Wendy Wright

Does adding wood to agricultural streams enhance biodiversity? An experimental approach

Riparian clearing and the removal of wood from channels have affected many streams in agricultural landscapes. As a result, these streams often have depauperate in-stream wood loads, and therefore decreased habitat complexity and lower levels of in-stream biodiversity. The introduction of wood was investigated as a possible rehabilitation technique for agricultural streams. Wood was re-introduced to eight streams in two separate high-rainfall, intensively grazed regions of Victoria, Australia and the effect on aquatic macroinvertebrate communities was measured. The addition of wood increased overall family richness and the richness of most functional feeding groups occupying edge and benthic habitats within the stream. Wood addition led to less overlap between benthic and edge macroinvertebrate communities, suggesting increased habitat heterogeneity within the stream ecosystem. Of all sampled habitats, wood supported the greatest density of families and was colonised by all functional feeding groups. Wood habitats also had the highest overall richness and supported the most taxa that were sensitive to disturbance. These findings suggest that re-introducing wood to agricultural streams is an appropriate rehabilitation technique where those streams are affected by reduced habitat complexity. Additional work is needed to confirm these findings over larger spatial and temporal scales.

Large versus small wood in streams: the effect of wood dimension on macroinvertebrate communities

Conventionally, most research and restoration involving in-stream wood focuses on large wood (> 0.1 m diameter), excluding any smaller pieces. However, this may neglect a major component of in-stream habitat, as small wood can constitute the majority of pieces, particularly in small streams. The ecological benefi t of large wood is well established, but corresponding benefi ts associated with small wood (0.05-0.1 m diameter) have not been demonstrated. To test the effect of wood dimension on macroinvertebrate community composition, we compared the fauna occupying large wood habitats with that occupying small wood at eight streams in south-eastern Australia. The relationships between wood dimensions and its macroinvertebrate fauna were complex. Community composi- tion did not vary with wood dimension, and no signifi cant correlations were found between other macroinvertebrate attributes (including family richness and evenness) and wood dimension, including diameter. However, analysis of covariance suggested that large wood supported a greater diversity and abundance of macroinvertebrates, indicat- ing that the method of analysis could infl uence the result. Adjustment for differences in sample dimension using rarefaction determined that these fi ndings were likely to be a result of the surface area and volumes sampled varying with the dimension of the wood. Per unit surface area, and per unit volume, small wood supported a similar number of families to large wood. Thus we conclude that, relative to the available surface area, small and large wood can be equivalent in their contribution to the available habitat in a stream. Therefore, the potential value of small wood as a habitat resource warrants its explicit consideration for inclusion in ecological and rehabilitation studies.

Thinning, Fire and Birds in Boola Boola State Forest, Victoria, Australia

Summary Thinning is a silvicultural technique used extensively throughout Australias production forests. The longer-term effects of thinning on forest biota are not well understood. This study provides an insight into the effects of thinning on avifauna and vegetation, 5–10 y after a thinning operation. A paired-site experimental design was used to compare bird density and species richness at thinned and unthinned sites in a mixed eucalypt production forest in Gippsland, Victoria. The 2006–2007 fires across Gippsland directly affected eight of twelve sites in this study, providing an opportunity to investigate the immediate effects of wildfire on birds. Significantly greater numbers of birds and bird species were found at thinned sites, compared with unthinned sites. Differences in vegetation structure and habitat quality were also apparent between thinned and unthinned sites. A reduction in both bird abundance and species richness occurred immediately after the wildfire. Research into the impact of silvicultural techniques, such as thinning, on forest biota is an important step towards achieving ecologically sustainable forestry. Improved understanding of the effect of forestry operations is imperative in order to maximise conservation in production environments.

Identification of key environmental variables associated with the presence of Toothed Leionema (Leionema bilobum serrulatum) in the Strzelecki Ranges, Victoria, Australia

Toothed Leionema is one of four subspecies of Leionema bilobum from the Rutaceae family. A dense shrub or small tree, growing to ~4u2009m high, it is a poorly investigated species which is considered rare in Victoria, Australia. This paper presents the results of a study using Geographical Information Systems and Weights-of-Evidence predictive modelling to assess the importance of seven environmental factors in determining habitat suitability for this species in the Strzelecki Ranges, Victoria. This method is particularly useful in understanding the distribution of rare species, especially where the ecology of the species of interest is not well understood. Of the seven environmental factors considered here, four were found to be important: elevation, aspect, distance to water and distance to plantation (disturbed) areas. The modelling results indicate that areas with elevations between 350 and 550u2009m and a dominant south-western aspect that are close to plantation areas (within 700u2009m), and to water (within 1100–1200u2009m), provide potentially suitable habitat for Toothed Leionema in the region.