Document: BRI-3-37-27

Tree seedling survival and growth in southern Appalachian forests: Effects of canopy gaps, understory removal, trenching and fertilization.

BECKAGE, B.* and J.CLARK

Duke University, Durham, NC 27708 USA ¹

Abstract:
A central goal of forest ecology is to understand the factors that promote tree diversity and, thus, would allow accurate predictions of future forest composition. The recruitment of tree seedlings plays a major role in determining later forest composition. Therefore, we investigated seedling survival and growth of three tree species, which are important components of eastern forests, under manipulated microenvironmental conditions. We planted three first-year seedlings each of Acer rubrum, Liriodendron tulipifera, and Quercus rubra in 1m² plots with one of five treatments: Removal of all understory vegetation (<2m), trenched, trenched plus removal of understory vegetation, fertilization, and a control. These treatments were replicated in 12 paired canopy and gap environments for a total of 1080 seedlings. We fit parametric survivor models to the survival data and linear models to the seedling growth data. At the end of the first two years, species had a large effect on survivorship with Q. rubra having the highest survival (68%), followed by A. rubrum (41%) and L. tulipifera (10%). Survivorship of seedlings was higher in canopy gaps (45%) compared to closed canopy (34%), as well as in all treatments compared to controls. In contrast to survival, L. tulipifera had a relative growth rate (for seedling height) that was more than 50% higher than for either A. rubrum or Q. rubra. Relative growth rates in canopy gaps were 45% above those in closed canopies. Trenching, trenching plus removal of understory vegetation, and fertilization all resulted in relative growth rates 35% greater than in controls, while removal of understory vegetation lowered growth rates by 5%.

Keywords: seedlings, recruitment, canopy, gaps, survival, growth

This abstract is being presented at: 10:30 AM in session:
Oral Session #22: Multiple Disturbance Effects, Including Fire.