Canopy gaps are an important mechanism for the maintenance of tree diversity in mature forests. The opening and closing of canopies across a landscape provides a range of light conditions in which species, depending on their shade tolerance, can experience a window of competitive advantage. However, the rate of gap formation may be increasing in temperate forests due to novel stressors such as hemlock woolly adelgid affecting common overstory trees. Thus, I investigated the niche in light availability tree species as seedlings occupy to illuminate how their regeneration may be differentially affected by opening canopies. In Harvard Forest in Central Massachusetts, 96 1m by 1m quadrats are located in the ForestGEO plot, which provides more spatial coverage and variation than most studies of seedlings. I tagged new recruits and recorded the status (live or dead) of old recruits of woody species as replicated through previous years. With 2 years of data, I analyzed survival across time and space of individual seedlings of the following overstory trees: red maple (Acer rubrum), eastern white pine (Pinus strobus), northern red oak (Quercus rubra), eastern hemlock (Tsuga canadensis), and birch (Betula spp.¬). To quantify the amount of light entering the understory, I took hemispherical photos of the canopies above quadrats using a fish-eye lens camera then used software to analyze the number of light versus dark pixels. Under novel stressors and a changing environment, certain tree species will display greater survivorship than others. I expect the advantage of hemlock seedlings, known to be shade-tolerant, will diminish with greater light, leading to replacement by more shade-intolerant species. Changes in light availability to the seedling layer has the potential to either release or constrain species, ultimately changing the future composition of temperate northeastern forests.