Niche responses of early and late successional tree seedlings on three resource gradients

The responses of early and late successional tree seedlings were compared on gradients of light, moisture, and nutrients in order to further test the hypothesis that competition resulting in niche separation has been a more important selective force in late successional communities than in early successional communities The mean calculated niche breadth and proportional similarity for the early successional seedlings, Pinus taeda, Crataegus mollis, and Gleditsia triacanthos, was higher than the mean breadth and proportional similarity of the late successional seedlings, Quercus rubra, Tilia americana, and Acer saccharum, on the moisture and nutrient gradients All species had broad responses to the light gradient. These results are consistent with our earlier work on herbaceous plant communities in finding broader, more similar niche responses among early successional than late successional species