Defining a regional approach for invasive plant research and management - Invasive Plants: Ecological and Agricultural Aspects - page 129

The research described here is being conducted in the Blue Mountains
Ecoregion of the interior PNW (Fig. 1). It consists of interrelated studies to
assess habitat risk, project species population spread, and determine the life
cycle, dispersal, competition, and containment strategies of the species.
Figure 2 depicts the interrelationships of these studies within our regional
invasive species research framework. We now briefly describe our ongoing
research and how these studies are used to develop a landscape-level projec-
tion of range expansion (Fig. 2) and management of P. recta .
Habitat-level research
Information on the underlying factors that influence P. recta abundance [53,
54, 57] indicates the species has broad ecological amplitude, yet no quantita-
tive assessment of which factors most strongly influence P. recta abundance
had been conducted. A study was implemented using a geographic information
system (GIS) to examine possible relationships between P. recta occurrence
and environmental, historical and landscape variables. These variables includ-
ed habitat type, vegetative canopy cover, slope, elevation, aspect, general soil
type, land use history (disturbance), and proximity to roads. Information from
this study provided insights on the relative contribution of the various factors
to P. recta occurrence and relative abundance, and is now integrated into the
risk assessment and landscape projections of species expansion described
below.
Risk assessment
Anticipating species that may become invasive in particular landscapes and
knowing where to look for them is a particularly important aspect of invasive
plant management. Byers et al. [44] identify four stages of invasive plant risk
assessment for biological invasions of non-indigenous species to occur: 1)
arrival (risk associated with entry pathways), 2) establishment (risk of forming
viable, reproducing populations), 3) spread (risk of expanding its extent), and
4) impact (risk of having a measurable effect on existing species or communi-
ties).
At the Starkey Experimental Forest and Range (SEFR) a risk assessment
(Figs 2 and 4) was conducted to determine what habitats are at risk to P. recta
invasion. SEFR encompasses 7,762 ha with elevations ranging from
1,122-1,500 m in northeastern Oregon. Major plant associations (habitats)
include Abies gradis , Pseudotsuga menzeiseii , Pinus ponderosa ,
Pseudoroegneria spicata , Festuca idahoensis , and Poa sandbergii communi-
ties. Habitats at risk to P. recta invasion were found by integrating three com-
ponents of habitat vulnerability using GIS technology. The three components
are: 1) Susceptibility - vulnerability of each habitat to P. recta establishment.
Susceptibility was determined for each habitat found in SEFR using reports of
P. recta occurrence in other areas of the Blue Mountains; 2) Disturbance his-