Effects of habitat, burial, age and passage through birds on germination and establishment of chinese tallow tree in coastal South Carolina

Journal of the Torrey Botanical Society, Apr-Jun 2001 by Renne, Ian J, Spira, Timothy P, Bridges, W C

Seed bank evolution is a consequence of unpredictable spatial and temporal events that affect seedling establishment (Cohen 1966; Templeton and Levin 1979; Venable and Brown 1988). Tallow tree seedlings (and adults) are relatively shade-tolerant (Jones and McLeod 1989, 1990) and persist under a well-developed canopy, but the creation of canopy gaps increases growth and reduces mortality of seedlings (Renne, unpubl. data). Hurricanes, for example, are a major structuring force of Southeastern coastal forests, but the magnitude and frequency of their effects are inherently variable in space and time. Under these circumstances, colonization of ephemeral safe sites would be maximized with a persistent seed bank (Horvitz and Schemske 1986; Cipollini et al. 1993).

MANAGEMENT CONSIDERATIONS. Fire can kill tallow tree seedlings and reduce adult growth, but an intense, growing season bum may be required (Grace 1998). Because seedling emergence was temporally broad and buried seeds remained viable in the Southeast (this study) and Gulf Coast (Harper 1995), late season annual bums may be most effective in killing the most individuals, particularly in recently invaded areas because larger individuals often resprout when top killed (Grace 1998). No data exist on how fire affects tallow tree seed survival.

CONCLUSIONS. Our data suggest that susceptibility of forest types to tallow tree invasion differs greatly, but effective avian seed dispersal (Renne et al. 2000), a regionally persistent seed bank and consistently successful seedling establishment contribute to its current invasion of many coastal forests in South Carolina. Because seed dormancy (both years) and seedling establishment (1998 only) were not affected by forest type, differences in seed dispersal and adult growth, survival and fecundity are other probable factors influencing its differential success among forests. Populations will likely become less seed-limited, and more microsite-limited, as available sites become colonized, but clearcuts and other canopy disturbances may reverse this trend. Future studies on tallow tree demographics can be used to identify important life history stages so that effective control efforts for this species may be achieved.

Literature Cited

BARNEA, A., Y. YoM-Tov, AND J. FRIEDMAN. 1991. Does ingestion by birds affect seed germination? Func. Ecol. 5: 394-402.

BARRILLEAUX, T. C., AND J. B. GRACE. 2000. Growth and invasive potential of Sapium sebiferum (Euphorbiaceae) within the coastal prairie region: the effects of soil and moisture regime. Amer. J. Bot. 87: 1099-1106.

BASKIN, C. C., AND J. M. BASKIN. 1998. Seeds: Ecology, Biogeography, and Evolution of Dormancy and Germination. Academic Press, San Diego, California. 850 p.

BONNER, F T 1974. Sapium sebiferum (L.) Roxb. Tallowtree. P 760. In C.S. Schopmeyer (ed.), Seeds of Woody Plants in the United States. Agric. Handb. 450, Forest Serv., USDA, Washington, D.C.

BROWN, J. S., AND D. L. VENABLE. 1986. Evolutionary ecology of seed-bank annuals in temporally varying environments. Am. Nat. 127: 31-47.