Applying Ecological Concepts to the Management of Widespread Grass Invasions - Management of Invasive Weeds - page 120

Chapter 7
Applying Ecological Concepts
to the Management of Widespread
Grass Invasions
Carla M. D'Antonio, Jeanne C. Chambers, Rhonda Loh,
and J. Tim Tunison
Abstract The management of plant invasions has typically focused on the removal of
invading populations or control of existing widespread species to unspecified but lower
levels. Invasive plant management typically has not involved active restoration of back-
ground vegetation to reduce the likelihood of invader reestablishment. Here, we argue
that land managers could benefit from the ecological principles of biotic resistance and
ecological resilience in their efforts to control invading plants and restore native spe-
cies. We discuss two similar but contrasting case studies of grass invasion that demon-
strate how these principles can be applied to control and management. In seasonally dry
Hawaiian woodlands, management of invasive fire-promoting grasses has focused on
seeding native species that are resilient to fire disturbance and can coexist with grasses.
Resistance to grass invasions appears to be weak in unburned native habitats. Thus, the
focus of management efforts has been to increase resilience of the native vegetation to
inevitable disturbance. We contrast this with the Great Basin of the western USA where
the annual Mediterranean grass, Bromus tectorum , also has promoted an increase in
fire frequency in shrublands and woodlands. Here, a three-tiered approach has been
employed in which preventative management in the form of fire or fire surrogates is
used in the initial stages of invasion to increase the resilience and resistance of the
native herbaceous vegetation. In transitional stages where B. tectorum is well estab-
lished but not dominant, mechanical or herbicide treatments are used to open up dense
and senescing shrub canopies, thereby increasing vigor of native perennial herbaceous
species through competitive release. The released competitors (perennial grasses) are
then assumed to provide resistance to B. tectorum invasion. Following complete B.
tectorum dominance, the focus of management is intensive seeding of native species to
create resistant plant communities that reduce the likelihood of reinvasion.
Keywords Biotic resistance ￿ Cheatgrass; Ecological resilience ￿ Ecological
restoration ￿ Exotic grasses ￿ Fire ￿ Grass/fire cycle ￿ Great Basin ￿ Hawaii ￿ State
and transition models
C.M. D'Antonio ( ), J.C. Chambers, R. Loh, and J.T. Tunison
Environmental Studies Program, University of California, Santa Barbara, CA 93106, USA
[e-mail]