Intraspecific plant–soil feedback and intraspecific overyielding in Arabidopsis thaliana

Understanding the mechanisms of community coexistence and ecosystem functioning may help to counteract the current biodiversity loss and its potentially harmful consequences. In recent years, plant–soil feedback that can, for example, be caused by below‐ground microorganisms has been suggested to play a role in maintaining plant coexistence and to be a potential driver of the positive relationship between plant diversity and ecosystem functioning. Most of the studies addressing these topics have focused on the species level. However, in addition to interspecific interactions, intraspecific interactions might be important for the structure of natural communities. Here, we examine intraspecific coexistence and intraspecific diversity effects using 10 natural accessions of the model species Arabidopsis thaliana (L.) Heynh. We assessed morphological intraspecific diversity by measuring several above‐ and below‐ground traits. We performed a plant–soil feedback experiment that was based on these trait differences between the accessions in order to determine whether A. thaliana experiences feedback at intraspecific level as a result of trait differences. We also experimentally tested the diversity–productivity relationship at intraspecific level. We found strong differences in above‐ and below‐ground traits between the A. thaliana accessions. Overall, plant–soil feedback occurred at intraspecific level. However, accessions differed in the direction and strength of this feedback: Some accessions grew better on their own soils, some on soils from other accessions. Furthermore, we found positive diversity effects within A. thaliana: Accession mixtures produced a higher total above‐ground biomass than accession monocultures. Differences between accessions in their feedback response could not be explained by morphological traits. Therefore, we suggest that they might have been caused by accession‐specific accumulated soil communities, by root exudates, or by accession‐specific resource use based on genetic differences that are not expressed in morphological traits. Synthesis. Our results provide some of the first evidence for intraspecific plant–soil feedback and intraspecific overyielding. These findings may have wider implications for the maintenance of variation within species and the importance of this variation for ecosystem functioning. Our results highlight the need for an increased focus on intraspecific processes in plant diversity research to fully understand the mechanisms of coexistence and ecosystem functioning.     

Effects of plant functional group removal on structure and function of soil communities across contrasting ecosystems

Loss of plant diversity has an impact on ecosystems worldwide, but we lack a mechanistic understanding of how this loss may influence below‐ground biota and ecosystem functions across contrasting ecosystems in the long term. We used the longest running biodiversity manipulation experiment across contrasting ecosystems in existence to explore the below‐ground consequences of 19 years of plant functional group removals for each of 30 contrasting forested lake islands in northern Sweden. We found that, against expectations, the effects of plant removals on the communities of key groups of soil organisms (bacteria, fungi and nematodes), and organic matter quality and soil ecosystem functioning (decomposition and microbial activity) were relatively similar among islands that varied greatly in productivity and soil fertility. This highlights that, in contrast to what has been shown for plant productivity, plant biodiversity loss effects on below‐ground functions can be relatively insensitive to environmental context or variation among widely contrasting ecosystems.     

植物与土壤微生物在调控生态系统养分循环中的作用

陆地生态系统的地上、地下是相互联系的。植物与土壤微生物作为陆地生态系统中的重要组成部分, 它们之间的相互作用是生态系统地上、地下结合的重要纽带。该文首先介绍了植物在养分循环中对营养元素的吸收、积累和归还等作用, 阐述了土壤微生物对养分有效性及土壤质量具有重要的作用。其次, 重点综述了植物与土壤微生物之间相互依存、相互竞争的关系。植物通过其凋落物与分泌物为土壤微生物提供营养, 土壤微生物作为分解者提供植物可吸收的营养元素, 比如共生体菌根真菌即可使植物根与土壤真菌达到互惠。然而, 植物的养分吸收与微生物的养分固持同时存在, 因而两者之间存在对养分的竞争。通过植物多样性对土壤微生物多样性的影响分析, 以及土壤微生物直接或间接作用于植物多样性和生产力的分析, 探讨了植物物种多样性与土壤微生物多样性之间的内在联系。针对当前植物与土壤微生物对养分循环的调控机制的争论, 提出植物凋落物是调节植物与土壤微生物养分循环的良好媒介, 植物与土壤微生物的共同作用对维持整个生态系统的稳定性具有重要意义。也指出了目前在陆地生态系统地上、地下研究中存在的不足和亟待解决的问题。     

Effects and mechanism of plant litter on grassland ecosystem: A review

Plant litter is dead, above and below ground; organic material i.e. leaves barks, needles, twigs and roots. Plant litter plays a key role in nutrient cycling and community organization in grassland ecosystems. Litter can have important consequences on recruitment of plant species through modification of biological, physical, and chemical features of microenvironment. Plant litter offers a major input of organic matter to the soil which modifies soil chemistry, hence impacts nutrient cycling. At early stages of litter decomposition, a particular amount of carbon is transporting to the soil nutrient pool. In terrestrial ecosystems, plant litter regulating biogeochemical cycles, maintain soil fertility, nutrient availability, and therefore influence plant growth, diversity, composition, structure, and productivity. Litter can also impact plant above net plant productivity and below net plant productivity in grassland ecosystem. Plant litter accumulation and decomposition can impact plant species composition and community structure through temperature, light and nutrient availability. The effects of plant litter on vegetation may be negative, positive or neutral due vegetation variability, study duration, habitat, latitude, quantity and quality of litter. These diverse effects of plant litter on grassland ecosystem might be due to, management practice type, management intensity, climate type, timing, precipitation and soil nutrient pool etc. Current review attempts to describe prominent effects of plant litter on vegetation, seed germination, soil fertility, Productivity, species composition, community structure and mechanism in grassland ecosystem.     

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.     

Long‐term nitrogen additions increase likelihood of climate stress and affect recovery from wildfire in a lowland heath

Increases in the emissions and associated atmospheric deposition of nitrogen (N) have the potential to cause significant changes to the structure and function of N‐limited ecosystems. Here, we present the results of a long‐term (13 year) experiment assessing the impacts of N addition (30 kg ha^?1 yr^?1) on a UK lowland heathland under a wide range of environmental conditions, including the occurrence of prolonged natural drought episodes and a severe summer fire. Our findings indicate that elevated N deposition results in large, persistent effects on Calluna growth, phenology and chemistry, severe suppression of understorey lichen flora and changes in soil biogeochemistry. Growing season rainfall was found to be a strong driver of inter‐annual variation in Calluna growth and, although interactions between N and rainfall for shoot growth were not significant until the later phase of the experiment, N addition exacerbated the extent of drought injury to Calluna shoots following naturally occurring droughts in 2003 and 2009. Following a severe wildfire at the experimental site in 2006, heathland regeneration dynamics were significantly affected by N, with a greater abundance of pioneering moss species and suppression of the lichen flora in plots receiving N additions. Significant interactions between climate and N were also apparent post fire, with the characteristic stimulation in Calluna growth in +N plots suppressed during dry years. Carbon (C) and N budgets demonstrate large increases in both above‐ and below‐ground stocks of these elements in N‐treated plots prior to the fire, despite higher levels of soil microbial activity and organic matter turnover. Although much of the organic material was removed during the fire, pre‐existing treatment differences were still evident following the burn. Post fire accumulation of below‐ground C and N stocks was increased rapidly in N‐treated plots, highlighting the role of N deposition in ecosystem C sequestration.     

Coupling of green and brown food webs and ecosystem stability

Ecosystems comprise living organisms and organic matter or detritus. In earlier community ecology theories, ecosystem dynamics were normally understood in terms of aboveground, green‐world trophic interaction networks, or food webs. Recently, there has been growing interest in the role played in ecosystem dynamics by detritus in underground, brown‐world interactions. However, the role of decomposers in the consumption of detritus to produce nutrients in ecosystem dynamics remains unclear. Here, an ecosystem model of trophic food chains, detritus, decomposers, and decomposer predators demonstrated that decomposers play a totally different role than that previously predicted, with regard to their relationship between nutrient cycling and ecosystem stability. The high flux of nutrients due to efficient decomposition by decomposers increases ecosystem stability. However, moderate levels of ecosystem openness (with movement of materials) can either greatly increase or decrease ecosystem stability. Furthermore, the stability of an ecosystem peaks at intermediate openness because open systems are less stable than closed systems. These findings suggest that decomposers and the food‐web dynamics of brown‐world interactions are crucial for ecosystem stability, and that the properties of decomposition rate and openness are important in predicting changes in ecosystem stability in response to changes in decomposition efficiency driven by climate change.     

Are traits measured on pot grown plants representative of those in natural communities?

Question: The quantification of functional traits in natural communities can be difficult (e.g. root traits, RGR). Can functional traits measured on pot grown plants be reliably applied to natural communities? Alternatively, can below‐ground plant traits be predicted from above‐ground traits? Location: Southeastern Australia. Methods: We compared 17 shoot, root and whole‐plant morphological traits measured on 14 plant species in a native grassland community to those measured under two different pot conditions: unfertilised and fertilised. Results: The majority of trait values for pot grown plants differed to plants in the field, however, species ranking remained consistent for most leaf traits between the field and the two pot growing conditions. In contrast, species ranking was not consistent for most whole plant traits when comparing field plants to fertilised pot grown plants, providing a caution against the tendency to grow plants in controlled conditions at ‘optimal’ (high) resource levels. Moderate to strong correlations were found between below‐ground and above‐ground plant traits, including between root dry matter content and leaf dry matter content, and between specific root area and specific leaf area. Conclusions: The utility of pot grown plants to quantify traits for field plants is highly dependent on the selection of the growing conditions in the controlled environment. The consistency we observed between above‐ground and below‐ground trait strategies suggests that below‐ground traits may be predictable based on above‐ground traits, reducing the need to quantify root traits on cultured plants.     

Depth-dependent effects of ericoid mycorrhizal shrubs on soil carbon and nitrogen pools are accentuated under arbuscular mycorrhizal trees

Plant mycorrhizal associations influence the accumulation and persistence of soil organic matter and could therefore shape ecosystem biogeochemical responses to global changes that are altering forest composition. For instance, arbuscular mycorrhizal (AM) tree dominance is increasing in temperate forests, and ericoid mycorrhizal (ErM) shrubs can respond positively to canopy disturbances. Yet how shifts in the co-occurrence of trees and shrubs with different mycorrhizal associations will affect soil organic matter pools remains largely unknown. We examine the effects of ErM shrubs on soil carbon and nitrogen stocks and indicators of microbial activity at different depths across gradients of AM versus ectomycorrhizal (EcM) tree dominance in three temperate forest sites. We find that ErM shrubs strongly modulate tree mycorrhizal dominance effects. In surface soils, ErM shrubs increase particulate organic matter accumulation and weaken the positive relationship between soil organic matter stocks and indicators of microbial activity. These effects are strongest under AM trees that lack fungal symbionts that can degrade organic matter. In subsurface soil organic matter pools, by contrast, tree mycorrhizal dominance effects are stronger than those of ErM shrubs. Ectomycorrhizal tree dominance has a negative influence on particulate and mineral-associated soil organic matter pools, and these effects are stronger for nitrogen than for carbon stocks. Our findings suggest that increasing co-occurrence of ErM shrubs and AM trees will enhance particulate organic matter accumulation in surface soils by suppressing microbial activity while having little influence on mineral-associated organic matter in subsurface soils. Our study highlights the importance of considering interactions between co-occurring plant mycorrhizal types, as well as their depth-dependent effects, for projecting changes in soil carbon and nitrogen stocks in response to compositional shifts in temperate forests driven by disturbances and global change.     

Comparison of soil microbial communities inhabiting vineyards and native sclerophyllous forests in central Chile

Natural ecosystems provide services to agriculture such as pest control, soil nutrients, and key microbial components. These services and others in turn provide essential elements that fuel biomass productivity. Responsible agricultural management and conservation of natural habitats can enhance these ecosystem services. Vineyards are currently driving land‐use changes in many Mediterranean ecosystems. These land‐use changes could have important effects on the supporting ecosystems services related to the soil properties and the microbial communities associated with forests and vineyard soils. Here, we explore soil bacterial and fungal communities present in sclerophyllous forests and organic vineyards from three different wine growing areas in central Chile. We employed terminal restriction fragment length polymorphisms (T‐RFLP) to describe the soil microbial communities inhabiting native forests and vineyards in central Chile. We found that the bacterial community changed between the sampled growing areas; however, the fungal community did not differ. At the local scale, our findings show that fungal communities differed between habitats because fungi species might be more sensitive to land‐use change compared to bacterial species, as bacterial communities did not change between forests and vineyards. We discuss these findings based on the sensitivity of microbial communities to soil properties and land‐use change. Finally, we focus our conclusions on the importance of naturally derived ecosystem services to vineyards.     

Permafrost collapse alters soil carbon stocks,respiration, CH4, and N2O in upland tundra

Release of greenhouse gases from thawing permafrost is potentially the largest terrestrial feedback to climate change and one of the most likely to occur; however, estimates of its strength vary by a factor of thirty. Some of this uncertainty stems from abrupt thaw processes known as thermokarst (permafrost collapse due to ground ice melt), which alter controls on carbon and nitrogen cycling and expose organic matter from meters below the surface. Thermokarst may affect 20–50% of tundra uplands by the end of the century; however, little is known about the effect of different thermokarst morphologies on carbon and nitrogen release. We measured soil organic matter displacement, ecosystem respiration, and soil gas concentrations at 26 upland thermokarst features on the North Slope of Alaska. Features included the three most common upland thermokarst morphologies: active‐layer detachment slides, thermo‐erosion gullies, and retrogressive thaw slumps. We found that thermokarst morphology interacted with landscape parameters to determine both the initial displacement of organic matter and subsequent carbon and nitrogen cycling. The large proportion of ecosystem carbon exported off‐site by slumps and slides resulted in decreased ecosystem respiration postfailure, while gullies removed a smaller portion of ecosystem carbon but strongly increased respiration and N₂O concentration. Elevated N₂O in gully soils persisted through most of the growing season, indicating sustained nitrification and denitrification in disturbed soils, representing a potential noncarbon permafrost climate feedback. While upland thermokarst formation did not substantially alter redox conditions within features, it redistributed organic matter into both oxic and anoxic environments. Across morphologies, residual organic matter cover, and predisturbance respiration explained 83% of the variation in respiration response. Consistent differences between upland thermokarst types may contribute to the incorporation of this nonlinear process into projections of carbon and nitrogen release from degrading permafrost.     

Impacts of moso bamboo (Phyllostachys pubescens) invasion on dry matter and carbon and nitrogen stocks in a broad‐leaved secondary forest located in Kyoto,western Japan

In western and central Japan, the expansion of exotic moso bamboo (Phyllostachys pubescens Mazel ex J. Houz.) populations into neighboring vegetation has become a serious problem. Although the effects of bamboo invasion on biodiversity have been well studied, shifts in nutrient stocks and cycling, which are fundamental for ecosystem functioning, are not fully understood. To explore the effects of P. pubescens invasion on ecosystem functions we examined above‐ and below‐ground dry matter and carbon (C) and nitrogen (N) stocks in a pure broad‐leaved tree stand, a pure bamboo stand, and two tree–bamboo mixed stands with different vegetation mix ratios in the secondary forest of Kyoto, western Japan. In the process of invasion, bamboo shoots offset broad‐leaved tree deaths; thus, no clear trend was apparent in total above‐ or below‐ground biomass or in plant C and N stocks during invasion. However, the ratio of above‐ground to below‐ground biomass (T/R ratio at the stand level) decreased with increasing bamboo dominance, especially in the early stages of invasion. This shift indicates that rapid bamboo rhizomatous growth is a main driver of substantial changes in stand structure. We also detected rises in the C/N ratio of forest‐floor organic matter during bamboo invasion. Thus major impacts of P. pubescens invasion into broad‐leaved forests include not only early shifts in biomass allocation, but also changes in the distribution pattern of C and N stored in plants and soil.     

Interactions between temperature and nutrients across levels of ecological organization

Temperature and nutrient availability play key roles in controlling the pathways and rates at which energy and materials move through ecosystems. These factors have also changed dramatically on Earth over the past century as human activities have intensified. Although significant effort has been devoted to understanding the role of temperature and nutrients in isolation, less is known about how these two factors interact to influence ecological processes. Recent advances in ecological stoichiometry and metabolic ecology provide a useful framework for making progress in this area, but conceptual synthesis and review are needed to help catalyze additional research. Here, we examine known and potential interactions between temperature and nutrients from a variety of physiological, community, and ecosystem perspectives. We first review patterns at the level of the individual, focusing on four traits – growth, respiration, body size, and elemental content – that should theoretically govern how temperature and nutrients interact to influence higher levels of biological organization. We next explore the interactive effects of temperature and nutrients on populations, communities, and food webs by synthesizing information related to community size spectra, biomass distributions, and elemental composition. We use metabolic theory to make predictions about how population‐level secondary production should respond to interactions between temperature and resource supply, setting up qualitative predictions about the flows of energy and materials through metazoan food webs. Last, we examine how temperature–nutrient interactions influence processes at the whole‐ecosystem level, focusing on apparent vs. intrinsic activation energies of ecosystem processes, how to represent temperature–nutrient interactions in ecosystem models, and patterns with respect to nutrient uptake and organic matter decomposition. We conclude that a better understanding of interactions between temperature and nutrients will be critical for developing realistic predictions about ecological responses to multiple, simultaneous drivers of global change, including climate warming and elevated nutrient supply.     

Environmental filtering by pH and soil nutrients drives community assembly in fungi at fine spatial scales

Whether niche processes, like environmental filtering, or neutral processes, like dispersal limitation, are the primary forces driving community assembly is a central question in ecology. Here, we use a natural experimental system of isolated tree “islands” to test whether environment or geography primarily structures fungal community composition at fine spatial scales. This system consists of isolated pairs of two distantly related, congeneric pine trees established at varying distances from each other and the forest edge, allowing us to disentangle the effects of geographic distance vs. host and edaphic environment on associated fungal communities. We identified fungal community composition with Illumina sequencing of ITS amplicons, measured all relevant environmental parameters for each tree—including tree age, size and soil chemistry—and calculated geographic distances from each tree to all others and to the nearest forest edge. We applied generalized dissimilarity modelling to test whether total and ectomycorrhizal fungal (EMF) communities were primarily structured by geographic or environmental filtering. Our results provide strong evidence that as in many other organisms, niche and neutral processes both contribute significantly to turnover in community composition in fungi, but environmental filtering plays the dominant role in structuring both free‐living and symbiotic fungal communities at fine spatial scales. In our study system, we found pH and organic matter primarily drive environmental filtering in total soil fungal communities and that pH and cation exchange capacity—and, surprisingly, not host species—were the largest factors affecting EMF community composition. These findings support an emerging paradigm that pH may play a central role in the assembly of all soil‐mediated systems.     

Organic nutrient uptake by mycorrhizal fungi enhances ecosystem carbon storage: a model-based assessment

Understanding the factors that drive soil carbon (C) accumulation is of fundamental importance given their potential to mitigate climate change. Much research has focused on the relationship between plant traits and C sequestration, but no studies to date have quantitatively considered traits of their mycorrhizal symbionts. Here, we use a modelling approach to assess the contribution of an important mycorrhizal fungal trait, organic nutrient uptake, to soil C accumulation. We show that organic nutrient uptake can significantly increase soil C storage, and that it has a greater effect under nutrient-limited conditions. The main mechanism behind this was an increase in plant C fixation and subsequent increased C inputs to soil through mycorrhizal fungi. Reduced decomposition due to increased nutrient limitation of saprotrophs also played a role. Our results indicate that direct uptake of nutrients from organic pools by mycorrhizal fungi could have a significant effect on ecosystem C cycling and storage.     

Non‐invasive techniques for investigating and modelling root‐feeding insects in managed and natural systems

1 Root‐feeding insects are now considered to play a greater role in ecosystem processes than previously thought, yet little is known about their specific interactions with host plants compared with above‐ground insect herbivores. Methodological difficulties associated with studying these insects in the soil, together with the lack of empirical and theoretical frameworks, have conventionally hindered progress in this area. 2 This paper reviews recent empirical and theoretical developments that have been adopted for studying root‐feeding insects, focusing on the non‐invasive techniques of X‐ray tomography and acoustic field detection and how these can be integrated with new mathematical modelling approaches. 3 X‐ray tomography has been used for studying the movements of several insects within the soil and has helped to characterize the host plant location behaviour of the clover root weevil, Sitona lepidus. Acoustic detection of soil insects has been used in various managed systems, ranging from nursery containers to citrus groves. 4 Mathematical modelling plays a complementary role for investigating root‐feeding insects, illustrated by a number of published models. A model is presented for the movement of S. lepidus in the soil, which suggests that these insects undergo Lévy movements, similar to those recently demonstrated for above‐ground organisms. 5 The future directions and challenges for investigating root‐feeding insects are discussed in the context of the wider ecosystem, incorporating both above and below‐ground organisms.     

Organic Layer Serves as a Hotspot of Microbial Activity and Abundance in Arctic Tundra Soils

Tundra ecosystem is of importance for its high accumulation of organic carbon and vulnerability to future climate change. Microorganisms play a key role in carbon dynamics of the tundra ecosystem by mineralizing organic carbon. We assessed both ecosystem process rates and community structure of Bacteria, Archaea, and Fungi in different soil layers (surface organic layer and subsurface mineral soil) in an Arctic soil ecosystem located at Spitsbergen, Svalbard during the summer of 2008 by using biochemical and molecular analyses, such as enzymatic assay, terminal restriction fragment length polymorphism (T-RFLP), quantitative polymerase chain reaction (qPCR), and pyrosequencing. Activity of hydrolytic enzymes showed difference according to soil type. For all three microbial communities, the average gene copy number did not significantly differ between soil types. However, archaeal diversities appeared to differ according to soil type, whereas bacterial and fungal diversity indices did not show any variation. Correlation analysis between biogeochemical and microbial parameters exhibited a discriminating pattern according to microbial or soil types. Analysis of the microbial community structure showed that bacterial and archaeal communities have different profiles with unique phylotypes in terms of soil types. Water content and hydrolytic enzymes were found to be related with the structure of bacterial and archaeal communities, whereas soil organic matter (SOM) and total organic carbon (TOC) were related with bacterial communities. The overall results of this study indicate that microbial enzyme activity were generally higher in the organic layer than in mineral soils and that bacterial and archaeal communities differed between the organic layer and mineral soils in the Arctic region. Compared to mineral soil, peat-covered organic layer may represent a hotspot for secondary productivity and nutrient cycling in this ecosystem.     

Quantitative losses vs. qualitative stability of ectomycorrhizal community responses to 3 years of experimental summer drought in a beech–spruce forest

Forest ecosystems in central Europe are predicted to face an increasing frequency and severity of summer droughts because of global climate change. European beech and Norway spruce often coexist in these forests with mostly positive effects on their growth. However, their different below‐ground responses to drought may lead to differences in ectomycorrhizal (ECM) fungal community composition and functions which we examined at the individual root and ecosystem levels. We installed retractable roofs over plots in Kranzberg Forest (11°39′42″E, 48°25′12″N; 490 m a.s.l.) to impose repeated summer drought conditions and assigned zones within each plot where trees neighboured the same or different species to study mixed species effects. We found that ECM fungal community composition changed and the numbers of vital mycorrhizae decreased for both tree species over 3 drought years (2014–2016), with the ECM fungal community diversity of beech exhibiting a faster and of spruce a stronger decline. Mixed stands had a positive effect on the ECM fungal community diversity of both tree species after the third drought year. Ectomycorrhizae with long rhizomorphs increased in both species under drought, indicating long‐distance water transport. However, there was a progressive decline in the number of vital fine roots during the experiment, resulting in a strong reduction in enzyme activity per unit volume of soil. Hydrolytic enzyme activities of the surviving ectomycorrhizae were stable or stimulated upon drought, but there was a large decline in ECM fungal species with laccase activity, indicating a decreased potential to exploit nutrients bound to phenolic compounds. Thus, the ectomycorrhizae responded to repeated drought by maintaining or increasing their functionality at the individual root level, but were unable to compensate for quantitative losses at the ecosystem level. These findings demonstrate a strong below‐ground impact of recurrent drought events in forests.     

长期不同养分投入对土壤养分和水稻生产持续性的影响

以中国科学院桃源农业生态试验站15a长期田间定位试验为研究对象,分析了不同养分投入对稻田土壤养分和水稻产量可持续性的影响.结果表明,化肥与系统内循环的有机物料循环的肥力效力和产量效应基本一致,有机物料循环更有利于土壤有机质和氮素的积累;在不同养分投入下,土壤耕层有机质和全氮均呈上升趋势,年均增长率分别为1.5%～5.8%和2.5%～9.4%;与试验前相比,不同养分投入耕层磷素变动幅度在-18.3%到30%之间,钾素养分有所亏缺,下降幅度在8.1%～22.6%之间;通过可持续性指数的分析得出,土壤N素养分的可持续性对化肥的依赖性较大,而P、K养分的可持续性则对有机肥的依赖性更高.稻田生态系统具有良好的自维持能力,系统内有机物循环有利于提高稻谷产量的稳定性和可持续性.     

Impact of metal pollution on fungal diversity and community structures

The impact of metal pollution on plant communities has been studied extensively in the past, but little is known about the effects of metal pollution on fungal communities that occur in metal‐polluted soils. Metal‐tolerant ecotypes of the ectomycorrhizal fungus Suillus luteus are frequently found in pioneer pine forests in the Campine region in Belgium on metal‐polluted soils. We hypothesized that metal pollution would play an important role in shaping below‐ground fungal communities that occur in these soils and that Suillus luteus would be a dominant player. To test these hypotheses, the fungal communities in a young pine plantation in soil polluted with zinc, and cadmium were studied using 454 amplicon pyrosequencing. Results show that zinc, cadmium and soil organic matter content were strongly correlated with the fungal community composition, but no effects on fungal diversity were observed. As hypothesized, S. luteus was found to be a dominant member of the studied fungal communities. However, other dominant fungal species, such as Sistotrema sp., Wilcoxina mikolae and Cadophora finlandica were found as well. Their presence in metal‐polluted sites is discussed.