Effects of alternative conifer release treatments on terrestrial gastropods in regenerating spruce plantations

This study examined changes in terrestrial gastropod density and species composition in the second and third years after the application of conifer release treatments in regenerating spruce plantations. Data were collected monthly from June to September during the summers of 1995 and 1996 from four conifer release treatments (herbicides (Vision® and Release®); motor-manual clearing (brushsaw); and mechanical clearing (Silvana Selective or Ford Versatile)) and an untreated control on each of four replicate blocks. A total of 15 083 terrestrial gastropods, comprising 18 genera and 21 species, was collected using cardboard sheets over the 2 years. Gastropod densities in untreated control areas were 50-60% greater than those in treated areas, in 1995 and 1996 (p = 0.033 and p = 0.0007, respectively). The greatest differences in densities among individual treatments were evident in the third summer following treatments (1996; p = 0.004). Declines may be attributable to decreased litter deposition and changed nearground microclimate on the treated sites. Gastropod densities in nonchemical, cutting treatments started to recover more quickly than those in herbicide-treated sites.