Impact of all-terrain vehicles (ATVs) on pickleweed ( Salicornia virginica L.) in a San Francisco Bay wetland

Abstract

All-terrain vehicles (ATVs) are widely used in a variety of wetland management activities, but their ecological effects on vegetation are poorly known. Two types of ATVs – the Argo^TM, and Lightfoot^TM – were tested in Petaluma Marsh, Sonoma Co., California, to determine their effects on pickleweed ( Salicornia virginica) in terms of: (1) stem-height reductions and stem breakage (as biomass), by simulating light (a path traversed twice) and heavy vehicle use (20 times), and by evaluating damage immediately after manipulation and one year later; and, (2) biomass and growth by using a BACI (before-after-control-impact) design, with two sets of replicated samples collected before a light-use treatment, two sets after treatment (during the same growing season), and one set the following year. Stem height was significantly reduced by both vehicles immediately following use, and was similar for both light and heavy use; biomass of broken stems was significantly higher for the Lightfoot^TM than for the Argo^TM, and with heavy use by both vehicles. One year later, biomass of broken stems was not significantly different in light use treatments with either vehicle, but lower stem height was still visually evident from Lightfoot^TM in heavy use treatments. Post-treatment biomass-growth measurements were significantly lower for both vehicles during the same growing season, but no significant differences were found between either vehicle treatment and controls one year later. However, the Lightfoot^TM treatment had lower productivity. Results indicated that even limited ATV use can cause immediate impact to pickleweed but that limited use with soft-tread vehicles, like the Argo, can recover within a year. Management of pickleweed wetlands should involve vehicles with non-damaging tracks or tire tread and, when possible, walking is preferable to reduce immediate habitat damage.