Berkeley, California
Dr. D'Antonio's research focuses on what processes control or limit invasions into natural communities and how ecosystem processes are altered by individual species. One goal of the work is to provide this information to land managers.
Native herbivores can be important at limiting plant invasions. For example, in ice plant (Carpobrodus edulis), seedling recruitment is uncommon. Once a plant gets established it becomes a big problem, because of its effects on germination, growth and survival of native species, so it is essential to control it early, at the seedling stage.
Carpobrodus edulis has important effects on soil environment. It causes a substantial decline in pH as well as changes in nitrogen levels and soil micro nutrients. Even two years after eradication, there is still no significant shift back to the original (pre- ice plant) soil conditions. Therefore, if restoration of the native environment is sought, the soil must be altered to promote the return of native vegetation.
In Hawaii, dry forests have been invaded by introduced perennial grasses. These invaders directly effect population dynamics of native species and also have ecosystem effects. One major effect is the promotion of fires. Since grass invasions have taken hold, the frequency and size of fires has increased dramatically. In the region of Hawaii that D'Antonio is studying, a South American grass invades unburned woodland and promotes fire. After fire, another aggressive introduced grass becomes abundant. Native woody components are lost from the system and many areas now look like African savannas.
In such circumstances, how can native biological diversity be restored? Few native trees and shrubs will germinate under the mats of grasses - the seeds are too small and not enough light penetrates the dense grass layers. Some native community may be created by promoting the few fire and grass tolerant native species, but it is not possible to bring back the original ecosystem.