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This study shows that debris flow disturbances that alter in-channel physical conditions or displace organisms exert greater impacts on stream macroinvertebrate community structure than clearcutting disturbances that change energy inputs in steep headwater systems. We surveyed abiotic characteristics and macroinvertebrate communities of 10 steep headwater streams in central Japan that contained a chronosequence of forest stands and debris flow occurrences. Streams of recently logged forests had higher light levels, nitrate concentrations, and stream temperature ranges than streams of mature forests. Streams of middle-aged forests, which experienced debris flows in recent years (1989–1998), had lower abundance of shredders, crawlers, and headwater-adapted taxa than the other streams. A shredder taxon, Gammarus nipponensis, was completely absent in the streams with recent debris flows, despite their dominance in the other streams. Decreases of depositional environment associated with depletion of large wood and loss of channel structure as well as replacement of community members by rapid colonizers appear to be the major mechanisms of structural changes in macroinvertebrate communities affected by debris flows. [ABSTRACT FROM AUTHOR]

The time series properties of unemployment rates for Germany, Japan, the UK and the US are re-examined. Evidence of nonlinear structure in the residuals of the most parsimonious linear ARMA models is reported for all countries except Japan. Modelling this nonlinearity using SETAR models suggests strong asymmetry in unemployment dynamics and the presence of a possible limit cycle for the UK. However, residual diagnostics for these models indicate remaining structure. Alternative TAR models conditioned on past growth rates of industrial production yield substantial reductions in residual variance over both linear and SETAR counterparts, iid residuals in all cases other than the US, and threshold values at or very near zero, clearly identifying the asymmetric behaviour of unemployment during expansionary and contractionary phases of the business cycle. [ABSTRACT FROM AUTHOR]