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10 Applicable Research Reviews

1. Caltrans Finds Success Fighting Invasive Weeds with Fire
Five acres of highway ROW were targeted to learn more about prescribed burns as a management tool in California. The Bear Creek Botanical Management Area contains a plant community remnant with more than 100 native California plant species. It is one of the last examples of Upland Wildflower Fields in California. After careful planning, the District 3 forces coordinated the safe passage of vehicles. The California Department of Forestry and Fire Protection (CDF) conducted the burn. The key target was yellow star thistle which had invaded half the site within a short time. Observations following the fire have shown the prescribed burn to be more effective than the preceding years of mowing, spot spraying, and hand pulling of star thistle. Remember only trained burn crews abiding strict burn protocol should be used in highway corridors.

2. Florida DOT Supports Commercialization of Local Ecotypes.
The University of Florida has worked with the Brooksville Plant Material Center to collect and propagate a Black-eyed Susan commonly used by the Florida DOT. Roadside testing of the Florida ecotype began in 1999 and seed has been made available to commercial growers. Much of the original collected seed was growing under a canopy of slash, loblolly, or longleaf pine that had been subjected to periodic prescribed burns. This kind of success is key to the Florida DOT who set the deadline of 1998 to start using florida-grown seed of native wildflowers. Before this time, no commercial sources of Florida ecotypes existed to supply their needs.

(For more information: Florida Black-eyed Susan Ecotype, Dr. Jeff Norcini at (850) 342-0988, University of Florida, 2002)

3. Iowa Roadside Restoration Benefits Butterfly Populations
Restoration of roadsides to native habitat has been suggested to benefit wildlife in two ways: by adding habitat and restoring connectivity between fragmented reserves. In Iowa, which has one of the highest road densities in the United States, roadside vegetation has traditionally been managed to maintain a monoculture of exotic grass. Recently, many counties have begun integrated roadside vegetation management which both restores native vegetation and reduces the use of herbicides and mowing. This study evaluated the effect of this management regime along central Iowa roadsides. 12 separate roadside areas were surveyed for abundance and species richness of disturbance-tolerant and habitat-sensitive butterflies and compared with nearby roadside dominated by primarily nonnative legumes and /or grasses.

Species richness of habitat-sensitive butterflies showed a two-fold increase on restored roadsides compared with grassy and weedy roadsides. Abundance increased five-fold for native grass and forb habitat over nonnative. Tracking studies found butterflies were less likely to exit the restored roadsides, indicating mortality rates may be lower and offering preliminary evidence that roadsides have the potential to be used as corridors.

(For the entire report, contact Leslie.Ries@NAU.EDU or (520) 523-7839.)

4. Wetland Disturbance Increases the Spread of Invasive Plants.
The spread of invasives like purple loosestrife (Lythrum salicaria), cattail (Typha x glauca), reed canary grass (Phalaris arundinacea), and phragmites (P. australis) has dramatically changed wetland vegetation in temperate North America. Three theories have been advanced: a. Growth is more favorable to the newcomer in new environmental conditions, b. Introduced plants have left their herbivore competition behind, and c. Interspecific hybridization of the new plant and one existing in an area results in a phenotype with advantages to conditions not favorable for either parent. A literature review was done to find support for these theories.

Studies revealed:
a. Few studies compare competition between growth in new range versus historic range.
b. Little evidence is found to support the herbivory idea; but hydrologic alterations could facilitate invasions by cattail and reed canary grass and increased salinity facilitates phragmites.
c. Hybridization is a cause of spread in purple loosestrife and cattail.

For more information, contact Susan M. Galatowitsch, University of Minnesota at 651-645-1715.

5. Erosion Control and Engineering Properties of Native Vegetation....
is an ongoing study by the Texas Transportation Institute. Native grasses and prairie plant associations are well adapted to the harsh open environments shared by many highway roadsides. Because Texas uses Bermudagrass, native and nonnative wildflower mixes, native grass, and crownvetch each were planted and compared. Because the project has only two years' results to report, no conclusions are drawn. Initially Bermudagrass outperformed the other plots. Eroding rain events are planned.

However, the study is continuing and will teach us more. Contact Harlow Landphair for more information at 979-845-1734.

6. Created Wetland Does Not Measure Up to Restored Wetland
An eight year study of wetland restoration and creation in Wisconsin mitigation efforts
underscored the fact that the best solution remains the avoidance of wetland impacts.
In addition the USGS research concluded:
a. the cost of the restored site was 1/15 the cost of the created wetland. The cost of earth-moving is the deal-breaker.
b. Implementation of the restoration was much shorter (two weeks) than wetland creation (six months). And 3) a 1993 wetland delineation compared the sites to find that 60% of the created site passed as wetland while 100% of the restored site was determined to be wetland. Rehabilitating a drained wetland was cheaper, faster, and more successful than creating an artificial wetland. For more information: Randall Hunt, USGS at 608-821-3847.

7. Native/nonnative Cost Comparison
a. Meanwhile, Australia is pushing to preserve native remnants as theirs disappear through continued land-clearing. Building the case includes a benefit cost analysis of remnant vegetation on private property.. Two benefit components underlie the results - a private benefit to the condition and productivity of landholders' properties, and a public benefit associated with biodiversity conservation and aesthetic values. Conservation incentives would be involved. Perceived benefits not documented in this study include: remnant vegetation species control of agricultural pests, riparian vegetation protecting fish stocks, and remnants increasing productivity of properties downstream.

(This ongoing study, Report No. 130 by Michael Lockwood -mlockwood@csu.edu.au)

b. Iowa, a State that lost all its native grasslands during settlement, began a cost analysis of roadside vegetation to compare the costs of using native and non-native species on Iowa roadsides over time. The study will be repeated a couple times to get a fair comparison. Although the results are not yet reported, IDOT continues to increase its native plantings, convinced of the benefits to be proven. (For updates, contact Mark Masteller at 515-239-1424 on Roadside Vegetation Maintenance on Iowa's State and County Roadsides: A Cost Analysis begun in 1995.)

8. ROADVEG Is a Roadside-specific GIS Tool
Developed by the Utah DOT out of necessity, ROADVEG provides roadside specific tool. Call Ira Bickford for your copy at
801-965-4119.

9. Analysis of Construction Soils Now Possible
A practical, cost-effective tool has been developed by Chris Allen of Brigham Young University and will be available soon..

10 Native Grassland Plantings Evaluated in Three State Studies:
a. Texas -Aimed at the best methods to establish and use native grass communities on roadsides, TTI research developed guidelines to aid managers in selecting appropriate management techniques. (Prairie Restoration: An Evaluation of Techniques for Management of Native Grass Communities in Highway roadsides in Texas, Research Report 944-1, TTI, James R. Schuttt and Michael A. Teal, 1994.)

b. Florida - The Florida DOT, University of Florida and The Nature Conservancy explored site preparation, seeding methods, and management treatments in the establishment of native plants on Sandhill roadsides. Conclusions include: 1. Mowing outside the clear zone need not happen more than once every three years; 2. Over the short term, a prescribed burn is not a substitute for mowing woody species, 3. Little bluestem may form a continuous turf,
4. comparison of many planting devices found the hayblower to be the easiest and most efficient, and 5. native cover, resembling natural areas, can be re-established on sandhill soils within 3 years of sowing.

(Native Sandhill Species Revegetation Techniques, The Nature Conservancy-Florida, Doria R. Gordon, 2001)

c. South Carolina - The South Carolina DOT and Clemson University analyzed the I-26 corridor that transects all the soil regions of the State. Generally their roadsides are infertile. Most sites sampled would not be suitable for pasture sods. Although the dominant roadside vegetation is planted to bahiagrass, native plants are found on rights-of-way that are less frequently mowed. The South Carolina natives tolerate infertile soils and are recommended for roadside use. (Establishment and Management of Native Grasses and Forbs in Highway Corridors, William C. Stringer, Clemson University, 2001.)

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This page last modified on August 4, 2004


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