PARENT SESSION
Oral Session #32: Testing Ecological Theory in Restoration Practice.
Presiding: C. Brown
Tuesday, August 6. 8:00 AM to 11:30 AM. Grand Ballroom West, Radisson.
Large-scale experimental tests of recruitment limitation and alien plant invasions.
Siemann, Evan*,1, Rogers, William1, 1 Rice University, Houston, TX
ABSTRACT- Local plant species abundances may be set by the magnitude of local seed supply with seedling success acting as an additional, subsequent filter. The maximum local density of plant species may be determined by the magnitude of seed input. In order to test whether the abundance of an invasive tree species, Sapium sebiferum (Chinese Tallow Tree), in bottomland hardwood forests can be reduced by suppressing local seed production, mature Sapium sebiferum trees were killed in eight 16 hectare plots in the Neches Bottom unit of the Big Thicket National preserve in summer 2000 (~10,000 trees). There has been no appreciable local seed production in these plots for two growing seasons. Eight 16 hectare control plots were also established. Preliminary data showed differences in the tree seedling communities in control and Sapium removal plots. Removal plots had greater Sapium seedling densities nearby killed trees compared to the densities near living Sapium trees in the control plots. This may reflect more open canopies in these areas. Seedling data more representative of the whole plots show the opposite pattern - lower densities of Sapium seedlings in the removal plots. On average the percent of the tree seedling community that was native seedlings tripled after two years in the removal plots. These results suggest that recruitment limitation may have an important role in determining understory composition in these forests. This has practical implications for the management of invasive species.
KEY WORDS: Sapium sebiferum, recruitment limitation, Texas, invasive species