Biology Reference
In-Depth Information
7.1 Introduction
While the control of some plant invasions may be as simple as removing a small
founding population, more often control is part of a larger vision for the ecological
management and eventual restoration of a natural area (D'Antonio and Meyerson
2002; D'Antonio and Chambers 2006). Ideally, attributes of a “fully restored
ecosystem” as described by the International Society for Ecological Restoration
(http://www.ser.org/) are applicable to the management of widespread invasions in
the context of ecosystem restoration rather than simple species removals. One of
these attributes states that the restored ecosystem should be “self-sustaining and
able to persist under existing environmental conditions.” Using this as a guiding
principle, long-term control of nonnative species should involve the creation of
systems that are resilient to future disturbance and resistant to reinvasion. Thus, two
ecological concepts that are particularly critical to long-term management of plant
invasions are
biotic resistance
and
ecological resilience
.
In this chapter we explore and contrast two case studies in which the concepts
of resistance and resilience play different roles in the management of specific plant
invasions. We focus on two examples of invasion by fire-promoting grasses, one in
Hawai'i and the other in the Great Basin region of the Western USA. These two
systems were chosen because together they provide a range of insights into how the
ecological principles of resistance and resilience can be applied to the management
of persistent or recalcitrant plant invaders. We focus on grass invaders because they
are widespread and difficult to control and because they often dramatically alter
ecosystem structure and functioning. Thus, efforts to manage them or the
communities of which they are now a part are critical to maintaining native
biodiversity and ecosystem functioning in some regions.
7.1.1
Ecological Resistance and Resilience
Since the rise in interest in the field of biological invasions, community ecologists
have explored the role of ecological resistance as an ecosystem property influencing
invasion success (e.g., Rejmanek 1989; D'Antonio 1993; Maron and Vila 2001;
Levine et al. 2004). Despite the extensive recent history of research in this area
(reviewed by Levine et al. (2004) and Bruno et al. (2005) ), land managers have
been slow to embrace the concept into their approaches to
weed
control. Instead,
weed invasions in natural areas have been controlled largely by chemical and
mechanical means, or through prescribed burning and grazing. Such approaches do
not explicitly engage ecological principles but focus instead on a
top-down
approach where the manager is acting as a predator removing the species from the
system (McEvoy and Coombs 1999). This approach has been successful at
eradication of invaders in many discrete isolated areas. Typically, however, little
attention is given to whether the post-removal community has higher resistance to
further weed invasion and increased resilience to future disturbance.
