Golf Courses as a Source of Potentially Invasive C3 Grasses.

Creeping bentgrass (Agrostis stolonifera L.; CBG), Kentucky bluegrass (Poa pratensis L.; KBG), and fine fescue species (Festuca spp.; FF) are commonly used as turf on golf courses.  All have been identified as invasive species by governmental or non-governmental groups.  We hypothesized that abundance of these grasses in naturalized areas would decline with distance from the golf course.  We surveyed naturalized areas surrounding 12 Wisconsin golf courses, classified by age groups (< 20, 25-50, and > 75 years), historical vegetation (hardwood or mixed forest, pine barrens, prairie), and current vegetation.  Sampling frames were placed at 3, 6, 9, 12, 24, 48, and 96 m along both sides of transects spaced 150 m apart.  A Daubenmire cover class rating was assigned for each turfgrass species (0=none, 1=>0-5%, 2=5-25%, 3=25-50%, 4=50-75%, 5=>75%).  KBG was found in 13% of 2433 quadrats, FF in 9%, and CBG in 1%.  Daubenmire scores for KBG and FF showed an inverse relationship with log-linear distance from maintained turf at most golf courses.  Scores never achieved a 2 except for FF at one golf course in a highly disturbed setting.  Age, historical, and current vegetation classes each accounted for less than 25% of treatment variability, indicating much of the turfgrass presence was due to other factors.  Turfgrasses were sometimes in disturbed sites (ant mounds, trails).  KBG and FF occurred most often in open, not wooded, areas.  These grasses existed only as a minor part of the ecosystems evaluated.