Journal of Long!term recolonization patterns of ants in Western Applied Ecology 0887\ 24\ Australian rehabilitated bauxite mines with reference to 050Ð071 their use as indicators of restoration success J[ D[ MAJER and O[ G[ NICHOLS$ School of Environmental Biology\ Curtin University of Technology\ PO Box U0876\ Perth\WA 5734\ Australia^ and $Alcoa of Australia Ltd\ PO Box 141\ Applecross\ WA 5042\ Australia Summary 0[ The return of invertebrate animals to rehabilitated mine pits is desirable for the re! establishment of ecosystem functioning[ A long!term ant monitoring programme is reported over 03 years in a jarrah Eucalyptus marginata forest control plot and in three bauxite mine pits\ one of which had been left unvegetated\ one planted with marri trees E[ calophylla and the other seeded with mixed native plant species[ 1[ The results con_rm published _ndings for the _rst 1 years of the succession that seeding with mixed species results in a more rapid attainment of a forest!like ant fauna\ although in the last 5 years of the study the ant fauna of the planted plot had become more similar to that of the seeded plot[ 2[ Changes in the nature of the ant fauna are described and it is concluded that although composition has substantially converged on that of the forest by the end of the study\ di}erences still persist[ 3[ Research on vegetation\ spiders and ants in bauxite mined areas which have been rehabilitated using more recent technology suggest that these di}erences will lessen with time and with the introduction of improved rehabilitation prescriptions[ 4[ An additional aim of the study was to validate the chronosequence approach to studying ecosystem recovery following disturbances such as mining[ It is concluded that long!term studies provide important information that is missed by the chrono! sequence approach[ Ideally\ rapid!feedback chronosequence approaches should be augmented by long!term case studies[ Key!words] Ants\ Formicidae\ long!term monitoring\ succession[ Journal of Applied Ecology "0887# 24\ 050Ð071 ern Australia "WA#\ completion criteria are not for! Introduction mally nominated but appear in various conditions of A commonly accepted goal of the rehabilitation of project approval under three classes of controlling mined land is to restore the structure\ diversity\ func! acts\ namely] the Environmental Protection Act tion and dynamics of the disturbed ecosystem\ all of "EPA# 0875^ the Mining Act "0867# as amended^ and which are attributes in which invertebrates play a piv! various agreement acts which pertain to the project otal role "Wilson 0876^ Erwin 0880#[ In the past\ the being developed "Mills\ Chandler + Caporn 0881#[ technology required to meet these goals has been Few regulatory bodies have formulated criteria for derived from experience\ although research over the the later stages of bond release and\ to the authors| past three decades into rehabilitation technologies has knowledge\ none require the re!establishment of resulted in considerable advances in such procedures[ adequate invertebrate communities to be taken into The need to carry out high!quality rehabilitation has account[ The latter may partly result from the auth! become more acute in the industry with the phasing orities not fully recognizing the importance of invert! in of performance standards and completion criteria ebrates in ecosystem functioning[ Inclusion of invert! "Mills\ Chandler + Caporn 0881#[ In some mining ebrate assessments is hindered by the lack of long! industries bonds are payable which are not returned term studies on which to assess whether rehabilitation Þ 0887 British until adequate rehabilitation\ which meets prescribed has been successful or not[ This generally results from Ecological Society completion criteria\ has been demonstrated[ In West! the absence of a long!term commitment to funding 050 051 rehabilitation research\ and attempts to circumvent marginata forest of south!west WA[ Following the Ant recolonization the problem are often made by sampling a range of de_nition of ore bodies\ the timber is harvested and of bauxite mines rehabilitated areas representing di}erent ages[ This the remaining vegetation is cleared from the required method\ which Twigg\ Fox + Luo "0878# and Fox area[ The top 049 mm of topsoil is then removed and\ "0885# refer to as the chronosequence approach\ pro! where possible\ is replaced directly onto an area being vides rapid feedback but can produce ambiguous data[ rehabilitated "prior to 0865 all topsoil was stockpiled#[ It makes the possibly incorrect assumption that sites The remaining overburden "up to 0 m# is removed and only di}er in terms of age\ although there may also stockpiled[ The cap rock is then blasted or ripped have been changes in the rehabilitation technology and the ore is removed to an average depth of 3=4 m[ over the time!scale represented by these plots "Majer Overburden and topsoil are returned and the com! 0874#[ It is therefore preferable that permanent plots pacted pallid clay zone is ripped to a depth of ¼ 0=4 m be established in representative areas and monitored to enhance water in_ltration and root penetration\ over the long!term in order to validate the chrono! and to reduce erosion[ sequence approach\ and also to provide more reliable Methods for rehabilitation of bauxite mine pits are feedback on the success of di}erent rehabilitation pro! currently evolving[ The earlier attempts utilized hand! cedures[ planting of nursery!reared Eucalyptus spp[ that are In view of their important role in the developing resistant to dieback disease Phytophthora cinnamomi\ ecosystem\ it is essential to understand how invert! such as E[ microcorys\ E[ resinifera\ E[ saligna and ebrate communities are developing in rehabilitated E[ maculata from eastern Australia\ and included no areas[ In 0864 a study was initiated on the reco! understorey component[ The current procedure uses lonization of invertebrates in three bauxite mined only native jarrah forest tree and understorey species[ plots in the south!west of WA[ One plot was planted In the mid!0879s there was a shift to direct!seeding\ with a single Eucalyptus species\ one was seeded with rather than replanting[ The procedure now follows mixed native vegetation and the other was unveg! the sequence of pit reshaping\ overburden and topsoil etated[ Majer "0870# reported on the initial 1 years of return\ ripping and spreading of seed and fertilizer in recolonization and concluded that seeding of mixed the pit[ The results of these two broad rehabilitation over! and understorey allowed for the return of con! approaches are quite di}erent[ The planted mine pits siderably more ant species than by simply planting a initially have the appearance of a plantation\ whereas tree monoculture\ where ant richness was only slightly direct seeding produces a regrowth of high structural greater than in the plot where no revegetation had and species diversity[ been established[ Pitfall trap catches indicated that the seeded plot also had the most abundant ant popu! SAMPLE SITES lations\ the greatest number of other epigaeic invert! ebrates and an ant fauna which\ in terms of its species A single example of each rehabilitation approach was composition\ was most similar to that of the forest selected for study[ Replication of plots was decided control plot[ Once again\ the planted plot was inter! against so that greater attention could be paid to suc! mediate between the seeded and unvegetated plot in cessional and seasonal trends within the study areas^ terms of all of these parameters[ These _ndings were the earlier chronosequence study "Majer et al[ 0873# subsequently supported by the results of short!term provided information about the variability of trends chronosequence!type studies of ants and Collembola between rehabilitation treatments[ Most of the work in 29 bauxite mines and three forest controls "Majer was conducted in the Del Park mine\ near Dwellingup et al[ 0873^ Greenslade + Majer 0882#[ "21>32?S\ 005>93?E# and in the Jarrahdale No[ 1 mine The three rehabilitated plots and the forest control "21>19?S\ 005>96?E#[ have been intermittently resampled until 0878[ This A 1 ha area at Del Park planted with a single paper describes these results and provides data that indigenous tree species "marri\ Eucalyptus calophylla# complement the _ndings from the short!term chrono! in June 0865 was selected as an example of the planting sequence study performed in the same area in 0867:68 approach[ An 07 × 07!m area was marked out in the "Majer et al[ 0873#[ It also provides much needed centre and is referred to as the {planted plot|[ A information on how ant communities develop over a 099 × 099!m area\ 44 m north!east of the planted area longer time!frame in rehabilitated areas and enables was also selected[ With the exception of topsoil the results of the chronosequence approach to be vali! replacement and ripping\ no rehabilitation was carried dated[ out in this experimental area[ The 07 × 07!m centre of this area is referred to as the {unvegetated plot|[ It was not possible to select a seeded area at Del Park Methods so a 1!ha area was chosen at the Jarrahdale mine[ This Þ 0887 British area was seeded with 03 tree and shrub species\ planted Ecological Society\ REHABILITATION PROCEDURES Journal of Applied with an additional nine tree species[ The 07 × 07!m Ecology\ 24\ Bauxite is currently being mined by Alcoa of Australia centre is referred to as the {seeded plot|[ Although 050Ð071 Ltd at various sites in the northern jarrah