Defining a regional approach for invasive plant research and management - Invasive Plants: Ecological and Agricultural Aspects - page 137

To detect P. recta infestations in open forest and grassland plant communi-
ties in the Blue Mountains Ecoregion, Naylor et al. [92] evaluated natural color
aerial photography at three spatial scales. Natural color aerial photography is
one of the least expensive remote sensing approaches and color photographs
are widely available. For example the Oregon Department of Forestry regular-
ly collects color photographs for a wide range of resource applications. The
objectives of this study are to 1) evaluate aerial photography effectiveness in
detecting and estimating percent cover of P. recta , 2) determine the minimum
percent cover of P. recta detected at each flight scale and 3) assess this detec-
tion method as a tool for resource managers. Naylor et al. [92] indicated that
natural color aerial photography can be used to identify P. recta populations,
even at low densities and is most effective in grassland communities or open
forests with little canopy cover to inhibit detection. Future research may
employ this technology to analyze more remote areas for P. recta invasion.
Containment and restoration
Containment and restoration experiments are critical when promoting region-
al invasive plant management research programs. There are, however, signifi-
cant conceptual and logistical challenges to implementing scientifically sound
restoration research. Michener [93] reviews these constraints and discusses
appropriate research approaches and analytical tools for ecological restoration
research.
In areas where invasive species are already well established, tools for effec-
tive containment and restoration activities are needed. In the past, weed con-
trol strategies that focused solely on the eradication of undesirable species by
herbicide or fire often failed, as other weeds quickly colonized the area [58].
For decades, herbicides have been an integral part of invasive species man-
agement. For example in 1997, 25% of the 988 million acres of rangeland in
the United States, were treated with herbicides [94]. The application of herbi-
cide alone, however, is rarely successful in controlling invasive species. In the
short term (1-5 years), herbicides may reduce invasive species abundance,
although in the absence of a source of native seeds the treated area is often re-
colonized by the same species or by other invasive plants. For example, areas
treated with herbicide for Centaurea spp and E. esula control often become
dominated by B. tectorum , thus further stressing the plant community [94]. As
a result, management approaches that integrate invasive species control with
habitat restoration through the evaluation of integrated containment/restoration
activities are of most value.
Little information exists to indicate whether herbicides are effective in
reducing P. recta abundance and vigor, or whether subsequent sowing of native
seeds facilitates the establishment of native species on treated areas.
Consequently, a study was established to address which herbicides, rates, and
timing of application are most effective to control P. recta , while minimizing
impacts on native plant species. A further objective is to determine if post-her-
bicide reseeding facilitates native plant establishment. This study involves