Factors Associated with Invasive Plant Distribution Along Wisconsin Roadsides. Mark Renz & Joslyn Mink University of Wisconsin-Madison

Transcription

1 Factors Associated with Invasive Plant Distribution Along Wisconsin Roadsides. Mark Renz & Joslyn Mink University of Wisconsin-Madison

2 Extent of Roadway System United States Roads cover 1% Ecologically impact 20% a Wisconsin 100,000 miles of roadways b a Forman (2000) b WisDOT (2000)

3 Roadways can facilitate invasive plant dispersal

4 Roadside Vegetation Establishment Prevent erosion control Buffer ecological impacts of road Reduce spread of invasive species Eurasian Turfgrasses Fast establishment

5 Seeding Native Plants on Roadsides Federal Regulations Persist with minimal management along roadsides a Can constrain spread of invasive species b a O Dell, Young, & Claassen, (2007) b Bakker & Wilson (2004)

6 Objectives 1. Determine if planted Eurasian and native seed mixtures inhibit invasive plant cover 2. Identify predictors of high invasive plant cover

7 WisDOT Methods 1. Remove topsoil and keep in piles 2. Road construction

8 WisDOT Methods 3. Return topsoil to roadside 4. Seeding Photo from: FHWA DOT

9 WisDOT Methods 5. Mulch and/or Erosion Blanket 6. Mowing

10 Eurasian Seed Mixes Turfgrasses - Kentucky Bluegrass (Poa pratensis) - Red Fescue (Festuca rubra) - Hard Fescue (Festuca brevipila) - Perennial Ryegrass (Lolium perenne)

11 Native Seed Mixes (used with an Eurasian mix) Grasses Sideoats Grama (Bouteloua curtipendula) Canada Wildrye (Elymus canadensis) Little Bluestem (Schizachyrium scoparium) Big Bluestem (Andropogon gerardii) Forbs Purple Prairie Clover (Dalea purpurea) New England Aster (Symphyotrichum novaeangliae) Western Sunflower (Helianthus occidentalis) Yellow Coneflower (Ratibida pinnata) Showy Goldenrod (Solidago gigantea)

12 Roadsides Visited Sites 24 Eurasian Seed Mixes 11 Native + Eurasian Seed Mixes

13 Methods: Vegetative Cover 300 foot transect 50 points 1 transect / zone Cover Classes (F vs G) Planted species IPAW invasive species Non-planted, non-invasive species Measurements Zone 4 = Backslope Zone 3 = Ditch Zone 2 = Sideslope

14 Additional Site Information DOT Construction Plans Seed Mixes Years since revegetation Soil Samples Salinity Phosphorus Nutrients Recorded at each site Surrounding area land use GPS Coordinates Historical weather and climatic factors Daily traffic levels

15 Overall Plant Cover Across Zones Zone 2 (sideslope) (n=35) Zone 3 (ditch) (n=34) Zone 4 (backslope) (n=27) Cover Class Grass Forb Grass Forb Grass Forb Planted Eurasian Planted Native Invasive Non-planted/ non-invasive Smooth Brome Reed Canary Grass Quack Grass Photo from: IL Wildflowers

16 Effect of Seeding Method on Grass Cover *, ** Significant at the 0.1 and 0.05 probability levels; NS = not significant at P 0.1.

17 Effect of seed mixture on forb cover Cover Class Planted Eurasian Planted Native Plant Zone 2 (sideslope) Non- Inv Inv Zone 3 (ditch) Plant Non -Inv Zone 4 (backslope) Inv Plant Non- Inv P value ns ns ns ns ns ns ns ns ns Inv

18 Most Common Invasive Forbs Plant Species Average Cover When Present (%) Wild Parsnip (Pastinaca sativa) 16 Multiflora Rose (Rosa multiflora) 16 Leafy Spurge (Euphorbia esula) 14 Spotted Knapweed (Centaurea 13 maculosa) Canada Thistle (Cirsium arvense) 11

19 Objective 2: Predictors of Seeding Establishment and Invasive Plants Regression Tree Analysis Exploratory analysis Used 41 factors: location information, soil data, timing and age, weather and climate, cover data Determines and ranks factors explaining the most variance of the dependent variable No predictors found for invasive forbs One predictor found for invasive grasses

20 Invasive Grass Cover: Regression Tree

21 Conclusions Planted native species Poor establishment (< 10% cover) Invasive grasses Not affected by seeding method Correlated with high daily traffic levels Invasive forbs Not affected by seeding method Not correlated with any measured variables

22 Implications Invasive plant spread is not reduced with seed establishment method Improve native seeding establishment Management/prioritization of invasive plants should target: high traffic areas Occur before establishment is initiated Control seed/propagule bank

23 Questions?