Comparison of the macroinvertebrate communities in streams in logged and undisturbed catchments 8 years after harvesting

Abstract

Changes in lotic macroinvertebrate communities 8 years after logging were examined in two sets of paired catchments (Sutton and Lewin) in south-western Western Australia by using analysis of variance, classification (TWINSPAN), and ordination (semi-strong hybrid multidimensional scaling). Both paired catchments contained an undisturbed stream and a stream where clearfelling had been taken to the stream edges. The Sutton catchment also contained a stream where clearfelling had occurred but a 100 m-wide strip of vegetation had been retained as a buffer zone. Differences in richness and abundance of animals between the undisturbed and clearfelled streams in the two catchments were obscured by differences between the sites within each stream. However, ordination of the samples revealed differences in the composition of the macroinvertebrate communities between the clearfelled and undisturbed streams in both catchments. Underlying environmental gradients that separated the invertebrate communities in the clearfelled streams from those in the undisturbed streams, in ordination space, were conductivity, the amount of coarse and fine particulate organic matter, and a reduction in total nitrogen. In all, 11 macroinvertebrate taxa were found to be associated with the separation of samples from the undisturbed and clearfelled streams, this response probably being due to increases in conductivity within the clearfelled streams. Macroinvertebrate community structure in the buffered stream was different from that in the undisturbed stream but was more similar to the latter than to that in the clearfelled stream. Physical and chemical parameters of the buffered stream were also more similar to those of the undisturbed stream. These results indicated that the 100 m-wide buffer zone appeared to be effective in ameliorating any disturbance due to clearfelling.