Effect on soil arthropods 1 year after application of chloropicrin to control laminated root rot. III Treatment effects on nontarget soil invertebrates

Soil arthropods were observed as nontarget bioindicators of chloropicrin fumigation used to control Phellinus in Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco) forests of Washington. Three dosages were investigated: 100% and 20% labeled dosages and a 0% control. Area-wide random samples from treated regions revealed few statistically significant (ANOVA, p < 0.05) shifts in abundance of functional guilds (one of eight). Treatment responses were shown by 23 species, a similar number decreased or increased along with increasing dosage. Stump-centered samples (0.5-2.0 m from trunk; "worst case scenarios") revealed significant changes (p < 0.05) in six of eight functional guilds of soil arthropods; most guilds were more abundant in the control and least abundant under 20% labeled dosage. Many common fungivorous oribatid mite species (20 of 63) showed significant stump-centered responses but most springtails (Collembola; 13 of 15) did not. Ordination analyses of random samples showed no area-wide effect of treatment dosage, whereas stump-centered samples revealed that the species compositions of treated versus nontreated communities of predaceous mites, oribatid mites, and endeostigmatid mites were distinct.