Defining a regional approach for invasive plant research and management - Invasive Plants: Ecological and Agricultural Aspects - page 125

Table 2. Primary disturbance types that may modify carrying capacity, K , of habitats comprised pri-
marily of native species in the Starkey Experimental Forest and Range, Oregon

Disturbance Affected plant communities

Fire Grand fir, Douglas-fir, mixed conifer, ponderosa pine, lodgepole pine,

(prescribed and wild) bunchgrass, Sandberg's bluegrass, Idaho fescue, wet meadow, low

sagebrush, and juniper communities

Livestock grazing Plant communities within current grazing allotments, including grand

fir, Douglas-fir, mixed conifer, ponderosa pine, lodgepole pine,
bunchgrass, Sandberg's bluegrass, and Idaho fescue communities

Timber harvest, fuels Grand fir, Douglas-fir, mixed conifer, ponderosa pine, and lodgepole

reduction, or canopy pine stands

thinning activities
Roads All plant communities

scale-dependent and range from individual species to landscapes. Land man-
agers need research that incorporates both specific biological and habitat-level
inputs over a broad landscape. Scales too large to detect local-level invasions
or too small to find and monitor invasive plants effectively are, therefore, of
limited use. Management policies for invasive plants are developed best for
broad regional scales, while managers require tools that directly aid detection,
monitoring, and containment of invasive plants at scales small enough for
eradication or control (Fig. 2).

Species
A regional research program to implement prevention tactics or control and
restoration after exotic plant introduction must necessarily focus on the biolo-
gy of the invading species and steps of the invasion process (above). However,
the species is also likely to affect the composition of plant communities (habi-
tats), and thereby the functions and patterns of those ecosystems and land-
scapes that are invaded.

Habitat
Habitat characteristics and their modification often have a direct bearing on the
success or failure of particular invasions [30]. The environmental factors most
responsible for floristic growth and persistence of invasive plant species are
soil, climate, and land use.
Many studies show that plant growth and invasive plant prevalence occur
within certain ranges of habitats [31], and usually species are most productive
within certain soil types. Although soil classification can be used to study and
develop predictive landscape-level models of plant invasions, soil mapping
units of extensive land management systems are generally too coarse to be of
use for that purpose. In addition, other microsite factors such as small mounds
or ephemeral pools may play a role in the overall invasive process. However,