Successional dynamics of soil fungal diversity along a restoration chronosequence post‐coal mining

Soil disruption from open‐cut mining practices can adversely impact microbial communities and the ecosystem services that they mediate. Despite this, assessment of impacts of soil disruption, and the subsequent recovery of microbial communities is rarely studied. Monitoring of ecological restoration success on mine sites has traditionally focused on vegetation; however, most plants rely, at least in part, on associations with soil fungi for enhanced nutrient and water acquisition. Here, we used high‐throughput phylogenetic marker gene sequencing to characterize the diversity of soil fungal communities along a restoration chronosequence ranging from 3 to 23 years at a rehabilitated mine site. We used nonmined analogue sites as a baseline for comparative purposes and examined the associations of soil fungal communities with soil physicochemical and aboveground vegetation variables. Fungal richness on rehabilitated sites was significantly larger than on nonmined sites, suggesting that mixing of topsoil during stockpiling resulted in a composite microbial community. Fungal community composition was significantly influenced by edaphic variables and the length of rehabilitation, with mined sites becoming more similar to nonmined sites over time. Fungal populations associated with ectomycorrhizae were relatively more abundant than those associated with arbuscular mycorrhizae and declined in response to disturbance, but recovered over time on the woody dominated sites indicating a strong coupling of these fungi with aboveground vegetation. Our data indicate that soil fungal diversity is a useful bioindicator of soil restoration in mined sites and may complement more traditional vegetation‐based surveys.     

Soil moisture dynamics and restoration of self‐sustaining native vegetation ecosystem on an open‐cut coal mine

Post‐mining landscape reconstruction on open‐cut coal mines aims to support restoration of self‐sustaining native vegetation ecosystems that in perpetuity require no extra inputs relative to unmined analogs. Little is known about the soil moisture retention capacity of the limited layer of topsoil replaced (often <30 cm deep), impacts of deep ripping of the profile, and the combined impacts of these on plant available water during the mine restoration process. We examined changes in soil moisture parameters (soil water potential, Ψ, and soil water content, Θ) daily using automated soil sensors installed at 30 and 45–65 cm depths on mine restoration sites aged between 3 and 22 years and on adjacent remnant vegetation sites following heavy rainfall events at Meandu mine, southeast Queensland, Australia. Consistent patterns in soil moisture attributes were observed among rehabilitated sites with generally marked differences from remnant sites. Remnant site soil profiles had generally higher Θ after drying than rehabilitated sites and maintained high Ψ for extended periods after rain events. There was a relatively rapid decline of Ψ on reconstructed soil profiles compared with remnant sites although the times of decline onset varied. This response indicated that vegetation restoration sites released soil moisture more rapidly than remnant sites but the rate of drying decreased with increasing rehabilitation age and increased with increasing tree stem density. The rapid drying of mine rehabilitated sites may threaten the survival of some remnant forest species, limit tree growth, and delay restoration of self‐sustaining native ecosystem.     

矿山生态恢复研究进展——基于连续三届的世界生态恢复大会报告

最近连续三届世界生态恢复大会都将矿山生态系统列为大会交流的主题之一。为了解矿山生态修复的最新进展,本文采用文献分析方法和统计分析法,全面对比了这三届大会的论文和报告,包括参会国家、主要机构、热点矿区、修复要素、矿山类型、修复技术等。在此基础上,归纳了新开发的生态修复技术,包括植被恢复、土壤修复和景观恢复等新技术;总结了当前的研究热点,主要有复垦的土壤和修复的植物之间相互作用的机理、矿山生态修复的监测新技术、本土物种保持、污染土壤修复新技术、应对全球气候变化的矿山生态修复新思维和矿山生态系统服务价值等;介绍了会议提出的新观点,如自然恢复和人工恢复选择的新标准、矿山生态恢复力新理论、新型矿山生态系统及其设计等。最后对未来研究趋势进行了预测。     

Woodland restoration on agricultural land: long‐term impacts on soil quality

Woodland restoration is underway globally to counter the negative soil quality and ecological impacts of agricultural expansion and woodland fragmentation, and restore or enhance biodiversity, ecosystem functions and services. However, we lack information about the long‐term effects of woodland restoration on agricultural soils, particularly at temporal scales meaningful to woodland and soil development. This study utilized soil and earthworm sampling across a chronosequence of sites transitioning from “agricultural land” to “secondary woodland” (50–110 years) and “ancient woodland” (>400 years), with the goal of quantifying the effects of woodland restoration on agricultural land, on key soil quality parameters (soil bulk density, pH, carbon and nitrogen stocks, and earthworm abundance, biomass, species richness and diversity). Broad‐leaved woodland restoration led to significantly greater soil organic carbon (SOC) stocks compared to arable land, and young (50–60 years) secondary woodland increased earthworm species and functional diversity compared to both arable and pasture agricultural land. SOC stocks in secondary broad‐leaved woodlands (50–110 years) were comparable to those found in long‐term ancient woodlands (>400 years). Our findings show that broad‐leaved woodland restoration of agricultural land can lead to meaningful soil ecological improvement and gains in SOC within 50–110 years, and provide intel on how restoration activities may be best targeted to maximize soil quality and functions.     

Evaluating soil seed banks of phosphate mining restoration in the hyper-arid Negev desert

Ecological systems are severely damaged by the anthropogenic disturbance of mining. Phosphate open-pit mining fields cover over 200 km² of the Negev desert, Israel. However, the effects of the ongoing mine site restoration efforts on the plant community have not been studied. Plants and their seed banks have a major role in ecosystem processes and restoration. In this study, we focused on three mining sites, restored in different years, along Zin River valley. We compared the plant community of restored mining plots within these areas to adjacent natural plots. We asked whether plant community germination potential from the soil seed bank differs between the restored plots and the adjacent natural plots within a mining site. We hypothesized that: (1) there is a lack of seed bank in the restored plots; (2) the altered soil composition at the restored plots inhibits germination. We used soil samples collected from the different mining sites and set up greenhouse experiments. One experiment compared natural and restored areas with different soil treatments. In another experiment, we added native seeds to test their germination potential on restored soil. Our results indicate that lack of seed bank is the major limiting factor hindering germination and not the composition of the soil after restoration. Our findings shed light on the constraints of seed bank establishment in post-mining areas of hyper-arid regions. We suggest considering active restoration practices to facilitate natural dispersal and improve seed bank establishment.     

Soil restoration under pasture after lignite mining: Management effects on soil biochemical properties and their relationships with herbage yields

The recovery of soil biochemical properties under grazed, grass-clover pasture, after simulated lignite mining, was studied over a 5-year period in a mesic Typic Dystrochrept soil at Waimumu, Southland, New Zealand. The restoration procedures involved four replacement treatments, after A, B, and C horizon materials had been separately removed, from all except the control, and stockpiled for 2–3 weeks. In each replacement treatment, the effects of ripping to 1.8 m depth, mole drainage, and the use of fertilizer nitrogen were also investigated.Replacement treatment markedly influenced the recovery of herbage production and soil organic C and total N contents, N mineralization, microbial biomass (as indicated by mineral-N flush) and invertase and sulphatase activities. The effectiveness of replacement treatments decreased in the order: 1. control (no stripping or replacement). 2 A, B, and C horizon materials replaced in the same order. 3. A, B, and C horizon materials each mixed with an equal amount of siltstone overburden and replaced in order, 4. A and B horizon materials mixed before replacing over C horizon material.Ripping increased herbage production, net N mineralization, and to some extent microbial biomass. Drainage had little, if any, effect.Fertilizer N also stimulated herbage production, but depressed clover growth. Over 2.5 years, it had little detectable effect on the soil properties.Increases in soil invertase and, to a lesser extent, sulphatase activity during the trial were closely related to changes in herbage production. Microbial biomass increased more rapidly than did soil organic C in the early stages of the trial.Rates of net N mineralization strongly suggest that N availability would have limited pasture growth, especially in the treatments with mixed soil materials.     

Long‐term regeneration of a tropical plant community after sand mining

Sandy coastal plant communities in tropical regions have been historically under strong anthropic pressure. In Brazil, these systems shelter communities with highly plastic plant species. However, the potential of these systems to regenerate without human assistance after disturbances has hardly been examined. We determined the natural regeneration of a coastal sandy plain vegetation (restinga) in Brazil, 16 years after the end of sand removal. We inventoried 38 plots: 20 within a sand‐mined site and 18 in an adjacent undisturbed site. We expected lower diversity values in the sand‐mined site compared to the undisturbed site, but similar species composition between the two sites due to the spatial proximity of the two sites and the high plasticity of restinga species. Species were ranked using abundance and importance value index in both sites, and comparisons were performed using Rényi entropy profiles, rarefaction curves, principal component analysis, and redundancy analysis. Species composition and dominant species differed markedly between the two sites. Bromeliads and Clusia hilariana, well‐known nurse plants, dominated the undisturbed site but were almost absent in the regenerating site. Species richness did not differ between both sites, but diversity was higher in the undisturbed site. Within‐site composition differences in the mined area were associated with field characteristics. Interestingly, species classified as subordinate or rare in the undisturbed site became dominants in the regenerating site. These newer dominants in the sand‐mined site are not those known as nurse plants in other restingas, thus yielding strong implications for restoration.     

Planning mine restoration through ecosystem services to enhance community engagement and deliver social benefits

Mining companies are expected to return land to a stable, productive, and self‐sustaining condition by rehabilitating degraded areas to also deliver social benefits, an essential dimension of sustainable land management. This research aimed to develop a framework for mine rehabilitation planning based on an integrated analysis of the social‐ecological system provided by the ecosystem services concept to facilitate community engagement and the delivery of social benefits. An Ecosystem Services Assessment for Rehabilitation framework was tested at two bauxite mines undergoing ecological restoration. The mines are operated by the same company in two countries. Key results showed that the framework can help companies, regulators, and community members alike identify whether biophysical restoration efforts translate into key human benefits. Overall the framework provides a means for enhancing community engagement to explicitly address social benefits that, with a business as usual focus on ecological goals, may not be delivered. The ecosystem services concept provides a practical approach to link ecological and social outcomes of mine restoration.     

不同植被恢复模式下矿区复垦土壤真菌群落组成及多样性

本研究利用Illumina MiSeq高通量测序技术,分析安太堡露天煤矿生态复垦区4种植被恢复模式(刺槐Robinia pseudoacacia、油松Pinus tabulaeformis、沙棘Hippophae rhamnoides和柠条锦鸡儿Caragana korshinskii)土壤真菌群落组成及多样性,并探究其与土壤环境因子的相关性。高通量测序结果共获得821 508条有效序列和1 841个OTUs,子囊菌门Ascomycota和担子菌门Basidiomycota为优势菌门,序列数占真菌总数的88.43%,此外还含有3.72%未被分类学鉴定的真菌。真菌α多样性分析结果表明：刺槐模式、沙棘模式和柠条锦鸡儿模式的Sobs指数、Chao1指数、Ace指数和Shannon指数均显著高于油松模式(P<0.01),而油松模式的Simpson指数显著高于其余3种植被恢复模式(P<0.05)。真菌β多样性分析结果显示：OTU水平下4种植被恢复模式土壤真菌群落组成差异显著(R=0.709 9,P=0.005),其中,油松模式的土壤真菌群落与其他3种模式距离较远,差异显著(P<0.01),而其余3种植被恢复模式之间两两组成相近,差异不显著(P>0.05)。通过土壤理化性质的测定、典范对应分析、冗余分析以及Spearman相关性分析,结果发现土壤有机质、全氮和有效磷是显著影响4种植被恢复模式土壤真菌群落组成的环境因子。综上所述,在矿区生态复垦过程中刺槐模式是物种相对多度最高的植被恢复模式,油松模式是优势菌群含量最高的植被恢复模式。研究结果可为植被修复煤矿复垦区土壤及真菌资源的开发利用提供理论依据。     

Deploying microbes as drivers and indicators in ecological restoration

Ecosystem degradation is a major environmental threat. Beyond conservation, restoration of degraded ecosystems is a prerequisite to reinstate their ability to provide essential services and benefits. Most of the restoration efforts focus on aboveground restoration, that is, plants, under the assumption that establishment of plant species will reestablish the faunal and microbial species. While this may be true for some cases, it is not a general rule. Reestablishment of microbial communities by dedicated efforts is also necessary for successful restoration, as cycling of essential nutrients for plant growth and decomposition of organic matter is dependent on them. The role of microbial fertilizers and efficient organisms used in agriculture needs to be explored in restoration. Testing of symbiotic interactions between potential plant growth-promoting Rhizobacteria and plants native to a degraded ecosystem can be conducted and utilized for successful establishment of plant species. However, utmost care must be taken while introducing new microbial species or non-native plant species to an area, as they can adversely affect the resident microbial community. Techniques like phospholipid fatty-acid analysis can be used for taxonomic identification of large microbial groups in non-degraded reference ecosystems before introducing microbial species into a degraded ecosystem. For use of microbes in restoration, more studies on microbe-plant interactions need to be conducted. For use of Soil Microbial Community (SMC) as indicators of restoration, their role and function in the ecology of the area need to be elucidated by employing all the available techniques.     

Long‐term effects of vegetational restoration on soil microbial communities on the Loess Plateau of China

Soil microbial communities are important indicators for evaluating the effectiveness of vegetational restoration. The ability of soil microbial communities to recover under six types of restoration was examined using Biolog, phospholipid fatty acid (PLFA), and denaturing gradient gel electrophoresis (DGGE). Soil samples were collected from eroded loessial soils that had been restored for 30 years on the Loess Plateau with natural grass, black locust, korshinsk peashrub, Chinese pine, and mixed forest of Chinese pine‐indigo and black locust‐indigo. Part of sloped farmland that had not been restored represented pre‐restoration conditions. An 80‐year‐old forest of Chinese arborvitae represented the end point of restoration. Soils that were originally farmed but have been under restoration treatments for the past 30 years had significantly higher average well‐color development, total PLFAs, bacterial PLFAs, fungal PLFAs, and Shannon indices of catabolic diversity, structural diversity, and bacterial phylogenetic diversity. These indicators, though, were lower than those for the native forest. Principal component analysis significantly separated the sloped farmland, Chinese arborvitae, and the six types of restoration. Redundancy analysis indicated that pH, total organic carbon, total nitrogen, available nitrogen, and available phosphorus were the most important environment factors in affecting soil functional diversity, and C/N ratio and available nutrients were the main properties in determining microbial community structure. Vegetational restoration substantially increased microbial biomass and microbial physiological activity, and shifted microbial community structure, but the community structures and compositions did not recover to the status of the natural forest during the early stage (<30 years) of vegetational restoration.     

沙坡头地区凋落物分解及其对土壤微生物群落的影响

以腾格里沙漠东南缘沙坡头人工固沙植被区典型植物种凋落物(小画眉草、藓类、油蒿叶片)为对象,运用凋落物分解袋法和高通量测序技术,分析了3种植物凋落物分解特征及其对土壤微生物群落的影响。结果表明: 分解时间和凋落物类型均显著影响分解速率,藓类分解最慢,13个月后质量损失比仅为15.4%,油蒿叶片和小画眉草的平均分解速率分别是藓类的4.9和3.4倍。经过11个月的分解,细菌群落的优势菌门为放线菌门和变形菌门,真菌群落的优势菌门是子囊菌门;藓类分解过程中,拟杆菌门和绿弯菌门的相对丰度显著增加,担子菌门的相对丰度显著降低。凋落物分解后,细菌和真菌群落物种多样性和丰富度显著增加,细菌群落组成在凋落物间变化不显著,真菌群落变化显著。凋落物的分解速率与细菌和真菌群落多样性及丰富度均呈负线性变化。植物多糖、全磷和土壤pH、微生物生物量氮、铵态氮含量是影响微生物群落结构的主要因子。凋落物分解改变了土壤微生物群落物种组成和种间相似性,显著增加了土壤中微生物群落的多样性和丰富度,促进了土壤生境的恢复。     

Differences in the soil microbial community and carbon‐use efficiency following development of Vochysia guatemalensis tree plantations in unproductive pastures in Costa Rica

This study shows that Vochysia guatemalensis tree plantations were associated with enhanced soil biotic and abiotic characteristics in previously cleared forests in the northern zone of Costa Rica, suggesting the possible use of this practice as a restoration strategy for local land owners. Soil samples from a primary forest, secondary forest, and a 13‐year‐old plantation of V. guatemalensis had greater relative abundances of DNA sequences of microbial genera critical for carbon‐use (C‐use) efficiency (i.e. the saprobe, complex C and wood rot/lignin decomposer fungi, and bacterial lignin and other complex C degraders), and greater levels of total organic carbon, C‐biomass, and microbial quotients as indicators of enhanced C‐use efficiency, than found in soils of adjacent 5‐year‐old V. guatemalensis plantations and abandoned non‐productive pasture/grasslands (GRs). The major research conclusions were that (1) conversion of forested land into abandoned pasture/GRs decreased the C‐use efficiency in the soils and the microbial groups associated with C‐use efficiency; (2) soils in plantations of V. guatemalensis were associated with increased abundances of the DNA of these same microbial groups and enhanced C‐use efficiency; (3) DNA‐based taxonomic analysis of microbes and analysis of the microbial quotient values can be used to monitor soil ecosystems for assessment of the efficacy of restoration activities. Thus, planting V. guatemalensis on damaged lands in the Maquenque National Wildlife Refuge should be encouraged to provide a sustainable forestry crop that can be harvested rotationally, while improving soil ecosystem health and reducing the pressure to harvest other forest sites.     

Legacy effects of soil homogenization on tallgrass prairie restoration: toward resolved understanding of the relationship between soil heterogeneity and plant species diversity

Within plant communities, niche‐based species sorting can occur among distinct soil patches (microsites), increasing coexistence and diversity. Microsite edges (microedges) may also offer additional niche space. Therefore, in recently abandoned croplands, which often have uniform soils caused by a legacy of tillage (soil homogenization), the plant species diversity of future restoration efforts may be reduced. We conducted an experiment during the early establishment phase (3 years) of a tallgrass prairie restoration on former cropland to determine if soil homogenization decreases species diversity and alters community composition, and if microedges offer additional niche space. Heterogeneous plots with sand‐ or woodchip‐enriched patches were compared to plots made up of the same components, but distributed homogeneously, and pits and mounds were compared to flat topsoil. Homogenization decreased diversity in flat topsoil plots relative to pit plots and increased diversity in woodchip plots. In both cases, the treatments with the lowest canopy cover and greatest plant density had the greatest diversity. Sand and topographic homogenization decreased diversity, but when a drought occurred in year two, the effect was suppressed in the sand treatment and magnified in the pit plots. Microedges had properties unique from adjacent patches. Overall, variability in heterogeneity–diversity relationships was affected by interactions with plant growth patterns and environmental conditions. Our results indicate that while the addition of contrasting soil microsites has the potential to promote increased diversity in grassland restoration on former cropland, the patch components and design must be optimized to achieve this management goal.     

Changes in soil bacterial community triggered by drought‐induced gap succession preceded changes in soil C stocks and quality

The aim of this study was to understand how drought‐induced tree mortality and subsequent secondary succession would affect soil bacterial taxonomic composition as well as soil organic matter (SOM) quantity and quality in a mixed Mediterranean forest where the Scots pine (Pinus sylvestris) population, affected by climatic drought‐induced die‐off, is being replaced by Holm‐oaks (HO; Quercus ilex). We apply a high throughput DNA pyrosequencing technique and ¹³C solid‐state Nuclear Magnetic Resonance (CP‐MAS ¹³C NMR) to soils within areas of influence (defined as an surface with 2‐m radius around the trunk) of different trees: healthy and affected (defoliated) pines, pines that died a decade ago and healthy HOs. Soil respiration was also measured in the same spots during a spring campaign using a static close‐chamber method (soda lime). A decade after death, and before aerial colonization by the more competitive HOs have even taken place, we could not find changes in soil C pools (quantity and/or quality) associated with tree mortality and secondary succession. Unlike C pools, bacterial diversity and community structure were strongly determined by tree mortality. Convergence between the most abundant taxa of soil bacterial communities under dead pines and colonizer trees (HOs) further suggests that physical gap colonization was occurring below‐ground before above‐ground colonization was taken place. Significantly higher soil respiration rates under dead trees, together with higher bacterial diversity and anomalously high representation of bacteria commonly associated with copiotrophic environments (r‐strategic bacteria) further gives indications of how drought‐induced tree mortality and secondary succession were influencing the structure of microbial communities and the metabolic activity of soils.     

植物群落和土壤理化性质对碧塔海湿地土壤细菌群落的影响

土壤微生物是湿地生态系统中土壤-植物系统生源要素迁移转化的引擎.探究湿地生态系统地上植物群落、土壤理化性质和空间结构与土壤细菌间的相互关系是维护湿地生态系统健康和稳定的关键.本研究运用双向指示种分析法(TWINSPAN)对碧塔海湿地采集的35个样方中的植物群落进行分类,并采用高通量测序技术对样方的表层土壤细菌进行测序,...     

Changes in ectomycorrhizal fungal community composition and declining diversity along a 2‐million‐year soil chronosequence

Ectomycorrhizal (ECM) fungal communities covary with host plant communities along soil fertility gradients, yet it is unclear whether this reflects changes in host composition, fungal edaphic specialization or priority effects during fungal community establishment. We grew two co‐occurring ECM plant species (to control for host identity) in soils collected along a 2‐million‐year chronosequence representing a strong soil fertility gradient and used soil manipulations to disentangle the effects of edaphic properties from those due to fungal inoculum. Ectomycorrhizal fungal community composition changed and richness declined with increasing soil age; these changes were linked to pedogenesis‐driven shifts in edaphic properties, particularly pH and resin‐exchangeable and organic phosphorus. However, when differences in inoculum potential or soil abiotic properties among soil ages were removed while host identity was held constant, differences in ECM fungal communities and richness among chronosequence stages disappeared. Our results show that ECM fungal communities strongly vary during long‐term ecosystem development, even within the same hosts. However, these changes could not be attributed to short‐term fungal edaphic specialization or differences in fungal inoculum (i.e. density and composition) alone. Rather, they must reflect longer‐term ecosystem‐level feedback between soil, vegetation and ECM fungi during pedogenesis.     

Changes in soil properties and resistance to concentrated flow across a 25‐year passive restoration chronosequence of grasslands on the Chinese Loess Plateau

Revegetation represents an effective measure for preventing soil erosion on the Loess Plateau. However, the effects of revegetation‐induced changes in soil and root properties on soil resistance to concentrated flow erosion (SRC) remain unclear. This study sampled soils and roots across a 25‐year chronosequence from farmland to grasslands of different ages (3, 7, 10, 18, and 25 years) to quantify variations in soil and root properties (soil bulk density, SBD; soil disintegration rate, SDR; saturated hydraulic conductivity, SHC; organic matter content, OMC; water‐stable aggregate, WSA; mean weight diameter, MWD; root mass density, RMD; root length density, RLD; and root surface area density, RSAD) and their effects on SRC. Farmland and grassland SRCs were obtained using a hydraulic flume. Soil properties and root density gradually improved with restoration time. In terms of the comprehensive soil property index calculated via principal component analysis, grassland values were 0.66 to 1.94 times greater than farmland values. Grassland SRCs increased and gradually stabilized (>18 years) over time and were 1.60 to 8.26 times greater than farmland SRC. SRC improvement was significantly related to increases in OMC, SHC, WSA, and MWD and decreases in SBD and SDR over time. SRC was effectively simulated by the Hill curve of RMD, RLD, and RSAD. SDR, SHC, and RMD (0.5–1.0 mm) affected SRC the most. This study scientifically describes how revegetation improves soil quality and soil resistance to flow erosion, and suggests that vegetations rich in 0.5–1.0 mm roots should be preferred during revegetation.     

有机稻鸭共作对土壤理化性状和细菌群落空间分布的影响

为探明有机稻鸭共作对不同深度耕层土壤理化性状和细菌群落的影响,采用田间实验,研究了有机稻鸭共作(12年)和转型期稻鸭共作(3年)田在0～6、6～13和13～20 cm土层的理化性状和细菌群落结构变化规律。结果表明:有机稻鸭共作12年后,0～6和6～13 cm土壤理化性状得到较大程度改善,但13～20 cm层改变较小;与转型期稻鸭共作相比,有机稻鸭共作显著改变了细菌群落组成,使不同耕层土壤具有了更高比例的共同细菌门;同时还提高了各耕层土壤细菌群落的丰富度和多样性,减小了各耕层土壤细菌群落结构分布差异性,这在0～6 cm层土壤中表现尤为明显,使细菌群落结构整体朝着更加稳定方向发展;相关分析表明,pH值、土壤容重、全氮和硝态氮是影响有机稻鸭共作后土壤细菌群落空间分布的重要因子。综合来看,有机稻鸭共作主要通过改变土壤理化性状来影响细菌群落的空间分布,是促进农业可持续发展的一种重要模式。