A MULTIYEAR QUALITATIVE STUDY OF AN ISOLATED INLAND POPULATION OF SALT HELIOTROPE (HEUOTROPIUM CURASSAVICUM VAR. CURASSAVICUM, BORAGINACEAE) IN ARKANSAS, U.S.A.

摘要

In Arkansas, Heliotropiutn curassavicum L. (salt heliotrope, seaside heliotrope) is known from only three locations in which higher salinity allows its existence. We examined one of these sites along Saline Bayou, Clark County, over a period of 10 years to examine the life history of one variety of the species, H. curassavicum L. var. curassavicum (salt heliotrope) in a patch habitat. Seedlings were found only where other plant species did not grow and in areas of soil activity (caused by salinity) much higher than sites upstream of a salt seep. Flood events scoured the streambed habitat, often uprooting established plants, but yearly recruitment was observed from dispersed seeds. Impoundment by beavers (Castor canadensis) more permanently flooded asection of the habitat, resulting in no growth of the plant in newly inundated spaces, but greater numbers of new sprouts were observed along the new banks in the salty portion of the stream. Shading seemed to limit growth of the heliotrope along the stream and under a bridge, as few plants sprouted in those areas and any that did were stunted compared to other specimens growing in full sun.