Document: INE-3-45-7

Effects of seed rain and fecundity variability on the successional dynamics of neighboring communities.

IBANEZ, I.*, J.S.CLARK and S.LADEAU

Duke Univerisity, Durham, NC 27708 USA ¹

Abstract:
The degree to which secondary succession is limited by seed dispersal from surrounding forest is poorly understood, because i) there are few studies comparing seed rain in closed forest and nearby successional sites, and ii) incoming seed rain is rarely compared with seedling recruitment. High variability in seed rain and recruitment success require sampling at several spatial scales and across years characterized by varying environmental conditions. To determine seed limitation on invading hardwood populations we quantified seed rain and stand fecundity in two neighboring forests, a loblolly pine (Pinus tadea) stand and a mature hardwood forest. Seed traps at seventy-two locations (12 traps nested within each of six 700 m² plots) in fourteen year-old successional pine plantation document changes in seed rain with time and spatial scale since 1997. The largest fecundity estimates (no. seeds/cm² basal area) for pine were in 1999, (0.15); 1997 was the most productive year for tulip-tree (Liriodendron tulipifera), (1.23); and red maple (Acer rubrum) showed its peak in 1998, (2.11). Thirty traps in the adjacent mature hardwood stand were monitor during a year, 1999. In the hardwood forest fecundity values among the studied species were higher, Pinus (1.47), Liriodendron (3.76), and Acer (9.09), in comparison to the successional pine stand, 0.15, 0.79 and 2.11 respectively, in 1999. Also for this year, seed rain values (no. seeds/m²) are greater in the hardwood forest (Pinus 11.76, Liriodendron 1.9, and Acer 11.92), than in the pine stand (5.46, 0.19 and 0.34 respectively). Our results indicate that the mature hardwood forest is characterized by high fecundity and seed rain. Dominant species on it, such us Liriodendron, Acer, Carpinus caroliniana, Carya spp., and Quercus spp., have such low dispersal rates into the successional pine stand that dispersal probably limits their abundance there. On the other hand, pine appears to be most limited in the areas where it is most abundant, i.e., in the successional stand.

Keywords: Seed rain, fecundity, secondary succession

This abstract is being presented at: 10:30 AM in session:
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