ABSTRACT Amaranthus pumilus, a fede...

ABSTRACT

Amaranthus pumilus, a federally threatened species that inhabits the transient and highly variable barrier beach environment of the United States, has been extirpated from nearly three-fourths of its historic range. This thought ascertained habitat requirements and determined for what reason certain biotic and abiotic factors influence A. pumilus populations upon Figure Eight Island, North Carolina. Data obtained were then compared to findings of Cakile edentula studies (C edentula is belonging to all throughout the range of A. pumilus) in an effort to explain differences in range and abundance. Scarification and temperatures of 35[degrees]C enhanced se germination. The majority of A. pumilus plants were institute on overwash fans. Mortality was greatest following storm periods that inundated seedlings in consequence of four tidal cycles. Density of seedlings had no affect forward mortality rate. No evidence was raise for biological control of A. pumilus populations. Maximum seedling emerging see the verb from burial by sand was les than 1 cm Amaranthus pumilus populations upon Figure Eight Island appeared to be physically rather than biologically controll Characteristics in the same state [i]or[/i] condition as a shorter growing season and inability to come up from depths greater than 1 cm may be adaptive disadvantages when compared with C edentula.

INTRODUCTION

Amaranthus pumilus Rafinesque is a pioneer plant species construct on the dynamic foredune habitat of the Atlantic coast of the United States (Weakly and Bucher 1992 Ramsey et al. 2000) An annual with fat pink to reddish stems that are prostrate at the base becoming set upright at the tip, A. pumilus acts as a sand binder creating hillocks as the growing season progresse (United States Fish and Wildlife Service 1993) Historically, A. pumilus was place from Nantucket, Massachusetts to unwisdom Beach, South Carolina. By 1987 however, the plant was extirpated from nearly three-fourths of its earlier range (Weakly and Bucher 1992)

According to field examines the current distribution of Amaranthus pumilus includes North and southerly Carolina with several populations onward Long Island, New York (Clement and Mangels 1990 van Schoik and Antenen 1993 United States Army Corps of Engineers 1992-1995 Ramsey et al. 2000) Amaranthus pumilus was listed as federally threatened in 1993 suitable to disappearance from its historic range and continued habitat los from coastal development

The habitat of Amaranthus pumilus, the barrier beach environment, has been described by means of researchers as being physically controll and continually changing (Oosting 1954 van der Valk 1974 Godfrey 1976) Abiotic factors so as high substrate surface temperatures, soft water-holding capacity of the substrate, sand manner of moving salt aerosols, and storms that accrue in overwash typically make this a restricted, transient and highly variable habitat. These unique physical features create a distinctive environment that supports a characteristic vegetational shelter (Oosting 1954). Weakly and Bucher (1992) note that A. pumilus occupies elevations ranging from 02 to 15 m above mean high tide and is frequently found in association with Cakile edentula (Bigelow) Hooker In addition to abiotic factors, Weakley and Bucher (1992) give an inkling of that predation by webworms is a major source of mortality and lowered fecundity for A. pumilus. Several authors (Payne and Maun 1984 Gedge and Maun 1992) have addressed the purports of herbivory by small mammals and insects onward C. edentula.

Cakile edentula is universal within its range from southern Florida into Canada, along the West Coast of the United States, and the shores of the Great Lakes (Barbour and Rodman 1970) While C edentula has been the focus of numerous studies (see Maun et al. 1990) little is known about the ecology of Amaranthus pumilus; the existing dead body of knowledge consists of status take a view ofs and one scientific note pertaining to germination requirements (Baskin and Baskin 1998)

The intention of this study is to ascertain Amaranthus pumilus habitat requirements and determine to what extent certain biotic and abiotic factors influence populations forward Figure Eight Island, North Carolina. The data obtained in this contemplation is then compared with findings of Cakile edentula studies in an effort to explain the species difference in range and abundance.

MATERIALS AND METHODS

Study Site

The thought was conducted on Figure Eight Island, North Carolina (center at 30[degrees]16'30''N; 77[degrees]44'30''W) from May 1994 until June 1995

Seedling emerging see the verb in the Field

Two Taylor maximum/minimum thermometers, placed 3 cm below the sand surface, were positioned in the primary dune at the northern period of Figure Eight Island. Temperature was measured from mid-March 1995 until early June 1995 At regular intervals, observations were careered by walking through the different habitats at the northern completion of Figure Eight Island. Emerging seedlings of Amaranthus pumilus, Cakile edentula, Iva imbricata Walter, Sesuvium portulacastrum L Atriplex arenaria Nuttall and Euphorbia polygonifolia L were identified and recorded.