Effects of recreational use on branchiopod egg and ephippia density, Black Rock Desert-High Rock Canyon emigrant trails National Conservation Area, Nevada, USA

Abstract

Numerous plays playas occur on valley floors of endorehic basins in arid regions of the western USA. Their openness makes them attractive for hiking, vehicle travel, military, and other uses when dry. Branchiopod crustacean dormant egg banks survive in these systems and are a rich food resource for migrating birds. Brachniecta gigas Lynch, 1937, B. mackini Dexter, 1956, and Lepiduras lemmoni Holmes, 1895, and Moina cf. macrocopa (Straus, 1820) occur in the Black Rock Desert playa, Nevada, USA. We collected playa egg bank samples to determine effects of human use in three studies. We compared intact egg and ephippia density in virgin playa areas with: 1) a heavily used vehicle track, and 2) recreational camping and vehicle activity mitigated by dust abatement in Black Rock City (site of the Burning Man Festival). We also attempted to quantify changes in intact egg and ephippia density through repeated vehicle travel over a track on virgin playa. We found no observed decrease in intact egg or ephippia density attributed to incrementally increased vehicle travel over virgin playa, which may be attributed to strength of the playa substrate matrix. Differences in intact egg and ephippia density were substantially lower in heavily used vehicle tracks than in adjacent playa, but differences were not statistically significant. Density of intact eggs and ephippia in Black Rock City were lower following the festival, but differences were statistically significant only for eggs in camping areas and not roads. Weak effects observed on these roads may be attributed to dust abatement that maintained substrate density.