Abstract: Native grasses and native wildflowers are declining, especially along roadside right-of-ways due to intensive mowing and herbicide management practices. Roadside right-of-ways undergo regular disturbances such as mowing, maintenance, and road developments that affect soils, groundwater, surface hydrology, and vegetation composition. We investigated species richness and percent coverage within plant communities along highway right-of-ways to determine if reduced mowing increased native plant coverage. The study was conducted using 10 research plots situated along Highway 25 in Oktibbeha and Winston counties, Mississippi. Each research plots consisted of three different treatments as follows: one that included greater than four mowings per year, one mowing only in fall, and one mowing only in fall with a supplemental native wildflower seeding. Using line transect sampling, we detected 277 plant species, which included native and non-native forbs, legumes, grasses, rushes, sedges, and woody perennials (vines, shrubs, and trees). Total percent coverage of native and non-native plants within different growth form categories did not differ among treatments (F2, 96 = 0.45, P = 0.83). However, coverage differed between uplands and lowlands (F1, 96 = 18.22, P {less than or equal to} 0.001), between years (F1, 96 = 14.54, P {less than or equal to} 0.001), between fall and spring seasons (F1, 96 = 16.25, P {less than or equal to} 0.001), and interacted between years and seasons (F1, 96 = 24.08, P {less than or equal to} 0.001) and seasons and elevations (F1, 96 = 5.00, P {less than or equal to} 0.001). Non-native agronomic grasses exhibited the greatest coverage ({greater than or equal to}90%) in all treatments. Percent coverage of each plant growth form was greatest in lowlands. Our research showed an increase of native grasses and wildflower species along roadsides with a reduced mowing regimen. We concluded that the timing and intensity of mowing for the duration of our study had little effect on the species composition of plant communities. However, one mowing per year retained agronomic plant coverage for erosion control and soil stabilization during roadside maintenance. Specific proactive management implementations can include native plantings, selective herbicide use to decrease non-native grasses, continual mowing from roadside edge to 10 meters (m), and only one mowing in late fall, but with an extension of the boundary to reach beyond 10 m from the roadside edge to suppress the invasion of woody plants, which could lead to lower long-term maintenance costs.
Reference S1. Project development procedures manual: chapter 29 – landscape architecture: section 2 highway planting, wildflower planting
Reference S1. California Department of Transportation. 2016. Project development procedures manual: chapter 29 – landscape architecture: section 2 highway planting, wildflower planting. California Department of Transportation, CalTrans. (Editor Gary Birch). Sacramento, California: Division of Design, Chief Office of Standards and Procedures. Pages 29-12 to 29-39. also available at http://www.dot.ca.gov/hq/oppd/pdpm/chap_pdf/chapt29.pdf (698 KB PDF).
Reference S3. Light disking to enhance early successional wildlife habitat in grasslands and old fields: wildlife benefits and erosion potential.
Reference S3. Greenfield KC, Burger LW Jr, Golden L, Graham P. 2005. Light disking to enhance early successional wildlife habitat in grasslands and old fields: wildlife benefits and erosion potential. USDA Natural Resources and Conservation Service, Technical Note No. 190–32. Also available at http://www.fwrc.msstate.edu/pubs/nrcs.pdf (2.55 MB PDF).
Reference S4. Alternative mowing regimes’ influence on native plants and deer.
Reference S4. Guyton JW, Jones JC, Entsminger ED. 2014. Alternative mowing regimes’ influence on native plants and deer. SS228 Final Project Report, Report No. FHWA/MDOT–RD–14–228. Jackson, Mississippi, Mississippi Department of Transportation. Available at http://trid.trb.org/view.aspx?id=1340960
Reference S5. Native warm-season grass restoration in Mississippi.
Reference S5. Hamrick R, Burger LW Jr, Jones JC, Strickland BK. 2007. Native warm-season grass restoration in Mississippi. Mississippi State University Extension Service Publication 2435:1–12. Mississippi State, Mississippi: Mississippi State University. also available at https://www.mdwfp.com/media/7890/nativewarmseason.pdf?iframe
Reference S6. Estimating wildlife habitat variables.
Reference S6. Hays RL, Summers C, Seitz W. 1981. Estimating wildlife habitat variables. Washington, D.C.: Office of Biological Services, FWS/OBS-81/47, U.S. Department of Interior, Fish and Wildlife Service. Available at http://tidalmarshmonitoring.org/pdf/Hays1981_EstimatingWildlifeHabitatVariables.pdf
Reference S7. Assessment of alternatives in roadside vegetation management.
Reference S7. Hill K, Horner R. 2005. Assessment of alternatives in roadside vegetation management. Washington State Transportation Commission. Seattle, Washington: Final Research Report Agreement T2695, Task 67: Roadside Vegetation. Also available at http://www.wsdot.wa.gov/nr/rdonlyres/0cb59701-542e-4df2-b8c8-1aca3cb72172/0/finaluwreport.pdf
Reference S8. Pollinators and roadsides: best management practices for managers and decision makers.
Reference S8. Hopwood J, Black S, Fleury S. 2016. Pollinators and roadsides: best management practices for managers and decision makers. U.S. Department of Transportation and the Federal Highway Administration (FHWA), Report No. FHWA-HEP-16-020. also available at https://www.environment.fhwa.dot.gov/ecosystems/Pollinators_Roadsides/BMPs_pollinators_roadsides.asp
Reference S9. Promoting native plant life along Mississippi’s highways.
Reference S9. Humber J, Entsminger ED. 2011. Promoting native plant life along Mississippi’s highways. The Mississippi Department of Transportation Magazine Connection, pg. 9. Jackson, Mississippi: Mississippi Department of Transportation. also available at https://www.researchgate.net/profile/Edward_Entsminger/publication/285235886_Promoting_Native_Plant_Life_along_Mississippi%27s_Highways/links/565cc65a08ae4988a7bb838a.pdf?origin=publication_detail&ev=pub_int_prw_xdl&msrp=PIUn0gHeToDnFkJXIqzBIpTvpeQetR_kj1gs5Atq55HRnXVMxTqNpfSKDexzXZez2vD51rxWrrmroZ7YHbyzFQ.Y1FuQY6Yk0AJcj3E7sOyRislBVtUIUY8hS7-fX0-IXeiXYGYZA5og09vXAiAKLiTJX_Qm32iM3VrW-sOfhvc1g.vvpKeL7EUOrCcZxBiIX-MVxFQcYWi2lWkg0_gbPuu3qPfd-_smddUaGUI7uCWjkdH1t2RWRbWWkMrywWWFPzdQ
Reference S10. Mitigation measures for highway-caused impacts to birds.
Reference S10. Jacobson SL. 2005. Mitigation measures for highway-caused impacts to birds. Pages 1043–1050 in Ralph CJ, Rich TD, editors. Bird conservation implementation and integration in the Americas: proceedings of the third international partners in flight conference, 20–24 March 2002. Albany, California: Department of Agriculture, U. S. Forest Service, Pacific Southwest Research Station. U.S. Forest Service General Technical Report PSW-GTR-191 Volume 2. also available at https://www.fws.gov/migratorybirds/pdf/management/jacobsen2005highwaymeasures.pdf
Reference S11. Best practices handbook on roadside vegetation management.
Reference S11. Johnson AM. 2000. Best practices handbook on roadside vegetation management. University of Minnesota, Minneapolis: Minnesota Technology Transfer. Minnesota Technology Transfer (T2)/LTAP Program, Center for Transportation Studies Report Number: Mn/DOT 2000-19. also available at http://www.lrrb.org/PDF/200019.pdf
Reference S12. Successional establishment, mowing response, and erosion control characteristics of roadside vegetation in Texas.
Reference S12. Li MH, Schutt JR, McFalls J, Bardenhagen EK, Yong Sung C, Wheelock L. 2008. Successional establishment, mowing response, and erosion control characteristics of roadside vegetation in Texas. Austin, Texas: Texas Department of Transportation Research and Technology Implementation Office. Technical Report: FHWA/TX-08/0-4949-1. also available at http://d2dtl5nnlpfr0r.cloudfront.net/tti.tamu.edu/documents/0-4949-1.pdf
Reference S13. Policy for roadside vegetation management.
Reference S13. Louisiana Department of Transportation and Development. 2000. Policy for roadside vegetation management. Louisiana Register: 1–60. also available at http://wwwsp.dotd.la.gov/Inside_LaDOTD/Divisions/Engineering/Misc%20Documents/Policy%20For%20Roadside%20Vegetation%20Management.pdf
Reference S14. A management guide for invasive plants in southern forests.
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Reference S15. A landowner’s guide to prairie management in Minnesota.
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Reference S18. Assessment of alternatives in vegetation management at the edge of pavement.
Reference S18. Willard R, Morin J, Tang O. 2010. Assessment of alternatives in vegetation management at the edge of pavement. Olympia, Washington: Washington State Department of Transportation. Washington State Department of Transportation, Pavement Edge Vegetation Management, Final Report: WA-RD 736.1. also available at http://www.wsdot.wa.gov/research/reports/fullreports/736.1.pdf
Reference S19. Evaluating alternative methods for vegetation control and maintenance along roadsides: study II.
Reference S19. Young S, Claassen V. 2007. Evaluating alternative methods for vegetation control and maintenance along roadsides: study II. Sacramento, California: California Department of Transportation/University of California Davis. Research Technical Agreement #65A0137. also available at http://www.dot.ca.gov/hq/LandArch/16_la_design/research/docs/Veg_Conversion_Final_Report.pdf
Data A2 Percent Cover by Species All Data
Data S2. Raw data from over 276 vegetation percent coverages by individual species that were collected along a 48.28-km stretch of roadside right-of-ways in northeastern Mississippi from 2010 to 2012. The data are categorized by elevation (upland, lowland), TRT (treatment; M = mow, NM = no-mow, and S = seed), season/year (fall10 = fall 2010, SP11 = spring 2011…), status (N = native, NN = nonnative, Un = unknown status), VegType (vegetation type = forb, grass, legume…), height of vegetation (< 18 in.es tall, 18–36-in. height category, > 36-in. height category), and actual scientific name of each species detected.
Entsminger Percent Cover by Species All_Data.xlsx
Data A3 Percent Coverage All Data
Data S3. Raw data from over 276 vegetation percent coverage within each status and height category that were collected along a 48.28-km stretch of roadside right-of-ways in northeastern Mississippi from 2010 to 2012. The data are categorized by a unique identification field with elevation (Low = lowland, Up = upland), site location number (1, 2, 3, 4, and 5), treatments (Mow = mowing, NMow = no-mowing, and Seed = no mowing with seeding), and season/year (F10 = fall2010, Sp11 = spring 2011…). The status (N = native, NN = nonnative, Un = unknown status), vegetation type (forb, grass, legume…), and the height of vegetation (< 18 in.es tall, 18–36-in. height category, > 36-in. height category) are displayed for an overall value of percent coverage.
Entsminger_Percent Coverage All_Data.xlsx
Data A1 Species Richness Data
Data S1. Raw data from over 276 plant species that were collected along a 48.28-km stretch of roadside right-of-ways in northeastern Mississippi from 2010 to 2012. The data are categorized by years (2010, 2011, and 2012), seasons (fall, spring), elevation (upland, lowland), site location number (1, 2, 3, 4, and 5), and by TRT (treatment; mow, no-mow, and seed). These categories are summarized with NativeSR (native species richness), NonNativeSR (nonnative species richness), UnknownSR (unknown genus), and Total SR (total species richness count).
Entsminger_SpeciesRichness_Data.xlsx
Reference S2. Wildflowers for Indiana highways.
Reference S2. Dana MN, Kemery RD, Boszor BS. 1996. Wildflowers for Indiana highways. West Lafayette, Indiana: Joint Transportation Research Program, Paper 227. Report No. FHWA/IN/JHRP-96/1. Purdue Libraries, Purdue e-Pubs Civil Engineering, 1–162. Found at DOI: 10.5703/1288284313350; also available at http://docs.lib.purdue.edu/cgi/viewcontent.cgi?article=1698&context=jtrp (5.78 MB PDF).
Reference S16. Integrated roadside vegetation management: a synthesis of highway practice.
Reference S16. Transportation Research Board. 2005. Integrated roadside vegetation management: a synthesis of highway practice. Washington, D.C.: National Cooperative Highway Research Program. Found at DOI: 10.17226/23323; also available at http://www.trb.org/Publications/Blurbs/155791.aspx (1.41 MB PDF).
Reference S17. Assessing and managing the ecological impacts of paved roads.
Reference S17. Transportation Research Board, National Research Council. 2005. Assessing and managing the ecological impacts of paved roads. Washington, D.C.: The National Academies Press. Found at https://doi.org/10.17226/11535; also available at https://www.nap.edu/catalog/11535/assessing-and-managing-the-ecological-impacts-of-paved-roads (2.43 MB PDF).