Dynamics of an Estuarine Forest and its Response to Rising Sea Level

Abstract

To address the impact of rising sea level in a rapidly submerging Maryland estuarine forest, 15 loblolly pines (Pinus taeda) were cored for dendroecological analysis. The study area is a pure stand of loblolly pine that extends down an elevation gradient into surrounding marsh where dead stumps and snags indicate a retreating forest margin. Although relative sea level has risen considerably and there are dead trees at the forest-marsh interface, there is no associated decline in ring width, making sea level–induced mortality unlikely. Instead, ring width is correlated positively with annual precipitation and winter temperature and negatively with summer temperatures. Although recruitment of new pines was continuous between 1910 and 1930, there has been no more active recruitment except for a small age class established immediately after regional drought. Because recruitment is failing in the present forest despite abundant seedlings and an open canopy, recruitment ability appears to be limited by saturated soils associated with periods of high sea level. We predict that the forest margin will retreat stepwise, following storm-induced mortality, or continuously, following age-related adult mortality. The position of the forest margin is then a function of sea level position, but it represents the failure to recruit new individuals, not the ability of adults to survive a long term rise in sea level.