Unmined Forest Research Articles

Assessing the success of mine restoration using Hemiptera as indicators

Understanding trends in assemblage composition of key invertebrate groups can provide important insight into the ‘condition’ of, or changes in, the environment. Species density, abundance and composition of Hemiptera (true bugs) were assessed in jarrah (Eucalyptus marginata) forest and a chronosequence of restored bauxite mine pits near Boddington, Western Australia, in order to evaluate how restoration was progressing. A significant difference was uncovered for hemipteran species density between the youngest restored treatment and forest. In contrast, hemipteran composition was distinct between the forest and all restored treatments. Hemipteran composition was associated with the presence of the plant species Conostylis setigera and Trichocline spathulata, and plant structure between 160–180 cm and 260–280, plus soil pH. Restoration was successful in returning Hemiptera with respect to species density, but restoration was yet to attain a similar composition of Hemiptera to that of unmined forest, despite some of the restored sites being almost 20 years old. These results are similar to those of other studies that have assessed the response of Hemiptera to disturbance, and highlight the need to wait for considerable periods in order to achieve restoration goals. This study also confirms the utility of Hemiptera as bioindicators of environmental ‘condition’ and change.

Arthropods in coarse woody debris in jarrah forest and rehabilitated bauxite mines in Western Australia

• Coarse woody debris (CWD) is returned to Alcoa’s rehabilitated mined areas in the jarrah forest as potential vertebrate fauna habitat, however, its value for invertebrate fauna has not been investigated. We sought to determine if CWD in rehabilitated areas supported a similar arthropod fauna to that on fallen logs in the adjacent unmined jarrah forest. • Using emergence tents, sampling from logs in 5-year old and 15-year old rehabilitated forest, and in unmined forest, yielded 2 266 specimens from 187 taxa. Collembola (43% of total) and Acarina (32%) were the most abundant groups, followed by Diptera (11%), Araneae (4%) and Coleoptera (3%). • There were no significant differences in either taxa richness or overall abundance among the three forest types. However, community composition varied significantly. Species richness from the Araneida, Coleoptera and Diptera was highest in the 5-year old rehabilitated forest, while Collembola and Acarina were better represented in the unmined forest; this was related to changes in the environment surrounding the logs as rehabilitated forest develops, and to log condition. The composition of arthropods on logs in the 15-year old rehabilitated forest was intermediate, indicating a trend of increasing similarity to the unmined forest in arthropod fauna as the rehabilitated forest ages. • We suggest that over longer time periods, CWD in rehabilitated forest will support arthropod communities similar to those found in unmined forest. Future work should determine if returning logs to mined areas facilitates the return of CWD-dependent taxa.

Do Thinning and Burning Sites Revegetated after Bauxite Mining Improve Habitat for Terrestrial Vertebrates?

Thinning and burning forests established on revegetated mine pits in jarrah (Eucalyptus marginata) forests of south-west Australia is being considered as a management option to accelerate succession in sites with excessive tree densities. To assess the impact of thinning and burning on reptiles and small mammals, we installed trapping grids in eight thinned and burned sites, each paired with untreated controls. Of the eight pairs, four were in rehabilitated sites (planted with nonlocal species) and four were in restored sites (seeded with local species). Thinning and burning had no significant impact on the small mammal community, although Cercatetus concinnus was more abundant in rehabilitated sites. In contrast, thinning and burning significantly increased reptile abundance and species richness, with two species (Morethia obscura and Menetia greyii) only recorded in thinned and burned sites. We concluded that thinning and burning was a successful management option in revegetated mine pits in jarrah forests, particularly because reptile communities created by thinning and burning were more similar to those in unmined forest. Although published studies for comparison are few, we expect thinning and burning to have generally positive effects on reptile communities in forest ecosystems where fire is an important disturbance agent. Our study emphasizes the importance of monitoring revegetated areas over time periods sufficient to detect deviations from desired successional trajectories, so that management options, such as thinning and burning, can be implemented if required.

Changes in the extent of surface mining and reclamation in the Central Appalachians detected using a 1976–2006 Landsat time series

Surface mining and reclamation is the dominant driver of land cover land use change (LCLUC) in the Central Appalachian Mountain region of the Eastern U.S. Accurate quantification of the extent of mining activities is important for assessing how this LCLUC affects ecosystem services such as aesthetics, biodiversity, and mitigation of flooding. We used Landsat imagery from 1976, 1987, 1999 and 2006 to map the extent of surface mines and mine reclamation for eight large watersheds in the Central Appalachian region of West Virginia, Maryland and Pennsylvania. We employed standard image processing techniques in conjunction with a temporal decision tree and GIS maps of mine permits and wetlands to map active and reclaimed mines and track changes through time. For the entire study area, active surface mine extent was highest in 1976, prior to implementation of the Surface Mine Control and Reclamation Act in 1977, with 1.76% of the study area in active mines, declining to 0.44% in 2006. The most extensively mined watershed, Georges Creek in Maryland, was 5.45% active mines in 1976, declining to 1.83% in 2006. For the entire study area, the area of reclaimed mines increased from 1.35% to 4.99% from 1976 to 2006, and from 4.71% to 15.42% in Georges Creek. Land cover conversion to mines and then reclaimed mines after 1976 was almost exclusively from forest. Accuracy levels for mined and reclaimed cover was above 85% for all time periods, and was generally above 80% for mapping active and reclaimed mines separately, especially for the later time periods in which good accuracy assessment data were available. Among other implications, the mapped patterns of LCLUC are likely to significantly affect watershed hydrology, as mined and reclaimed areas have lower infiltration capacity and thus more rapid runoff than unmined forest watersheds, leading to greater potential for extreme flooding during heavy rainfall events.

Vertebrate Fauna Recolonization of Restored Bauxite Mines—Key Findings from Almost 30 Years of Monitoring and Research

Abstract Studies into the processes of vertebrate fauna colonization of Alcoa’s restored bauxite mines began around 1975. This recognized the key role of vertebrate fauna in jarrah forest ecosystem processes, and also the fact that some species were rare, so priority was given to determining their status in unmined forest, and promoting their return to restored areas following mining. Long‐term studies have since taken place on mammals, birds, and reptiles both in unmined forest and in restored areas of varying ages and techniques. Mammal recolonization varies between species depending on species’ food and shelter requirements and their distribution and abundance in the surrounding forest. Birds rapidly recolonize and 95% of species have been recorded in restoration. Bird community structure changes with restoration type and age, and in current restoration, it is similar to that of unmined forest by the age of 10 years. Studies on reptiles have shown that 21 of 24 species have recolonized. The remaining three include one legless lizard and two snakes, all of which feed on small vertebrates (e.g., skinks) and require shelter in the form of logs, stumps, and coarse woody debris. Some other reptile species consistently occur in restoration in lower densities than in unmined forest, and current studies are investigating the causes of this. Together, studies on these three vertebrate fauna groups have provided valuable, complementary information on their habitat requirements, and the extent to which Alcoa’s restoration program has been successful in reestablishing this important component of the jarrah forest’s biodiversity.

Return of Ecosystem Function to Restored Bauxite Mines in Western Australia

AbstractA critical aspect of reestablishing a self‐sustaining Jarrah (Eucalyptus marginata) forest ecosystem to bauxite‐mined areas is to ensure that vital ecosystem functions such as litter decomposition and nutrient cycling are returned. Significant research has been undertaken over the past 20 years relating to litter decomposition and nutrient cycling. Studies have shown that litter accumulates rapidly in restored areas (1–4 ton ha−1yr−1) and the accumulated litter tends to be richer in nitrogen due to intentionally elevated densities of nitrogen‐fixing species. This leads to a lower (carbon:nitrogen) C:N ratio (60:1 compared to 130:1 in unmined forest) that may promote mineralization of organic N to inorganic forms in restored areas. The major nutrient store in the unmined forest is in the soil and returning soil during the restoration process largely conserves this resource, particularly in relation to P. Short‐term plant macronutrient requirements for growth are readily restored by fertilizer application. Studies on the reaccumulation of nutrient pools in the successional development of restored areas have shown that pools equivalent to the unmined forest are established within 10–20 years. Ongoing research is focusing on the rates of cycling processes in burnt and unburnt restored areas, and comparing these to the unmined forest to ensure that key functions have been reestablished. To date, all measured ecosystem function parameters are indicating that restored areas have achieved or are on a trajectory toward a self‐sustaining Jarrah forest ecosystem.

Restoring Jarrah Forest Trees after Bauxite Mining in Western Australia

Abstract The overstory of the jarrah forest is dominated by Jarrah (Eucalyptus marginata) with a smaller proportion of Marri (Corymbia calophylla). There are also several smaller tree species in the areas where Alcoa mines. Alcoa’s restoration aims to restore all these species at densities similar to the unmined forest. This paper describes the establishment, survival, and growth of these trees with particular focus on Jarrah. Factors affecting the growth and form of Jarrah are also discussed. Establishment of Jarrah from seed in restored sites is variable (mean 10%), and once established, survival is high over two summer droughts (96%) and still high (mean 83%) after about a decade regardless of the presence of the Jarrah dieback disease Phytophthora cinnamomi. High establishment densities (10,000 stems/ha) show mortality rates of 22% after a decade. Growth rates of Jarrah trees are high (1.5–2.7 m2·ha−1·yr−1 basal area), similar to tree growth in unmined forest following clear‐fell operations. Jarrah responds to both N and P fertilizers when very young but the response to early N application is not significant after approximately one decade. Between one‐ and two‐thirds of Jarrahs established from seed grow into saplings, but this proportion decreases with increasing tree density. Closer tree spacing results in more single‐stemmed Jarrah trees at the expense of growth. Tree seed used for restoration should be sourced from northern Jarrah forest areas with similar soil type and rainfall. Seed from outlier populations and coastal plain vegetation types should not be used.

Hydrology and Bauxite Mining on the Darling Plateau

Abstract A review was undertaken of the interaction between bauxite mining, its restoration, and the hydrology of the Darling Plateau. Alcoa’s mining operation is predominately within the water supply catchments of Perth, giving rise to three hydrological issues: turbidity, stream yields, and stream salinity. Turbidity management is effected through attention to detail in day‐to‐day operations. Due to the high rates of evapotranspiration, yields from Jarrah forest catchments are low by normal standards, varying from 25% of rainfall in the highest rainfall area to less than 1% of rainfall in the lowest; this has been further exacerbated by the below‐average rainfall since 1975. These low yields have resulted in increased interest in stream yields from mined and restored mine areas and how these may be maintained compared with unmined forest. Under current rainfall regimes, it is unlikely that there will be a significant salinity response due to Alcoa’s mining, but it is inadvisable to discount the salinity issue in the lower rainfall zone, and research will need to consider the possibility of further climate change.

Restoring a Jarrah Forest Understorey Vegetation after Bauxite Mining in Western Australia

Abstract The Southwest of Western Australia is one of the world’s biodiversity hotspots. In the jarrah forest there are at least 300–400 plant species in vegetation that is typically mined and as many as 163 species per 0.1 ha. Hence, restoring the plant species to post‐mining areas is seen as a priority. Approximately 70% of understorey richness is returned via the direct transfer of fresh topsoil. Additions of provenance‐correct seeds of between 78 and 113 native jarrah forest species add significantly to post‐mining species richness. Many of the broadcast seeds receive a prebroadcast heat or smoke treatment to increase germinability. Approximately 20 additional species are produced by vegetative multiplication or tissue culture and planted into restored areas. Though sequential improvements during the past 30 years, Alcoa now achieves its target to establish in restored areas the same number of native plant species per 80 m2 as the natural forest. Resampling of permanent plots revealed that species composition of older post‐mining areas does not become more similar to unmined forest over one to three decades. Few species (mostly orchids) establish after the first year of restoration and adherence to the initial floristic composition model of forest succession applies to jarrah forest mine site restoration in Western Australia. Alcoa’s strategy, therefore, is to maximize the diversity of understorey species in newly restored sites at the first attempt. Future research will investigate methods to further increase the density of the fire resprouter species, a group of species currently under‐represented in the restored bauxite mining sites.

Fire and Silvicultural Management of Restored Bauxite Mines in Western Australia

Abstract To be self‐sustaining in the longer‐term and meet defined completion criteria, it is important that the management of restored bauxite mines can be integrated with the surrounding unmined Jarrah (Eucalyptus marginata) forest. A number of research projects relating to fire management have been undertaken in restored areas over the past 15 years. The broad objectives of these studies have been to assess the resilience of different‐aged restored sites to fire and define the most suitable fire regime (season, intensity, and frequency) to utilize in the management of these areas. Restored areas were found to be a low fire risk up to five years of age because litter fuel was discontinuous and could not normally carry the fire. Between the ages of five and 12–15 years, restored areas were very susceptible to fire due to high fuel loads and a prominent midstory of senescent legume species. However, if burnt at this age, restoration areas were extremely resilient. Restored areas that are older than 12–15 years can be integrated with prescribed burning of the surrounding unmined forest because the midstory layer has collapsed and the overstory is now separated from the understory fuel. The most suitable fire regime to utilize in restored areas is low‐ to moderate‐intensity spring burns. Silvicultural management of restored areas has recently been investigated incorporating noncommercial thinning and commercial harvesting operations in association with prescribed burning. Restored areas of suitable ages appear to be able to be integrated with the management regimes commonly used in the Jarrah forest.

Ectomycorrhizal fungal communities of rehabilitated bauxite mines and adjacent, natural jarrah forest in Western Australia

Species richness and species composition of ectomycorrhizal (EM) fungi were compared among rehabilitated mine sites and unmined jarrah forest in southwest Western Australia. Species richness, measured in 50 m × 50 m plots, was high. In the wetter, western region, mean species richness per plot in 16-year-old rehabilitated mine sites (63.7 ± 2.5, n = 3) was similar to that of unmined jarrah forest (63.6 ± 9.6, n = 9). In the drier, eastern region, species richness in 12-year-old rehabilitated mine sites (40.3 ± 2.1, n = 3) approached that of nearby forest (52.4 ± 9.3, n = 9). Species composition was analysed by detrended correspondence analysis. Rehabilitated sites of similar age clustered together in the analysis and species composition was closer to the native jarrah forest in the older rehabilitated plots. In unmined forest, species composition of fungal communities in the wetter, western region was different from communities in the drier, eastern region.

Colonisation of jarrah forest bauxite-mine rehabilitation areas by orchid mycorrhizal fungi

Orchids require mycorrhizal fungi for germination of seed and growth of seedlings. The colonisation of bauxite-mine rehabilitation areas by orchids is therefore dependent on the availability of both seed and mycorrhizal fungi. Orchid mycorrhizal fungi baiting trials were carried out in rehabilitation areas that were 1, 10 and 26 years old (established in 2001, 1992 and 1976) and adjacent unmined jarrah forest areas at Jarrahdale, Western Australia. Fungal baits consisted of buried six-chambered nylon-mesh packets containing seed of six jarrah forest orchid taxa, Caladenia flava subsp. flava R.Br., Disa bracteata Sw., Microtis media subsp. media R.Br., Pterostylis recurva Benth., Pyrorchis nigricans (R.Br.) D.L.Jones & M.A.Clem. and Thelymitra crinita Lindl. Detection of orchid mycorrhizal fungi was infrequent, especially at the youngest rehabilitation sites where only mycorrhizal fungi associated with P. recurva were detected. Mycorrhizal fungi of the other orchid taxa were widespread but sparsely distributed in older rehabilitation and forest areas. Detection of mycorrhizal fungi varied between taxa and baiting sites for the two survey years (2002 and 2004). Caladenia flava subsp. flava and T. crinita mycorrhizal fungi were the most frequently detected. The presence of C. flava mycorrhizal fungi was correlated with leafy litter cover and maximum depth, and soil moisture at the vegetation type scale (50 × 5 m belt transects), as well as tree and litter cover at the microhabitat scale (1-m2 quadrats). The presence of T. crinita mycorrhizal fungi was positively correlated with soil moisture in rehabilitation areas and low shrub cover in forest. The frequency of detection of orchid mycorrhizal fungi both at rehabilitated sites (15–25% of baits) and in unmined forest (15–50% of baits) tended to increase with rehabilitation age as vegetation recovered. The failure of some orchid taxa to reinvade rehabilitation areas is unlikely to be entirely due to absence of the appropriate mycorrhizal fungi. However, since the infrequent detection of fungi suggests that they occur in isolated patches of soil, the majority of dispersed orchid seeds are likely to perish, especially in recently disturbed habitats.

Ecology of the western bearded dragon (Pogona minor) in unmined forest and forest restored after bauxite mining in south-west Western Australia

Forest areas restored after mining typically take decades, or longer, before they resemble the original vegetation community. Understanding how fauna succession varies with plant succession requires detailed knowledge of an animal’s ecology. Knowledge of an animal’s ecology can also be used to predict faunal responses to management manipulations and enable techniques to be developed that accelerate the return of fauna to restored sites. We radio-tracked western bearded dragons (Pogona minor) in a mix of unmined forest sites and sites restored after bauxite mining, in the jarrah forest of south-west Western Australia, to determine critical resources and important microhabitats for dragons. Dragons were generalists – utilising a range of microhabitats – and adaptable, adjusting their microhabitat use depending on availability. Individuals also differed significantly in their microhabitat use and did not appear to have a defined home range. We concluded that the species would rapidly recolonise restored sites and that no modifications to current restoration practices were required to accelerate their return. Prescribed burning of restored areas could negatively affect this species but the effect would be short-term (<2 years). The approach used in this study could be used to develop management prescriptions that accelerate the return of late-successional species to restored sites.

Vegetation Succession After Bauxite Mining in Western Australia

Abstract Alcoa World Alumina Australia has been rehabilitating bauxite mines in the jarrah forest of Western Australia for more than 35 years. An experiment was established in 1988 using three different seed treatments (legume and small understorey mix, small understorey mix only, and no seed) and two fertilizer treatments (N and P, and P only). The objectives of this study were to (1) document vegetation changes in the first 14 years after bauxite mining; (2) assess whether the vegetation is becoming more similar to the unmined forest; and (3) gain a better understanding of successional processes. Seed treatments significantly affected 13 of the 14 measured vegetation characteristics. Native species richness was higher in seeded than in unseeded sites at 1, 2, and 5 years of age, whereas diversity and evenness were generally higher at all assessment ages. Exotic species density was higher in unseeded than in seeded sites from 5 years onward, whereas richness was higher from 8 years onward. Nitrogen fertilizer significantly increased exotic species richness, density, and cover. Ephemerals dominated plant density in all rehabilitation treatments over time, whereas seeder species dominated cover. In contrast, resprouting species dominated density and cover in the unmined forest. Orchids were the only species that were not present in the first year in rehabilitated sites but increased in abundance over time. Vegetation composition in rehabilitated areas did not become more similar to the unmined forest during the 14 years since seeding, instead strongly reflected the initial species mix. Rehabilitated bauxite mines appear to follow the initial floristic composition model of succession.

Restoration of a forest ecosystem: The effects of vegetation and dispersal capabilities on the reassembly of plant-dwelling arthropods

Restoration of degraded forest ecosystems is critical to conservation, but it is unknown if all components can be successfully restored. Despite the obvious dependence of plant-dwelling arthropods on plants, there are few empirical tests to show if restoring the plants also restores the plant-dwelling arthropods, or if other factors inhibit recolonisation. This paper tests the congruence in reassembly trajectory between these two groups and the role of dispersal capabilities on arthropod recolonisation, using Hemiptera. Plants and arthropods were sampled along a chronosequence of individual mine pits representing increasing ages since restoration works, and surrounding unmined forest. Changes in the richness, composition and structural complexity of the vegetation are described. These data are compared to Hemiptera sampled by beating and vacuuming over 18 months. Following the initial establishment of vegetation, the richness of plant species remains at a plateau as pits age, and below that found in unmined forest. In contrast, some structural attributes of the vegetation in pits become more similar to the forest with time. As pits age, dead vegetation below 20 cm thickens and living midstorey vegetation thins. Plant species composition changes with time but is not tracking directly toward unmined forest. The abundance and richness of hemipteran species remain constant as pits age (∼74.5 species), at a similar value to that in the forest. Recolonisation by Hemiptera that are brachypterous (with permanently reduced wings) is markedly slower than for winged taxa. That said, the compositions of plant and hemipteran species follow a similar trajectory after mining (i.e., there is high congruence between the two taxa). Hemipteran species composition in the oldest pits sampled (9-year-old) is not tracking directly toward that found in unmined forest. We conclude that for plant-dwelling arthropods, the early stages of reassembly are characterised by a high abundance of a generalist species and the slow recolonisation by specialist taxa and fauna with limited dispersal abilities (e.g., brachypters). Thereafter, return to a composition similar to that prior to the disturbance depends upon the progress of vegetation reassembly. To obtain plant-dwelling arthropod assemblages characteristic of unmined forest, restoration must reinstate the plant species and structural complexity of the vegetation found in the forest (particularly long-lived species and ground covers).

Thirteen-year growth of jarrah (Eucalyptus marginata) on rehabilitated bauxite mines in south-western Australia

Summary Alcoa's objective is to restore its bauxite mines in south-western Australia to a productive self-sustaining jarrah forest. This paper describes the growth and form of 13-y-old jarrah (Eucalyptus marginata) trees established from seed and planted seedlings, and subject to various fertiliser, understorey seed and spacing treatments. Seeded jarrah had a mean establishment density of 2662 stems ha−1 and a density of 2300 stems ha−1 after 13 y, a survival rate of 86%. Sixty-two per cent of the seeded trees developed into saplings (> 1.5 m tall). The saplings had a mean height of 9.0 m and dbhob of 14.4 cm after 13 y. The mean density of potential sawlogs (trees with a single stem to at least 2 m) was 1297 stems ha−1 after 13 y. The presence of tall native legumes (acacias) decreased the percentage of trees that became saplings from 72% to 53%. When N fertiliser was not provided the legumes had a suppressive effect on the basal area and bole volume of potential sawlogs, reducing them to 60% and 57%, respectively, of the values without legumes. Planted jarrah trees had a mean survival rate over all treatments of 84% after 13 y. Closer tree spacing (particularly 1 m × 1 m) resulted in significantly lower survival (77%) than the wider spacings. Inclusion of tall native legumes with closer tree spacing reduced survival even more (69% at 1 m × 1 m). The mean sapling height across all planted treatments was 9.1 m. The mean dbhob was 15.2 cm with 67% becoming saplings. Closer tree spacing had the strongest effect in significantly reducing all of these parameters. Tall native legumes reduced the dbhob of the jarrah trees and reduced the overall mean height of all jarrah by limiting the proportion of jarrah that became saplings. Absence of added N fertiliser also significantly reduced these measures. Basal areas were similar in rehabilitated and unmined forest after 13 y. Mean annual growth increments (1.52 m2 ha−1 seeded, 2.72 m2 ha−1 planted) were similar to those reported for similar aged regrowth forest (2.62 m2 ha−1) and higher than older thinned (0.45 m2 ha−1) or unthinned (0.19 m2 ha−1) unmined forest. Basal area increments were higher from 8–13 y than 0–8 y, indicating that growth rates were not slowing down over this period. The optimum stocking rate for jarrah in rehabilitated bauxite mines will be a balance between growth rate, tree form, other environmental factors and cost considerations. The current rehabilitation prescription aims to establish 1300 stems ha−1 of ‘total eucalypts’ by broadcast seeding (jarrah and marri — Corymbia calophylla). This study indicates that an initial stocking of 1300 stems ha−1 is optimum and meets Alcoa's mine rehabilitation completion criterion of providing at least 300 potential sawlogs ha−1 at 15 y of age.

Interaction of multiple disturbances: importance of disturbance interval in the effects of fire on rehabilitating mined areas

Abstract Multiple disturbance regimes are increasingly common as novel anthropogenic disturbances are added to existing natural disturbances. However, it is generally unknown whether simultaneous or sequential effects of different forms of disturbance are predictable from the independent effects of each disturbance. This study examines the short‐term effects of sequential disturbance by mineral sand‐mining followed by fire in a forest community in south‐eastern Australia. Four combinations of disturbance were sampled: unburned mined, burned mined, unburned forest (unmined) and burned forest (unmined, with between‐fire interval matching the disturbance interval between mining and fire of the burned mined treatment). All combinations were sampled approximately 12 months following fire on the burned sites. The impact of fire after mining depended on disturbance interval. Sites burned 0.5–2.4 years since mining had fewer native vascular plant species than unburned mined sites of the same mined age, whereas sites with 10–16 years or 20–26 years between mining and fire had greater native species richness than unburned mined sites of the same age. Burning 20–26 years after mining brought native species richness within the range of burned forest. For both unmined and mined sites native seedling densities increased with burning, and with longer disturbance intervals. Weed species richness and weed seedling densities were greater on mined sites than in forest, and burning mined sites elevated weed seedling densities further, particularly for short intervals. Both disturbance interval and fire intensity are likely to have contributed to these results, as intensity on mined areas increased with interval, and at 20–26 years post‐mining was equivalent to unmined forest. These results suggest that fire could be used to promote rehabilitation of these mined areas after at least 10 years, but should be excluded from earlier stages of post‐mining regeneration. However, other sources of spatial and temporal variability should be considered in addition to interval and intensity, as variation among mined areas was correlated with post‐fire weather conditions and available weed sources. Finally, the combined effects of mining and fire could not be predicted from knowledge of the disturbances operating separately, indicating that effects of multiple disturbance may be synergistic rather than additive.

Reproduction in sympatric lizards: comparison of two species of Ctenotus (Scincidae) in south-eastern Australia

The scincid lizards Ctenotus robustus and C. taeniolatus occur sympatrically in regenerating, sand-mined areas in the Port Stephens–Myall Lakes region, coastal New South Wales, Australia. They are absent from the unmined open forest of the area. The reproductive characteristics of these two species were compared. Males reached sexual maturity at a smaller snout–vent length (SVL) than females in C. robustus (72 mm v. 78 mm) and C. taeniolatus (49 mm v. 52 mm). Males were reproductive from August to December and maximum testis volume in both species occurred in early spring; minimum testis volume was recorded in early autumn. Females of both species contained yolking follicles or eggs from October to January (spring–summer). Clutch size in C. robustus (4–9) did not differ significantly from that in C. taeniolatus (2–7) when SVL was accounted for. Both species laid eggs in nests dug 4–5 cm deep in open sandy areas with sparse vegetation, and nesting requirements might explain their absence from open forest. At hatching, C. robustus averaged 35.9 mm SVL and C. taeniolatus averaged 29.9 mm SVL. Hatchlings of both species were at field sites from mid-January to early April. Overall, reproductive characteristics of C. robustus and C. taeniolatus were generally similar.

Long-term impact of prescribed burning on the nutrient status and fuel loads of rehabilitated bauxite mines in Western Australia

Alcoa World Alumina Australia has been rehabilitating bauxite mines in the jarrah ( Eucalyptus marginata) forest of Western Australia for more than 35 years. It is a requirement of Alcoa’s completion criteria that rehabilitated areas can be incorporated into the prescribed burning program implemented in the surrounding forest. Rehabilitated areas may be more susceptible to nutrient losses following burning because of their relatively young age and reliance on N fixation from a legume understorey. The objective of this study was to assess the impact that prescribed burning has on the nutrient pools within rehabilitated ecosystems 5 and 8 years after fire, and compare these responses to unburnt rehabilitated areas and the unmined forest. The nutrient status of sites established in previous studies were assessed five (burnt and unburnt forest, 1989 and 1992 rehabilitation) and 8 (spring, autumn and unburnt 1981/1982 rehabilitation) years after burning. Soil, litter and understorey samples were collected and analysed for nutrient content. Burning 1981/1982 rehabilitation in either season 8 years earlier had no long-term negative effect on the nutrient status of the rehabilitation compared to the unburnt controls. Spring burning increased the nitrogen status of the rehabilitated areas by 52 kg ha −1 compared with the unburnt control. Sites rehabilitated in 1989 and burnt 5 years ago showed similar post-fire recovery of nitrogen status to that of the burnt native forest sites (77–85%), while 1992 rehabilitation sites had only recovered 52% of the of the nitrogen of the unburnt sites. Therefore, the impact of burning on nitrogen status was greatest in the 5-year-old rehabilitation and least in the 12–13-year-old sites. Phosphorus was less affected by burning than nitrogen largely because the majority of P is bound in the soil in the jarrah forest. It is recommended that rehabilitated sites are burnt under low intensity in spring when they are 12–15-year-old to ensure rapid post-fire recovery of nutrients.

Long‐Term Trends in Faunal Recolonization After Bauxite Mining in the Jarrah Forest of Southwestern Australia

Abstract Fauna serve a key role in many forest ecological processes. Despite this, few studies have considered long‐term faunal recolonization after mining and rehabilitation of forest ecosystems. In the jarrah forest of southwestern Australia, permanent fauna monitoring sites have been established in bauxite mined areas rehabilitated in 1990 and in a range of representative unmined forest control sites. At each site mammals, birds, reptiles, and ants were surveyed in 1992, 1995, and 1998. The aims of the monitoring were to develop a better understanding of faunal recolonization trends, to produce recommendations for promoting fauna return, and to consider which techniques and fauna groups are best suited for monitoring recolonization. The results showed that successional trends varied between fauna groups. Generalist foraging mammals recolonized rapidly, whereas small predators took longer. Feral mice were initially abundant and then declined. Birds gradually recolonized, and after 8 years bird communities were very similar to those in unmined forest sites. Reptile species took longer, and after 8 years numbers of species remained lower than in unmined forests. Species richness and diversity of ants in 8‐year‐old rehabilitation were comparable with those of unmined forest in some rehabilitated sites but were lower in others. The composition of ant communities was still different from that of unmined sites. Ant species that only use disturbed forest declined rapidly in abundance as rehabilitation aged. The results suggest that although the rates of faunal recolonization will vary, with time most or all mammal, bird, reptile, and ant species should inhabit rehabilitated bauxite mines. The densities of many are likely to be similar to those in unmined forest, but for others it is too early to know whether this will be the case. Techniques for promoting fauna return are discussed. This study demonstrates that no single fauna group is suitable for use as an overall “indicator” of faunal recolonization; different fauna species and groups reflect different aspects of faunal succession.