Microtopography Influences Early Successional Plant Communities on Experimental Coal Surface Mine Land Reclamation

Surface mining for coal represents one of the dominant forms of anthropogenic disturbance to forests of the eastern United States. Reclamation methods adopted under federal law in the 1970s have led to a state of arrested succession, failing to achieve pre‐disturbance conditions. New methods of reclamation have been proposed with the goal of returning mined land to its former forested state through the use of compaction reducing techniques that significantly increase fine‐scale heterogeneity. The Forestry Reclamation Approach creates topographic heterogeneity by loosely dumping overburden material into large piles to serve as a tree‐planting medium. We examined the effect of fine‐scale topographic relief, soil physical properties, and reclamation method on early plant community development on a mine site in eastern Ohio. We sampled plots at four microtopographic positions and three distances from the remaining forest edge in both experimentally and traditionally reclaimed areas of a surface mine. Multivariate analysis of variance (ANOVA) on distance matrices indicated significant differences in plant community composition among microtopographic positions and reclamation methods. Microtopographic positions also exhibited significant differences in measured soil properties significantly affecting plant community composition. Plots in the traditionally reclaimed areas had no woody plant colonization, indicating arrested succession common to sites reclaimed using traditional methods. Our results suggest that the creation of topographic heterogeneity at the time of reclamation markedly accelerates ecological succession and promotes enhanced plant community diversity. Expanded application of the methods used here could allow for a faster return to the former forested state of mined lands than traditional reclamation methods.     

Microbial Activity in High-Sulfur Reclaimed Coal Mine Overburden Sites

The high-sulfur containing coalmine overburden (OB) dumping ground of the Tirap colliery under the northeastern coalfields in Assam, India, was reclaimed by phytoremediation techniques. Native plant species were planted with line and field methods and by amending with cow dung and unmined soil. In this study, the changes in microbial activity of the reclaimed mine OB wasteland of the Tirap colliery are examined. The enzyme activities of urease, dehydrogenase, and phosphatase were compared over time. Improvements in soil pH, bulk density, and water-holding capacity in the mine OB were found. After four years of reclamation, 1.01% of particles were soil sized (=0.255 mm grain size) with the maximum degradation in the mine OB grain sizes of ?20 mm to +12 mm and of +25 mm. A 1,000-fold increase in microbial colony forming units (CFU) in the four years at the remediated site along with an increase in total DNA were evident for the mine OB reclaimed sites. The increase of microbial CFUs in the mine OB was related to a 100- to 2,000-fold increase in enzyme activity for the reclaimed areas. From this investigation, it can be concluded that the improvement of enzyme activities and the increase in microbial populations of reclaimed mine OB will yield information pertaining to the reclamation index of mine OB.     

Soil dumping techniques and afforestation drive ground-dwelling beetle assemblages in a 25-year-old open-cast mining reclamation area

The open-cast lignite mine “Hambach” (NW-Germany) and the accompanying land reclamation replace a large ancient forest. Reclamation of an 1000 ha large overburden dump started 25 years ago and is still in progress. Reclamation methods comprise combinations of different topsoil dumping techniques and reclamation measures such as seeding or afforestation. In accordance with the spatial heterogeneity hypothesis, we hypothesize that beetle assemblages from sites where the topsoil was left structured are more diverse than those from sites with levelled topsoil, and that richly structured mid-successional sites harbour more heterogeneous assemblages than afforested sites. We tested the influence of environmental variables on assemblage characteristics of pitfall-trapped beetles from 17 sites on the overburden dump. The results are based on 35,588 individuals from 339 species. Species assemblages differed significantly between almost all sites. Habitat age did not affect assemblage characteristics, while species richness was significantly influenced by surface structure. Sites that were not levelled and that additionally included pits that slope down for several meters exhibited the highest species richness. Abundance of beetles increased in parallel to the canopy cover, whereas assemblage heterogeneity (MVDISP) decreased. Successional and grassland sites usually exhibited higher diversity (Fisher's α) than afforested sites, but diversity was not significantly predicted by a single environmental factor. Instead, diversity increased along with increasing MVDISP-values. Afforestations speed up the successional process and some euryecious forest species are already well established, but stenecious forest specialists have not yet been found.     

Plant community development following reclamation of oil sands mines using four cover soil types in northern Alberta

Understanding the effects of reclamation treatments on plant community development is an important step in setting realistic indicators and targets for reclamation of upland oil sands sites to forest ecosystems. We examine trends in cover, richness, evenness, and community composition for four cover soil types (clay over overburden, clay over tailings sand, peat‐mineral mix over overburden, and peat‐mineral mix over tailings sand) and natural boreal forests over a 20 year period in the mineable oil sands region of northern Alberta, Canada. Tree, shrub, and nonvascular plant species cover showed similar increases over time for all reclamation treatments, with corresponding declines in forb and graminoid cover with time. These trends resemble those in the natural boreal forests of the region and the trajectory of community development for the reclamation treatments appears to follow typical early successional trends for boreal forests. Species richness and diversity of natural forest differed significantly from reclamation treatments. Nonmetric multidimensional scaling ordination and multi‐response permutation procedure revealed that species composition was not affected by reclamation treatment but clearly differed from natural forest. Analysis of species co‐occurrence indicated random plant community assembly following reclamation, in contrast to a higher proportion of nonrandom plant community assembly in natural forests. Thus, reclaimed plant communities appear to be unstructured through year 20 and assembly is still in progress on these reclaimed sites.     

Growth of Quailbush in Acidic, Metalliferous Desert Mine Tailings: Effect of Azospirillum brasilense Sp6 on Biomass Production and Rhizosphere Community Structure

Mine tailing deposits in semiarid and arid environments frequently remain devoid of vegetation due to the toxicity of the substrate and the absence of a diverse soil microbial community capable of supporting seed germination and plant growth. The contribution of the plant growth promoting bacterium (PGPB) Azospirillum brasilense Sp6 to the growth of quailbush in compost-amended, moderately acidic, high-metal content mine tailings using an irrigation-based reclamation strategy was examined along with its influence on the rhizosphere bacterial community. Sp6 inoculation resulted in a significant (2.2-fold) increase in plant biomass production. The data suggest that the inoculum successfully colonized the root surface and persisted throughout the 60-day experiment in both the rhizosphere, as demonstrated by excision and sequencing of the appropriate denaturing gradient gel electrophoresis (DGGE) band, and the rhizoplane, as indicated by fluorescent in situ hybridization of root surfaces. Changes in rhizosphere community structure in response to Sp6 inoculation were evaluated after 15, 30, and 60 days using DGGE analysis of 16S rRNA polymerase chain reaction amplicons. A comparison of DGGE profiles using canonical correspondence analysis revealed a significant treatment effect (Sp6-inoculated vs. uninoculated plants vs. unplanted) on bacterial community structure at 15, 30, and 60 days (p?<?0.05). These data indicate that in an extremely stressed environment such as acid mine tailings, an inoculated plant growth promoting bacterium not only can persist and stimulate plant growth but also can directly or indirectly influence rhizobacterial community development.     

煤矸石山生态恢复的主要路径

煤矿开采过程伴随着大量煤矸石和废弃物的堆积,对当地生态环境造成巨大危害,恢复受损煤矿区煤矸石山生态系统成为近年来研究的热点。目前,许多研究者从煤矸石山土壤和植被恢复技术、监督管理等方面进行归纳总结,各有侧重地提出相应恢复措施,对于指导当地生态恢复实践发挥了重要作用。然而,绝大部分研究综述均未深入分析煤矸石山生态恢复过程中的关键问题,同时也未从生态系统的整体性和长期稳定性考虑设置恢复路径。基于此,通过梳理前人研究成果,归纳出煤矸石山恢复过程中的地质安全、土壤环境、植被恢复、种群繁衍、生态系统稳定等方面关键问题,从恢复前后逻辑关系和生态系统整体性考虑,设计出边坡稳定性处理及整形、土地复垦、物种选择、人工建植、土壤种子库形成、种群繁衍与更新、生态系统健康和稳定性评价、补充措施等一整套煤矸石山生态恢复的主要路径和方法,对煤矸石山生态系统恢复的基本途径从六个方面进行了总结,同时提出存在的问题和未来需要进一步研究的方向,为煤矸石山生态系统恢复实践提供重要理论指导。     

铜尾矿废弃地土壤动物多样性特征

土壤动物的恢复、群落演替及其多样性对于铜尾矿废弃地的生态重建具有重要意义.为了解铜尾矿废弃地土壤动物群落多样性特征,在铜陵市铜尾矿区设置4个样地23采样点,共捕获土壤动物4622只个体,隶属5门10纲18目29类.结果表明,铜尾矿自然废弃地与其对照组土壤动物多样性差异明显,自然废弃地土壤动物丰富度指数d、大型土壤动物密度、中小型土壤动物密度、多样性指数H'和D·G指数均小于其对照组且存在显著差异.而复垦废弃地中小型土壤动物密度和D·G指数小于其对照组且存在显著差异,多样性指数H'大于其对照组且差异极显著,其他土壤动物群落指标与其对照组均无显著差异.相似系数q表明,外围林地间土壤动物群落相似性最大,其次是复垦废弃地与外围林地间,自然废弃地与其它3个样地间相似性最小.从垂直分层来看,复垦废弃地土壤动物表聚性强于自然废弃地,尾矿废弃地表聚性强于外围林地.灰色关联分析表明,铜尾矿区土壤理化性质与土壤动物群落结构指标关系密切,其中最重要的因素是土壤含水量和总钾含量,重金属全镉含量也不容忽视,植被因素和土壤全铜含量对土壤动物的影响相对较小.由此可见,土壤含水量、土壤基质的优劣、土壤有机质与营养元素的含量等因素限制了铜尾矿废弃地土壤动物的恢复与重建,而这些因素的改善主要归功于尾矿废弃地的土地复垦和作物种植.所以,尾矿废弃地的复垦与利用有利于土壤动物的恢复与重建.     

Mine tailing disposal sites: contamination problems,remedial options and phytocaps for sustainable remediation

Mining practices and the absence of proper mine land reclamation has led to heavy metal contaminated sites with serious impact on the ecosystems and risk for human health. The origin of the contamination is often associated to mine tailing deposits because they are a source of the acid mine drainage (AMD). These areas are devoid of vegetation due to the harsh soil conditions that prevent the rooting of plant species. The remediation of these areas followed by revegetation is necessary to suppress the generation of the AMD and its negative effects on the ecosystems. Conventional remediation technologies for heavy metal contaminated sites are usually not applicable because of the high cost associated with chemicals and energy requirements, as well as the long treatment time to remediate large areas. In this study, the use of phytocapping for the remediation of mine tailing deposits and abandoned mine areas is reviewed. Phytocapping is cost effective, environmentally friendly and has multifunctional role against various problems of mine tailings: it provides erosion control, landscape rehabilitation, enhances the soil properties for further colonization of other more demanding vegetal species, reduces the leachability of metals downwards the groundwater, and favors the immobilization of metals forming less bioavailable species. The most critical step in phytocapping is the developing of the first vegetative cover because of the biotoxicity of the mine soil and mine tailings. Several amendment materials can be used to ameliorate soil conditions creating a favorable environment for the rooting of plants, as well as serving as a source of nutrients. Local plant species with fast growing are preferable because their adaptation to the soil and climate conditions favors their self-propagation.     

Actinorhizal Alder Phytostabilization Alters Microbial Community Dynamics in Gold Mine Waste Rock from Northern Quebec: A Greenhouse Study

Phytotechnologies are rapidly replacing conventional ex-situ remediation techniques as they have the added benefit of restoring aesthetic value, important in the reclamation of mine sites. Alders are pioneer species that can tolerate and proliferate in nutrient-poor, contaminated environments, largely due to symbiotic root associations with the N₂-fixing bacteria, Frankia and ectomycorrhizal (ECM) fungi. In this study, we investigated the growth of two Frankia-inoculated (actinorhizal) alder species, A. crispa and A. glutinosa, in gold mine waste rock from northern Quebec. Alder species had similar survival rates and positively impacted soil quality and physico-chemical properties in similar ways, restoring soil pH to neutrality and reducing extractable metals up to two-fold, while not hyperaccumulating them into above-ground plant biomass. A. glutinosa outperformed A. crispa in terms of growth, as estimated by the seedling volume index (SVI), and root length. Pyrosequencing of the bacterial 16S rRNA gene for bacteria and the ribosomal internal transcribed spacer (ITS) region for fungi provided a comprehensive, direct characterization of microbial communities in gold mine waste rock and fine tailings. Plant- and treatment-specific shifts in soil microbial community compositions were observed in planted mine residues. Shannon diversity and the abundance of microbes involved in key ecosystem processes such as contaminant degradation (Sphingomonas, Sphingobium and Pseudomonas), metal sequestration (Brevundimonas and Caulobacter) and N₂-fixation (Azotobacter, Mesorhizobium, Rhizobium and Pseudomonas) increased over time, i.e., as plants established in mine waste rock. Acetate mineralization and most probable number (MPN) assays showed that revegetation positively stimulated both bulk and rhizosphere communities, increasing microbial density (biomass increase of 2 orders of magnitude) and mineralization (five-fold). Genomic techniques proved useful in investigating tripartite (plant-bacteria-fungi) interactions during phytostabilization, contributing to our knowledge in this field of study.     

干旱胁迫下AM真菌对矿区土壤改良与玉米生长的影响

以神东矿区塌陷区退化土壤为供试基质,以玉米为宿主植物,研究在干旱胁迫下,丛枝菌根真菌(arbuscular mycorrhizalfungi)对玉米生长和养分吸收的影响,以及对矿区退化土壤的改良作用.结果表明:干旱胁迫下,接种AMF显著提高了玉米根系侵染率和生物量,玉米叶片相对含水量和叶色值明显高于对照组;接种组玉米地上部分磷、氮、钙和根系部分磷、钾、钙含量显著增加;接种AMF后,玉米根际土壤总球囊霉素和易提取球囊霉素含量分别增加了36.2％和33％,且根际土壤中有机质含量显著增加.由此可见,接种AMF促进了玉米对矿质养分的吸收,缓解了干旱造成的玉米生长的不利影响,提高了根际土壤中有机质含量,对矿区退化土壤改良有重要意义.     

Establishment of Restoration Trajectories for Upland Tundra Communities on Diamond Mine Wastes in the Canadian Arctic

Mining in the arctic amplifies restoration challenges due to inherent environmental conditions by removing soil, vegetation, and the propagule bank, adding coarse textured wastes with low water holding capacity and nutrients, and introducing salt and metal contamination. Short‐term reclamation focuses on rebuilding soil and providing rapid native plant cover for erosion control, supporting longer term reestablishment of ecological processes for sustainable tundra communities that provide essential wildlife habitat. This study evaluated methods to restore soil and plant communities 5 years after implementation of treatments at a diamond mine in the Canadian arctic. Five substrates including mine waste materials (processed kimberlite, glacial till, gravel, and mixes), four amendments (inorganic fertilizer, salvaged soil, sewage sludge, and water treatment sludge), five native species seed mixes and natural recovery were investigated. Soil and plant response were assessed annually. Soil chemistry was ameliorated with time. Chromium, cobalt, and nickel concentrations in processed kimberlite remained high and potentially toxic to plants. Adding fine textured materials such as glacial till to mine wastes improved nutrient and water retention, which in turn enhanced revegetation. Sewage and inorganic fertilizer increased available nitrogen and phosphorus, plant density and cover. Soil amendment increased species richness. Seeding was essential to establish a vegetation cover. After 5 years, seed mix composition and diversity had no effect on plant community development; soil and plant community properties among treatments changed considerably, providing evidence that restoration in the arctic is dynamic yet slow and success cannot be determined in the short term.     

Abandoned metalliferous mines: ecological impacts and potential approaches for reclamation

The lack of awareness for timely management of the environment surrounding a metal mine site results in several adverse consequences such as rampant business losses, abandoning the bread-earning mining industry, domestic instability and rise in ghost towns, increased environmental pollution, and indirect long-term impacts on the ecosystem. Although several abandoned mine lands (AMLs) exist globally, information on these derelict mines has not been consolidated in the literature. We present here the state-of-the-art on AMLs in major mining countries with emphasis on their impact towards soil health and biodiversity, remediation methods, and laws governing management of mined sites. While reclamation of metalliferous mines by phytoremediation is still a suitable option, there exist several limitations for its implementation. However, many issues of phytoremediation at the derelict mines can be resolved following phytostabilization, a technology that is effective also at the modern operational mine sites. The use of transgenic plant species in phytoremediation of metals in contaminated sites is also gaining momentum. In any case, monitoring and efficacy testing for bioremediation of mined sites is essential. The approaches for reclamation of metalliferous mines such as environmental awareness, effective planning and assessment of pre- and post-mining activities, implementation of regulations, and a safe and good use of phytostabilizers among the native plants for revegetation and ecological restoration are discussed in detail in the present review. We also suggest the use of microbially-enhanced phytoremediation and nanotechnology for efficient reclamation of AMLs, and identify future work warranted in this area of research. Further, we believe that the integration of science of remediation with mining policies and regulations is a reliable option which when executed can virtually balance economic development and environmental destruction for safer future.     

Remediation of Copper from Copper Mine Wastes and Contaminated Soils Using (S,S)-Ethylenediaminedisuccinic Acid and Acidophilic Bacteria

The biodegradable chelating agent (S,S)-Ehylenediaminedisuccinic acid (EDDS), autochthonous acidophilic bacteria, and a combination of the two means were investigated for the removal of pseudo-total and ethylenediaminetetraacetic acid (EDTA)-available content of Cu from surface layers of three soil categories in the Bor copper mining area. Their efficiencies were compared at mine overburden, flotation tailings, and agricultural land sites in order to determine the potential role of these approaches in the soil remediation process. The most effective removal of Cu was achieved on flotation tailings, where combined treatment showed significant reduction of pseudo-total and EDTA-available concentrations of Cu (40.5?±?27.3% and 99.6?±?0.2%, respectively). Acidophilic bacteria treatment showed high efficiency on flotation tailings, removing 94.1?±?1.2% of EDTA-available Cu. EDDS treatment showed discernible results in the removal of EDTA-available Cu from agricultural land soil (44.4?±?13.9%). In the case of overburden soil material, selected agents did not have statistically significant results in the removal of pseudo-total or EDTA-available fraction of Cu. Chosen remediation approaches showed diverse efficiency for soil categories on investigated sites. Combined approach showed synergistic results in the case of EDTA-available Cu removal from flotation tailings soils, suggesting that this combination deserves further attention as a potentially promising environmentally friendly remediation option.     

Establishment of Moose Browse on Four Growth Media on a Proposed Mine Site in Southcentral Alaska

The objective of this study was to evaluate seven woody plant species on four growth media for their potential contribution to moose habitat and establishment of viable plant communities on a proposed mine site in southcentral Alaska. Populus balsamifera (balsam poplar), Salix alaxensis (feltleaf willow), S. barclayi (Barclay willow), S. bebbiana (Bebb willow), Alnus tenuifolia (thinleaf alder), Betula papyrifera (paper birch), and Picea glauca (white spruce) were selected for their functions in moose habitat, ease of propagation, and presence in the existing native vegetation. Three native soils were selected for biological characteristics such as different potential to form mycorrhizae and to regenerate local plant species, both of which are governed partly by existing vegetation. The fourth growth medium, glacial till or overburden, was expected to have little or no biological activity. A mining disturbance was simulated on three sites by removing existing vegetation from the plots, stripping the native soils, and then spreading these soil materials over the respective study plots. Rooted cuttings of the Salicaceae and nursery seedlings of the other species were planted in each of the four growth media. Height and survival of all plant species were greater on the three soil media than on the glacial till during the second and third years. Percentage of ectomycorrhizal infection on transplants was similar among growth media, although lower ectomycorrhizal infection occurred on volunteers in grassland soils than in the other growth media. Browsable plants were produced within three years on the disturbed native soils but not on the glacial till.     

Screening of plant growth promoting traits in heavy metals resistant bacteria: Prospects in phytoremediation

Phytoremediation is considered as a novel environmental friendly technology, which uses plants to remove or immobilize heavy metals. The use of metal-resistant plant growth-promoting bacteria (PGPB) constitutes an important technology for enhancing biomass production as well as tolerance of the plants to heavy metals. In this study, we isolated twenty seven (NF1-NF27) chromium resistant bacteria. The bacteria were tested for heavy metals (Cr, Zn, Cu, Ni, Pb and Co) resistance, Cr(VI) reduction and PGPB characters (phosphate solubilization, production of IAA and siderophores). The results showed that the bacterial isolates resist to heavy metals and reduce Cr(VI), with varying capabilities. 37.14% of the isolates have the capacity of solubilizing phosphate, 28.57% are able to produce siderophores and all isolates have the ability to produce IAA. Isolate NF2 that showed high heavy metal resistance and plant growth promotion characteristics was identified by 16S rDNA sequence analysis as a strain of Cellulosimicrobium sp.. Pot culture experiments conducted under greenhouse conditions showed that this strain was able to promote plant growth of alfalfa in control and in heavy metals (Cr, Zn and Cu) spiked soils and increased metal uptake by the plants. Thus, the potential of Cellulosimicrobium sp. for both bioremediation and plant growth promotion has significance in the management of environmental pollution.     

Use of Arbuscular Mycorrhiza and Organic Amendments to Enhance Growth of Macaranga peltata (Roxb.) Müll. Arg. in Iron Ore Mine Wastelands

Macaranga peltata (Roxb.) Mull. Arg. is a disturbance tolerant plant species with potential in mine wasteland reclamation. Our study aims at studying the phyto-extraction potential of M. peltata and determining plant-soil interaction factors effecting plant growth in iron ore mine spoils. Plants were grown in pure mine spoil and spoil amended with Farm Yard Manure (FYM) and Vermicompost (VC) along with arbuscular mycorrhizal (AM) species Rhizophagus irregularis. Pure and amended mine spoils were evaluated for nutrient status. Plant growth parameters and foliar nutrient contents were determined at the end of one year. FYM amendment in spoil significantly increased plant biomass compared to pure mine spoil and VC amended spoil. Foliar Fe accumulation was recorded highest (594.67μg/g) in pure spoil with no mortality but considerably affecting plant growth, thus proving to exhibit phyto-extraction potential. FYM and VC amendments reduced AM colonization (30.4% and 37% resp.) and plants showed a negative mycorrhizal dependency (–30.35 and –39.83 resp.). Soil pH and P levels and, foliar Fe accumulation are major factors determining plant growth in spoil. FYM amendment was found to be superior to VC as a spoil amendment for hastening plant growth and establishment in iron ore mine spoil     

Anthyllis vulneraria/Mesorhizobium metallidurans, an efficient symbiotic nitrogen fixing association able to grow in mine tailings highly contaminated by Zn, Pb and Cd

The excessive concentrations of toxic heavy metals in mine tailings and their very low N content make soil reclamation strategies by phytostabilization difficult. Our objective was to test if the symbiotic association between the legume Anthyllis vulneraria subsp. carpatica and the bacteria Mesorhizobium metallidurans originating from highly polluted mine tailings is able to increase N concentration in soils with contrasting Zn, Pb and Cd contents. Plants of A. vulneraria subsp. carpatica from a mine site and of a non-metallicolous subsp. praeopera from non-polluted soil were inoculated with a metallicolous or a non-metallicolous compatible Mesorhizobium spp. and grown on low and high heavy metal-contaminated soils. In contaminated soil, many nodules were observed when the metallicolous A. vulneraria was inoculated with its rhizobium species M. metallidurans, whereas the non-metallicolous A. vulneraria died after a few weeks regardless of the rhizobium inoculant. Eighty percent of the total nitrogen was derived from biological nitrogen fixation through the association between metallicolous A. vulneraria and the rhizobium grown on metal-enriched soil. The ability of the metallicolous A. vulneraria to develop a high nitrogen fixing potential opens new possibilities for promoting a low-maintenance plant cover and for stabilizing the vegetation in high heavy metal-contaminated soils.     

Management of nursery practices for efficient ectomycorrhizal fungi application in the production of Quercus ilex

The application of ectomycorrhizal (ECM) fungi on forest nursery production is regarded as part of good management practice. However, before employing large scale inoculations in a nursery the interaction between ECM symbionts, growth substrate and fertilisation input should be studied to select the most suitable nursery practices for promoting plant growth and ECM colonisation. In this study, seedlings of Quercus ilex were inoculated with Paxillus involutus, Hebeloma mesophaeum or Cenococcum geophilum and grown in three different substrates commonly used in forest nurseries: peat-based compost, forest soil or composted pine bark. The effect of various fertilisation regimes was also studied. The choice of substrate had a significant effect on plant growth and ECM colonisation. The most appropriate combination of substrate and ECM fungus for Q. ilex growth and nutrition was peat and H. mesophaeum. Plants grown on a peat-based compost and inoculated with H. mesophaeum had a significantly greater biomass and leaf phosphorus concentration without fertilisation. Composted pine bark was found not to be suitable for growth or for mycorrhization. If the appropriate growth substrate is selected, it is possible to replace the use of chemical fertilisers by inoculation with selected ECM fungi. This results in a significant increase in plant development, and thus ECM fungi can be recommended as a more environmental friendly biotechnological approach to plant management in the nursery.     

Bacterial functional redundancy along a soil reclamation gradient

A strategy to measure bacterial functional redundancy was developed and tested with soils collected along a soil reclamation gradient by determining the richness and diversity of bacterial groups capable of in situ growth on selected carbon substrates. Soil cores were collected from four sites along a transect from the Jamari tin mine site in the Jamari National Forest, Rondonia, RO, Brazil: denuded mine spoil, soil from below the canopy of invading pioneer trees, revegetated soil under new growth on the forest edge, and the forest floor of an adjacent preserved forest. Bacterial population responses were analyzed by amending these soil samples with individual carbon substrates in the presence of bromodeoxyuridine (BrdU). BrdU-labeled DNA was then subjected to a 16S-23S rRNA intergenic analysis to depict the actively growing bacteria from each site. The number and diversity of bacterial groups responding to four carbon substrates (L-serine, L-threonine, sodium citrate, and alpha-lactose hydrate) increased along the reclamation-vegetation gradient such that the preserved forest soil samples contained the highest functional redundancy for each substrate. These data suggest that bacterial functional redundancy increases in relation to the regrowth of plant communities and may therefore represent an important aspect of the restoration of soil biological functionality to reclaimed mine spoils. They also suggest that bacterial functional redundancy may be a useful indicator of soil quality and ecosystem functioning.     

Humic matter enrichment in reclaimed soils under semiarid conditions

Changes in humic matter of overburden and replaced topsoils receiving four different treatment combinations of fertilizer and an organic amendment were investigated on reclaimed surface mine spoil in southeastern Montana. Nine years after revegetation, the maximum increases of organic matter and humic acid content, respectively, were 53% and 23% on overburden soils and 14% and 16% on replaced topsoils. The C:N ratio increased in the overburden soil from 11.0 to 13.5 with treatments; in the topsoil the C:N ratio changes were variable. C:N ratios of 9–11 were characteristic of humic acids, with no consistent relation to treatments. The increases in the soil organic matter, humic matter, and total soil nitrogen content were greater than the amounts of C and N added as amendments, probably because of the increased plant litter availability and retention in soil and possible nitrogen input by dinitrogen fixation.