Vegetation and soil environment influence the spatial distribution of root-associated fungi in a mature beech-maple forest

Fallopia japonica and Impatiens glandulifera are colonized by species-poor root-associated fungal communities but have minor impacts on soil properties in riparian habitats

Fallopia japonica and Impatiens glandulifera are major plant invaders on a global scale that often become dominant in riparian areas. However, little is known about how these species affect interactions in soil–plant systems. The aim of this study was to investigate the impact of both species on abiotic and biotic soil properties, with a special focus on fungi. We investigated eight sites along small streams invaded by F. japonica and I. glandulifera, respectively, and compared each with nearby sites dominated by the native species Urtica dioica. Three different types of samples were collected: bulk soil, rhizosphere soil and roots from invasive and native stands at each site. Bulk soil samples were analysed for soil physicochemical, microbial properties (soil microbial respiration and ergosterol) and soil arthropod abundance (Acari and Collembola). Soil respiration was also evaluated in rhizosphere samples. The fungal community composition of both bulk soil and roots were analysed using a metabarcoding approach. Soil physicochemical properties as well as soil microbial activity, fungal biomass and soil fungal operational unit taxonomic unit (OTU) richness did not differ between invaded and native riparian habitats, indicating only minor belowground impacts of the two invasive plant species. Soil microbial activity, fungal biomass and soil fungal OTU richness were rather related to the soil physicochemical properties. In contrast, Acari abundance decreased by 68% in the presence of F. japonica, while Collembola abundance increased by 11% in I. glandulifera sites. Moreover, root-associated fungal communities differed between the invasive and native plants. In F. japonica roots, fungal OTU richness of all investigated ecological groups (mycorrhiza, endophytes, parasites, saprobes) were lower compared to U. dioica. However, in I. glandulifera roots only the OTU richness of mycorrhiza and saprobic fungi was lower. Overall, our findings show that F. japonica and I. glandulifera can influence the abundance of soil arthropods and are characterized by lower OTU richness of root-associated fungi.

Factors in the Distribution of Mycorrhizal and Soil Fungi

Soil fungi are crucial microorganisms in the functioning of ecosystems. They shape the soil properties, facilitate nutrient circulation, and assist with plant growth. However, their biogeography and distribution studies are limited compared to other groups of organisms. This review aims to provide an overview of the main factors shaping the spatial distribution of soil fungi (with a special focus on mycorrhizal fungi). The review also tries to identify the field frontier where further studies are needed. The main drivers of soil fungal distribution were classified and reviewed into three groups: soil properties, plant interactions, and dispersal vectors. It was apparent that ectomycorrhizal and arbuscular fungi are relatively overrepresented in the body of research, while the other mycorrhiza types and endophytes were grossly omitted. Notwithstanding, soil pH and the share of ectomycorrhizal plants in the plant coverage were repeatedly reported as strong predictors of mycorrhizal fungal distribution. Dispersal potential and vector preferences show more variation among fungi, especially when considering long-distance dispersal. Additionally, special attention was given to the applications of the island biogeography theory to soil fungal assemblages. This theory proves to be a very efficient framework for analyzing and understanding not only the soil fungal communities of real islands but even more effective islands, i.e., isolated habitats, such as patches of trees discontinuous from more enormous forests.

Effects of Flurochloridone Application on Rhizosphere Soil Fungal Community and Composition in Potato Growing Areas of the Qinghai-Tibet Plateau

The application of herbicides to arable land is still the most effective and accepted method to protect plants from weeds. Extensive use of chemicals in conventional agricultural practices has resulted in continuous and serious environmental pollution. Flurochloridone (FLC) is a monophenyl pyrrolidinone selective herbicide that is commonly used to inhibit weeds that occur during the growth of potatoes. In recent years, research on the toxicity of FLC has gradually increased. However, it is relatively rare to analyze the role of FLC by studying the composition of soil microorganisms. Therefore, we used NGS methods to identify the fungal community structure of the low content soil (LS) and high content soil (HS) samples in this study. Subsequently, we identified the fungal community and composition differences of these two group samples using the statistical analysis. Despite the variances of fungal community and composition across the different samples within the group, the fungal composition of the LS samples and the HS samples. LS samples were predominated by Ascomycota, while the HS samples were predominated by Mortierellomycota and Basidiomycota. The major species in the LS samples were Plectosphaerellacucumerina and Trichocladiumasperum, whereas the dominant species in the HS samples were Epicoccum nigrum and Cladosporium chasmanthicola. These results suggested that the LS samples and the HS samples had different rhizosphere soil fungal community and composition changes resulting from implementation of FLC in potato growing areas.

Tree Root Zone Microbiome: Exploring the Magnitude of Environmental Conditions and Host Tree Impact

Tree roots attract their associated microbial partners from the local soil community. Accordingly, tree root-associated microbial communities are shaped by both the host tree and local environmental variables. To rationally compare the magnitude of environmental conditions and host tree impact, the "PhytOakmeter" project planted clonal oak saplings (Quercus robur L., clone DF159) as phytometers into different field sites that are within a close geographic space across the Central German lowland region. The PhytOakmeters were produced via micro-propagation to maintain their genetic identity. The current study analyzed the microbial communities in the PhytOakmeter root zone vs. the tree root-free zone of soil two years after out-planting the trees. Soil DNA was extracted, 16S and ITS2 genes were respectively amplified for bacteria and fungi, and sequenced using Illumina MiSeq technology. The obtained microbial communities were analyzed in relation to soil chemistry and weather data as environmental conditions, and the host tree growth. Although microbial diversity in soils of the tree root zone was similar among the field sites, the community structure was site-specific. Likewise, within respective sites, the microbial diversity between PhytOakmeter root and root-free zones was comparable. The number of microbial species exclusive to either zone, however, was higher in the host tree root zone than in the tree root-free zone. PhytOakmeter "core" and "site-specific" microbiomes were identified and attributed to the host tree selection effect and/or to the ambient conditions of the sites, respectively. The identified PhytOakmeter root zone-associated microbiome predominantly included ectomycorrhizal fungi, yeasts and saprotrophs. Soil pH, soil organic matter, and soil temperature were significantly correlated with the microbial diversity and/or community structure. Although the host tree contributed to shape the soil microbial communities, its effect was surpassed by the impact of environmental factors. The current study helps to understand site-specific microbe recruitment processes by young host trees.

Coyle K, A. Kluber L, J. Burke D. Fungal and Bacterial Communities Exhibit Consistent Responses to Reversal of Soil Acidification and Phosphorus Limitation over Time

Chronic acid deposition affects many temperate hardwood forests of the northeastern United States, reduces soil pH and phosphorus (P) availability, and can alter the structure and function of soil microbial communities. The strategies that microorganisms possess for survival in acidic, low P soil come at a carbon (C) cost. Thus, how microbial communities respond to soil acidification in forests may be influenced by plant phenological stage as C allocation belowground varies; however, this remains largely unexplored. In this study, we examined microbial communities in an ecosystem level manipulative experiment where pH and/or P availability were elevated in three separate forests in Northeastern Ohio. Tag-encoded pyrosequencing was used to examine bacterial and fungal community structure at five time points across one year corresponding to plant phenological stages. We found significant effects of pH treatment and time on fungal and bacterial communities in soil. However, we found no interaction between pH treatment and time of sampling for fungal communities and only a weak interaction between pH elevation and time for bacterial communities, suggesting that microbial community responses to soil pH are largely independent of plant phenological stage. In addition, fungal communities were structured largely by site, suggesting that fungi were responding to differences between the forests, such as plant community differences.

The importance of plot size and the number of sampling seasons on capturing macrofungal species richness

The species-area relationship is an important factor in the study of species diversity, conservation biology, and landscape ecology. A deeper understanding of this relationship is necessary, in order to provide recommendations on how to improve the quality of data collection on macrofungal diversity in different land use systems in future studies, a systematic assessment of methodological parameters, in particular optimal plot sizes. The species-area relationship of macrofungi in tropical and temperate climatic zones and four different land use systems were investigated by determining the macrofungal species richness in plot sizes ranging from 100 m² to 10 000 m² over two sampling seasons. We found that the effect of plot size on recorded species richness significantly differed between land use systems with the exception of monoculture systems. For both climate zones, land use system needs to be considered when determining optimal plot size. Using an optimal plot size was more important than temporal replication (over two sampling seasons) in accurately recording species richness.

Basidiospores attach to the seed of Shorea leprosula in lowland tropical dipterocarp forest and form functional ectomycorrhiza on seed germination

This research aimed to study the ectomycorrhiza formed by basidiospores attached to the outer surface of Shorea leprosula (Dipterocarpaceae) seed collected from a lowland tropical dipterocarp forest. Two groups of seeds were collected: control seeds collected from plastic net hanging 2 m above the ground and forest floor seeds collected on the forest floor. Before planting, 15 seeds from each group were observed for basidiospores attached to the seed. Ten of the 3-week-old S. leprosula seedlings of each group were individually grown in 1.5 kg of sterile zeolite for 8 months in a greenhouse. Pots were fertilized with MMN solution containing half the strength of phosphate. Fungal identity, ectomycorrhizal root tip colonization and anatomy, plant growth, and phosphate uptake were measured. The control seeds did not have basidiospores attached, whereas the forest floor seeds had 2 × 10⁵ basidiospores of Tomentella. Bioassay test results indicate that the seedlings from the control seeds did not form ectomycorrhiza, whereas those seedlings from the forest floor seeds formed 3 morphotypes of ectomycorrhizae. Based on ITS1, 5.8S, and ITS2 rDNA region analyses, the 3 morphotypes belonged to Tomentella sp. HBT2, Tomentella sp. HBT4, and Scleroderma sp. HBS3. Root colonization percentage was above 70% for all three morphotypes. Root colonization in general increased plant growth and phosphate uptake. This is the first report of Tomentella basidiospores attached on the seed surface as a functional inoculum and of Tomentella ectomycorrhiza from dipterocarps lowland tropical forest.

Rhizospheric microbial communities associated with wild and cultivated frankincense producing Boswellia sacra tree

Boswellia sacra, a frankincense producing endemic tree, has been well known for its cultural, religious and economic values. However, the tree has been least explored for the associated microsymbiota in the rhizosphere. The current study elucidates the fungal and bacterial communities of the rhizospheric regions of the wild and cultivated B. sacra tree populations through next generation sequencing. The sequence analysis showed the existence of 1006±8.9 and 60.6±3.1 operational taxonomic unit (OTUs) for bacterial and fungal communities respectively. In fungal communities, five major phyla were found with significantly higher abundance of Ascomycota (60.3%) in wild population and Basidiomycota (52%) in cultivated tree rhizospheres. Among bacterial communities, 31 major phyla were found, with significant distribution of Actinobacteria in wild tree rhizospheres, whereas Proteobacteria and Acidobacteria were highly abundant in cultivated trees. The diversity and abundance of microbiome varied significantly depending upon soil characteristics of the three different populations. In addition, significantly higher glucosidases, cellulases and indole-3-acetic acid were found in cultivated tree’s rhizospheres as compared to wild tree populations. for these plants to survive the harsh arid-land environmental conditions. The current study is a first comprehensive work and advances our knowledge about the core fungal and bacterial microbial microbiome associated with this economically important tree.

Plant functional diversity enhances associations of soil fungal diversity with vegetation and soil in the restoration of semiarid sandy grassland

The trait-based approach shows that plant functional diversity strongly affects ecosystem properties. However, few empirical studies show the relationship between soil fungal diversity and plant functional diversity in natural ecosystems. We investigated soil fungal diversity along a restoration gradient of sandy grassland (mobile dune, semifixed dune, fixed dune, and grassland) in Horqin Sand Land, northern China, using the denaturing gradient gel electrophoresis of 18S rRNA and gene sequencing. We also examined associations of soil fungal diversity with plant functional diversity reflected by the dominant species' traits in community (community-weighted mean, CWM) and the dispersion of functional trait values (FD is). We further used the structure equation model (SEM) to evaluate how plant richness, biomass, functional diversity, and soil properties affect soil fungal diversity in sandy grassland restoration. Soil fungal richness in mobile dune and semifixed dune was markedly lower than those of fixed dune and grassland (P < 0.05). Soil fungal richness was positively associated with plant richness, biomass, CWM plant height, and soil gradient aggregated from the principal component analysis, but SEM results showed that plant richness and CWM plant height determined by soil properties were the main factors exerting direct effects. Soil gradient increased fungal richness through indirect effect on vegetation rather than direct effect. The negative indirect effect of FDis on soil fungal richness was through its effect on plant biomass. Our final SEM model based on plant functional diversity explained nearly 70% variances of soil fungal richness. Strong association of soil fungal richness with the dominant species in the community supported the mass ratio hypothesis. Our results clearly highlight the role of plant functional diversity in enhancing associations of soil fungal diversity with community structure and soil properties in sandy grassland ecosystems.

Seasonal variation in mycorrhizal fungi colonizing roots of Allium tricoccum (wild leek) in a mature mixed hardwood forest

The community of arbuscular mycorrhizal (AM) fungi colonizing roots of the forest herb Allium tricoccum Ait. (wild leek) was examined to assess whether colonization varied seasonally and spatially within the forest. Whole plants were collected to coincide with observed phenological stages, and the perennial tissue (i.e., the bulb) was used to analyze total C, N, and P over the growing season. AM fungal community composition, structure, and abundance were assessed in roots by terminal restriction fragment length polymorphism analysis and quantitative PCR. It was found that A. tricoccum rDNA co-amplified using the general AM primers NS31/AM1, and a new primer for qPCR was designed that discriminated against plant DNA to quantify AM colonization. Community structure of AM fungi did not vary seasonally, but did change spatially within the forest, and AM fungal communities were correlated with the presence of overstory tree species. Fungal colonization of roots, however, did change seasonally with a maximum observed in late winter and early spring following leaf emergence. Maximum AM fungal colonization was associated with declines in bulb N and P, suggesting that leaf emergence and growth were responsible for both declines in stored nutrients and increases in AM fungal colonization. Plant N and P contents increased between late summer and early spring while C contents remained unchanged. The observed increase in nutrient content during a time when A. tricoccum lacks leaves indicates that the roots or AM fungi are metabolically active and acquire nutrients during this time, despite an absence of photosynthesis and thus a direct supply of C from A. tricoccum.

Effects of annual and interannual environmental variability on soil fungi associated with an old-growth, temperate hardwood forest

Seasonal and interannual variability in temperature, precipitation and chemical resources may regulate fungal community structure in forests but the effect of such variability is still poorly understood. In this study, I examined changes in fungal communities over two years and how these changes were correlated to natural variation in soil conditions. Soil cores were collected every month for three years from permanent plots established in an old-growth hardwood forest, and molecular methods were used to detect fungal species. Species richness and diversity were not consistent between years with richness and diversity significantly affected by season in one year but significantly affected by depth in the other year. These differences were associated with variation in late winter snow cover. Fungal communities significantly varied by plot location, season and depth and differences were consistent between years but fungal species within the community were not consistent in their seasonality or in their preference for certain soil depths. Some fungal species, however, were found to be consistently correlated with soil chemistry across sampled years. These results suggest that fungal community changes reflect the behavior of the individual species within the community pool and how those species respond to local resource availability.

Impact of seasonal changes on fungal diversity of a semi-arid ecosystem revealed by 454 pyrosequencing

Fungi play fundamental ecological roles in terrestrial ecosystems. However, their distribution and diversity remain poorly described in natural communities, particularly in arid and semi-arid ecosystems. In order to identify environmental factors determining fungal community structure in these systems, we assessed their diversity in conjunction with soil physicochemical characteristics in a semi-arid ecosystem in Baja California, Mexico, endemic for Coccidioidomycosis (Valley Fever). Two different microhabitats, burrows (influenced by rodent activity) and topsoil, were compared in winter and summer. Using a metagenomic approach, the ITS1 region of nuclear ribosomal DNA was used as barcode. A total of 1940 Operational Taxonomic Units (OTUs) were identified from 362 332 ITS1 sequences obtained by 454 pyrosequencing. Differences in fungal composition between seasons were clearly identified. Moreover, differences in composition between microhabitats were mainly correlated to significant differences in environmental factors, such as moisture and clay content in topsoil samples, and temperature and electrical conductivity in burrow samples. Overall, the fungal community structure (dominated by Ascomycota and Basidiomycota) was less variable between seasons in burrow than in topsoil samples. Coccidioides spp. went undetected by pyrosequencing. However, a nested PCR approach revealed its higher prevalence in burrows.

Arctic fungal communities associated with roots of Bistorta vivipara do not respond to the same fine-scale edaphic gradients as the aboveground vegetation

Soil conditions and microclimate are important determinants of the fine-scale distribution of plant species in the Arctic, creating locally heterogeneous vegetation. We hypothesize that root-associated fungal (RAF) communities respond to the same fine-scale environmental gradients as the aboveground vegetation, creating a coherent pattern between aboveground vegetation and RAF. We explored how RAF communities of the ectomycorrhizal (ECM) plant Bistorta vivipara and aboveground vegetation structure of arctic plants were affected by biotic and abiotic variables at 0.3-3.0-m scales. RAF communities were determined using pyrosequencing. Composition and spatial structure of RAF and aboveground vegetation in relation to collected biotic and abiotic variables were analysed by ordination and semi-variance analyses. The vegetation was spatially structured along soil C and N gradients, whereas RAF lacked significant spatial structure. A weak relationship between RAF community composition and the cover of two ECM plants, B. vivipara and S. polaris, was found, and RAF richness increased with host root length and root weight. Results suggest that the fine-scale spatial structure of RAF communities of B. vivipara and the aboveground vegetation are driven by different factors. At fine spatial scales, neighbouring ECM plants may affect RAF community composition, whereas soil nutrients gradients structure the vegetation.

Sharing rotting wood in the shade: ectomycorrhizal communities of co-occurring birch and hemlock seedlings

Coarse woody debris (CWD) is an important nursery environment for many tree species. Understanding the communities of ectomycorrhizal fungi (ECMF)and the effect of ECMF species on tree seedling condition in CWD will elucidate the potential for ECMF-mediated effects on seedling dynamics. In hemlock-dominated stands, we characterized ECMF communities associated with eastern hemlock (Tsuga canadensis (L.) Carr) and yellow birch (Betula alleghaniensis Britt) seedling pairs growing on CWD. Seedling foliage and CWD were analyzed chemically, and seedling growth, canopy cover, and canopy species determined. Thirteen fungal taxa, 12 associated with birch, and 6 with hemlock, were identified based on morphology and ITS sequencing. Five species were shared by co-occurring birch and hemlock, representing 75% of ectomycorrhizal root tips. Rarified ECMF taxon richness per seedling was higher on birch than hemlock. Nonmetric multidimensional scaling revealed significant correlations between ordination axes, the mutually exclusive ECMF Tomentella and Lactarius spp., foliar N and K, CWD pH, and exchangeable Ca and Mg. Seedlings colonized by Lactarius and T. sublilacina differed significantly in foliar K and N, and CWD differed in exchangeable Ca and Mg. CWD pH and nutrient concentrations were low but foliar macro-nutrient concentrations were not. We hypothesize that the dominant ECMF are adapted to low root carbohydrate availability typical in shaded environments but differ in their relative supply of different nutrients.

Fungi at a small scale: spatial zonation of fungal assemblages around single trees

Biological communities are often structured by environmental factors even at small spatial scales. Fungi are no exception, though the patterns and mechanisms underlying their community structure are usually unknown. Previous work documented zonation in fungi under tree canopies primarily through their fruiting patterns. Here we investigate the existence of zonation patterns in fungal communities around isolated Pinus muricata trees of different ages in northern coastal California. Using a combination of ingrowth bags and pyrosequencing to target underground mycelium we found highly diverse soil fungal communities associated with single trees. Both ectomycorrhizal and non-ectomycorrhizal fungi were present in all samples, but the latter were more species rich, dominated the samples by sequence read abundance, and showed partitioning by canopy-defined zones and tree age. Soil chemistry was correlated with fungal zonation, but host root density was not. Our results indicate different guilds of fungi partition space differently and are driven by distinct environmental parameters.

Forest Age and Plant Species Composition Determine the Soil Fungal Community Composition in a Chinese Subtropical Forest

Fungal diversity and community composition are mainly related to soil and vegetation factors. However, the relative contribution of the different drivers remains largely unexplored, especially in subtropical forest ecosystems. We studied the fungal diversity and community composition of soils sampled from 12 comparative study plots representing three forest age classes (Young: 10-40 yrs; Medium: 40-80 yrs; Old: ≥80 yrs) in Gutianshan National Nature Reserve in South-eastern China. Soil fungal communities were assessed employing ITS rDNA pyrotag sequencing. Members of Basidiomycota and Ascomycota dominated the fungal community, with 22 putative ectomycorrhizal fungal families, where Russulaceae and Thelephoraceae were the most abundant taxa. Analysis of similarity showed that the fungal community composition significantly differed among the three forest age classes. Forest age class, elevation of the study plots, and soil organic carbon (SOC) were the most important factors shaping the fungal community composition. We found a significant correlation between plant and fungal communities at different taxonomic and functional group levels, including a strong relationship between ectomycorrhizal fungal and non-ectomycorrhizal plant communities. Our results suggest that in subtropical forests, plant species community composition is the main driver of the soil fungal diversity and community composition.

Mycorrhizal response to experimental pH and P manipulation in acidic hardwood forests

Many temperate forests of the Northeastern United States and Europe have received significant anthropogenic acid and nitrogen (N) deposition over the last century. Although temperate hardwood forests are generally thought to be N-limited, anthropogenic deposition increases the possibility of phosphorus (P) limiting productivity in these forest ecosystems. Moreover, inorganic P availability is largely controlled by soil pH and biogeochemical theory suggests that forests with acidic soils (i.e., Collapse

Key Words Collapse

MESH Headings

• Biomass
• Ecosystem
• Hydrogen-Ion Concentration
• Mycorrhizae/metabolism
• Ohio
• Phosphorus/metabolism
• Plant Roots/metabolism
• Plant Roots/microbiology
• Soil
• Soil Microbiology
• Trees/metabolism
• Trees/microbiology

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Affiliation(s)

Laurel A Kluber Department of Biology, Case Western Reserve University, Cleveland, OH, USA.
Sarah R Carrino-Kyker
Kaitlin P Coyle
Jared L DeForest
Charlotte R Hewins
Alanna N Shaw
Kurt A Smemo
David J Burke

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Differences in soil fungal communities between European beech (Fagus sylvatica L.) dominated forests are related to soil and understory vegetation

Fungi are important members of soil microbial communities with a crucial role in biogeochemical processes. Although soil fungi are known to be highly diverse, little is known about factors influencing variations in their diversity and community structure among forests dominated by the same tree species but spread over different regions and under different managements. We analyzed the soil fungal diversity and community composition of managed and unmanaged European beech dominated forests located in three German regions, the Schwäbische Alb in Southwestern, the Hainich-Dün in Central and the Schorfheide Chorin in the Northeastern Germany, using internal transcribed spacer (ITS) rDNA pyrotag sequencing. Multiple sequence quality filtering followed by sequence data normalization revealed 1655 fungal operational taxonomic units. Further analysis based on 722 abundant fungal OTUs revealed the phylum Basidiomycota to be dominant (54%) and its community to comprise 71.4% of ectomycorrhizal taxa. Fungal community structure differed significantly (p≤0.001) among the three regions and was characterized by non-random fungal OTUs co-occurrence. Soil parameters, herbaceous understory vegetation, and litter cover affected fungal community structure. However, within each study region we found no difference in fungal community structure between management types. Our results also showed region specific significant correlation patterns between the dominant ectomycorrhizal fungal genera. This suggests that soil fungal communities are region-specific but nevertheless composed of functionally diverse and complementary taxa.

Membranomyces species are common ectomycorrhizal symbionts in Northern Hemisphere forests

Membranomyces (Clavulinaceae, Cantharellales) Jülich consists of two described species of resupinate (crust-like) basidiomycetes. Previous studies indicated that Membranomyces falls within the Clavulinaceae, but the phylogenetic position of the genus has not been fully resolved. Membranomyces species were thought to be saprotrophic until 2003 when Tedersoo et al. detected Membranomyces delectabilis on ectomycorrhizal roots of Populus and Picea. Membranomyces was previously known only from collections made in eastern Canada and Europe. We recently sequenced the ITS rDNA barcode region from Scandinavian herbarium specimens identified as M. delectabilis and Membranomyces spurius. Phylogenetic analyses of these sporocarp sequences and similar environmental sequences indicated that Membranomyces is more diverse than previously thought and forms ectomycorrhizas with hosts from a diverse range of plant families in many north temperate ecosystems.

Soil microbial community successional patterns during forest ecosystem restoration

Soil microbial community characterization is increasingly being used to determine the responses of soils to stress and disturbances and to assess ecosystem sustainability. However, there is little experimental evidence to indicate that predictable patterns in microbial community structure or composition occur during secondary succession or ecosystem restoration. This study utilized a chronosequence of developing jarrah (Eucalyptus marginata) forest ecosystems, rehabilitated after bauxite mining (up to 18 years old), to examine changes in soil bacterial and fungal community structures (by automated ribosomal intergenic spacer analysis [ARISA]) and changes in specific soil bacterial phyla by 16S rRNA gene microarray analysis. This study demonstrated that mining in these ecosystems significantly altered soil bacterial and fungal community structures. The hypothesis that the soil microbial community structures would become more similar to those of the surrounding nonmined forest with rehabilitation age was broadly supported by shifts in the bacterial but not the fungal community. Microarray analysis enabled the identification of clear successional trends in the bacterial community at the phylum level and supported the finding of an increase in similarity to nonmined forest soil with rehabilitation age. Changes in soil microbial community structure were significantly related to the size of the microbial biomass as well as numerous edaphic variables (including pH and C, N, and P nutrient concentrations). These findings suggest that soil bacterial community dynamics follow a pattern in developing ecosystems that may be predictable and can be conceptualized as providing an integrated assessment of numerous edaphic variables.