- Vera, Christopher J.
The Graduate School, University of Maine
I studied the effects of landspreading pulp and paper miIl sludge in regenerating forest stands on populations of breeding birds, small mammals, and amphibians and on habitat characteristics, and invertebrate abundance (food resources for insectivorous vertebrates). Eight study sites were selected in western Maine and paired based on vegetative structure and composition in summer 1989. Sludge was applied to 1 randomly selected site from each pair in fall 1990. Pre-treatment and post-treatment population and habitat studies were conducted on treatment and control sites in summer 1990 -1992.
Breeding bird diversity was high on all sites in all years. Total small mammal abundance differed among years (p=0.01), but was similar on treatment and control groups and there was no year x treatment interaction (p=0.36). Because densities of most species were low, I analyzed effects on groups of breeding bird and small mammal species with similar feeding or nesting habits (guilds). The abundance of several foraging and nesting guilds and individual species did change (positive and negative) following sludge application, but evidence suggests that these changes were due to minor habitat alteration. Amphibians were not abundant on either treatment or control sites.
Because many species of breeding birds and small mammals occurred inconsistently and at low densities I can not conclude that effects due to sludge application did not occur. However, abundance of most species was similar on treatment and control sites which suggest that large negative effects are not likely. Habitat characteristics exhibited little change after sludge application (increased foliage below 1.0 m on sludge amended sites) and total invertebrate abundance (food resources for insectivores) was similar on treatment and control sites after sludge application.
In addition to the lack of overt effects on wildlife populations, several lines of evidence suggest that sludge did not have a direct effect on individuals or populations: 1) 2,3,7,8- tetrachlorodibenzo-p-dioxin (TCDD) and 2 ,3,7 ,8 tetrachlorodibenzofuran (TCDF) concentrations were low in shrews and bird egg tissues studied by Martin (1991) , 2) earthworms, considered a major pathway for transfer of TCDD and TCDF to some small mammal and bird species, were rare, 3) some small mammal populations increased substantially despite the presence of sludge , and 4) I found no evidence of effects on reproduction in red-backed voles.