SREL Reprint #2232

Why do early-emerging tree seedlings have survival advantages?: a test using Acer rubrum (Aceraceae)

Robert H. Jones1, Bruce P. Allen2, and Rebecca R. Sharitz2

1Department of Biology, Virginia Tech, Blacksburg, Virginia 24061-0406
2Savannah River Ecology Laboratory, Drawer E, Aiken, South Carolina 29802

Abstract: In forest understories, tree seedlings that germinate and emerge early in the growing season have significant survival advantages. We hypothesized that (a) early emergence is related to seed size and half-sib family, and (b) increased survival is due to reduced competition for resources. To test these hypotheses, we collected seeds of Acer rubrum from four half-sib families and planted them in the understory of a South Carolina floodplain forest. In one experiment, date of emergence was not related to seed size or half-sib family. However, our method of seed collection may have underestimated variability among half-sib families. In a second experiment, seeds were spread onto 20 understory plots, half of which were trenched to reduce root competition with overstory trees. One-year survival and biomass were greater for early- than for later-emerging cohorts. Trenching changed biomass distribution among aboveground parts and may have increased total biomass, but had essentially no impact on survival or root mass. Variation in plot flooding resulted in large differences in timing of emergence, survival, and biomass. For Acer rubrum, the survival advantage accorded by early emergence may be more related to flooding, light conditions, and genetic heterogeneity than to seed size or avoidance of root competition.

Keywords: Acer; Aceraceae; flooding; forest understory; forested wetlands; germination; half-sib family; microsites; root competition; seeds

SREL Reprint #2232

Jones, R.H., B.P. Allen, and R.R. Sharitz. 1997. Why do early-emerging tree seedlings have survival advantages?: a test using Acer rubrum (Aceraceae). American Journal of Botany 84:1714-1718.

This information was provided by the University of Georgia's Savannah River Ecology Laboratory (srel.uga.edu).