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Closely related species often conserve similar niches despite interacting negatively. We suggest that close relatives may interact positively via ecosystem feedbacks: leaf litter produced or exposed in a closely related neighbourhood (low phylogenetic isolation) may decompose more quickly, leading to more rapid nutrient recycling. We studied decomposition of leaf litter of oaks Quercus petraea across 8 and 14 months, reciprocally transplanting leaf litters between low and high phylogenetic isolation to distinguish between effects mediated by leaf litter quality and by decomposition environment. We found that, by affecting litter quality, phylogenetic isolation reduced decomposition across 14 months (loss of litter mass and C). Moreover, by affecting litter quality and decomposition environment, phylogenetic isolation reduced microbial biomass and extensively altered relationships between C and N losses and abundances/diversities of different soil organisms across 8 and 14 months. Phylogenetic isolation was to a large extant driven by percentage of gymnosperms, explaining the decomposition‐environment mediated effects. Such environment‐mediated effects reflected decreasing soil humidity and pH with phylogenetic isolation, while litter‐quality mediated effects reflected decreasing leaf phytophagy or increasing leaf phenolics. Tree‐species richness, in contrast, did not explain effects of phylogenetic isolation, and had little effect overall. To conclude, coexistence of oaks with distant relatives partly impedes recycling of leaf litter and re‐organizes the trajectories of this recycling. In contrast, oaks coexisting with close relatives may profit from a positive ecosystem feedback through increased nutrient recycling, possibly contributing to the conservation of the oak's niches. We suggest that such a positive ecosystem feedback among close relatives might exist in other late successional tree species. [ABSTRACT FROM AUTHOR]

The rhizosphere microbial community helps govern biogeochemical cycling and facilitates complex plant-soil feedback. Understanding the evolutionary dynamics of microbial community structure and functional genes during vegetation succession is crucial for quantifying and understanding ecosystem processes and functions in restored sandy deserts. In this study, the rhizosphere microbial community structure of 11–66-year-old dominant shrubs in a desert revegetation area was examined using shotgun metagenomic sequencing. The interactions between the microbial community structure, functional gene abundances, soil properties, and plant characteristics of different stand ages were comprehensively investigated. The abundance of unique species first increased before subsequently decreasing with stand age, with shared species accounting for only 47.33%–59.42% of the total operational taxonomic units (OTUs). Copiotrophs such as Actinobacteria and Proteobacteria were found to dominate the rhizosphere soil microbial community, with their relative abundance accounting for 75.28%–81.41% of the total OTUs. There was a gradual shift in dominant microbial functional genes being involved in cellular processes towards those involved in environmental information processing and metabolism as stand age increased. Additionally, temporal partitioning was observed in both the microbial co-occurrence network complexity and topological parameters within the rhizosphere soil. Redundancy analysis revealed that dissolved organic carbon was the primary determinant influencing shifts in microbial community structure. Understanding the evolution of microbial community structure and function contributes to identifying potential mechanisms associating the soil microbiome with dominant sand-fixing shrubs as well as understanding the rhizosphere microbiome assembly process. These results shed light on the role of the rhizosphere microbiome in biogeochemical cycling and other ecosystem functions following revegetation of temperate sandy deserts. [ABSTRACT FROM AUTHOR]

The 'home‐field advantage (HFA)' for decomposition means that leaf litter decomposes faster on soils under the conspecific species (i.e. the home field) than on soils under different species (i.e. 'away'). Many previous studies have demonstrated the HFA, but the underlying mechanisms remain unclear. We conducted a reciprocal litter‐decomposition experiment using two species with different leaf traits: Abies mariesii, an evergreen conifer, and Fagus crenata, a deciduous broad‐leaved tree. Dominance of these species shifts along an elevation gradient with a transition zone where both species coexist. In mixed forests of the transition zone along the elevation gradient, we explored how the magnitude of HFA between these two species was influenced by temperature, soil properties, or leaf litter traits which could directly affect the decomposition rate. The magnitude of HFA observed between the two species varied widely from −3.89 to 28.3%. Our modeling showed that the magnitude of HFA increased with decreasing soil pH and leaf litter N, i.e. in more acidic soil and for less decomposable litter. Soil pH affected leaf litter decomposition in the home plots of each species, whereas leaf litter N did not. The magnitude of the HFA increased as the difference in soil pH between the F. crenata and A. mariesii plots at the same elevation became greater, but decreased as the difference in soil C became greater. Thus, the response of leaf litter decomposition to environmental changes might vary not only through direct effects of vegetation traits but also through indirect effects of the HFA. This highlights the importance of considering HFA for accurately predicting the response of local carbon and nutrient cycles to climate change, particularly in communities where a replacement of dominant species by others is expected due to climate change. [ABSTRACT FROM AUTHOR]

Kudzu (Pueraria lobata), a fast-growing leguminous vine with broad global distribution, is one of the main species occurring in roadside vegetation, particularly in Asia and the United States. Kudzu has been reported to have negative effects on ecosystem functions by increasing nitrification and nitric oxide emissions. Because of these negative effects and its extensive growth, roadside kudzu vegetation is often targeted for herbicide management, despite its contribution to erosion control. The effects of kudzu removal on soil nitrogen (N) dynamics and N leaching from roadside vegetation remain unclear. In this study, we established experimental plots alongside a highway in central Japan and used herbicide to manage the roadside kudzu vegetation. We then measured the effects on soil N dynamics and N leaching from the ecosystem during the growing season using a polyvinyl chloride core to exclude N uptake by plant roots. Our experiment showed that kudzu management with herbicide strongly affected soil N dynamics by altering soil temperature and moisture through the removal of kudzu coverage. The net nitrification rate in the herbicide-treated plots was higher than that in the control plots; therefore, nitrate–N leaching increased. In contrast, herbicide management did not significantly affect net ammonium–N production or leaching. The results demonstrate that kudzu removal results in a spike of belowground nitrate leaching. [ABSTRACT FROM AUTHOR]

Consumers can directly (e.g., consumption) and indirectly (e.g., trophic cascades) influence carbon cycling in blue carbon ecosystems. Previous work found that large grazers have nuanced effects on carbon stocks, yet, small, bioturbating‐grazers, which remove plant biomass and alter sediment properties, remain an understudied driver of carbon cycling. We used field‐derived and remote sensing data to quantify how the purple marsh crab, Sesarma reticulatum, influenced carbon stocks, flux, and recovery in salt marshes. Sesarma caused a 40%–70% loss in carbon stocks as fronts propagated inland (i.e., ungrazed to recovered transition), with front migration rates accelerating over time. Despite latitudinal differences, front migration rate had no effect on carbon stocks, flux, or time to replacement. When we included Sesarma disturbance in carbon flux calculations, we found it may take 5–100 years for marshes to replace lost carbon, if at all. Combined, we show that small grazers cause a net loss in carbon stocks as they move through the landscape, and irrespective of migration rate, these grazer‐driven impacts persist for decades. This work showcases the significant role of consumers in carbon storage and flux, challenging the classic paradigm of plant–sediment feedbacks as the primary ecogeomorphic driver of carbon cycling in blue carbon ecosystems. [ABSTRACT FROM AUTHOR]

A self‐reinforcing positive feedback is regarded as a critical process for maintaining alternative stable states (ASS); however, identification of ASS and quantification of positive feedbacks remain elusive in natural ecosystems. Here, we used large‐scale field surveys to search for ASS and a positive feedback mechanism under a wide range of habitats on the Tibetan Plateau. Using multiple methods, we proved that three stable states exist that accompany alpine marsh degradation. Positive feedbacks between changing soil moisture and plant community composition forced the ecosystem into another stable state, and the alteration of water use efficiency (WUE) of the component species contributed to this shift. This study provides the first empirical evidence that positive feedback loops maintain ASS in the alpine marsh ecosystem on the Tibetan Plateau. Our research revealed the powerful driving role of plants in transitions between states, which may support the conservation and restoration of global alpine marsh ecosystems. [ABSTRACT FROM AUTHOR]

Background: Soil microbial community composition with stand development may be changed due to the variations in canopy structure, understory vegetation, root traits, edaphic conditions, and litter inputs. However, it is still uncertain to what extent these biotic and abiotic factors shape the soil microbial community composition in Chinese fir (Cunninghamia lanceolata) plantations, which are widely planted in southern China. Methods: Amplicon sequencing was used to analyze the diversity and composition of soil bacterial and fungal communities at two soil depths across four developmental stages of Chinese fir plantations. Results: Both the bacterial and fungal communities were significantly different between stand age groups. As stand aged, oligotrophic bacteria decreased in abundance while copiotrophic bacteria increased. Meanwhile, fungal functional groups connected to plants decreased in abundance while that of saprotrophic fungi significantly increased. The variance in bacterial community was mainly attributed to soil variables regarding carbon and nutrient availability, whereas the greatest fraction of fungal community dissimilarity was determined by plant-specific factors such as aboveground stand structure and tree root traits. The chemical composition of litter had a major effect on the soil fungal community, whereas the litter traits had no effect on the bacterial community. Conclusions: The potential drivers of soil fungi and bacteria differ in Chinese fir plantations. By accounting for the impacts of various environmental components, it is possible to anticipate the response of soil bacterial and fungal assemblages to forest management regime implemented in Chinese fir plantations. [ABSTRACT FROM AUTHOR]

Soil organisms play a key role in carbon and nutrient cycling in forest ecosystems. While soil organisms are strongly influenced by litter chemistry and are highly sensitive to abiotic conditions, little is known about the interactive effects of these two factors. To address this gap in knowledge, we conducted a 10 week microcosm experiment in which we simulated the effects of climate change on soil ecology. More specifically, we studied relationships among litter nutrient concentration, microbial biomass, Collembola demographic parameters, and litter decomposition, exploring the potential impacts of increasing air temperature and decreasing soil moisture. To develop a gradient of nutrient concentrations, we created six tree litter mixtures with materials gathered from Quercus pubescens and its companion species. In contrast to microbes, we observed that Collembola abundance and litter decomposition were interactively affected by soil moisture and air temperature: the negative effect of increasing air temperature on Collembola abundance was amplified by reduced soil moisture, whereas the positive effect of increasing air temperature on litter decomposition disappeared under reduced soil moisture conditions. In contrast to fungi, the response of bacterial biomass and Collembola abundance to litter nutrient concentration was dependent on abiotic conditions. More specifically, the relationships between nutrients, especially calcium and magnesium, and bacterial biomass and Collembola abundance were less robust or disappeared under drier or warmer conditions. In conclusion, our findings underscore that ongoing climate change could affect soil organisms directly as well as indirectly, by altering their responses to litter nutrient concentrations. In addition, we found that nutrient‐rich habitats might be more affected than nutrient‐poor habitats by altered climatic conditions. [ABSTRACT FROM AUTHOR]

Plant-microbe-soil interactions control over the forest biogeochemical cycling. Adaptive plant-soil interactions can shape specific microbial taxa in determining the ecosystem functioning. Different trees produce heterogeneous soil properties and can alter the composition of soil microbial community, which is relevant to the forest internal succession containing contrasting stand types such as the pine-oak forests. Considering representative microbial community characteristics are recorded in the original soil where they had adapted and resided, we constructed a soil transplant incubation experiment in a series of in situ root-ingrowth cores in a subtropical pine-oak forest, to simulate the vegetational pine-oak replacement under environmental succession. The responsive bacterial and fungal community discrepancies were studied to determine whether and how they would be changed. The pine and oak forest stands had greater heterogeneity in fungi composition than bacteria. Original soil and specific tree root status were the main factors that determined microbial community structure. Internal association network characters and intergroup variations of fungi among soil samples were more affected by original soil, while bacteria were more affected by receiving forest. Specifically, dominant tree roots had strong influence in accelerating the fungi community succession to adapt with the surrounding forest. We concluded that soil microbial responses to forest stand alternation differed between microbiome groups, with fungi from their original forest possessing higher resistance to encounter a new vegetation stand, while the bacteria community have faster resilience. The data would advance our insight into local soil microbial community dynamics during ecosystem succession and be helpful to enlighten forest management. [ABSTRACT FROM AUTHOR]

Monodominant woody species are frequent in the Pantanal. Monodominant forests of Erythrina fusca (Fabaceae) occur in Northern Pantanal, but little is known about the environmental factors that influence this dominance. This work investigated the relationship between flooding and soil characteristics and the E. fusca monodominance. We hypothesized that the dominance of E. fusca is mainly associated with extended flooding periods and lower soil fertility, factors frequently related to monodominance. We sampled 16 sites within the study area of 115 km2. We sampled three 50 × 5 m vegetation plots in each site, for species composition and abundance in multispecies forests and E. fusca monodominant forests. Soil samples were taken in each plot, and the duration of flooding was determined. We performed Canonical Correspondence Analysis and Regression Trees to verify the variation of species composition along environmental gradients and to identify which environmental factors influence this monodominance. We observed that flooding is the main factor driving E. fusca dominance, where higher flooding duration led to higher dominance. Further, the dominance of E. fusca is related to low soil fertility and higher concentration of sulfur and organic matter, than multispecies forests. Our findings confirm the hypothesis that dominance of E. fusca is associated with high flooding regimes with low soil fertility, which together act as a strong filter for other riparian forest species, thus favoring the dominance of E. fusca. [ABSTRACT FROM AUTHOR]

The rhizosphere microbial community helps govern biogeochemical cycling and facilitates complex plant-soil feedback. Understanding the evolutionary dynamics of microbial community structure and functional genes during vegetation succession is crucial for quantifying and understanding ecosystem processes and functions in restored sandy deserts. In this study, the rhizosphere microbial community structure of 11–66-year-old dominant shrubs in a desert revegetation area was examined using shotgun metagenomic sequencing. The interactions between the microbial community structure, functional gene abundances, soil properties, and plant characteristics of different stand ages were comprehensively investigated. The abundance of unique species first increased before subsequently decreasing with stand age, with shared species accounting for only 47.33%–59.42% of the total operational taxonomic units (OTUs). Copiotrophs such as Actinobacteria and Proteobacteria were found to dominate the rhizosphere soil microbial community, with their relative abundance accounting for 75.28%–81.41% of the total OTUs. There was a gradual shift in dominant microbial functional genes being involved in cellular processes towards those involved in environmental information processing and metabolism as stand age increased. Additionally, temporal partitioning was observed in both the microbial co-occurrence network complexity and topological parameters within the rhizosphere soil. Redundancy analysis revealed that dissolved organic carbon was the primary determinant influencing shifts in microbial community structure. Understanding the evolution of microbial community structure and function contributes to identifying potential mechanisms associating the soil microbiome with dominant sand-fixing shrubs as well as understanding the rhizosphere microbiome assembly process. These results shed light on the role of the rhizosphere microbiome in biogeochemical cycling and other ecosystem functions following revegetation of temperate sandy deserts.

Macrophytes influence nitrogen (N) removal from wetlands. However, the specific plant traits responsible for this effect and the related microbial mechanisms remain largely unknown, especially root traits. In a mesocosm experiment, we determined the rhizosphere effect (RE) on microbial N removal processes by incubating rhizosphere and bulk soils collected from 11 macrophyte species. In addition, we examined root traits (involved in chemistry and morphology), along with examining the diversity, compositions, and abundance of bacterial communities involved in denitrification (nirS and nirK) and anammox (hzsB). Across the 11 macrophyte species, the positive RE on denitrification ranged from 66% to 412%, with an average of 194.72%. RE on denitrification was significantly and positively correlated with the recruitment of nir-type denitrifiers in the rhizosphere. We found that higher specific root length (SRL) root promoted the stronger RE, by increasing the abundance of nir-type denitrifiers and further enhancing N removal. Net N removal from water in the wetlands increased with a higher positive RE on nir-type denitrifiers. In addition, SRL significantly influenced the compositions of denitrifiers in the rhizosphere soil. We further found that the enrichment of Azospira, Bradyrhizobium, Sinorhizobium, Rhodopseudomonas, Alcaligenaceae, Bradyrhizobiaceae, and Pleomorphomonas improved the denitrification rate. These findings highlight the potential of root morphology in regulating plant–microbe interactions, thereby improving water purification.

Herbivore grazing affects plant growth and community structure in grasslands. This effect could be directly through foraging and dung/urine return or indirectly through plant–soil feedbacks (PSFs). Addressing the grazing effect on the feedback of plants can explicate the causes of community changes in the grazing system. However, how grazing and PSF interact to affect plant growth remains unclear. Here, we conducted a classic PSF experiment. In the conditioning stage, two native plant species (a grass Bromus inermis and a legume Medicago sativa) were planted in the field with four simulated grazing treatments (ambient, mowing, dung/urine addition, and mowing + dung/urine addition) in a meadow grassland of northern China. In the feedback stage, B. inermis and M. sativa were planted in the soils (both unsterilized and sterilized) from each treatment in the field experiment. Plant biomass of M. sativa showed positive feedback while B. inermis showed negative feedback across all the simulated grazing treatments. Simulated grazing (mowing and dung/urine addition) increased the positive feedback of M. sativa, while decreasing the negative feedback of B. inermis. The addition of dung/urine to the soil was found to have a significantly stronger impact on plant growth feedback compared to the effect of mowing. Dung/urine addition enriches the soil with higher levels of available nitrogen and phosphorus. Our results suggested that legume plants should have positive PSFs while grass should have negative feedback, which might be amplified by grazing because of the dung/urine fertilization effect. Our study improves the understanding of PSF effects on plant growth and community change in grazed grassland. [ABSTRACT FROM AUTHOR]

Summary: Species‐specific differences in nutrient acquisition strategies allow for complementary use of resources among plants in mixtures, which may be further shaped by mycorrhizal associations. However, empirical evidence of this potential role of mycorrhizae is scarce, particularly for tree communities.We investigated the impact of tree species richness and mycorrhizal types, arbuscular mycorrhizal fungi (AM) and ectomycorrhizal fungi (EM), on above‐ and belowground carbon (C), nitrogen (N), and phosphorus (P) dynamics.Soil and soil microbial biomass elemental dynamics showed weak responses to tree species richness and none to mycorrhizal type. However, foliar elemental concentrations, stoichiometry, and pools were significantly affected by both treatments. Tree species richness increased foliar C and P pools but not N pools. Additive partitioning analyses showed that net biodiversity effects of foliar C, N, P pools in EM tree communities were driven by selection effects, but in mixtures of both mycorrhizal types by complementarity effects. Furthermore, increased tree species richness reduced soil nitrate availability, over 2 yr.Our results indicate that positive effects of tree diversity on aboveground nutrient storage are mediated by complementary mycorrhizal strategies and highlight the importance of using mixtures composed of tree species with different types of mycorrhizae to achieve more multifunctional afforestation. [ABSTRACT FROM AUTHOR]

Question: Do shrubs negatively affect the germination of perennial grass species in regeneration microsites? We experimentally analyzed the effect of soils from plant patches dominated by two shrub species (Larrea divaricata and Schinus johnstonii) and their propagules on the germination of three co‐dominant herbivore‐preferred perennial grass species (Poa ligularis, Nassella tenuis and Pappostipa speciosa). Location: Patagonian Monte, Chubut Province, Argentina (42°07′ S, 64°59′ W; 43°06′ S, 65°43′ W; 42°29′ S, 66°34′ W). Methods: We conducted two simultaneous microcosm experiments. In the first experiment, we sowed perennial grass propagules of the three species alone and combined with non‐scarified shrub propagules in Petri dishes with three substrate types (filter paper, inert soil and soil from shrub patches). In the second experiment, we sowed perennial grass propagules of each species combined with scarified and non‐scarified propagules of both shrub species in Petri dishes with soil taken from plant patches dominated by L. divaricata and by S. johnstonii. Both experiments lasted 3 months. We calculated the germination proportion and mean germination time (MGT) of propagules for each perennial grass species in each treatment. Results: Propagules from neighboring shrubs had a clearer negative effect on grass germination compared with shrub soils. Shrub propagules negatively affected the germination proportion of P. ligularis and N. tenuis, and induced longer MGT in the three perennial grass species. The combination of S. johnstonii soil and propagules negatively affected P. ligularis and P. speciosa germination. The combination of L. divaricata soil and scarified propagules completely inhibited P. speciosa germination. Conclusions: Our results highlighted the complexity of interactions between shrubs with high phenolic contents (soils and propagules) and the germination of perennial grass species in arid environments. Schinus johnstonii soil and propagules had stronger effects on perennial grass germination than L. divaricata soil and propagules. The negative effects of shrubs on microsite quality and germination processes depended on the specific shrub/grass interaction. [ABSTRACT FROM AUTHOR]

Background and aims: Supporting arbuscular mycorrhizal (AM) nutrient acquisition in crops may reduce the need for fertilizer inputs, leading to more cost effective and sustainable crop production. In wheat, AM fungal responsiveness and benefits of symbiosis vary among varieties. This study explored the role of soil compaction in this variation. Methods: We examined in a field experiment how soil compaction affects AM fungal colonization and biomass in five spring wheat varieties, and how these varieties differ in their AM-mediated phosphorus (P) uptake. We also studied soil properties, and AM fungal community composition in roots and soil. Results: Soil compaction increased AM fungal colonization in the variety Alderon, characterized by root traits that indicate inefficient P uptake. Wheat P concentration and P:N ratio in Alderon and Diskett increased with increased root AM fungal colonization and biomass. In Diskett, which is the most cultivated spring wheat variety in Sweden and has intermediate root traits, total P content per m2 also increased with root AM fungal colonization and biomass. Conclusions: Some wheat varieties, potentially those characterized by P inefficient root traits, such as Alderon, may depend more on AM-mediated P uptake in compacted than in non-compacted soil. Increased P uptake with increased AM fungal colonization in Diskett suggests that efficient root and AM-mediated nutrient uptake can occur simultaneously in a modern variety. Breeding varieties that use roots and AM symbiosis as complementary strategies for nutrient uptake could improve nutrient uptake efficiency and help farmers achieve stable yields in varying conditions. [ABSTRACT FROM AUTHOR]

Both enemies and mutualists play crucial roles in shaping plant invasion processes. Recent studies have suggested that resource fluctuations could indirectly promote plant invasion through higher trophic levels, such as enemies. However, the influence of mutualists like arbuscular mycorrhizal fungi (AMF) on plant invasion under nitrogen fluctuations remains untested.We conducted a pot mesocosm experiment using a three‐factorial experimental design to assess the individual and interactive effects of nitrogen availability, nitrogen fluctuation and AMF on invasive success of alien plants. We grew nine invasive alien species alongside five different native communities in pot mesocosms. These were then subjected to varied nitrogen availabilities (low vs. high), nitrogen fluctuations (constant vs. pulsed) and AMF presence or absence within a sterile substrate.We found that pulsed nitrogen supply increased the dominance of invasive alien species in low nitrogen availability, regardless of the presence or absence of AMF inoculation. However, in high nitrogen availability, pulsed nitrogen supply only enhanced this dominance in pots without AMF inoculation. This was tentatively evidenced by the three‐way interaction among nitrogen‐availability, nitrogen‐fluctuation and AMF‐inoculation treatments. Furthermore, the dominance promotion by nitrogen addition was greater than that by AMF inoculation.Synthesis and applications. Our findings present, for the first time, evidence that AMF may play a crucial role in mediating the promotion effects of nitrogen fluctuations on alien plant invasion. To better understand the invasion process of alien plants and evaluate their impact on native communities, future research should integrate abiotic and biotic drivers into a single framework. Furthermore, our findings underscore the importance of prioritizing habitats with higher nutrient availability and variability for protection against alien plant invasions. [ABSTRACT FROM AUTHOR]

The split-root system technique has been used to analyse plant biology for several decades, but woody plants have not received enough attention in this experimental approach. Historically, several methods have been developed, ranging from the simplest method of dividing a root into two parts and placing them in separate containers to more complex methods, such as grafting a second root from another plant. Each method has advantages and disadvantages that determine the goals of the experiment. Thus far, research using the split-root system has covered only 62 species of woody plants, mainly to investigate the water shortage effect on water acquisition. Many studies have also considered the significance of functional root-system diversity for plant fertilisation, which allows a better understanding of ion transport regulation mechanisms and some anatomical and functional features of woody plants. Ion uptake and transport have been studied frequently using isotope labelling. The split-root system method also offers interesting possibilities for studying the interactions of plants with other organisms. For example, this method was used to study root colonization strategies by mycorrhizal fungi. The comprehensive analysis of the split-root system technique in this review provides fine-scale information on the future concepts needed to study root-system biology, as the ability of roots to play a range of functions in the plant remains largely untested. [ABSTRACT FROM AUTHOR]

Afforestation on degraded lands is an effective measure to control desertification and soil erosion, but these functions are often constrained by soil nitrogen (N) availability. Moreover, soil N availability usually shifts along plantation development, yet we have a limited understanding of factors driving this shift. Here, we examined dynamics of soil N mineralization and nitrification rates along plantation development, and explored mechanisms behind these dynamics from the perspective of N‐cycling microbes. We measured needle litter quality, N‐hydrolyzing enzyme activity, biomass and community composition of soil microbes (phospholipid fatty acid analysis) and ammonia oxidizers (real‐time quantitative PCR and high‐throughput sequencing), and net N mineralization and nitrification rates along a chronosequence of Pinus sylvestris var. mongolica stands with six age classes ranging from 15‐ to 61‐year‐old in the Three‐North region of China. Results showed that stand development increased net N mineralization rate by 54%, nitrate‐N concentration by 106%, and nitrate‐N:ammonium‐N ratio from 1.09 to 2.63. Gram‐positive:gram‐negative bacterial ratio and β‐N‐acetylglucosaminidase activity initially increased and subsequently decreased along stand development with the highest values in 40‐year‐old stands, while fungal:bacterial ratio showed the opposite pattern with the lowest value in 40‐year‐old stands. These shifts in soil microbial properties were associated with age‐related changes in needle litter C:N ratio and soil pH. Net N mineralization rate was positively related to β‐N‐acetylglucosaminidase activities, but not to soil microbial biomass and community composition. Net nitrification rate was negatively correlated with ammonia‐oxidizing archaeal abundances and positively with ammonia‐oxidizing bacterial abundances. Collectively, our results indicate that soil N availability increases and N cycling accelerates with plantation growth, and suggest that microbial N recycling driven by β‐N‐acetylglucosaminidase is tightly related to soil N dynamics along stand development. [ABSTRACT FROM AUTHOR]

Foliar fertilization is an important agricultural practice. How crop plants considerably response to small amounts of foliar-applied minerals is not fully understood. In this study, we tested whether foliar-applied potassium (K) stimulates soil K uptake by plant roots. Firstly, K uptake from nutrient solution by wheat seedling was investigated with and without foliar application of K. To dissect net K uptake, quantified amount of foliar-applied K (∼19.2 mg pot−1), and K uptake by non-foliar-fertilized plants was subtracted from whole plant K uptake (foliar-treated). In the second set of experiment, maize was grown in soil, and 2% K2SO4 (∼45.4 mg K pot−1) was foliar-applied to dissect soil indigenous K uptake. In addition to elevated K level in both crops, the net K uptake via wheat and maize roots quantified ∼23% and 55%, respectively higher with foliar application of K. It is coupled with improving phenotypic observations, comprising root biomass (32–56%), root-to-shoot ratios (7–38%), and water contents (13–15%) by plotting multivariate analysis. Further, the elevated leaf gas exchange measurements and chlorophyll contents by 10% in wheat and 14% in maize ensured the optimum photosynthetic activity in foliar-applied seedlings. Notably, after crop harvesting, ∼10% lower biological available K in the soil of foliar-applied maize was found. In sum, our findings provide scientific basis that foliar K fertilization improves soil K uptake by wheat, maize, and probably, closely related to cereal crops. It also suggests a novel aspect for further investigation to understand the underlying signaling pathway(s). [ABSTRACT FROM AUTHOR]

Background: Plants can directly affect litter decomposition by producing litter materials of different qualities. However, whether living plants have indirect effects on litter decomposition by affecting changes in forest microenvironments is presently unclear in plantation forests. Methods: We addressed this issue by studying the decomposition of the leaf litter and fine roots of Chinese fir [Cunninghamia lanceolata (Lamb.) Hook.], a timber species widely planted in China, in 113 non-neighboring quadrats of varying basal area of the dominant plant species (i.e., Chinese fir) and distinct basal areas and species richness of regenerated woody plants (i.e., species other than Chinese fir) in a subtropical Chinese fir forest. Results: Our results showed that fine roots decomposed significantly more rapidly than leaf litter possibly because fine roots were easier access to mineralized nutrients and microbes compared with leaf litter. Further analyses showed that leaf litter and fine root decomposition rates were significantly controlled by the plant community attributes. The decomposition of both leaf litter and fine roots was mainly controlled by woody species regenerated during stand development rather than by Chinese fir. Specifically, leaf litter and fine root decomposition rates decreased with increasing basal area of regenerated woody plants, possibly due to nutrient competition and/or reduced photodegradation. Conclusions: This study provides empirical evidence that woody species regenerated during stand development play a certain role in determining litter decomposition rates through plant-soil interactions in Chinese fir plantations. Regenerated woody plants should be considered in future studies on soil carbon and nutrient cycling in plantation forest. [ABSTRACT FROM AUTHOR]

Establishing an artificial grassland is a common measure employed to restore heavily degraded alpine grasslands for regional sustainability. The Three-River Headwaters Region in China has significant areas of black-soil-type grassland which is typified by heavy degradation; nearly 35% of the grassland regions in the Three-River Headwaters Region has degraded into this type. There are different plant community types of black-soil-type grasslands, however, it is not clear which restoration measures should be adopted for different kinds of black-soil-type grasslands. Here, we investigate the plant community characteristics and soil physicochemical properties of artificial grasslands, two types of black-soiltype grasslands, and native undegraded grassland in the Three-River Headwaters Region, then analyzed the direct and indirect interactions between the plant and soil properties by partial least squares path models (PLS-PM). Our results revealed that establishing artificial grassland significantly increased aboveground biomass and plant community coverage, and also decreased plant species richness and diversity and soil water content, soil organic carbon and total nitrogen in the 0-10 cm soil layer as compared with black-soil-type grasslands. Plant community diversity had a positive effect on plant community productivity, soil nutrient, and soil water content in native undegraded grassland. These results suggest that more management interventions are needed after establishing an artificial grassland, such as reducing dominant species in two types of black-soil-type grasslands, water regulation in the A. frigida-dominated meadow, diversifying plant species (i.e., Gramineae and sedges), and fertilizer addition. [ABSTRACT FROM AUTHOR]

Purpose: Plant-associated microbes enhance nutrient access and stress tolerance of the host species, and therefore, are crucial for plant traits and resource strategies. However, the links between aboveground plant traits and belowground microbes related to plant resource strategies under stressful conditions remain poorly understood. Methods: We tested the relationships between leaf traits linked to water (carbon isotopic composition, δ13C) and nutrient use (elemental concentrations and stoichiometry) with microbial compositions in roots and rhizospheres of two dominant species (Artemisia ordosica and Leymus secalinus) in the Mu Us Desert, northern China. Results: L. secalinus exhibited higher Mg and Mn concentrations, N:P ratios, stoichiometric flexibility, and root fungi:bacteria ratios, but lower foliar K and Ca concentrations and δ13C values than A. ordosica. The leaf N:P of L. secalinus increased with the root fungi:bacteria ratios, whereas the leaf N:P of A. ordosica decreased with the root fungi:bacteria ratios. The plant elemental levels (P, N, K, Ca, Mn, and δ13C) of L. secalinus but not A. ordosica were significantly related to their root fungal composition. Additionally, the random forest model identified four key fungal families in predicting leaf elemental traits for both plant species. Conclusion: The results suggested tight coupling and coordination between leaf elemental traits and root microbial compositions (especially fungal communities) related to plant resource acquisition strategies. By regulating aboveground and belowground feedback loops through trait flexibility and root microbial compositions, the studied plant species can sustain their resource strategies under stressful environmental conditions. [ABSTRACT FROM AUTHOR]

Arbuscular mycorrhizal (AM) fungi traditionally form symbioses with most plant species. Although AM fungi have critical effects on microbial communities, the pathways showing how AM fungi shape rhizosphere bacterial communities and their functions are rarely explored.Here, through three systematic experiments, AM fungi–bacteria interactions were first investigated in the rhizosphere of Lotus japonicus, then the interactions were confirmed by a second experiment with wild‐type and a mycorrhiza‐defective mutant ljcbx of L. japonicus. The mechanisms were presented by adding core bacteria and AM fungi to the plant rhizosphere in the third experiment.We found that AM fungi–bacteria interactions enhanced host plant growth and identified a core bacterial group that uniquely enhanced host plant growth. Adding core bacteria and AM fungi promoted host growth and nutrient acquisition compared to adding AM fungi or core bacteria independently.Allelopathic substances secreted by AM fungal colonizing host roots to recruit the rhizosphere bacteria were detected by the multi‐omics joint analysis, showing that arachidonic acid was the main allelopathic substance that affected AM fungi–bacteria interactions.Our findings provide direct evidence that mycorrhizal infection simulated root exudation, such as arachidonic acid, recruited a beneficial microbiome to the host rhizosphere, increasing plant growth and soil nutrient turnover. Read the free Plain Language Summary for this article on the Journal blog. [ABSTRACT FROM AUTHOR]

White lupin is a promising high-protein crop, the cultivation of which is limited by a lack of adaptation to soils that are even just mildly calcareous. This study aimed to assess the phenotypic variation, the trait architecture based on a GWAS, and the predictive ability of genome-enabled models for grain yield and contributing traits of a genetically-broad population of 140 lines grown in an autumn-sown environment of Greece (Larissa) and a spring-sown environment of the Netherlands (Ens) that featured moderately calcareous and alkaline soils. We found large genotype × environment interaction and modest or nil genetic correlation for line responses across locations for grain yield, a lime susceptibility score, and other traits, with the exception of individual seed weight and plant height. The GWAS identified significant SNP markers associated with various traits that were markedly inconsistent across locations, while providing direct or indirect evidence for widespread polygenic trait control. Genomic selection proved to be a feasible strategy, owing to a moderate predictive ability for yield and lime susceptibility in Larissa (the site featuring greater lime soil stress). Other supporting results for breeding programs where the identification of a candidate gene for lime tolerance and the high reliability of genome-enabled predictions for individual seed weight. [ABSTRACT FROM AUTHOR]

In light of global warming, the interaction between plant nutrient traits and soil nutrients is still unclear. Plant nutrient traits (e.g., N and P) and their stoichiometric relationships (N/P ratio) are essential for plant growth and reproduction. However, the specific role of soil nutrients in driving variation in plant nutrient traits remains poorly understood. Fifty natural Pinus tabuliformis forests were used as the research object to clarify the interaction between plant nutrient traits and soil nutrients. We show that: (1) The Nmass, Pmass and N/P ratios of leaves were significantly higher than those of roots. The N/P ratio of both leaves and roots was less than 14. (2) Leaf nutrient traits showed diverse relationship patterns with root nutrient traits throughout the growing period. Significant changes were found in root nutrient PC2 (the second principal component of root nutrient traits) and leaf nutrient PC1 (the first principal component of leaf traits), and non-significant changes were found in other relationships between leaf and root traits (p > 0.05). Root nutrient traits explained 36.4% of the variance in leaf nutrient traits. (3) With the increase in soil nutrient PC2 (related to N), leaf PC2 (related to N) showed a significant trend of first decreasing and then increasing (p < 0.05). Only the soil Nmass was significantly correlated with the leaf Nmass (p < 0.05), which demonstrated that the growth and survival of Pinus tabuliformis forests were mainly affected by N-limitation. [ABSTRACT FROM AUTHOR]

Tree species are known to predominantly interact either with arbuscular mycorrhizal (AM) or ectomycorrhizal (EM) fungi. However, there is a knowledge gap regarding whether these mycorrhizae differently influence biodiversity–ecosystem functioning (BEF) relationships and whether a combination of both can increase community productivity. In 2015, we established a tree‐diversity experiment by growing tree communities with varying species richness levels (one, two, or four species) and either with AM or EM tree species or a combination of both. We investigated basal area and annual basal area increment from 2015 to 2020 as proxies for community productivity. We found significant positive relationships between tree species richness and community productivity, which strengthened over time. Further, AM and EM tree species differently influenced productivity; however, there was no overyielding when AM and EM trees grew together. EM tree communities were characterized by low productivity in the beginning but an increase of increment over time and showed overall strong biodiversity effects. For AM tree communities the opposite was true. Although young trees did not benefit from the presence of the other mycorrhizal type, dissimilar mechanisms underlying BEF relationships in AM and EM trees indicate that maximizing tree and mycorrhizal diversity may increase ecosystem functioning in the long run. [ABSTRACT FROM AUTHOR]

Background and aims: Studies that consider the effects of screes plant communities on the soil properties are lacking and whether the plant cover could be used as an indicator of biotic and/or abiotic parameters of the scree colonization has never been assessed. Here we aimed to identify plant communities-soil relationships in the process of colonization of alpine limestone screes. Methods: Plant communities and chemical-physical soil properties were studied on 50 plots from an area of the Italian Alps, and related to plant cover (colonization). Correlation and regression analysis were performed to determine the relationships and define the best trend models. Results: At the varying of plant cover, plant communities and the soil properties changed greatly. Floristic analysis especially showed how the pioneer/early stages of colonization revealed a limited number of species (< 20) typical of unstable screes (Thlaspietea rotundifolii) while the late/final stage has a greater number of species (> 25), mainly of basophilic grasslands (Elyno-Seslerietea). Statistical analysis showed high correlation between plant cover and number of species, shear vane strength (τ), soil depth, pH, organic matter (OM), total nitrogen (TN), sand and medium gravel content. The number of species and the values of τ, soil depth, OM, TN and sand content increased over the colonization/succession, albeit with different trends. Conclusion: This research allowed a better comprehension of the phenomenon of colonization of alpine limestone screes and showed how plant cover is a parameter useful to estimate some soil and vegetation features, therefore to facilitate the study/management of these environments. [ABSTRACT FROM AUTHOR]

Intense human activities break the grassland–livestock balance and accelerate grassland degradation. We evaluated the use of native dominant species combined with arbuscular mycorrhizal fungi (AMF) in order to recover grassland and restrain grassland degradation. We conducted a full factorial greenhouse experiment to evaluate the interaction effects of native species of distinct traits grass Lolium perenne (L) and legume Trifolium repens (T) with arbuscular mycorrhizal fungi (AMF) inoculation on grass productivity and soil properties across non-degraded, lightly degraded, and severely degraded soils. The grass–legume mixture was manipulated with five ratios (T:L = 1:0, T:L = 1:1, T:L = 3:1, T:L = 1:3, T:L = 0:1). The results showed that L. perenne significantly increased grassland productivity at different grass–legume ratios, regardless of AMF presence or absence. AMF inoculation increased plant N and P content uptake and improved the productivity of degraded grasslands, especially in severely degraded grasslands. The NO3−-N and available P concentrations increased in soil when the legume component increased from T:L = 0:1 (grass monoculture) to T:L = 1:0 (legume monoculture). This may be because the presence of Lolium perenne (L) can promote nitrogen fixation in legumes. Structural equation modeling indicated that grass–legume mixtures directly affected plant biomass, whereas AMF affected plant biomass via providing plant nutrients. A soil quality index based on minimum datasets indicated a significant positive effect of artificial grassland establishment on soil quality. We conclude that planting T:L = 0:1 and T:L = 1:3 combined with AMF inoculation can be used to recover degraded grassland production, and planting T:L = 1:1 and T:L = 1:3 plus AMF inoculation can be applied for grassland nutrient accumulation and stability maintenance. [ABSTRACT FROM AUTHOR]

Aims: Phosphorus (P), like nitrogen (N), commonly impacts the structures and functions of terrestrial ecosystems. Global changes (N deposition) and land-use intensification (mowing) may influence the components of P cycling in grassland ecosystems, especially soil organic P mineralization, which provides P for plants and microbes. It remains unclear how soil annual organic P mineralization rate responds to mowing and N addition and its potential mechanisms in the semi-natural grasslands. Methods: We conducted a five-year field experiment that included mowing (mown and unmown) and N additions (0, 2.5, 5, 10, 20, and 40 g N m−2 yr−1) to explore the responses of and main factors controlling soil organic P mineralization to these treatments in a semi-natural grassland—Songnen Meadow Steppe. Results: We found that N additions enhanced the rate of soil organic P mineralization in semi-natural grassland. The magnitude of positive effects of N additions was larger in mown plots than unmown plots. Compared with no N addition, the rates of soil annual organic P mineralization increased 39.04, 46.88, 90.57, 58.82, and 67.97% under mown as the N input increased, and 23.89, 24.13, 25.46, 33.42 and 34.81% under unmown. The alkaline phosphatase (ALP) activity was the main driver which controlled soil annual organic P mineralization rates under N additions in unmown plots, and the plant aboveground biomass, soil microbial community composition, and ALP activities were the main drivers under N additions in mown plots. Our results indicate that mowing modulated the effects of N additions on the annual organic P mineralization rate in soil. Conclusions: The soil annual organic P mineralization rate had stronger dependence on the shifts in plant-soil–microbe variables with N additions in the mown conditions than in the unmown conditions, which highlighted that P cycling may be more susceptible to future environmental changes induced by N deposition under mowing in semi-natural ecosystems. Our study provided the new insight of that plant and soil interactions have an important role in maintaining the supply of P, and they may drive soil organic P mineralization in P-deficient ecosystems as N deposition increases. [ABSTRACT FROM AUTHOR]

The vitality of European forests continues to decline due to new pests and diseases, climate-change related disturbances and high loads of atmospheric nitrogen deposition. Deteriorating soil health is a major factor underpinning the low vitality of West-European forests. Selecting tree species with soil ameliorative traits is proposed as an avenue to counteract soil acidification and improve overall forest vitality. Here we evaluate the impact of black cherry (Prunus serotina Ehrh.), a known rich litter species, on the vitality of neighboring pedunculate oak (Quercus robur L.) in ten mixed forests on sand in Germany, Belgium and the Netherlands. We found that black cherry admixture increases foliar N and P to a surplus whereas it causes deficiencies in foliar Mg, thereby resulting in an overall negative effect on oak foliar nutrient concentrations. Contrary, defoliation of oak leaves by herbivory decreases with the proximity of black cherry. Using structural equation modelling (SEM), we tested the hypothesized 'improved soil health' pathway. Our analyses showed that black cherry admixture leads to lower accumulation in the humus layer, resulting in higher soil base saturation which has a positive effect on foliar Ca yet a negative effect on total chlorophyll. Moreover, the SEM illustrated that herbivory of oak leaves decreases when black cherry is admixed, both via dilution and improved soil health. Indirect effects of black cherry on oak vitality via "improved soil health" in our SEM are however small in comparison to direct relations. Hence, our study showed that the combined positive and negative impacts of black cherry on oak vitality are limited, which tempers the potential benefits of using the rich litter species to counteract oak decline via improved soil health - yet, the concern of black cherry as an invasive alien species negatively affecting the vitality of mature pedunculate oak trees may also be exaggerated. [ABSTRACT FROM AUTHOR]

While biodiversity is expected to enhance multiple ecosystem functions (EFs), the different roles of multiple biodiversity dimensions remain difficult to disentangle without carefully designed experiments. We sowed plant communities with independent levels of functional (FD) and phylogenetic diversities (PD), combined with different levels of fertilization, to investigate their direct and indirect roles on multiple EFs, including plant‐related EFs (plant biomass productivity, litter decomposability), soil fertility (organic carbon and nutrient pool variables), soil microbial activity (respiration and nutrient cycling), and an overall multifunctionality. We expected an increase in most EFs in communities with higher values of FD and/or PD via complementarity effects, but also the dominant plant types (using community weighted mean, CWM, independent of FD and PD) via selection effects on several EFs. The results showed strong direct effects of different dimensions of plant functional structure parameters on plant‐related EFs, through either CWM or FD, with weak effects of PD. Fertilization had significant effects on one soil microbial activity and indirect effects on the other variables via changes in soil abiotic properties. Dominant plant types and FD showed only indirect effects on soil microbial activity, through litter decomposition and soil abiotic properties, highlighting the importance of cascading effects. This study shows the relevance of complementary dimensions of biodiversity for assessing both direct and cascading effects on multiple EFs. [ABSTRACT FROM AUTHOR]

ABSTRACT Negative plant-soil feedback (NPSF) due to the buildup of soilborne pathogens in soil is a major obstacle in sustainable agricultural systems. Beneficial rhizosphere microfloras are recruited by plants, and mediating this has become a strategic priority to manipulate plant health. Here, we found that foliar infection of Panax notoginseng by Alternaria panax changed plant-soil feedback from negative to positive. Foliar infection modified the rhizosphere soil microbial community and reversed the direction of the buildup of the soilborne pathogen Ilyonectria destructans and beneficial microbes, including Trichoderma, Bacillus, and Streptomyces, in rhizosphere soil. These beneficial microbes not only showed antagonistic ability against the pathogen I. destructans but also enhanced the resistance of plants to A. panax. Foliar infection enhanced the exudation of short- and long-chain organic acids, sugars, and amino acids from roots. In vitro and in vivo experiments validated that short- and long-chain organic acids and sugars play dual roles in simultaneously suppressing pathogens but enriching beneficial microbes. In summary, foliar infection could change root secretion to drive shifts in the rhizosphere microbial community to enhance soil health, providing a new strategy to alleviate belowground disease in plants through aboveground inducement. IMPORTANCE Belowground soilborne disease is the main factor limiting sustainable agricultural production and is difficult to manage due to the complexity of the soil environment. Here, we found that aboveground parts of plants infected by foliar pathogens could enhance the secretion of organic acids, sugars, and amino acids in root exudates to suppress soilborne pathogens and enrich beneficial microbes, eventually changing the plant and soil feedback from negative to positive and alleviating belowground soilborne disease. This is an exciting strategy by which to achieve belowground soilborne disease management by manipulating the aboveground state through aboveground stimulation.

"Acid soil syndrome" is a worldwide phenomenon characterized by low pH (pH < 5.5), scarce nutrient availability (K+, Ca2+, Mg2+, P), and mineral toxicity such as those caused by soluble aluminium (Al) forms. Regardless of the mineral toxicity, the low pH by itself is detrimental to crop development causing striking sensitivity responses such as root growth arrest. However, low pH-induced responses are still poorly understood and underrated. Here, we review and discuss the core evidence about the action of low pH upon specific root zones, distinct cell types, and possible cellular targets (cell wall, plasma membrane, and alternative oxidase). The role of different players in signaling processes leading to low pH-induced responses, such as the STOP transcription factors, the reactive oxygen species (ROS), auxin, ethylene, and components of the antioxidant system, is also addressed. Information at the molecular level is still lacking to link the low pH targets and the subsequent actors that trigger the observed sensitivity responses. Future studies will have to combine genetic tools to identify the signaling processes triggered by low pH, unraveling not only the mechanisms by which low pH affects root cells but also finding new ways to engineer the tolerance of domesticated plants to acidic stress. • The acidic pH by itself can cause rhizotoxicity regardless of the prominent factors within the " acid soil syndrome ". • The cell wall and plasma membrane seem to be targets of acidic stress but the pattern of acidic pH-induced responses is confined within root-specific zones. • The central players (e.g. ethylene, reactive oxygen species, transcription factors) control the cellular responses in accord with the acidic stress. [ABSTRACT FROM AUTHOR]

Rubber cultivation is primarily rainfed agriculture, which means that water supplies are not stable in most rubber cultivated areas. Therefore, improving the water use of rubber trees through fertilization management seems to be a breakthrough for enhancing the growth and latex yield of rubber trees and carrying out the intensive management of rubber agriculture. However, the relationships among the nutrient status of rubber trees, their water uptake, and soil resources, including water and nutrients, remain unclear. To address this issue, we measured C, N, P, K, Ca, and Mg concentrations in soil and leaves, stems, and roots in a monoculture rubber plantation and distinguished the water uptake depths based on stable isotope analysis throughout the year. We found that the rubber trees primarily absorbed water from the 5–50 cm depth layer, and soil water and nutrients (usually N, P, K) decreased with depth. In addition, the water uptake depth of rubber trees exhibited positive correlations with the nutrient status of their tissues. The more water the rubber trees absorb from the intermediate soil layer, the more nutrients they contain. Therefore, applying fertilizer to intermediate soil layers, especially those rich in C content, could greatly promote rubber tree growth. [ABSTRACT FROM AUTHOR]

Soil microorganisms play an important role in maintaining soil quality and function, although the response of soil microbial biodiversity to heavy metals has been extensively investigated, the microbe-microbe associations under the influence of both native plant species and extremely high heavy metal contamination are not well documented. We examined the diversity and composition of microbial communities and the physicochemical properties in the rhizosphere of three native plant species, Carex breviculmis, Buddleja davidii, and Artemisia annua growing on and around a Pb-Zn waste heap with a nearly 100-year history of natural recovery. Both plant species and heavy metals influence soil microbial diversity and composition. C. breviculmis and A. annua showed a prominent advantage in increasing rhizosphere microbial diversity and richness as well as network complexity compared with plant Buddleja davidii at severely contaminated soil, which was mainly related to the accumulation of soil nutrients such as soil organic carbon (SOC), total nitrogen ammonium nitrogen and nitrate nitrogen rather than a reduction in heavy metal concentrations. Moreover, the heavy metal concentration and soil nutrient levels significantly affected the microbial groups affiliated with Proteobacteria, Chloroflexi, Ascomycota, and Basidiomycota, in which those affiliated with Chloroflexi and Ascomycota were positively associated with heavy metals. Soil microbial network on the Pb-Zn waste heap exhibited higher average degree and a higher proportion of positive links than those around the waste heap, and thus soil microbial structure became more complexity and unstable with increasing heavy metal pollution.

Soil properties and soil microbial communities can greatly affect plant communities, especially in disturbed ecosystems. However, their relative contribution to the final effect on plants has rarely been assessed.We manipulated the soil microbial community in microcosms by inoculating sterilized soils originating from preserved species‐rich meadow and a restored meadow with a high and low diversity of microbial inoculum (manipulated by the dilution of microbial community extract) from those soils in full factorial manner, yielding eight treatments (2 soil origins × 2 inoculum sources × 2 levels of inoculum diversity).In general, the biomass of plant meadow specialists (Filipendula vulgaris, Phleum phleoides, and Prunella grandiflora) was greater with the preserved meadow inoculum than with the restored meadow inoculum but tended to be greater in the restored meadow soil than in the preserved meadow soil. Two meadow generalists (Festuca rubra and Centaurea jacea) were not significantly affected by soil origin, inoculum source, or inoculum diversity, but the third generalist Plantago media produced greater biomass in the preserved meadow soil than in the restored meadow soil.Total above‐ground biomass was not affected by the treatments, but total below‐ground biomass was greater with microbial inoculum from the preserved meadow than from the restored meadow, and this increase was greater in the restored meadow soil than in the preserved meadow soil.Our results indicate strong responses of the preserved meadow specialists to the soil microbial community, which may explain why they are rare in the meadows that were restored following agricultural use. Read the free Plain Language Summary for this article on the Journal blog. [ABSTRACT FROM AUTHOR]

Background and aims: An increase in nitrogen deposition is expected to increase the phosphorus-limited primary productivity of grassland ecosystems. However, it remains unclear as to whether the primary productivity of grasslands is co-limited by nitrogen and phosphorus, or only by one or the other. Methods: Nitrogen and phosphorus addition experiments were conducted at an alpine steppe site in North Tibet from 2013 to 2017. The biomass of plant community, the N and P content of plant leaf, soil chemical property, and changes in abundance and function and composition of bacterial and fungal community with N and P treatment were analyzed after five years. Results: Results from analyzing the response ratios of shoot biomass and leaf nitrogen and phosphorus concentrations to nitrogen and phosphorus addition suggested that nitrogen is the main limiting factor for the biomass of alpine steppe. Based on the ratio of nitrogen and phosphorus stoichiometry, plants must increase their phosphorus absorption following nitrogen addition. From the results of a structural equation model, plants and fungi both promoted the activity of phosphatase. The abundance of fungi and the saprotrophic group associated with decomposition increased following nitrogen addition, and more substrate is provided by the plants, which will accelerate the organic phosphorus cycle. These results suggest that the phosphorus deficit of plants owing to nitrogen addition will be alleviated. On the contrary, phosphorus did not limit the biomass, but its addition did increase the absorption of nitrogen by plants. Although the activity of urease was enhanced by soil microbes and plants, there was little substrate for microbes because the plant biomass was limited by nitrogen. Conclusions: The biomass is mainly limited by nitrogen and soil microbes will influence the effect of nitrogen on biomass in alpine steppe. [ABSTRACT FROM AUTHOR]

Tree–fungal symbioses are increasingly recognized to affect soil nitrogen (N) transformations, yet the role of free-living soil microbes in the process is largely unclear. Soil microbes directly interact with trees and are a primary driver of many N transformation processes. Here, we explored the linkage among tree mycorrhizal associations, free-living soil microbes and N transformation rates in a temperate forest of Northeast China. Across a gradient of increasing ectomycorrhizal (ECM) tree dominance, we measured soil acid–base chemistry, bacterial and fungal abundances, N-hydrolyzing enzyme activities, abundances and community composition of ammonia-oxidizing archaea (AOA) and bacteria, and net N mineralization and net nitrification rates. Results showed that soil pH, exchangeable base cations, inorganic N concentrations and N transformation rates decreased with increasing ECM tree dominance. The ECM tree dominance was negatively related to soil bacterial and AOA amoA gene abundances, and positively to soil fungal abundances and β-N-acetylglucosaminidase activities. These shifts in soil microbial abundances and enzyme activities along the mycorrhizal gradient were linked with the increase in soil acidity with increasing ECM tree dominance. Piecewise structural equation models revealed that ECM tree dominance was not directly related to N transformation rates, but indirectly to net N mineralization rates by affecting bacterial and fungal abundances, and indirectly to net nitrification rates by influencing AOA amoA gene abundances. Collectively, our results indicate that soil microbes provide a mechanistic link between mycorrhizal associations and soil N transformations, and suggest that shifts in forest mycorrhizal associations under global change could have profound consequences for biogeochemical cycling of temperate forests. [ABSTRACT FROM AUTHOR]