PARENT SESSION
Oral Session #44: Disturbance ecology of forests: Animals, wind, gaps, edges. Presiding: S. Archer.
Wednesday, August 8, 2001. 8:00 AM to 11:45 AM. Hall of Ideas G.
Understory abundance following logging in northern hardwood forests: the role of seed predation and myrmecochory.
DEJOODE, DANIEL1, HORJUS, KATHERINE1, CURRAN, LISA1, 1
ABSTRACT- Understory plants comprise approximately 85 percent of vascular plant species in northern forests where ants disperse seeds (myrmecochory) of at least 50 percent of herbaceous stems. Myrmecochorous seeds attract ants with an edible food body (elaiosome). We observed a decreased abundance of many myrmecochores after logging on Wisconsin's Menominee Indian Reservation. Previous studies found that the ant communities may differ between disturbed and unlogged forests. We investigated whether lower abundances may be due to 1) different ants present after logging, 2) increased seed predation, or 3) reduced seed acquisition by dispersers. A preliminary collection of ants suggests little difference in the ant fauna among logging treatments. Seeds of three common myrmecochores were set out in 20 forest stands with four logging histories: clear-cut (1-3 or 15-20 years after logging), selectively cut and uncut. Exclosures restricted access by either ants or rodents. Five sites of each logging treatment were selected and ranged between 1 and 40 km apart. Higher levels of seed predation occurred in selectively logged stands compared to other treatments. Seed removal by ants did not differ among the logging treatments, although removal rate varied according to seed species. Elaiosomes degraded significantly in recent clear-cuts, presumably due to microclimate conditions. These preliminary results indicate that logging does not disrupt acquisition of seeds by dispersers, although elaiosome degradation in clear-cuts and predation after selective logging may limit seed dispersal.
KEY WORDS: myrmecochory, seeds, predation, forest