ability of Schinus terebinthifolius to establish and expand following agriculture: (1) abandonment and exposure of an artificial soil and (2) reduced fire frequency (see Figure B–1). The rapid growth and high productivity of this invasive tree are likely due to changes in the soil brought about by rock plowing— namely, increased nutrient release and increased soil depth that allows seedlings to withstand 2–5 months of drought each year (Doren 1997).

Several attempts were made to remove Schinus in the 1970s and 1980s (Doren 1997). These involved herbicides, disking, bulldozing, burning, mowing, and planting and seeding of natives, hardwoods, and pines. All failed. One treatment in 1974 and another in 1983 involved the removal of rock-plowed soil down to the level of hard porous limestone substrate. The promising results led to larger soil-removal treatments 1989; soil was partially removed on 6 ha and completely removed on 18 ha. The site with partial soil removal was recolonized by Schinus, but the area without soil was not (Doren 1997).

The present effort to remove Schinus from about 2,529 ha (6,250 ac= about 10 miles2) grew out of the success of the earlier trial with total soil removal. The restoration target is a muhly grass-sawgrass prairie over 90% of the area and upland hammocks covering about 10% of the area. The hammocks, or mounds, would support pineland and hardwoods. The current plan (ENP 1998) proposes to remove about 5,000,000 yd3 of material over 20 years. Trees are first bulldozed and then shredded and composted. Sediment is trucked to fill old limestone quarries and borrow pits. Once the nearby borrow pits are filled, the spoils will be mounded in place to create upland hammocks and mowed to prevent Schinus dominance. Trees will then be planted on the mounds to restore 40 to 60 ha (100–150 ac) of pineland and hardwood forest. It is expected that one mound would be about 7 m (20 ft) high with 3:1 slopes, covering about 10 ha (25 ac). One mound could accommodate the spoils from about 7% of

FIGURE B–1 Conceptual model of factors facilitating the invasion of Schinus terebinthifolius.



The National Academies | 500 Fifth St. N.W. | Washington, D.C. 20001
Copyright © National Academy of Sciences. All rights reserved.
Terms of Use and Privacy Statement