Growth and survivorship of American beech (Fagus grandifolia Ehrh.) seedlings in a northern hardwood forest following a mast event1

Abstract

Despite the recognized importance of root sprout production in northern populations of American beech (Fagus grandifolia Ehrh.), further consideration of the relative role of regeneration from seed in this species appears warranted and timely. A careful examination of the literature revealed that seed- and sprouts-origin individuals co-occurred within all published study sites where the two were differentiated and that presence of a seedling bank may be the rule rather than the exception for American beech. We compared the effects of canopy gaps and root trenching on the growth and survival of a cohort of beech seedlings in Hubbard Brook Experimental Forest (HBEF) in northern New Hampshire, USA. Seedlings in gap plots became larger both above- and belowground. Foliar nitrogen concentrations were affected by both above- and belowground treatments and increased the most for seedlings in trenched gap plots. Seedling height and canopy treatment were important predictors of seedling survivorship with the highest survival in gap locations. The relationship between seedling height and survival was more complex. In the first two years, taller seedlings had a higher probability of dying, while after the second year taller seedlings were more likely to survive to be four-years old. The relatively high survivorship of seedlings at HBEF and their response to gap openings taken together with literature documentation of the long-term presence of seed-origin beech stems in the understory strongly suggest the presence of a beech seedling bank in this forest. This is one of a few manipulative studies on naturally regenerating American beech seedlings, and the first study to relate the likelihood of survival to seedling traits for this important species in the northern hardwood forest.