APPLICATION OF CHLOROPICRIN TO CONTROL LAMINATED ROOT-ROT - RESEARCH DESIGN AND SEASONAL DYNAMICS OF CONTROL POPULATIONS OF SOIL ARTHROPODS

A methodology using soil arthropods as a nontarget assay of chloropicr in fumigation against Phellinus root rot is described. Significant dif ferences in seasonal abundances in control plot populations occurred f or each of the 6 most common trophic guilds. Population densities were highest for springtails (Collembola) and oribatid miles (Cryptostigma ta) during the late summer dry season; densities were highest in early spring for worms (Oligochaeta), mesostigmatid mites, and fungivorous macroarthropods. Biomass was highest for worms and mesostigmatid mites in spring, but fungivorous macroarthropods peaked in late summer. Spr ingtails and oribatids were equivalent throughout the year measured as biomass; population peaks in dry summer are composed primarily of imm atures. Nearly all individual species of springtails and oribatid mite s had population densities that differed significantly by season; indi vidual springtail abundances fluctuated with greater amplitudes than t hose of oribatids. Both springtails and oribatid mites increased signi ficantly in population density and biomass from the Ist to the 2nd yr postharvest. Experiments using soil arthropods as bioindicators in for est soils beneath clearcuttings should be monitored throughout the yea r to avoid confusing treatment effects with normal life history cycles .