A temporal approach to linking aboveground and belowground ecology

Biochar improves fertility in waste derived manufactured soils, but not resilience to climate change

We present a soil manufactured from waste materials, which could replace the use of peat and topsoil in plant production and reduce the pressure on natural soil resources. We tested the effect of the manufactured soil on ecosystem functions and microbial communities with and without plants present, and with and without biochar addition (Experiment 1). The resilience of the soil in response to drought and flooding, and also the effect of biochar was also tested (Experiment 2). Biochar increased soil C and N regardless of plant presence and negated the effect of the plant on soil peroxidase enzyme activity. The manufactured soil was largely resilient to drought, but not flooding, with negative impacts on microbial communities. Results indicate that biochar could improve soil properties, but not resilience to climatic perturbations. Results suggest that manufactured soils amended with biochar could offer a useful alternative to natural soil in many contexts.

Decreased snow depth inhibits litter decomposition via changes in litter microbial biomass and enzyme activity

Decreased snow depth resulting from global warming has the potential to significantly impact biogeochemical cycles in cold forests. However, the specific mechanisms of how snow reduction affects litter decomposition and the underlying microbial processes remain unclear, this knowledge gap limits our ability to precisely predict ecological processes within cold forest ecosystems under climate change. Hence, a field experiment was conducted in a subalpine forest in southwestern China, involving a gradient of snow reduction levels (control, 50 %, 100 %) to investigate the effects of decreased snow on litter decomposition, as well as microbial biomass and activity, specifically focused on two common species: red birch (Betula albosinensis) and masters larch (Larix mastersiana). After one year of incubation, the decomposition rate (k-value) of the two types of litter ranged from 0.12 to 0.24 across three snow treatments. A significant lower litter mass loss, microbial biomass and enzyme activity were observed under decreased snow depth in winter. Furthermore, a hysteresis inhibitory effect of snow reduction on hydrolase activity was observed in the following growing season. Additionally, the high initial quality (lower C/N ratio) of red birch litter facilitated the colonization by a greater quantity of microorganisms, making it more susceptible to snow reduction compared to the low-quality masters larch litter. Structural equation models indicated that decreased snow depth hindered litter decomposition by altering the biological characterization of litter (e.g., microbial biomass and enzyme activity) and environmental variables (e.g., mean temperature and moisture content). The findings suggest that the potential decline in snow depth could inhibit litter decomposition by reducing microbial biomass and activity, implying that the future climate change may alter the material cycling processes in subalpine forest ecosystems.

Heavy grazing reduces soil bacterial diversity by increasing soil pH in a semi-arid steppe

Background

In a context of long-term highly intensive grazing in grassland ecosystems, a better understanding of how quickly belowground biodiversity responds to grazing is required, especially for soil microbial diversity.

Methods

In this study, we conducted a grazing experiment which included the CK (no grazing with a fenced enclosure undisturbed by livestock), light and heavy grazing treatments in a desert steppe in Inner Mongolia, China. Microbial diversity and soil chemical properties (i.e., pH value, organic carbon, inorganic nitrogen (IN, NH 4 + -N and NO 3 - -N), total carbon, nitrogen, phosphorus, and available phosphorus content) both in rhizosphere and non-rhizosphere soils were analyzed to explore the responses of microbial diversity to grazing intensity and the underlying mechanisms.

Results

The results showed that heavy grazing only deceased bacterial diversity in the non-rhizosphere soil, but had no any significant effects on fungal diversity regardless of rhizosphere or non-rhizosphere soils. Bacterial diversity in the rhizosphere soil was higher than that of non-rhizosphere soil only in the heavy grazing treatment. Also, heavy grazing significantly increased soil pH value but deceased NH4+-N and available phosphorus in the non-rhizosphere soil. Spearman correlation analysis showed that soil pH value was significantly negatively correlated with the bacterial diversity in the non-rhizosphere soil. Combined, our results suggest that heavy grazing decreased soil bacterial diversity in the non-rhizosphere soil by increasing soil pH value, which may be due to the accumulation of dung and urine from livestock. Our results highlight that soil pH value may be the main factor driving soil microbial diversity in grazing ecosystems, and these results can provide scientific basis for grassland management and ecological restoration in arid and semi-arid area.

Ranking environmental and edaphic attributes driving soil microbial community structure and activity with special attention to spatial and temporal scales

The incredibly complex soil microbial communities at small scales make their analysis and identification of reasons for the observed structures challenging. Microbial community structure is mainly a result of the inoculum (dispersal), the selective advantages of those organisms under the habitat-based environmental attributes, and the ability of those colonizers to sustain themselves over time. Since soil is protective, and its microbial inhabitants have long adapted to varied soil conditions, significant portions of the soil microbial community structure are likely stable. Hence, a substantial portion of the community will not correlate to often measured soil attributes. We suggest that the drivers be ranked on the basis of their importance to the fundamental needs of the microbes: (i) those that supply energy, i.e., organic carbon and electron acceptors; (ii) environmental effectors or stressors, i.e., pH, salt, drought, and toxic chemicals; (iii) macro-organism associations, i.e., plants and their seasonality, animals and their fecal matter, and soil fauna; and (iv) nutrients, in order, N, P, and probably of lesser importance, other micronutrients, and metals. The relevance of drivers also varies with spatial and time scales, for example, aggregate to field to regional, and persistent to dynamic populations to transcripts, and with the extent of phylogenetic difference, hence phenotypic differences in organismal groups. We present a summary matrix to provide guidance on which drivers are important for particular studies, with special emphasis on a wide range of spatial and temporal scales, and illustrate this with genomic and population (rRNA gene) data from selected studies.

Climate change disrupts the seasonal coupling of plant and soil microbial nutrient cycling in an alpine ecosystem

The seasonal coupling of plant and soil microbial nutrient demands is crucial for efficient ecosystem nutrient cycling and plant production, especially in strongly seasonal alpine ecosystems. Yet, how these seasonal nutrient cycling processes are modified by climate change and what the consequences are for nutrient loss and retention in alpine ecosystems remain unclear. Here, we explored how two pervasive climate change factors, reduced snow cover and shrub expansion, interactively modify the seasonal coupling of plant and soil microbial nitrogen (N) cycling in alpine grasslands, which are warming at double the rate of the global average. We found that the combination of reduced snow cover and shrub expansion disrupted the seasonal coupling of plant and soil N-cycling, with pronounced effects in spring (shortly after snow melt) and autumn (at the onset of plant senescence). In combination, both climate change factors decreased plant organic N-uptake by 70% and 82%, soil microbial biomass N by 19% and 38% and increased soil denitrifier abundances by 253% and 136% in spring and autumn, respectively. Shrub expansion also individually modified the seasonality of soil microbial community composition and stoichiometry towards more N-limited conditions and slower nutrient cycling in spring and autumn. In winter, snow removal markedly reduced the fungal:bacterial biomass ratio, soil N pools and shifted bacterial community composition. Taken together, our findings suggest that interactions between climate change factors can disrupt the temporal coupling of plant and soil microbial N-cycling processes in alpine grasslands. This could diminish the capacity of these globally widespread alpine ecosystems to retain N and support plant productivity under future climate change.

Monotonic trends of soil microbiomes, metagenomic and metabolomic functioning across ecosystems along water gradients in the Altai region, northwestern China

To investigate microbial communities and their contributions to carbon and nutrient cycling along water gradients can enhance our comprehension of climate change impacts on ecosystem services. Thus, we conducted an assessment of microbial communities, metagenomic functions, and metabolomic profiles within four ecosystems, i.e., desert grassland (DG), shrub-steppe (SS), forest (FO), and marsh (MA) in the Altai region of Xinjiang, China. Our results showed that soil total carbon (TC), total nitrogen, NH4+, and NO3- increased, but pH decreased with soil water gradients. Microbial abundances and richness also increased with soil moisture except the abundances of fungi and protists being lowest in MA. A shift in microbial community composition is evident along the soil moisture gradient, with Proteobacteria, Basidiomycota, and Evosea proliferating but a decline in Actinobacteria and Cercozoa. The β-diversity of microbiomes, metagenomic, and metabolomic functioning were correlated with soil moisture gradients and have significant associations with specific soil factors of TC, NH4+, and pH. Metagenomic functions associated with carbohydrate and DNA metabolisms, as well as phages, prophages, TE, plasmids functions diminished with moisture, whereas the genes involved in nitrogen and potassium metabolism, along with certain biological interactions and environmental information processing functions, demonstrated an augmentation. Additionally, MA harbored the most abundant metabolomics dominated by lipids and lipid-like molecules and organic oxygen compounds, except certain metabolites showing decline trends along water gradients, such as N'-Hydroxymethylnorcotinine and 5-Hydroxyenterolactone. Thus, our study suggests that future ecosystem succession facilitated by changes in rainfall patterns will significantly alter soil microbial taxa, functional potential, and metabolite fractions.

Unraveling the spatial-temporal distribution patterns of soil abundant and rare bacterial communities in China's subtropical mountain forest

Introduction

The pivotal roles of both abundant and rare bacteria in ecosystem function are widely acknowledged. Despite this, the diversity elevational patterns of these two bacterial taxa in different seasons and influencing factors remains underexplored, especially in the case of rare bacteria.

Methods

Here, a metabarcoding approach was employed to investigate elevational patterns of these two bacterial communities in different seasons and tested the roles of soil physico-chemical properties in structuring these abundant and rare bacterial community.

Results and discussion

Our findings revealed that variation in elevation and season exerted notably effects on the rare bacterial diversity. Despite the reactions of abundant and rare communities to the elevational gradient exhibited similarities during both summer and winter, distinct elevational patterns were observed in their respective diversity. Specifically, abundant bacterial diversity exhibited a roughly U-shaped pattern along the elevation gradient, while rare bacterial diversity increased with the elevational gradient. Soil moisture and N:P were the dominant factor leading to the pronounced divergence in elevational distributions in summer. Soil temperature and pH were the key factors in winter. The network analysis revealed the bacteria are better able to adapt to environmental fluctuations during the summer season. Additionally, compared to abundant bacteria, the taxonomy of rare bacteria displayed a higher degree of complexity. Our discovery contributes to advancing our comprehension of intricate dynamic diversity patterns in abundant and rare bacteria in the context of environmental gradients and seasonal fluctuations.

Prolonged water limitation shifts the soil microbiome from copiotrophic to oligotrophic lifestyles in Scots pine mesocosms

Reductions in soil moisture due to prolonged episodes of drought can potentially affect whole forest ecosystems, including soil microorganisms and their functions. We investigated how the composition of soil microbial communities is affected by prolonged episodes of water limitation. In a mesocosm experiment with Scots pine saplings and natural forest soil maintained at different levels of soil water content over 2 years, we assessed shifts in prokaryotic and fungal communities and related these to changes in plant development and soil properties. Prolonged water limitation induced progressive changes in soil microbial community composition. The dissimilarity between prokaryotic communities at different levels of water limitation increased over time regardless of the recurrent seasons, while fungal communities were less affected by prolonged water limitation. Under low soil water contents, desiccation-tolerant groups outcompeted less adapted, and the lifestyle of prokaryotic taxa shifted from copiotrophic to oligotrophic. While the abundance of saprotrophic and ligninolytic groups increased alongside an accumulation of dead plant material, the abundance of symbiotic and nutrient-cycling taxa decreased, likely impairing the development of the trees. Overall, prolonged episodes of drought appeared to continuously alter the structure of microbial communities, pointing to a potential loss of critical functions provided by the soil microbiome.

Dynamics of soil microbial communities involved in carbon cycling along three successional forests in southern China

Dynamics of plant communities during forest succession have been received great attention in the past decades, yet information about soil microbial communities that are involved in carbon cycling remains limited. Here we investigated soil microbial community composition and carbohydrate degradation potential using metagenomic analysis and examined their influencing factors in three successional subtropical forests in southern China. Results showed that the abundances of soil bacteria and fungi increased (p ≤ 0.05 for both) with forest succession in relation to both soil and litter characteristics, whereas the bacterial diversity did not change (p > 0.05) and the fungal diversity of Shannon-Wiener index even decreased (p ≤ 0.05). The abundances of microbial carbohydrate degradation functional genes of cellulase, hemicellulase, and pectinase also increased with forest succession (p ≤ 0.05 for all). However, the chitinase gene abundance did not change with forest succession (p > 0.05) and the amylase gene abundance decreased firstly in middle-succession forest and then increased in late-succession forest. Further analysis indicated that changes of functional gene abundance in cellulase, hemicellulase, and pectinase were primarily affected by soil organic carbon, soil total nitrogen, and soil moisture, whereas the variation of amylase gene abundance was well explained by soil phosphorus and litterfall. Overall, we created a metagenome profile of soil microbes in subtropical forest succession and fostered our understanding of microbially-mediated soil carbon cycling.

Spatial patterns of historical crop yields reveal soil health attributes in US Midwest fields

Attaining high crop yields and increasing carbon storage in agricultural soils, while avoiding negative environmental impacts on water quality, soil erosion, and biodiversity, requires accurate and precise management of crop inputs and management practices. The long-term analysis of spatial and temporal patterns of crop yields provides insights on how yields vary in a field, with parts of field constantly producing either high yields or low yields and other parts that fluctuate from one year to the next. The concept of yield stability has shown to be informative on how plants translate the effects of environmental conditions (e.g., soil, climate, topography) across the field and over the years in the final yield, and as a valuable layer in developing prescription maps of variable fertilizer rate inputs. Using known relationships between soil health and crop yields, we hypothesize that areas with measured constantly low yield will return low carbon to the soil affecting its heath. On this premises, yield stability zones (YSZ) provide an effective and practical integrative measure of the small-scale variability of soil health on a field relative basis. We tested this hypothesis by measuring various metrics of soil health from commercial farmers' fields in the north central Midwest of the USA in samples replicated across YSZ, using a soil test suite commonly used by producers and stakeholders active in agricultural carbon credits markets. We found that the use of YSZ allowed us to successfully partition field-relative soil organic carbon (SOC) and soil health metrics into statistically distinct regions. Low and stable (LS) yield zones were statistically lower in normalized SOC when compared to high and stable (HS) and unstable (US) yield zones. The drivers of the yield differences within a field are a series of factors ranging from climate, topography and soil. LS zones occur in areas of compacted soil layers or shallow soils (edge of the field) on steeper slopes. The US zones occurring with high water flow accumulation, were more dependent on topography and rainfall. The differences in the components of the overall soil health score (SHS) between these YSZ increased with sample depth suggesting a deeper topsoil in the US and HS zones, driven by the accumulation of water, nutrients, and carbon downslope. Comparison of the field management provided initial evidence that zero tillage reduces the magnitude of the variance in SOC and soil health metrics between the YSZ.

Plant-soil synchrony in nutrient cycles: Learning from ecosystems to design sustainable agrosystems

Redesigning agrosystems to include more ecological regulations can help feed a growing human population, preserve soils for future productivity, limit dependency on synthetic fertilizers, and reduce agriculture contribution to global changes such as eutrophication and warming. However, guidelines for redesigning cropping systems from natural systems to make them more sustainable remain limited. Synthetizing the knowledge on biogeochemical cycles in natural ecosystems, we outline four ecological systems that synchronize the supply of soluble nutrients by soil biota with the fluctuating nutrient demand of plants. This synchrony limits deficiencies and excesses of soluble nutrients, which usually penalize both production and regulating services of agrosystems such as nutrient retention and soil carbon storage. In the ecological systems outlined, synchrony emerges from plant-soil and plant-plant interactions, eco-physiological processes, soil physicochemical processes, and the dynamics of various nutrient reservoirs, including soil organic matter, soil minerals, atmosphere, and a common market. We discuss the relative importance of these ecological systems in regulating nutrient cycles depending on the pedoclimatic context and on the functional diversity of plants and microbes. We offer ideas about how these systems could be stimulated within agrosystems to improve their sustainability. A review of the latest advances in agronomy shows that some of the practices suggested to promote synchrony (e.g., reduced tillage, rotation with perennial plant cover, crop diversification) have already been tested and shown to be effective in reducing nutrient losses, fertilizer use, and N2 O emissions and/or improving biomass production and soil carbon storage. Our framework also highlights new management strategies and defines the conditions for the success of these nature-based practices allowing for site-specific modifications. This new synthetized knowledge should help practitioners to improve the long-term productivity of agrosystems while reducing the negative impact of agriculture on the environment and the climate.

Microbial dynamics in soils of the Damma glacier forefield show succession in the functional genetic potential

Glacier retreat is a visible consequence of climate change worldwide. Although taxonomic change of the soil microbiomes in glacier forefields have been widely documented, how microbial genetic potential changes along succession is little known. Here, we used shotgun metagenomics to analyse whether the soil microbial genetic potential differed between four stages of soil development (SSD) sampled along three transects in the Damma glacier forefield (Switzerland). The SSDs were characterized by an increasing vegetation cover, from barren soil, to biological soil crust, to sparsely vegetated soil and finally to vegetated soil. Results suggested that SSD significantly influenced microbial genetic potential, with the lowest functional diversity surprisingly occurring in the vegetated soils. Overall, carbohydrate metabolism and secondary metabolite biosynthesis genes overrepresented in vegetated soils, which could be partly attributed to plant-soil feedbacks. For C degradation, glycoside hydrolase genes enriched in vegetated soils, while auxiliary activity and carbohydrate esterases genes overrepresented in barren soils, suggested high labile C degradation potential in vegetated, and high recalcitrant C degradation potential in barren soils. For N-cycling, organic N degradation and synthesis genes dominated along succession, and gene families involved in nitrification were overrepresented in barren soils. Our study provides new insights into how the microbial genetic potential changes during soil formation along the Damma glacier forefield.

Metabarcoding data reveal vertical multitaxa variation in topsoil communities during the colonization of deglaciated forelands

Ice-free areas are expanding worldwide due to dramatic glacier shrinkage and are undergoing rapid colonization by multiple lifeforms, thus representing key environments to study ecosystem development. It has been proposed that the colonization dynamics of deglaciated terrains is different between surface and deep soils but that the heterogeneity between communities inhabiting surface and deep soils decreases through time. Nevertheless, tests of this hypothesis remain scarce, and it is unclear whether patterns are consistent among different taxonomic groups. Here, we used environmental DNA metabarcoding to test whether community diversity and composition of six groups (Eukaryota, Bacteria, Mycota, Collembola, Insecta, and Oligochaeta) differ between the surface (0-5 cm) and deeper (7.5-20 cm) soil at different stages of development and across five Alpine glaciers. Taxonomic diversity increased with time since glacier retreat and with soil evolution. The pattern was consistent across groups and soil depths. For Eukaryota and Mycota, alpha-diversity was highest at the surface. Time since glacier retreat explained more variation of community composition than depth. Beta-diversity between surface and deep layers decreased with time since glacier retreat, supporting the hypothesis that the first 20 cm of soil tends to homogenize through time. Several molecular operational taxonomic units of bacteria and fungi were significant indicators of specific depths and/or soil development stages, confirming the strong functional variation of microbial communities through time and depth. The complexity of community patterns highlights the importance of integrating information from multiple taxonomic groups to unravel community variation in response to ongoing global changes.

Potentilla parvifolia strongly influenced soil microbial community and environmental effect along an altitudinal gradient in central Qilian Mountains in western China

The Qilian Mountains (QLMs) form an important ecological security barrier in western China and a priority area for biodiversity conservation. Potentilla parvifolia is a widespread species in the mid-high altitudes of the QLMs and has continuously migrated to higher altitudes in recent years. Understanding the effects of P. parvifolia on microbial community characteristics is important for exploring future changes in soil biogeochemical processes in the QLMs. This study found that P. parvifolia has profound effects on the community structure and ecological functions of soil microorganisms. The stability and complexity of the root zone microbial co-occurrence network were significantly higher than those of bare soils. There was a distinct altitudinal gradient in the effect of P. parvifolia on soil microbial community characteristics. At an elevation of 3204 m, P. parvifolia promoted the accumulation of carbon, nitrogen, and phosphorus and increased sucrase activity and soil C/N while significantly improving the community richness index of fungi (p < .05) compared with that of bacteria and the relative abundance of Ascomycota. The alpha diversity of fungi in the root zone soil of P. parvifolia was also significantly increased at 3550 m altitude. Furthermore, the community similarity distance matrix of fungi showed an evident separation at 3204 m. However, at an altitude of 3750 m, P. parvifolia mainly affected the bacterial community. Potentilla parvifolia increased the bacterial community richness. This is in agreement with the findings based on the functional prediction that P. parvifolia favors the growth and enrichment of denitrifying communities at 3550 and 3750 m. The results provide a scientific basis for predicting the evolutionary trends of the effects of P. parvifolia on soil microbial communities and functions and have important implications for ecological governance in the QLMs.

Stoichiometric characteristics of woody plant leaves and responses to climate and soil factors in China

The main research content of the field of ecological stoichiometry is the energy of various chemical elements and the interaction between organisms and the environment throughout ecological processes. Nitrogen and phosphorus are the main elements required for the growth and development of plants and these also form the constituent basis of biological organisms. Both elements interact and jointly regulate the growth and development of plants, and their element ratios are an indication of the nutrient utilization rate and nutrient limitation status of plants. Previous research developed a general biogeography model of the stoichiometric relationship between nitrogen and phosphorus in plant leaves on a global scale. Further, it was shown that the relative rate of nitrogen uptake by leaves was lower than that of phosphorus, and the scaling exponent of nitrogen and phosphorus was 2/3. However, it is not clear how the stoichiometric values of nitrogen and phosphorus, especially their scaling exponents, change in the leaves of Chinese woody plants in response to changing environmental conditions. Therefore, data sets of leaf nitrogen and phosphorus concentrations, and nitrogen to phosphorus ratios in Chinese woody plants were compiled and classified according to different life forms. The overall average concentrations of nitrogen and phosphorus in leaves were 20.77 ± 8.12 mg g-1 and 1.58 ± 1.00 mg g-1, respectively. The contents of nitrogen and phosphorus in leaves of deciduous plants were significantly higher than those of evergreen plants. In leaves, life form is the main driving factor of nitrogen content, and mean annual temperature is the main driving factor of phosphorus content; soil available nitrogen is the main driving factor of the nitrogen to phosphorus ratio. These values can be used for comparison with other studies. In addition, the scale index was found to be significantly different among different life forms. The scaling exponents of N-P of woody plants of different life forms, such as trees, shrubs, evergreen, deciduous, and coniferous plants are 0.67, 0.72, 0.63, 0.72, and 0.66, respectively. The N-P scaling exponent of shrubs was higher than that of trees, and that of deciduous plants was higher than that of evergreen plants. These results suggest that the internal attributes of different life forms, the growth rate related to phosphorus, and the relative nutrient availability of soil are the reasons for the unsteady relationship between nitrogen and phosphorus in leaves.

Synergistic effects of succession and microtopography of moraine on the fungal spatial diversity in a glacier forefield

Primary succession and microtopography result in environmental changes and are important processes influencing the community assembly of soil fungi in the Arctic region. In glacier forefields that contain a series of moraine ridges, both processes contribute synchronously to fungal spatial diversity. To reveal the synergistic effects of succession and microtopography, we investigated the fungal community structure and environmental variables in the moraines of the Arklio Glacier, Ellesmere Island. The study sites were established at four locations from the top to the bottom of the ridge slope within each of the three moraine ridges of different post-glacial ages. The location-dependent community composition was equally diverse in both the initial and later stages of succession, suggesting that successional time could alter the effects of microtopography on the fungal community. Moreover, our results suggest that fungal communities at different locations follow different successional trajectories, even if they have passed through the same time lapse. Such a synergistic effect of succession and microtopography of moraines does not allow for parallel changes in fungal communities among moraines or among locations, suggesting that the moraine series contributes substantially to fungal spatial diversity in the glacier forefield.

Soil bacterial community structure in the habitats with different levels of heavy metal pollution at an abandoned polymetallic mine

Heavy metal pollution caused by mining activities can be harmful to soil microbiota, which are highly sensitive to heavy metal stress. This study aimed to investigate the response of soil bacterial communities to varying levels of heavy metal pollution in four types of habitats (i.e., tailing, remediation, natural recovery, and undisturbed areas) at an abandoned polymetallic mine by high-throughput 16 S rRNA gene sequencing, and to determine the dominant ecological processes and major factors driving the variations in bacterial community composition. The diversity and composition of bacterial communities varied significantly between soil habitats (p < 0.05). Heterogeneous selection played a crucial role in shaping the difference of bacterial community composition between distinct soil habitats. Redundancy analysis and Pearson correlation analysis revealed that the total contents of Cu and Zn were key factors causing the difference in bacterial community composition in the tailing and remediation areas, whereas bioavailable Mn and Cd, total nitrogen, available nitrogen, soil organic carbon, vegetation coverage, and plant diversity were key factors shaping the soil bacterial structure in the undisturbed and natural recovery areas. These findings provide insights into the distribution patterns of bacterial communities in soil habitats with different levels of heavy metal pollution, and the dominant ecological processes and the corresponding environmental drivers, and expand knowledge in bacterial assembly mechanisms in mining regions.

The current state of forest ecosystems in the Khosta Yew-Boxwood Grove

In this study, we aimed to assess the current state of forest ecosystems on the Black Sea coast of the Caucasus after the mass mortality of boxwoods. Soil and geobotanical studies were carried out in the Khosta Yew-Boxwood Grove, a convenient proving ground for assessment of the consequences of Cydalima perspectalis expansion. Hierarchical cluster analysis (nearest-neighbour and Euclidean distance methods), One-way ANOVA, and correlation analysis (Euclidean distance matrices for standardised data) were applied to process the soil and vegetation data. An increase in the illumination of the lower forest tiers due to the Buxus colchica destruction resulted in an intensive growth of vegetation cover and the formation of a soddy horizon in soils. These processes contributed to the accumulation of organic matter and high biological activity of the soils. The number of Buxus colchica seedlings was negatively correlated with the vegetation coverage and the number of grass and shrub species, as well as with some biological parameters of the soils. The most intensive seed regeneration of Buxus colchica was observed in forest plots with high crown density in the upper tier, undeveloped vegetation cover, and soddy soil horizon.

Soil properties rather than plant diversity mediate the response of soil bacterial community to N and P additions in an alpine meadow

The alpine meadow on the Qinghai-Tibetan Plateau, which is susceptible to global climate change and human activities, is subject to nutrient addition such as nitrogen (N) and phosphorus (P) to enhance soil available nutrients and ecosystem productivity. Soil bacterial community partly drivers the effects of nutrient additions on ecosystem processes, whereas the factors influencing N and P additions on bacterial community in alpine meadows are not well documented. We conducted a N and P addition experiment in an alpine meadow ecosystem on the Qinghai-Tibetan Plateau with four treatments: untreated control (CK), N addition (N), P addition (P), and NP addition (NP). We employed a high-throughput Illumina Miseq sequencing technology to investigate the response of soil bacterial community to short-term N and P additions. N and P additions decreased soil bacterial richness (OTU numbers and Chao 1 index), and P addition decreased soil bacterial diversity (Shannon and Simpson indices). N addition directly induced the change of soil NH4+−N, and decreased plant diversity. The N and P additions reduced soil bacterial community diversity, whose response was independent with plant diversity. Additionally, nutrient additions altered soil bacterial community composition, which were highly correlated with soil properties (i.e. pH, NH4+−N, and TP) as shown by RDA. Consistently, structural equation modeling results revealed that N addition indirectly acted on soil bacterial community through altering soil available nutrients and pH, while P addition indirectly affected bacterial community by increasing soil P availability. These findings imply that more attention should be paid to soil properties in regulating belowground biodiversity process in alpine meadows under future environmental change scenario.

Change in composition and potential functional genes of microbial communities on carbonatite rinds with different weathering times

Organisms and time are important factors for rock weathering to form soils. However, weathering time is usually difficult to quantitatively study, and the potential microorganisms involved in rock weathering are difficult to identify qualitatively. Currently, there is no clear conclusion on how ecological strategies of carbonatite weathering rind microorganisms change with weathering time, and how the microbial composition and functional genes involved in element cycling change over two century-scale weathering time. In this study, we selected abandoned carbonate tombstones as the subject and used the date when the tombstones were erected by humans as the onset of weathering. Using metagenome sequencing methods, we investigated the trends in the composition of fungal, bacterial and archaeal communities of carbonate weathering rind and related elemental cycle functional genes during a weathering time of 19 to 213 years. The results showed that: (1) with the increase in weathering time, at the phylum level, microbial taxa gradually shifted from r-strategists (faster turnover rates, higher mortality rates, higher reproduction, lower competition rate) to K-strategists (slower turnover rates, lower mortality rates, lower reproduction, higher competition rate), which correspondingly increased the abundance of functional genes related to C and N cycles. (2) The properties of the parent rock layer determines the colonization and distribution of weathering rind microorganisms (especially prokaryotic microorganisms) and the corresponding functional gene abundance. Our study provides new insights into the weathering process of carbonate rocks.

Ultra-light photosensor collars to monitor Arctic lemming activity

Background

Studying the anti-predatory behavior of mammals represents an important challenge, especially for fossorial small mammals that hide in burrows. In the Arctic, such behaviors are critical to the survival of lemmings considering that predation risks are high every summer. Because detailed information about how lemmings use burrows as hideouts is still lacking, we developed a 1.59 g photosensitive collar to record any event of a small mammal moving between a dark area (e.g., burrow) and a bright area (e.g., outside the burrow). Tests of how collars affected lemming behavior were conducted in captivity in Cambridge Bay, Nunavut, Canada, in November 2019 and field tests were conducted on Bylot Island, Nunavut, Canada, in August 2021.

Results

The device was made of two chemical batteries and a printed circuit board (PCB) equipped with a photosensor and a real-time clock that recorded amplitude transient thresholds of light (lux) continuously. In accordance with ethical use of such devices, we verified that no abnormal loss of body mass was observed in captive or free-ranging lemmings, and no difference in recapture rates were observed between those with and without a collar, though we could not test this for periods longer than 108 h. Measurements of light intensities revealed consistent patterns with high lux levels at mid-day and lowest during the night. Lemmings showed clearly defined behavioral patterns alternating between periods outside and inside burrows. Despite 24-h daylight in the middle of the summer, August nighttime (i.e., 11 PM to 4 AM) lux levels were insufficient for amplitude transient thresholds to be reached.

Conclusion

By taking advantage of the long periods of daylight in the Arctic, such technology is very promising as it sets new bases for passive recording of behavioral parameters and builds on the prospect of further miniaturization of batteries and PCBs.

The below-ground carbon and nitrogen cycling patterns of different mycorrhizal forests on the eastern Qinghai-Tibetan Plateau

Mycorrhizal fungi can form symbiotic associations with tree species, which not only play an important role in plant survival and growth, but also in soil carbon (C) and nitrogen (N) cycling. However, the understanding of differences in soil C and N cycling patterns among forests with different mycorrhizal types is still incomplete. In order to determine the similarities and differences of soil C and N cycling patterns in different mycorrhizal forest types, three primary forests dominated by ectomycorrhizal (EcM), arbuscular mycorrhizal (AM) and ericoid mycorrhizal (ErM) trees respectively were studied on the eastern Qinghai-Tibetan Plateau. Indicators associated with soil C and N cycling, including leaf litter quality, soil C and N contents, soil C and N fluxes, and soil microbial biomass C and N contents were measured in each mycorrhizal type forest. The results showed that leaf litter quality was significantly lower with high C:N ratio and lignin: N ratio in ErM forest than that in AM and EcM forests. Soil CO₂ flux (508.25 ± 65.51 mg m^-2 h^-1) in AM forest was significantly higher than that in EcM forest (387.18 ± 56.19 mg m^-2 h^-1) and ErM forest (177.87 ± 58.40 mg m^-2 h^-1). Furthermore, soil inorganic N content was higher in the AM forest than that in EcM and ErM forests. Soil net N mineralization rate (-0.02 ± 0.03 mg kg^-1 d^-1) was lower in ErM forest than that in EcM and AM forests. We speculated that AM and EcM forests were relatively characterized by rapid soil C cycling comparing to ErM forest. The soil N cycling in EcM and ErM forests were lower, implying they were 'organic' N nutrition patterns, and the pattern in ErM forest was more obvious.

Nitrogen fertilisation disrupts the temporal dynamics of arbuscular mycorrhizal fungal hyphae but not spore density and community composition in a wheat field

Elucidating the temporal dynamics of arbuscular mycorrhizal (AM) fungi is critical for understanding their functions. Furthermore, research investigating the temporal dynamics of AM fungi in response to agricultural practices remains in its infancy. We investigated the effect of nitrogen fertilisation and watering reduction on the temporal dynamics of AM fungi, across the lifespan of wheat. Nitrogen fertilisation decreased AM fungal spore density (SD), extraradical hyphal density (ERHD), and intraradical colonisation rate (IRCR) in both watering conditions. Nitrogen fertilisation affected AM fungal community composition in soil but not in roots, regardless of watering conditions. The temporal analysis revealed that AM fungal ERHD and IRCR were higher under conventional watering and lower under reduced watering in March than in other growth stages at low (≤ 70 kg N ha^-1  yr^-1 ) but not at high (≥ 140) nitrogen fertilisation levels. AM fungal SD was lower in June than in other growth stages and community composition varied with plant development at all nitrogen fertilisation levels, regardless of watering conditions. This study demonstrates that high nitrogen fertilisation levels disrupt the temporal dynamics of AM fungal hyphal growth but not sporulation and community composition.

Grazing influences biomass production and protein content of alpine meadows

Alpine grasslands are essential for carbon sequestration and food supply for domestic and wild herbivores inhabiting mountainous areas worldwide. These biomes, however, are alternatively threatened by the abandonment of agricultural and livestock practices leading to a fast-growing shrubification process while other mountain grasslands are suffering from the impacts of overgrazing. The functioning of alpine meadow ecosystems is primarily driven by climatic conditions, land-use legacies and grazing. However, although it is critically important, the role of large herbivores on the aboveground biomass and protein content of palatable plants is poorly understood for most alpine meadows. In this work, we explore the effects of grazing on grassland vegetation at two different spatial and temporal scales in the Eastern Pyrenees, Spain. Remote sensing was used to assess the effect of high and moderate grazing (HG and MG respectively) on grass biomass using the leaf area index (LAI) at the meso-scale (patches between 2.3 and 38.7 ha). We also explored the impact of null (NG), overgrazing (MO, mimicked overgrazing) and high (HG) grazing intensities at local scale setting eighteen 1 m² exclusion boxes in six meadows (three boxes each) commonly used by domestic and wild ungulates. Historical satellite data showed that LAI values are greater in high than in low grazed areas (HG, mean = 0.66, LG, mean = 0.55). Along the same lines, high and moderate grazing pressures improved biomass production at the local-scale (HG, mean = 590.3 g/m², MO, mean = 389.3 g/m² and NG, mean = 110.8 g/m²). Crude protein content reached higher values under MO pressure than under HG pressure. Our results confirm that grazing intensity exerts significant changes on the above-ground biomass production and the protein content of plants consumed by domestic (cattle and horses) and wild ungulates (Southern Chamois, Rupicapra pyrenaica). We can conclude that ungulates sustain biomass and nutritive values of grass exerting a negligible effect on biomass and protein content of woody vegetation. Our results will inform management guidelines to support profitable grazing activities and promote conservation of the open landscapes in the alpine ecosystems under the current global change scenario.

Changes in soil total, microbial and enzymatic C-N-P contents and stoichiometry with depth and latitude in forest ecosystems

Soil microorganisms and their extracellular enzymes are key factors determining the biogeochemical cycles of carbon (C), nitrogen (N) and phosphorus (P). Relevant studies mainly focus on surface soils (0-20 cm), while deep soils (>20 cm) are often neglected, let alone comparing multiple ecosystems simultaneously. In this study, we studied the latitudinal (19-48°N) and vertical (0-100 cm) patterns of soil total, microbial and enzymatic C-N-P contents and ratios (stoichiometry) in eight temperate, subtropical and tropical forest ecosystems in eastern China. We found that the C-N-P contents and their stoichiometry in soil, microbial biomass and extracellular enzymes all varied significantly with depth and latitude. Soil total C, N and P declined with depth, as did microbial biomass and enzyme activity, while microbial and enzymatic C:N ratios showed increasing or no trend with increasing soil depth. Moreover, soil total and microbial C-N-P contents in surface soils (0-20 cm) showed positive correlations with increasing latitude, and such correlations tended to be weaker or disappeared in deep soils (>20 cm). Overall, changes in total, microbial and enzymatic C-N-P contents and ratios among latitudes suggested a shift from relative N limitation in the north to relative P limitation in the south.

Effects of vegetation on soil cyanobacterial communities through time and space

Photoautotrophic soil cyanobacteria play essential ecological roles and are known to exhibit large changes in their diversity and abundance throughout early succession. However, much less is known about how and why soil cyanobacterial communities change as soil develops over centuries and millennia, and the effects that vegetation have on such communities. We combined an extensive field survey, including 16 global soil chronosequences across contrasting ecosystems (from deserts to tropical forests), with molecular analyses to investigate how the diversity and abundance of photosynthetic and nonphotosynthetic soil cyanobacteria are affected by vegetation change during soil development, over time periods from hundreds to thousands of years. We show that, in most chronosequences, the abundance, species richness and community composition of soil cyanobacteria are relatively stable as soil develops (from centuries to millennia). Regardless of soil age, forest chronosequences were consistently dominated by nonphotosynthetic cyanobacteria (Vampirovibrionia), while grasslands and shrublands were dominated by photosynthetic cyanobacteria. Chronosequences undergoing drastic vegetation shifts (e.g. transitions from grasslands to forests) experienced significant changes in the composition of soil cyanobacterial communities. Our results advance our understanding of the ecology of cyanobacterial classes, and of the understudied nonphotosynthetic cyanobacteria in particular, and highlight the key role of vegetation as a major driver of their temporal dynamics as soil develops.

Effect of Simulated Combined N and P on Soil Acidity within Soil Aggregates in Natural and Planted Korean Pine Forest in Northeast China

Globally, atmospheric nitrogen (N) deposition is rising, adversely impacting soil health, i.e., increasing soil acidity. While phosphorus (P) is the limiting element in the temperate environment and plays a key role in making the ecosystem more vulnerable to N-derived acidification. The impact of elevated N and P inputs on soil acidity and exchangeable base cations have been extensively studied; however, few studies have focused on these parameters, especially within various soil aggregate fractions in the temperate forest. In 2017, a field experiment was conducted under N and P additions with four soil aggregate fractions (>5 mm, 2–5 mm, 0.25–2 mm, and <0.25 mm) in two forests, i.e., the broad leave Korean pine forest (BKPF) and Korean pine plantation (KPP) in the Liangshui National Natural Reserves in Northeast China. Results showed that high NP addition decreases pH, base cations, Mg2+ Ca2+, and BS% and increases in Fe3+, Al3+, and E.A (effective acidity) in all four aggregate fractions, in descending order; overall concentration of the base cations is ranked as BKPF > KPP. Thus, soil acidification is primarily caused by a decrease in base cations, such as Ca2+ and Mg2+, and increase in exchangeable Fe3+ and Al3+ ions in large macro-aggregates and macro-aggregates, which leads to the depletion of soil nutrients. The initial pH value (5.69) in >5 mm soil aggregate was decreased to (5.4) under high fertilizer application, while a minimum value of 5.36 was observed in 0.25–2 mm aggregates under high fertilizer application. The same trend was observed in all aggregates because of decrease in base cations, which, in turn, affects the vitality and health of the forests.

Seasonal taxonomic composition of microbial communal shaping the bioaerosols milieu of the urban city of Lanzhou

Here, the taxonomical composition and seasonal dynamics of airborne microbial communities were described in the urban city of Lanzhou, Northwest China. Year-long samples were studied in two filter membranes (Quartz and PTFE). Higher microbial loads were reported in the PTFE than in the quartz filter. Onefold decrease was reported in bacterial loads in spring and summer than winter and autumn for both filters. The fungal loadings were lowest during winter and highest during autumn, followed by summer. The microbial communities included Actinobacteria and Proteobacteria, Ascomycota, and Basidiomycota as major components. Maximum abundance of the members from Gammaproteobacteria, Coriobacteria and Clostridia were studied in all seasons on PTFE membrane, followed by, Erysipelotrichia, Negativicutes and Fusobacteria. Members of Actinobacteria and Bacilli showed higher abundance in spring and winter, with a small proportion during autumn. Members of Clostridia, Gammaproteobacteria, Bacilli, and Actinobacteria showed maximum abundance on the quartz filter in all the seasons. Similarly, on the PTFE, fungi including Dothideomycetes and Agaricomycetes were dominant, followed by Saccharomycetes during summer and winter. The result showed that PM_2.5, SO₄^2-, NO₂^-, Na⁺, EC, and OC are important environmental parameters influencing the seasonal microbial community. However, the relation of the microbiome with the environment cannot be confidently defined because the environmental factors are changeable and yet interrelated.

Unravelling the ecological complexity of soil viromes: Challenges and opportunities

Viruses are extremely abundant and ubiquitous in soil, and significantly contribute to various terrestrial ecosystem processes such as biogeochemical nutrient cycling, microbiome regulation and community assembly, and host evolutionary dynamics. Despite their numerous dominance and functional importance, understanding soil viral ecology is a formidable challenge, because of the technological challenges to characterize the abundance, diversity and community compositions of viruses, and their interactions with other organisms in the complex soil environment. Viruses may engage in a myriad of biological interactions within soil food webs across a broad range of spatiotemporal scales and are exposed to various biotic and abiotic disturbances. Current studies on the soil viromes, however, often describe the complexity of their tremendous diversity, but lack of exploring their potential ecological roles. In this article, we summarized the major methods to decipher the ecology of soil viruses, discussed biotic and abiotic factors and global change factors that shape the diversity and composition of soil viromes, and the ecological roles of soil viruses. We also proposed a new framework to understand the ecological complexity of viruses from micro to macro ecosystem scales and to predict and unravel their activities in terrestrial ecosystems.

Environmental Variables Including Heavy Metals Significantly Shape the Soil Bacterial Community Structure in the Tatun Volcano Group, Northern Taiwan

Recent studies suggested the presence of magma chambers from the Tatun volcano group under northern Taiwan's surface, the result of episodic volcanism for 0.2-2.8 million years. However, the microbial community in volcanic soil has not yet been characterized. Therefore, the present study investigated the spatial distribution of microbial communities and their relationships with environmental variables, including heavy metals. Next-generation sequencing was used to analyze the microbial community structures in three areas with different land uses: Lengshuikeng (recreational area), Zhuzihu (agricultural area), and Huangzuishan (conservation area). High contents of environmental factors, such as nitrogen (0.46-1.14%) and phosphorus (2.01-13.88 ppm), were detected. Large concentrations of heavy metals, such as copper (55.90-127.60 ppm) and zinc (36.13-147.73 ppm), were found among the three sites, whereas those of lead (83.13 ppm) and chromium (48.33 ppm) were higher in the Zhuzihu area. The most prevalent phylum across all sites was Proteobacteria, followed by Actinobacteria, Acidobacteria, and Chloroflexi, while the most abundant bacterial species was Koribacteraceae: NA_01, followed by Cyanobacteria: NA. A network ana-lysis showed that Koribacteracea: NA_01 positively correlated with bacterial groups, including Flavisolibacter sp., Oxalobacteraceae: NA, and Actinomycetales: NA_01. Based on Shannon and Simpson's diversity indices, the diversity of bacteria was significantly less in the Huangzuishan area than in the Lengshuikeng and Zhuzihu areas. Bacterial assemblages also significantly differed (P<0.05) among the three sites. The present results provide clear evidence to show that environmental variables, including heavy metals, are key factors affecting the bacterial community structure in volcanic soil.

Root traits as drivers of plant and ecosystem functioning: current understanding, pitfalls and future research needs

The effects of plants on the biosphere, atmosphere and geosphere are key determinants of terrestrial ecosystem functioning. However, despite substantial progress made regarding plant belowground components, we are still only beginning to explore the complex relationships between root traits and functions. Drawing on the literature in plant physiology, ecophysiology, ecology, agronomy and soil science, we reviewed 24 aspects of plant and ecosystem functioning and their relationships with a number of root system traits, including aspects of architecture, physiology, morphology, anatomy, chemistry, biomechanics and biotic interactions. Based on this assessment, we critically evaluated the current strengths and gaps in our knowledge, and identify future research challenges in the field of root ecology. Most importantly, we found that belowground traits with the broadest importance in plant and ecosystem functioning are not those most commonly measured. Also, the estimation of trait relative importance for functioning requires us to consider a more comprehensive range of functionally relevant traits from a diverse range of species, across environments and over time series. We also advocate that establishing causal hierarchical links among root traits will provide a hypothesis-based framework to identify the most parsimonious sets of traits with the strongest links on functions, and to link genotypes to plant and ecosystem functioning.

Shrub expansion modulates belowground impacts of changing snow conditions in alpine grasslands

Climate change is disproportionately impacting mountain ecosystems, leading to large reductions in winter snow cover, earlier spring snowmelt and widespread shrub expansion into alpine grasslands. Yet, the combined effects of shrub expansion and changing snow conditions on abiotic and biotic soil properties remains poorly understood. We used complementary field experiments to show that reduced snow cover and earlier snowmelt have effects on soil microbial communities and functioning that persist into summer. However, ericaceous shrub expansion modulates a number of these impacts and has stronger belowground effects than changing snow conditions. Ericaceous shrub expansion did not alter snow depth or snowmelt timing but did increase the abundance of ericoid mycorrhizal fungi and oligotrophic bacteria, which was linked to decreased soil respiration and nitrogen availability. Our findings suggest that changing winter snow conditions have cross-seasonal impacts on soil properties, but shifts in vegetation can modulate belowground effects of future alpine climate change.

Camera traps reveal interspecific differences in the diel and seasonal patterns of cicada nymph predation

Cicadas, a group of large-bodied insects, are preyed upon at both nymphal and adult stages by diverse range of vertebrates such as birds and mammals. Although the behavior of predators toward adult cicadas is well documented, there is a lack of research on the predation on cicada nymphs. In this study, camera traps deployed in conifer plantations, in which high population densities of cicadas Lyristes bihamatus emerge, were used to evaluate the seasonal and diel patterns of predation upon cicada nymphs by three predator species, namely brown bears, red foxes, and jungle crows, from May to September in 2018 and 2019 in northern Japan. Among all three species, cicada nymph predation occurred until early August when the final instar nymphs fully emerged. Bears were observed to constantly dig for cicada nymphs until early August, whereas foxes and crows were frequently observed foraging from late July to early August, during the season of L. bihamatus emergence. In contract to the powerful digging ability of bears, which facilitates efficient predation upon subterranean cicada nymphs, it is generally difficult for foxes and crows with limited or no digging ability to gain access these nymphs until the period of emergence. Cicada nymph predation by bears and crows was observed primarily during the daytime, despite the typical crepuscular/nocturnal emergence schedules of these insects. Contrastingly, the predatory activities of foxes tended to be nocturnal during the period prior to the beginning of cicada emergence, although subsequently became diurnal during the cicada emergence period. These observations indicate that the temporal activity patterns of cicada nymph predators are determined by interspecific differences in predation abilities and cicada emergence schedules. Accordingly, the findings of this study provide evidence to indicate that the timing and duration of trophic interactions between above- and belowground communities might vary among predator species, depending on their predation abilities.

Seasonal Variation in Fungal Community Composition Associated with Tamarix chinensis Roots in the Coastal Saline Soil of Bohai Bay, China

Coastal salinity typically alters the soil microbial communities, which subsequently affect the biogeochemical cycle of nutrients in the soil. The seasonal variation of the soil fungal communities in the coastal area, closely associated with plant population, is poorly understood. This study provides an insight into the fungal community's variations from autumn to winter and spring to summer at a well-populated area of salt-tolerant Tamarix chinensis and beach. The richness and diversity of fungal community were higher in the spring season and lower in the winter season, as showed by high throughput sequencing of the 18S rRNA gene. Ascomycota was the predominant phylum reported in all samples across the region, and higher difference was reported at order level across the seasonal variations. The redundancy analysis suggested that the abundance and diversity of fungal communities in different seasons are mainly correlated to total organic carbon and total nitrogen. Additionally, the saprotrophic and pathotrophic fungi decreased while symbiotic fungi increased in the autumn season. This study provides a pattern of seasonal variation in fungal community composition that further broadens our limited understanding of how the density of the salt-tolerant T. chinensis population of the coastal saline soil could respond to their seasonal variations.

Endophytic fungus Phomopsis liquidambaris B3 induces rice resistance to RSRD caused by Fusarium proliferatum and promotes plant growth

BACKGROUND

Rice spikelet rot disease (RSRD) is an emerging disease that significantly reduces rice yield and quality. In this study, we evaluated the potential use of the broad-spectrum endophytic fungus Phomopsis liquidambaris B3 as a biocontrol agent against RSRD. We also compared the control effects of different treatments, including chemical fungicides and treatment with multiple strains and single strains in combination or individually, against RSRD. The objective of this study was to find an effective and environmentally friendly control strategy to reduce the occurrence of RSRD and improve the rice yield.

RESULTS

In pot experiments, the effect of B3 alone was better than that of fungicide or combined measures. The results showed that root colonization by B3 significantly reduced the incidence and disease index of RSRD by 41.0% and 53.8%, respectively. This was related to enhanced superoxide dismutase (SOD), peroxidase (POD), and polyphenol oxidase (PPO) activity, and to significantly upregulated expression levels of OsAOX, OsLOX, OsPAL, and OsPR10 in rice. Moreover, B3 improved the diversity of the bacterial community rather than the fungal community in the rice rhizosphere. It also led to a decrease in Fusarium proliferatum colonization and fumonisin content in the grain. Finally, root development was markedly promoted after B3 inoculation, and the yield improved by 48.60%. The result of field experiments showed that the incidence of RSRD and the fumonisin content were observably reduced in rice receiving B3, by 24.41% and 37.87%, respectively.

CONCLUSION

The endophytic fungus Phomopsis liquidambaris B3 may become an effective tool to relieve rice spikelet rot disease. © 2020 Society of Chemical Industry.

Diversity and Interactomics of Bacterial Communities Associated with Dominant Trees During Tropical Forest Recovery

Bacterial communities have been identified as functional key members in soil ecology. A deep relation with these communities maintains forest coverture. Trees harbor particular bacteriomes in the rhizosphere, endosphere, or phyllosphere, different from bulk-soil representatives. Moreover, the plant microbiome appears to be specific for the plant-hosting species, varies through season, and responsive to several environmental factors. This work reports the changes in bacterial communities associated with dominant pioneer trees [Tabebuia rosea and Handroanthus chrysanthus [(Bignoniaceae)] during tropical forest recovery chronosequence in the Mayan forest in Campeche, Mexico. Massive 16S sequencing approach leads to identifying phylotypes associated with rhizosphere, bulk-soil, or recovery stage. Lotka-Volterra interactome modeling suggests the presence of putative regulatory roles of some phylotypes over the rest of the community. Our results may indicate that bacterial communities associated with pioneer trees may establish more complex regulatory networks than those found in bulk-soil. Moreover, modeled regulatory networks predicted from rhizosphere samples resulted in a higher number of nodes and interactions than those found in the analysis of bulk-soil samples.

Habitat, Snow-Cover and Soil pH, Affect the Distribution and Diversity of Mortierellaceae Species and Their Associations to Bacteria

Mortierellaceae species are among the most frequent and globally distributed soil fungi. However, the factors shaping their diversity and distribution remain obscure. Several species have been reported to be associated to bacteria, but the kind and frequency of such associations were not addressed up to now. We hypothesized that such associations could be important for Mortierellaceae ecology. Therefore, our aim was to understand the driving factors responsible for the Mortierellaceae diversity, community composition and bacterial associations in alpine and subalpine habitats. For answering our question, we collected both snow-free and snow-covered soil at sampling sites from different habitats: bare alpine soil in a glacier forefield, alpine dwarf-willow habitats, and high-altitude Pinus cembra forests. The isolations were carried out by direct cultivation without any antibiotics to the isolation media. Altogether, we obtained 389 Mortierellaceae isolates representing 29 operational taxonomic units (OTUs). Many OTUs could be placed to the genera Mortierella sensu stricto, Dissophora, Entomortierella, Gamsiella, Linnemannia, and Podila, but others could not unambiguously be assigned to a genus. Our results demonstrate that both, the distribution as well as the diversity of the Mortierellaceae species, were significantly influenced by habitat, soil pH, and snow-cover. We noticed that >30% of our isolates were associated to a non-contaminant bacterium. The bacteria associated to our Mortierellaceae isolates belonged to seven different genera. Pseudomonas was the most frequently detected genus associated to the isolated Mortierellaceae species and it was found to be species-specific. Mortierellaceae–bacteria pairs, including those with Pseudomonas, were influenced by location, habitat, and snow-cover. The majority of the fungus–bacterium associations were potentially epihyphal, but we also detected potential endohyphal bacterial species belonging to Mycoavidus, Burkholderiaceae, and Paraburkholderia. Taken together, the non-random associations we detected suggest that fungus–bacterium associations are ecologically meaningful – an interesting path that needs to be investigated further.

Soil microbial community variation with time and soil depth in Eurasian Steppe (Inner Mongolia, China)

Purpose

Soil microorganisms play an indispensable role in the material and energy cycle of grassland ecosystems. The abundance of these organisms vary according to environmental factors, such as time of year and soil depth. There have been few studies on the transformation of soil microbial communities in degraded typical steppe according to these temporal and spatial changes. In this study, we analyze the community structure and diversity of soil bacteria and fungi, and the impact of these changing temporal and spatial factors upon the community structure.

Methods

From May to September 2018, we collected 90 soil samples from different depths (10, 20, and 30 cm) from the typical degraded steppe area of Xilingol. We carried out studies on soil physical and chemical properties and soil microbial diversity using high-throughput sequencing technology.

Results

We found that depth significantly affected abundance and diversity of bacteria and fungi. Bacteria and fungi diversity at 10 cm was higher than that at 20 cm and 30 cm. The abundance of Acidobacteria, Proteobacteria, Actinomycetes, Ascomycetes, and Basidiomycetes varies significantly with depth. In addition, soil pH increased significantly with increasing depth, while soil organic matter (SOM), available nitrogen (AN), volume water content of soil (VWC), and soil temperature (ST) decreased significantly with increasing depth. Finally, the depth, total organic carbon (TOC), and AN had a significant impact on the bacterial and fungal communities’ abundance (p < 0.05).

Conclusions

Spatial heterogeneity (in soil depth) is more significant than the time of year (month) in predicting changes in microbial community composition and soil properties. SOM, VWC, and the abundance of Proteobacteria and Actinomycetes positively correlate with soil depth, while pH and the abundance of Acidobacteria, Ascomycetes, and Basidiomycetes negatively correlate with soil depth. We speculate that SOM and VWC account for the variations in the abundance of Acidobacteria and Proteobacteria, while pH causes variations in the abundance of Actinomycetes, Ascomycetes and Basidiomycota.

Forage Species Identity Shapes Soil Biota in a Temperate Agroecosystem

Increasing plant diversity in the perennial phase of pasture-crop rotations is predicted to positively affect belowground productivity and microbial communities and, in turn, augment belowground agroecosystem services including soil health and carbon storage. Using two grass and one legume forage species grown as monocultures and combined in four intercropped combinations, we evaluated how species identity and richness influence belowground productivity, soil microbial communities, and soil C pools. Though grass-legume intercrops demonstrated higher aboveground productivity than component species grown in monoculture, higher species richness was not associated with increased productivity belowground. Root biomass was greatest in tall fescue (Festuca arundinacea Schreb.) monoculture, and intercrops including this species. Species identity was similarly associated with soil microbial community attributes. Orchardgrass (Dactylis glomerata L.) monoculture exhibited lower total microbial abundance and lower bacterial abundance than grass-legume intercrops. Bacterial abundance was also lower in orchardgrass compared to white clover (Trifolium repens L.) monoculture. A common indictor of soil function, the fungal:bacterial ratio, was higher in grass-only than clover-only stands. The prevalence of species-specific impacts on roots and microbial communities in this study suggests that species identity may have a stronger influence than species richness on belowground agroecosystem services from perennial forages in temperate regions.

Type of organic fertilizer rather than organic amendment per se increases abundance of soil biota

Addition of organic amendments is a commonly used practice to offset potential loss of soil organic matter from agricultural soils. The aim of the present study was to examine how long-term addition of organic matter affects the abundance of different soil biota across trophic levels and the role that the quality of the organic amendments plays. Here we used a 17-year-old fertilization experiment to investigate soil biota responses to four different organic fertilizers, compared with two mineral nitrogen fertilizers and no fertilization, where the organic fertilizers had similar carbon content but varied in their carbon to nitrogen ratios. We collected soil samples and measured a wide range of organisms belonging to different functional groups and trophic levels of the soil food web. Long-term addition of organic and mineral fertilizers had beneficial effects on the abundances of most soil organisms compared with unfertilized soil, but the responses differed between soil biota. The organic fertilizers generally enhanced bacteria and earthworms. Fungi and nematodes responded positively to certain mineral and organic fertilizers, indicating that multiple factors influenced by the fertilization may affect these heterogeneous groups. Springtails and mites were less affected by fertilization than the other groups, as they were present at relatively high abundances even in the unfertilized treatment. However, soil pH had a great influence on springtail abundance. In summary, the specific fertilizer was more important in determining the numerical and compositional responses of soil biota than whether it was mineral or organic. Overall, biennial organic amendments emerge as insufficient, by themselves, to promote soil organisms in the long run, and would need to be added annually or combined with other practices affecting soil quality, such as no or reduced tillage and other crop rotations, to have a beneficial effect.

Plant intraspecific competition and growth stage alter carbon and nitrogen mineralization in the rhizosphere

Plant roots interact with rhizosphere microorganisms to accelerate soil organic matter (SOM) mineralization for nutrient acquisition. Root-mediated changes in SOM mineralization largely depend on root-derived carbon (root-C) input and soil nutrient status. Hence, intraspecific competition over plant development and spatiotemporal variability in the root-C input and nutrients uptake may modify SOM mineralization. To investigate the effect of intraspecific competition on SOM mineralization at three growth stages (heading, flowering, and ripening), we grew maize (C4 plant) under three planting densities on a C3 soil and determined in situ soil C- and N-mineralization by ¹³ C-natural abundance and ¹⁵ N-pool dilution approaches. From heading to ripening, soil C- and N-mineralization rates exhibit similar unimodal trends and were tightly coupled. The C-to-N-mineralization ratio (0.6 to 2.6) increased with N availability, indicating that an increase in N-mineralization with N depletion was driven by microorganisms mining N-rich SOM. With the intraspecific competition, plants increased specific root lengths as an efficient strategy to compete for resources. Root morphologic traits rather than root biomass per se were positively related to C- and N-mineralization. Overall, plant phenology and intraspecific competition controlled the intensity and mechanisms of soil C- and N- mineralization by the adaptation of root traits and nutrient mining.

Evaluating long-term success in grassland restoration: an ecosystem multifunctionality approach

It is generally assumed that restoring biodiversity will enhance diversity and ecosystem functioning. However, to date, it has rarely been evaluated whether and how restoration efforts manage to rebuild biodiversity and multiple ecosystem functions (ecosystem multifunctionality) simultaneously. Here, we quantified how three restoration methods of increasing intervention intensity (harvest only < topsoil removal < topsoil removal + propagule addition) affected grassland ecosystem multifunctionality 22 yr after the restoration event. We compared restored with intensively managed and targeted seminatural grasslands based on 13 biotic and abiotic, above- and belowground properties. We found that all three restoration methods improved ecosystem multifunctionality compared to intensively managed grasslands and developed toward the targeted seminatural grasslands. However, whereas higher levels of intervention intensity reached ecosystem multifunctionality of targeted seminatural grasslands after 22 yr, lower intervention missed this target. Moreover, we found that topsoil removal with and without seed addition accelerated the recovery of biotic and aboveground properties, and we found no negative long-term effects on abiotic or belowground properties despite removing the top layer of the soil. We also evaluated which ecosystem properties were the best indicators for restoration success in terms of accuracy and cost efficiency. Overall, we demonstrated that low-cost measures explained relatively more variation of ecosystem multifunctionality compared to high-cost measures. Plant species richness was the most accurate individual property in describing ecosystem multifunctionality, as it accounted for 54% of ecosystem multifunctionality at only 4% of the costs of our comprehensive multifunctionality approach. Plant species richness is the property that typically is used in restoration monitoring by conservation agencies. Vegetation structure, soil carbon storage and water-holding capacity together explained 70% of ecosystem multifunctionality at only twice the costs (8%) of plant species richness, which is, in our opinion, worth considering in future restoration monitoring projects. Hence, our findings provide a guideline for land managers how they could obtain an accurate estimate of aboveground-belowground ecosystem multifunctionality and restoration success in a highly cost-efficient way.

Changes in Soil Features and Phytomass during Vegetation Succession in Sandy Areas

This research was conducted on an area of inland sands characterised by various degrees of overgrowth by vegetation and soil stabilisation. This landscape’s origin is not natural but is connected to human industrial activities dating from early medieval times, which created a powerful centre for mining and metallurgy. This study aims to identify the changes in the above- and belowground phytomass in the initial stages of succession and their influence on the chemical properties and morphology of the soil. It was found that Salix arenaria dominated in primary phytomass production in all plots tested. The amounts of this species found in each community were as follows: 8.55 kg/400 m2 (algae–mosses), 188.97 kg/400 m2 (sand grassland–willow), 123.44 kg/400 m2 (pine–willow–mosses), 14.63 kg/400 m2 (sand grassland–mosses–willow), and 196.55 kg/400 m2 (willow–pine–sand grassland). A notable share of Koeleria glauca was found in the phytomass production of Plots IV (45.73 kg) and V (86.16 kg). Basic soil properties (pH, Corg, Nt), available plant elements (P), and plant nutrients (Ca, Mg, K, P, Fe) beneath the dominant plant species were examined. Soil acidity (pH) varied greatly, ranging from acidic (pH = 3.2) to weakly acidic (pH = 6.3). The content of organic carbon (Corg) in individual plots beneath the dominant species in the humus horizon ranged from 0.28% to 1.42%. The maximum contents of organic carbon and total nitrogen were found in organic (O) and organic-humus (OA) horizons. The highest Pavail content was found in organic and organic-humus horizons, ranging from 10.41 to 65.23 mg/kg, and in mineral horizons under K. glauca (24.10 mg/kg) and Salix acutifola (25.11 mg/kg). The soil features and phytomass were varied differently across individual sites, representing different stages of succession.

Soil properties and root traits jointly shape fine-scale spatial patterns of bacterial community and metabolic functions within a Korean pine forest

Spatial heterogeneity of soil bacterial community depends on scales. The fine-scale spatial heterogeneity of bacterial community composition and functions remains unknown. We analyzed the main driving factors of fine-scale spatial patterns of soil bacterial community composition and carbon metabolic functions across a 30 m × 40 m plot within a Korean pine forest by combining Illumina 16S rRNA sequencing with Biolog Ecoplates based on 53 soil samples. Clear spatial patterns in bacterial community composition and metabolic functions were observed in the forest soil. The bacterial community composition and metabolic functions both showed distance-decay of similarity within a distance of meters. Structural equation model analysis revealed that environmental variables and geographic distance together explained 37.9% and 63.1% of community and metabolic functions, respectively. Among all environmental factors, soil organic carbon (SOC) and root biomass emerged as the most important drivers of the bacterial community structure. In contrast, soil pH explained the largest variance in metabolic functions. Root biomass explained the second-largest variance in soil bacterial community composition, but root traits made no difference in metabolic functions variance. These results allow us to better understand the mechanisms controlling belowground diversity and plant-microbe interactions in forest ecosystems.

Climate change alters temporal dynamics of alpine soil microbial functioning and biogeochemical cycling via earlier snowmelt

Soil microbial communities regulate global biogeochemical cycles and respond rapidly to changing environmental conditions. However, understanding how soil microbial communities respond to climate change, and how this influences biogeochemical cycles, remains a major challenge. This is especially pertinent in alpine regions where climate change is taking place at double the rate of the global average, with large reductions in snow cover and earlier spring snowmelt expected as a consequence. Here, we show that spring snowmelt triggers an abrupt transition in the composition of soil microbial communities of alpine grassland that is closely linked to shifts in soil microbial functioning and biogeochemical pools and fluxes. Further, by experimentally manipulating snow cover we show that this abrupt seasonal transition in wide-ranging microbial and biogeochemical soil properties is advanced by earlier snowmelt. Preceding winter conditions did not change the processes that take place during snowmelt. Our findings emphasise the importance of seasonal dynamics for soil microbial communities and the biogeochemical cycles that they regulate. Moreover, our findings suggest that earlier spring snowmelt due to climate change will have far reaching consequences for microbial communities and nutrient cycling in these globally widespread alpine ecosystems.