Jayne Balmer

Living near the edge: Being close to mature forest increases the rate of succession in beetle communities

In increasingly fragmented landscapes, it is important to understand how mature forest affects adjacent secondary forest (forest influence). Forest influence on ecological succession of beetle communities is largely unknown. We investigated succession and forest influence using 235 m long transects across boundaries between mature and secondary forest at 15 sites, sampling a chronosequence of three forest age classes (5-10, 23- 29, and 42-46 years since clear-cutting) in tall eucalypt forest in Tasmania, Australia. Our results showed that ground-dwelling beetle communities showed strong successional changes, and in the oldest secondary forests, species considered indicators of mature forest had recolonized to abundance levels similar to those observed within adjacent mature forest stands. However, species composition also showed forest influence gradients in all age classes. Forest influence was estimated to extend 13 m and 20 m in the youngest and intermediate-aged secondary forests, respectively. However, the estimated effect extended to at least 176 m in the oldest secondary forest. Our environmental modeling suggests that leaf litter, microclimate, and soil variables were all important in explaining the spatial variation in beetle assemblages, and the relative importance of factors varied between secondary forest age classes. Mature-forest beetle communities can recolonize successfully from the edge, and our results provide a basis for land managers to build mature habitat connectivity into forest mosaics typical of production forests. Our results also indicate the importance of forest influence in determining potential conservation value of older secondary forest for beetles.

Moving with the times: baseline data to gauge future shifts in vegetation and invertebrate altitudinal assemblages due to environmental change

Abstract A long-term monitoring program has been established in Tasmania, Australia, as a Satellite Project for the International Biodiversity Observation Year (IBOY). This program aims to monitor distributional change in vegetation and fauna assemblages along an altitudinal gradient (70–1300 m) in response to climate change and other environmental events. Baseline data collected over a two-year period will be available for comparison with data collected in future decades. The vegetation varies with altitude and fire history. The rate of change in vegetation is not continuous along the altitudinal gradient, but is most rapid above 700 m and below the treeline at 1000–1100 m. Most vascular plant species reach the limit of their distribution within this zone. Despite their preliminary nature, the invertebrate data also display altitudinal and seasonal patterns. The treeline and the 700–1000 m zone again appear to be notable in terms of invertebrate distribution. While the composition of ground-based taxa may be closely related to the floristic composition of the vegetation (or its environmental drivers), the airborne invertebrate fauna appears to be more closely related to structural characteristics such as height and density. Of all taxa, the Coleoptera appear to be the best potential indicators across most altitudes and times. Although the current data provide a wealth of inventory and distributional information over altitude, their greatest potential value lies in long-term comparative information. Future sampling should focus not only on changes at and above the treeline, but also on the zone below this where many species are at their altitudinal limits and may be particularly sensitive to climate change.

Distance, environmental and substrate factors impacting recovery of bryophyte communities after harvesting

Aims: Bryophyte re-colonization after disturbance is largely governed by environmental conditions within disturbed forests. In particular, distance to a forest edge is an important predictor of bryophyte community re-colonization, through either direct constraints, such as dispersal limitation, or indirectly by altering environmental conditions. This study examines a range of factors – environmental, distance to an edge, substrate specific environment or local-level environment – to determine which are important in the re-colonization of bryophyte communities after forest harvesting. As bryophyte communities vary with the particular substrate inhabited, responses were examined across four substrates (rock, exposed roots, ground and CWD). Location: Tasmanian southern forests, Australia. Methods: Bryophyte composition was examined on four substrates (ground, coarse wood debris, exposed roots, rocks) within three ages (~7, ~27 and ~45 yr post-disturbance) of harvested wet eucalypt forest. Re-colonization success of bryophyte communities was determined by comparing communities in regeneration forest to mature forest communities using axis scores from one-dimensional constrained ordination. The importance of various environmental conditions for re-colonization success was then modelled. Finally, path analysis was used to determine whether the impact of distance to a forest edge was meditated through its effects on key environmental variables. Results: Multiple environmental factors impacted re-colonization of mature bryophyte communities. Local-level conditions such as microclimate (temperature, humidity and VPD) and LAI were the most important in determining re-colonization across substrates. Path analysis showed that distance to a forest edge had a significant impact on re-colonization success, but only a relatively small part of this was mediated through its impact on environmental factors. Conclusions: Bryophyte re-colonization is driven by a combination of microclimate conditions and factors related to distance from a forest edge (most likely dispersal distance). While some substrate-specific factors impact bryophyte re-colonization success, the consistent impact of local environmental factors across substrates suggests that harvesting management strategies that develop more ‘mature’ microclimate conditions and increase proximity to nearby mature forest patches will be beneficial for all bryophytes communities. As bryophyte re-colonization was correlated with temporally dynamic environmental conditions, we suggest that forest age needs to be considered in future work.