Growth and survival of tree seedlings in a large-scale rainfall manipulation experiment

Seedlings of three species with different tolerance to shade and drought, Acer saccharum, Liriodendron tulipifera, and Quercus alba, were planted on the hillslope site of the Walker Branch Throughfall Displacement Experiment during the winter of 1993-1994, and their growth measured during the following growing season. Volumetric soil moisture in the upper 35cm of soil was measured twice monthly, and relative light availability above each seedling was measured in August. The most shade tolerant species, sugar maple, leafed out earlier and by the beginning of April had produced 80% of its total leaf area, compared with only 16% for tulip poplar and 39% for white oak. Leaf area and stem growth of sugar maple were positively correlated with soil moisture, but not with light, while stem growth of tulip poplar and white oak were positively correlated with light, but not with soil moisture. Tulip poplar had the highest mortality (15%) followed by sugar maple (3%). Mortality was higher in dry locations, but was not related to growth during the season.