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.

Relationships between riparian buffer widths and the effects of logging on stream habitat, invertebrate community composition and fish abundance

“…Inputs of organic matter were associated with material felled and disturbed in the stream in the clearfelled areas. It should be noted that despite the apparent ameliorative actions of 100-m buffers in the study reported by Growns and Davis (1991), macroinvertebrate community composition in buffered streams was intermediate between unlogged and clearfelled streams. This suggests that even logging within 100-m buffers may still cause community responses at the species level.…”

“…Growns and Davis (1991), in the only intensive study of the effects of logging on stream biota in Australia to date, found that despite evidence for differences in macroinvertebrate community composition (primarily identified to species level) between logged and unlogged streams eight years after logging, there were no significant differences in richness or abundance. The influence of season and location, combined with the small number of treatment replicates, may have precluded observation of real differences in richness or abundance (the combined problems of confounding and Type I1 error).…”

“…Published Australian studies of impacts from logging operations on stream habitats and biota are few (Richardson 1985;Borg et al 1988;Growns and Davis 1991). Growns and Davis (1991), in the only intensive study of the effects of logging on stream biota in Australia to date, found that despite evidence for differences in macroinvertebrate community composition (primarily identified to species level) between logged and unlogged streams eight years after logging, there were no significant differences in richness or abundance.…”

“…Fifty random starts were made to the analysis and the solution with the lowest stress value selected (see Growns and Davis 1991). (Faith and Norris 1989;Belbin 1993).…”

“…Borg et al (1988) reported on the relationship between buffer strip width and both water quality and channel form in several Western Australian catchments, examining differences between streams without buffers or with buffers 50-200 m in width. Growns and Davis (1991) reported changes in stream invertebrate communities that were related to eight-year-old clearfelling operations in Western Australia. Barton and Davies (1993) described the relationship between stream pesticide concentrations, macroinvertebrate drift and buffer strip widths in Tasmanian forestry plantations.…”