Effects of Three Vegetation Management Strategies on Shore-Flies (Diptera: Ephydridae) in Newly Constructed Treatment Wetlands

Abstract

We tested the effects of three vegetation management strategies for constructed treatment wetlands on adult shore-fly (Diptera: Ephydridae) successional occurrence and emergence in southern California. Before flooding with effluent from a nearby wastewater treatment plant, eight 0.1-ha research cells were randomly assigned to (1) control cells which were burned to reduce the above ground plant biomass, (2) scoured cells which were burned and then scoured with a rock bucket attached to a backhoe, and (3) hummock cells which were burned and scoured before the placement of earthen mounds that provided shallow areas to concentrate vegetation growth within a small area. Emergence traps and pan traps were used simultaneously to capture adult Ephydridae from July 1998 to September 1999. Twenty-eight species of ephydrids from 23 genera were collected; the cumulative number of shore-fly taxa reached its maximum at 135 d after flooding, and exhibited a hyperbolic pattern over time. Only Brachydeutera sturtevanti Wirth differed significantly in its successional mean occurrence in pan traps among vegetation management treatments, being virtually absent from hummocked cells during 1998 but becoming one of the numerically dominant taxa in all treatments by August 1999. Both emergence and pan traps in the hummocked cells captured significantly fewer B. sturtevanti and Notiphila spp. in the other treatments during 1998, but there were no differences in numbers collected among the vegetation management treatments during 1999. Vegetation management significantly slowed the appearance of Ephydridae in constructed treatment wetlands, but only a short period of time (<1 yr) was needed for traps in all treatment cells to capture statistically equal numbers of individuals.