Growth patterns of Carolina wolfberry (Lycium carolinianum L.) in the salt marshes of Aransas National Wildlife Refuge, Texas, USA

Abstract

The coastal salt marshes of the Aransas National Wildlife Refuge (ANWR), Texas, USA support a wintering population of the endangered Whooping Crane (Grus americana). Although the bulk of their winter diet is comprised of blue crabs, berries from the Carolina wolfberry (Lycium carolinianum) can contribute 21–52% of crane energy intake early in the wintering period. Monthly, from November 2003 to February 2005, we tracked L. carolinianum growth in nine 1-m² permanent macrophyte plots along the estuarine gradient to understand the spatial and temporal variability of this perennial halophyte. Lycium carolinianum showed strong seasonal growth patterns, with leaf production peaks in late winter and again in late summer, just prior to flowering, but little significant spatial variation. Flowering of L. carolinianum occurred in October and November, and peak berry abundance coincided with the arrival of the cranes in late October and early November. During this period, the total number of flowers per plant and total number of leaves per plant across all sites were positively related to surfacewater depth and pore-water salinity. The numbers of flowers and berries per plant were significantly higher at our lowest elevation site during the 2004 fruiting season. Berries were rarely observed in the marshes for the remainder of each calendar year. Stem diameter was the best estimator of L. carolinianum aboveground biomass in ANWR marshes, accounting for approximately 94% of the variability (p < 0.001). Monthly changes in estimated aboveground biomass at each site revealed no distinguishable spatio-temporal trends. This is likely a result of L. carolinianum’s woody stem, which accounts for much of the total plant biomass but is much less dynamic than photosynthetic and reproductive tissues.