Is thirty-seven years sufficient for full return of the ant biota following restoration?

Introduction: An assessment of whether rehabilitated mine sites have resulted in natural or novel ecosystems requires monitoring over considerable periods of time or the use of space-for-time substitution (chronosequence) approaches. Methods: To provide an assessment of ecosystem recovery in areas mined for bauxite in 1975, the ant fauna of one area planted with Eucalyptus resinifera, one seeded with mixed native species, one topsoiled but unrestored, and a forest reference was subjected to a ‘long-term’ study by sampling monthly and latterly annually between 1976 and 1989 using pitfall traps. These plots were resampled in 2012. A companion ‘short-term’ chronosequence study was performed in 1979 in 28 bauxite mines of various ages and restored by a range of different methods, plus three forest references. In order to examine the assertion that the observed differences between restored areas and forest references will lessen with time, sampling using comparable methods was repeated in 2012 in seven of the original plots, representing progressive advances in rehabilitation technology: planted pines; planted eastern states eucalypts; planted native eucalypts; planted eucalypts over seeded understorey; and planted eucalypts on fresh, double-stripped topsoil, plus two forest reference sites. Results: Ant and other invertebrate richness in the long-term study was initially superior in the seeded plot, with little difference between the planted and unplanted plots. It was concluded that although composition of the ant fauna had converged on that of the forest over the 14-year period, differences still persisted.The 2012 resampling revealed that ant species richness and composition had deteriorated in the seeded plot, while values in the unplanted plot, which now supported naturally colonised trees and an understorey, had increased. Differences between all rehabilitated plots and forest still persisted. As with the long-term study, the rate of fauna return and the type of ants present in the short-term study plots differed with the method of rehabilitation used, and, in 1979, no plots had converged on the forest in terms of the ant assemblage. By 2012 ant richness increased, and more so with each advance in rehabilitation technology, except for seeding, in which the understorey had collapsed. Double-stripping of topsoil resulted in the greatest improvements in ant species richness, although none of the areas had converged on the forest reference areas in terms of assemblage composition or ant functional group profiles. Furthermore, assemblage composition in the forest had changed over time, possibly due to reductions in rainfall, which further complicates rehabilitation objectives. Conclusions: It is concluded that although rehabilitation can achieve its objective of restoring diversity, the original assemblage has still not been achieved after 37 years, suggesting that a degree of novelty has been introduced into these older-style rehabilitated areas. The company’s current rehabilitation practices reflect multiple advances in their approach, lending optimism that current restoration may achieve something close to the original ecosystem, an outcome that can only be verified by extended studies like the one described here

What caused seven consecutive years of low puerulus settlement in the western rock lobster fishery of Western Australia?

Puerulus settlement in the western rock lobster fishery has remained below average for seven consecutive years (2006/2007–2012/2013), with 2008/2009 being the lowest in over 40 years. Examination of the timing of the start of spawning using fishery-independent data since the mid 2000s indicated that spawning has been occurring earlier. The low settlement appears related to higher water temperatures at the time of the onset of spawning (October) since the mid 2000s. Statistical analysis shows that the most (71%) of the variation in puerulus settlement was explained by the timing of spawning, storm activity during autumn/spring, and offshore water temperatures in February. Earlier spawning may cause a mismatch with other environmental factors such as peaks in ocean productivity and/or storms that assist the larvae return to the coast and offshore water temperatures that help the early stage larval growth. These variables produced a plausible hypothesis to explain the decline in puerulus settlement for these 7 years, including the recruitment failure of 2008/2009. They also predicted the substantial improvement in settlement for 2013/2014. Egg production levels did not to have a significant relationship with puerulus settlement levels after taking environmental variables into account. Further verification with additional years is required to see whether this relationship is maintained. Global climate change may influence these environmental factors: the timing of spawning is influenced by water temperature and there has been a reduced trend of autumn to spring storms off southwest Australia