LAND-WATER LINKAGES - INFLUENCES OF RIPARIAN DEFORESTATION ON LAKE THERMOCLINE DEPTH AND POSSIBLE CONSEQUENCES FOR COLD STENOTHERMS

The purpose of the present study was to determine if riparian deforest ation would expose lake surfaces to stronger winds and therefore bring about deepening of thermoclines and resulting habitat losses for cold stenotherms such as lake trout (Salvelinus namaycush). Removal of pro tective riparian trees through wind blowdown and two wildfires was fou nd to triple the overwater windspeeds and produce thermocline deepenin g in two lakes at the Experimental Lakes Area. A survey of thermal str atification patterns in 63 northwestern Ontario lakes showed that lake s around which riparian trees had been removed a decade before through either clearcutting or by a wildfire were found to have thermocline d epths over 2 m deeper per unit fetch length compared with lakes surrou nded by mature forests. Riparian tree removal will therefore exacerbat e hypolimnion habitat losses for cold stenotherms that have already be en documented to be occurring as a result of lake acidification, eutro phication, and climate warming.