Factors Influencing Stem Density of Creekbank Spartina alterniflora in a New England Salt Marsh

Stem density patterns for smooth cordgrass, Spartina alterniflora, are highly variable both among years and within the growing season. These variations can have consequences for the overall primary productivity of the salt marsh system, as well as its ability to provide essential ecosystem functions. In this study, I explored factors that could be driving observed variations in four tidal creeks of the Plum Island Sound Estuary, Massachusetts. End of season stem densities were measured at two of the creeks over eight years. Seasonal stem densities were measured at all four of the creeks four times during a single growing season. My objectives were to assess the influence of temperature, precipitation, tide level, and solar radiation on stem density variations among years, and to determine whether seasonal loss of stems was due to self-thinning or tidal action. Years with higher precipitation were associated with higher densities (p = 0.001), which may be due to an alleviation of salt stress in those years. Patterns of seasonal stem loss were more consistent with patterns of self-thinning, which has not been previously considered for S. alterniflora, than tidal action, which has been the predominant assumption. However, self-thinning and tidal action may be working in conjunction to cause seasonal stem loss. These results increase our ability to estimate S. alterniflora productivity, and our understanding of the species’ ecology and its responses to current and future climatological events. Introduction An estimated 40% of the world’s population lives within 100km of the coast (Martinez et al 2011). As a result, coastal ecosystems are some of the most threatened in