Life History Strategies of Florida Scrub Plants

Most Florida scrub plants are top-killed by fire but use resprouting (often with clonal growth) to recover (Schmalzer and Hinkle 1992b, Menges and Kohfeldt 1995). Woody plants are usually strong resprouters, but so are dwarf palm species (Abrahamson 1999). Even tiny palm plants can resprout (Abrahamson 1995); they are essentially forming a seedling bank although the factors causing their “release” are not well known. Some herbs are very strong resprouters (McConnell and Menges 2002) but others are weak resprouters (Weekley and Menges 2003). Resprouting is probably affected by fire intensity, but little research has been conducted in this area.

While resprouters dominate most types of Florida scrub, other mechanisms also are important. Resistance to fire is an uncommon adaptation, but does occur in longleaf and south Florida slash pine. The thick bark of pine and grass stage of these pines helps them survive fire. Mortality in fires increases with fire intensity and time-since-fire and also varies seasonally (Menges and Deyrup 2001). When scrub oaks get to be tree-sized, they may also resist fire, making the use of fire to top kill shrubs in long-unburned areas difficult.

Florida rosemary (Ceratiola ericoides) and many herbaceous plants are killed by fire but recover from seeds in soil seed banks (Johnson 1982, Carrington 1996, Quintana-Ascencio et al. 2003). This creates a characteristic increase in herbaceous plant diversity and density in recently burned Florida scrub (Hawkes and Menges 1996, Carrington 1999) but this pulse of seedlings is lower than in similar situations in California chaparral (Carrington and Keeley 1999). Sand pine (Pinus clausa) stores seeds in an aerial seed bank. A few species have no adaptation to fire per se, but are able to disperse from unburned patches back into burned areas. Fire patchiness must affect their distribution, although this has not been well studied.

Combinations of postfire recovery strategies occur in many species (Menges and Kohfeldt 1995). For example, large postfire increases in the density of scrub morning glory are due to both resprouting and germination from a persistent seed bank (Hartnett and Richardson 1989). This combination is also found in Lechea species (Maliakal Witt et al. in preparation). The herbaceous goldenrod Solidago odora var. chapmanii recovers from fire via resprouts, clonal shoots, and seedling recruitment (Menges and Root 2004).

Variation in postfire recovery strategy affects vegetation structure in Florida scrub. Areas dominated by Florida rosemary, which recovers via a soil seed bank, remain relatively open and afford opportunities for herbaceous species including many scrub endemic plants (Menges and Hawkes 1998). Aggressive clonal growth by blueberries postfire (Menges and Kohfeldt 1995) is probably the cause of their peak in cover within a few years of fire (Abrahamson 1984b). Postfire flowering by resprouting plants (Ostertag and Menges 1994) can lead to delayed pulses in seedling recruitment, as in scrub buckwheat (McConnell and Menges 2002). Obligate seeders with delayed reproductive maturation (e.g. Florida rosemary) may be eliminated by frequent fires, while resprouters are vulnerable to high fire intensities that can kill root systems, although this occurs rarely.

See also: Fire Effects in Florida Scrub.