A study of aquatic vegetation of 31 small, dilute, and unproductive lakes in the Adirondack Mountains of New York shows that macrophyte species composition is primarily related to variation in pH and associated factors. Among the lakes, surface water pH ranged from 4.5 to 7.8; conductivity ranged from 11.9 to 58.7ensp;mu;S/cm. Relationships between aquatic vegetation and environmental factors were studied using detrended correspondence analysis (DCA). Submersed and floating-leaved taxa were analyzed separately from emergent taxa. Correlations between DCA axis 1 and pH-related factors (pH, alkalinity, Ca, Mg, Na, Al, conductivity, elevation) were strong for both submersed plus floating-leaved and emergent taxa. No significant correlations were found with water color, transparency, or trophic status indicators (total P and chlorophylla). Between-lake variation in composition of aquatic vegetation in Adirondack lakes follows a pH "complex-gradient." Influences of elevation, morphometry, and substrate are secondary. Our results indicate that acidification of softwater lakes could be accompanied by significant changes in aquatic macrophyte assemblages.
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