temperature patterns were associated only with air temperature. Where riparian deforestation significantly reduces littoral shading, the main effect on littoral water temperatures is likely to be an increase in diurnal temperature fluctuation. Daily average water temperatures are strongly associated with regional air temperature, and are not likely to be affected significantly by localized riparian deforestation.
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