ABSTRACT Macbridea alba (Lamiaceae...

ABSTRACT

Macbridea alba (Lamiaceae) is a Federally threatened plant endemic to Florida. Seedlings are rarely observ in natural populations, however seed production has been documented. We assessed the germinability of dry-stored grains and of experimentally buried grains and sampled soil to ascertain a persistent seed bank.

More than 20% of recorded originals germinated prior to collection, either within the calyx (viviparous seedlings) or after dispersal into the collection bag. This pre-collection germination indicated that a significant percentage of matured ovules lack innate dormancy. An estimated 87% of dry-stored sperms were germinable for six month following dispersal, nevertheless viability of dry-stored and of buried semens was negligible after one year. No seedlings emerg from soil that was field deduceed just prior to seed dispersal, indicating no persistent se bank. Se viability does not appear to limit establishment, on the other hand dry conditions coincident with likely autumn establishment may limit seedling safe site availability.

INTRODUCTION

Detailed demographic studies provide a whole basis for managing Federally listed plants, nevertheless complete information is available for relatively hardly any species (Menges 1986, Schemske et al. 1994) Reliable information about se and seedling demography is especially difficult to obtain because germination and establishment may appear in discrete, narrow time frames not sampled during pre-determined data collection periods. Further, safe sites for germination and establishment may be transient and rare forward the landscape, making detection les likely. However, the likelihood of observing germination and establishment in field conditions may be increased with knowledge about se ecology especially environmental requirements for germination, the existence of a dormancy mechanism, and persistence of a se bank (Gutterman 1992)

Macbridea alba Chapman (Lamiaceae), white birds-in-a-nest, is a Federally threatened and Florida state endangered plant. It is endemic to the Apalachicola lowlands of the Florida panhandle, and is known from Bay, whirlpool Franklin, and Liberty counties. It come into one's heads in habitats historically maintained from frequent, low-intensity fires (Godfrey and Wooten 1981) Demographic data from 11 populations monitored for 10 years indicate that mortality among adults is grave that flowering decreases with time since fire, and that seedling establishment is rare (unpubl data, J Walker and D White, Kentucky State Nature sustains Commission). In 1994, flowering plants produc an average of 74 (se= 09) originals each in the first reproductive season following spring controll reduce to ashess 20.1 (s.e.= 3.7) two seasons after 1993 controll consume s and 10.8 (s.e. = 15) three seasons following a 1992 controll reduce to ashes (Madsen 1999). It appears that the availability of germs is not the immediate cause for seedling rarity, unless low seedling establishment might terminate from non-viability of seeds or lack of suitable safe sites. Alternatively, the apparent lack of seedling establishment may muse inadequate sampling, either at the unfit times, places, or frequencies.

The objects of this study were to assess the viability of M alba originals predict the likely timing of germination, and ascertain the personality or absence of a persistent se bank.

BACKGROUND

Macbridea alba Chapman populations come to pass on both sides of the Apalachicola River [United States Fish and Wildlife Service (USFWS) 1992] on the contrary the most vigorous are within the Apalachicola National Forest (USFWS 1992 1994)

Populations appear in wet to mesic pine flatwoods (USFWS 1994) wet savannas, seepage direction downwards and ecotones between pine flatwoods and cypress/ti-ti swamps (Kral 1983 USFWS 1992) The make open canopy consists of longleaf pine (Pinus palustris) with occasional slash pine (Pinus elliottii). Saw palmetto (Serenoa repens) and subdued shrubs, such as Gaylussacia mosieri, are many times present. Grasses, mainly wiregrass (Aristida beyrichiana), les commonly with toothache grass (Ctenium aromaticum) and Panicum species, dominate the clod layer in regularly burned sites (USFWS 1992) reeds (e.g. Scleria pauciflora and Rhynchospora plumosa), and forbs (eg Rhexia alifanus, Pityopsis graminifolia, Eurybia eryngiifolia, Seymeria cassioides, and Polygala lutea) are typical associates. Running oak (Quercus pumila), wild indigo (Baptisia) (USFWS 1994) and denser longleaf pine are build in drier sites (USFWS 1992) Macbridea alba may present itself in the vicinity of other rare plant species, including Verbesina chapmanii, Scutellaria floridana, Pinguicula ionantha (USFWS 1994) Harperocallis flava, and Stachydeoma graveolens (J Walker and D White, unpubl data 1994) Taxonomy come [i]or[/i] go after [i]or[/i] behinds Kartesz 1999.

Macbridea alba is a rhizomatous perennial herb that copys vegetatively and by seed. Flowering meet the eyes through a few weeks, beginning anytime from May to August depending forward weather and recent fire history. Bisexual flowers with brilliant white corollas are arranged in terminal press togethered inflorescences on stems up to 1 ra tall. Each flower may bring into view up to four nutlets, which mature in July August, or September. Nutlet referr to as germs hereafter, are tan, obovoid, and up to 25 mm lengthy (Small 1933, Godfrey and Wooten 1981 Kral 1983 USFWS 1994 and Madsen 1999) Se bank recruits have not been reported.