Effect of Browsing by Deer on the Growth and Reproductive Success of Lactuca canadensis (Asteraceae)

Abstract

-We studied the effect of deer-browsing on reproductive success of the forb Lactuca canadensis (Asteraceae) in an old field at Cedar Creek Natural History Area, Minn. Height and vertical growth between 2 sample dates were significantly reduced as a result of browsing by deer. The number of flower heads per plant was over seven times greater on unbrowsed vs. browsed plants. Fruits from browsed and unbrowsed plants showed a bimodal weight distribution. Unbrowsed plants had a greater proportion of large fruits, with the result that average fruit weight was greater for unbrowsed plants than for browsed plants. Our data indicate that Lactuca canadensis is not able to compensate for damage resulting from browsing by deer.