Biology Reference
In-Depth Information
research opportunities for understanding ecological interactions and processes
(Wilkinson 2004; Young et al. 2005). They may allow for real-time observation of
the effects of immigration history or rapid evolutionary processes for community
assembly and the occurrence of alternative ecosystem states (Suding et al. 2004;
Young et al. 2005; Strayer et al. 2006), or help to clarify the roles of biota-environ-
ment feedbacks, such as plant-soil feedbacks, in shaping ecosystem functioning
(Ehrenfeld et al. 2005). Abandoned habitat may be particularly valuable to test
hypothesis in invasion biology. For example, it may be expected that an alien spe-
cies profits less from the release from specialist enemies (enemy release, Keane and
Crawley 2002) in abandoned habitat compared with reference habitat because com-
petitors are more likely to be alien and likewise benefit from enemy release, or
native competitors may also benefit from enemy release in recently assembled
communities.
5.6 Designed Habitat
5.6.1 Habitat Characteristics
Designed habitat is deliberately and strongly manipulated by humans to create a
new habitat that suites conservation objectives (e.g., Conservation Management
Areas in Mauritius and Rodrigues, Mauremootoo and Payendee 2002; Kaiser et al.
2008) (Fig. 5.5). In our classification, designed habitat is characterized by its con-
stant dependence on management (conservation-reliant
sensu
Scott et al. 2005). In
an early management phase, designed habitat will typically be ecologically similar
to anthropogenic habitat insofar as ecosystem patterns and processes are often sim-
plified, and light availability will typically be high because of the removal of former
vegetation. In contrast to anthropogenic habitat, however, soils will often be
degraded and fertility low. With time designed habitat may, depending on habitat
quality and intensity of management, become similar to either abandoned or refer-
ence habitat; and if management stops it will become, by definition, either aban-
doned or reference habitat.
5.6.2
Functional Type of Invasive Alien Species
Alien species present in designed habitat may either invade the habitat without
assistance or be deliberately introduced. Deliberate introductions to designed habi-
tat are not considered invasive because they are part of the design. However, delib-
erate introductions of alien species may later become invasive. In the case of
unassisted invasions, the specific land management regime (e.g., low intensity but
