Riparian buffers mitigate effects of pine plantation logging on New Zealand streams: 2. Invertebrate communities

Abstract

The influences on forest stream invertebrate communities of riparian forest type (native/exotic Pinus radiata) and logging, with or without native forest riparian buffers, were investigated at 28 stream sites on Coromandel Peninsula, New Zealand. Stream reaches were surveyed under summer, baseflow conditions in six riparian/forest vegetation types: native forest, mature pine plantations with pines planted to the stream edge, mature pine plantations with native forest in the riparian area, clearcut pine plantations, and logged pine plantations with patch buffers of native forest vegetation (upstream areas clearcut) or continuous buffers along the perennially flowing stream length. Multivariate analyses showed that clearcut reaches differed in invertebrate community structure from pine and native forested reaches, and from logged reaches with continuous riparian buffers. Communities at patch buffer sites were intermediate between these groups. Amongst the common taxa, mayflies were the most sensitive to clearcut logging, with three species less abundant at clear-cut and/or patch buffer sites; only the algal-piercing caddis Oxyethira albiceps (Hydroptilidae) responded positively to logging. Clearcut reaches had lowest diversity, taxon richness, relative abundance and numbers of the sensitive mayfly, stonefly and caddisfly taxa, and index of biotic integrity. In contrast, sites that had been logged leaving continuous buffers did not differ in these biometrics from those in intact native or mature plantation forest, indicating that buffers greatly reduced disturbance associated with logging. Logged sites with patch buffers had biometric values intermediate between clearcut and forested/continuous buffered reaches, indicating less protection from logging impact. Correlation and multiple regression analyses showed that logging impacts are strongly related to increases in periphyton biomass and water temperature, associated with changes in stream lighting, and increased channel instability/fine sediment. The findings indicate that late-rotation exotic pine plantations can support very similar stream invertebrate communities to native forests, and highlight the benefit of retaining forested buffers along stream riparian areas to avoid harvesting impacts on stream habitat and invertebrate communities.