Implications of Soil Microbial Community Assembly for Ecosystem Restoration: Patterns, Process, and Potential

Legacy effects of an invasive legume more strongly impact bacterial than plant communities in a Mediterranean-type ecosystem

The impacts of invasive plants on ecosystem processes and functions may persist as "legacy effects" after their removal. Understanding these effects on native plant-soil interactions is critical for guiding ecological restoration efforts. This study examines the legacy effects of the invasive legume Acacia saligna (Labill.) H.L. Wendl. in South Africa's Cape Fynbos to evaluate restoration potential post-removal. We compared cleared, invaded, and uninvaded reference sites across three conservation areas, examining soil chemical properties, nitrogen (N) isotope signatures (as a proxy for the sources of N uptake by a native plant and A. saligna), and the diversity and composition of plant and soil bacterial communities. The effects of A. saligna removal was contingent on conservation area, though consistent patterns emerged for plant and bacterial diversity across sites. Recovery toward reference site levels were evident for soil organic carbon and potassium, but nitrate and available phosphorous only improved in one area. Invader removal was linked to higher soil pH in one area and higher phosphorus availability in two. Soil conditions in cleared sites influenced the nitrogen sources used by A. saligna, shifting towards soil-derived nitrogen, but did not influence those used by the native species assessed. While we observed signs of native plant community recovery after clearing, soil bacterial communities remained comparable to those in invaded sites. The lag in bacterial community recovery was linked to soil pH changes caused by A. saligna invasion. Our findings demonstrate that removing A. saligna can promote native vegetation recovery, though legacy effects may impede or delay the recovery of soil bacterial communities. The influence of these soil legacy effects may also depend on the management or invasion history of sites.

Grazing increases the complexity of networks and ecological stochastic processes of mycorrhizal fungi

Arbuscular mycorrhizal fungi (AMF) form extensive symbiotic relationships with plants, which are critical for plant-driven biogeochemical cycles and ecosystem functions. Grazing and mowing, which are common grassland utilization patterns globally, significantly alter plant community characteristics as well as soil nutrients and structure, thereby potentially influencing AMF communities. However, the effects of these grassland managements on AMF community structure and ecological processes remain unclear. Here, we investigated AMF communities in cattle grazing, sheep grazing, and mowing grasslands. We examined AMF community diversity, composition, assembly processes, and network interactions. Our results revealed distinct AMF compositions across different grassland managements. In cattle and sheep grazing grasslands, the AMF community assembly processes were determined by dispersal limitation and drift, with increased importance of stochasticity. Although AMF abundance did not alter by grassland managements, AMF diversity decreased under sheep grazing, associated with reduced pH levels compared to cattle grazing or mowing. AMF formed more complex (higher average degree and graph density) and integrated (lower modularity) networks in grazing grasslands than mowing grasslands. The AMF network in cattle grazing grasslands showed the highest stability, associated with a broader habitat niche, balanced interspecies competition, and higher soil AP and MBN. Meanwhile, some species with high adaptability to grazing became key nodes in the AMF network, such as Funneliformis. Our findings highlight significant AMF responses to grazing, including increased network complexity and ecological stochasticity, providing new insights into how grassland managements influence the composition and assembly patterns of soil symbiotic microbial communities.

Measuring and predicting disturbance resilience in ecosystems, with emphasis on fire: A review and meta-analysis

As disturbance regimes change in response to anthropogenic activities, ecosystem resilience is critically important to the persistence of biodiversity and ecological functions. However, resilience in literature is often treated as an abstract concept, with widely varying definitions. Achieving common and reliable resilience metrics that cross systems and contexts remains elusive. Here, we performed a systematic review and meta-analysis of studies that have performed ecological resilience quantification, aiming to identify factors that significantly promote resilience across systems, as well as indicators of resilience. Due to the recent emergence of costly megafires in many parts of the world, we additionally separately examined the subset of studies that focused on resilience to wildfire disturbance, specifically. For those studies that presented quantitative data on the strength of relationship between resilience and these variables, dispersal and connectivity as well as nutrients and chemistry emerged as significantly predictive of resilience, whereas animal communities and ecological functions were significant indicators of resilience. Meanwhile, other studies mapped or modeled resilience without testing the effects of individual variables; in these studies, resilience was bolstered by the presence of increased resources, increased habitat connectivity and diversity, and reduced disturbance severity. For fire studies, abiotic factors including light, moisture, and soil texture were significantly predictive of resilience, and the health of individual ecosystem components (such as tree survival) was significantly indicative of resilience. The power of meta-analysis in this arena remains limited due to few quantitative studies that test individual variables. Nevertheless, insights from the range of studies examined here are in alignment with resilience theory, which posits that resilience should be facilitated by reduced system change during disturbance, as well as by the removal of barriers to recovery. Our review therefore provides evidence to support management that lowers the severity of disturbance as well as restoration efforts that enhance resource availability and connectivity.

Effective cadmium immobilization in paddy soil by the interaction of sulfate reducing bacteria and manganese fertilizer

Manganese fertilizer (MnSO4) was widely applied to control the Cadmium (Cd) uptake by rice, but the overall process of microbial activities controlling Cd mobilization in paddy soil is poorly understood. This study investigated the stimulation effect of sulfate reducing bacteria (SRB) on Cd bioavailability with the input of different doses MnSO4 (0.5, 1.0, 2.0 g/kg) under the anaerobic paddy soil. The results show that the input of MnSO4 generated soil H+ release. However, the stimulation of SRB remarkedly increased soil pH and reduced the redox potential (Eh) by inhibiting the exchange of Mn2+ and H+, resulting in the available Cd decreased and the amorphous Fe/Mn Oxide-Cd increased significantly. In the co-existed SRB and 1.0 g/kg MnSO4, the available Cd decreased remarkedly by 40.18%, which was transformed to reducible Cd. Meanwhile, the addition of MnSO4 and SRB enhanced the abundance of Cd immobilization related bacteria, including Desulfobacterota, Chloroflexi, Bacteroidota, and Myxococcota. KEGG results showed that MnSO4 and SRB treatment enhanced the ability of microbial sulfur and secondary metabolites. Furthermore, the sulfate reduction related genes (i.e. aprA, sat) obviously enriched in soils. Structural equation modeling showed that Mn, Fe, DOC, Eh, and pH are the key factors affecting available Cd. These findings add to the current knowledge of how MnSO4 and microorganisms affect the mobilization and availability of Cd under paddy soil media, providing new ideas and a theoretical basis for reducing the environmental risk of Cd.

Bioremediation Potential of Rhodococcus qingshengii PM1 in Sodium Selenite-Contaminated Soil and Its Impact on Microbial Community Assembly

Soil microbial communities are particularly sensitive to selenium contamination, which has seriously affected the stability of soil ecological environment and function. In this study, we applied high-throughput 16S rRNA gene sequencing to examine the effects of low and high doses of sodium selenite and the selenite-degrading bacterium, Rhodococcus qingshengii PM1, on soil bacterial community composition, diversity, and assembly processes under controlled laboratory conditions. Our results indicated that sodium selenite and strain PM1 were key predictors of bacterial community structure in selenium-contaminated soils. Exposure to sodium selenite initially led to reductions in microbial diversity and a shift in dominant bacterial groups, particularly an increase in Actinobacteria and a decrease in Acidobacteria. Sodium selenite significantly reduced microbial diversity and simplified co-occurrence networks, whereas inoculation with strain PM1 partially reversed these effects by enhancing community complexity. Ecological modeling, including the normalized stochasticity ratio (NST) and Sloan's neutral community model (NCM), suggested that stochastic processes predominated in the assembly of bacterial communities under selenium stress. Null model analysis further revealed that heterogeneous selection and drift were primary drivers of community turnover, with PM1 inoculation promoting species dispersal and buffering against the negative impacts of selenium. These findings shed light on microbial community assembly mechanisms under selenium contamination and highlight the potential of strain PM1 for the bioremediation of selenium-affected soils.

Influence of Drugs and Toxins on Decomposition Dynamics: Forensic Implications

Drug and toxin-related deaths are common worldwide, making it essential to detect the postmortem concentration of various toxic substances at different stages of decomposition in a corpse. Indeed, determining the postmortem interval (PMI) and cause of death in an advanced stage of decomposed corpses has been a significant challenge in forensic investigations. Notably, the presence of drugs or toxins can have a significant impact on the microbial profile, potentially altering the succession of microbial communities and subsequent production of volatile organic compounds (VOCs), which, in turn, affect insect colonization patterns. This review aims to highlight the importance of investigating the interactions between drugs or toxins, microbial succession, VOC profiles, and insect behavior, which can provide valuable insights into forensic investigations as well as the ecological consequences of toxins occurring in decomposition. Overall, the detection of drugs and other toxins at different stages of decomposition can yield more precise forensic evidence, thereby enhancing the accuracy of PMI estimation and determination of the cause of death in decomposed remains.

Response of soil microbial community structure to temperature and nitrogen fertilizer in three different provenances of Pennisetum alopecuroides

Soil microorganisms are key indicators of soil health, and it is crucial to investigate the structure and interactions of soil microbial communities among three different provenances of Pennisetum alopecuroides under varying nitrogen fertilizer and temperature levels in Northwest China. This study aims to provide theoretical support for the sustainable use of artificial grassland in this region. Employing a two-factor pot-control experiment with three nitrogen fertilizer treatments and three temperature treatments, a total of all treatments was utilized to examine the composition and abundance of soil microbial communities associated with Pennisetum alopecuroides using high-throughput sequencing, PCR technology, and molecular ecological network analysis. The results revealed that Proteobacteria was the dominant bacterial phylum while Ascomycota was the dominant fungal phylum in the soil samples from three provenances of Pennisetum. Specifically, Proteobacteria exhibited higher abundance in the N3T2 treatment compared to other treatments under N3T2 (25-30°C, 3 g/pot) treatment conditions in Shaanxi and Gansu provinces; similarly, Proteobacteria was more abundant in the N1T2 (25-30°C, 1 g/pot) treatment in Inner Mongolia under N1T2. Moreover, Ascomycota displayed higher abundance than other treatments in both Inner Mongolia and Gansu provinces. Additionally, Pennisetum Ascomycota demonstrated greater prevalence under (25-30°C, 3 g/pot) treatment compared to other treatments; furthermore, Shaanxi's Pennisetum Ascomycota exhibited increased prevalence under N3T1 (18-23°C, 3 g/pot) treatment compared to other treatments. The richness and diversity of soil microbial communities were significantly influenced by nitrogen fertilizer and temperature changes, leading to notable alterations in their structure. Molecular ecological network analyses revealed strong collaborative relationships among microbial species in Shaanxi Pennisetum and Inner Mongolia Pennisetum under high nitrogen and high temperature treatments, while competitive relationships were observed among microbial species in Gansu Pennisetum under similar conditions. Redundancy analysis indicated that soil pH, total potassium, and total phosphorus were the primary environmental factors influencing microorganisms. In summary, this study offers a theoretical foundation for assessing the sustainable utilization of Pennisetum artificial grasslands in Northwest China by investigating the shifts in soil microbial communities and the driving factors under varying nitrogen fertilizer and temperature levels.

Nutrient limitation mediates soil microbial community structure and stability in forest restoration

Soil microorganisms are often limited by nutrients, representing an important control of heterotrophic metabolic processes. However, how nutrient limitations relate to microbial community structure and stability remains unclear, which creates a knowledge gap to understanding microbial biogeography and community changes during forest restoration. Here, we combined an eco-enzymatic stoichiometry model and high-throughput DNA sequencing to assess the potential roles of nutrient limitation on microbial community structure, assembly, and stability along a forest restoration sequence in the Qinling Mountains, China. Results showed that nutrient limitations tended to decrease during the oak forest restoration. Carbon and phosphorus limitations enhanced community dissimilarity and significantly increased bacterial alpha diversity, but not fungal diversity. Stochastic assembly processes primarily structured both bacterial (average contribution of 74.73 % and 74.17 % in bulk and rhizosheath soils, respectively) and fungal (average contribution of 77.23 % and 72.04 % in bulk and rhizosheath soils, respectively) communities during forest restoration, with nutrient limitation also contributing to the importance of stochastic processes in the bacterial communities. The migration rate (m) for bacteria was 0.19 and 0.23, respectively in both bulk soil and rhizosheath soil, and was greater than that for the fungi (m was 1.19 and 1.41, respectively), indicating a stronger dispersal limitation for fungal communities. Finally, nutrient limitations significantly affected bacterial and fungal co-occurrence with more interconnections occurring among weakly nutrient-limited microbial taxa and nutrient limitations reducing community stability when nutrient availability changed during forest restoration. Our findings highlight the fundamental effects of nutrient limitations on microbial communities and their self-regulation under changing environmental resources.

Fertilization regime changes rhizosphere microbial community assembly and interaction in Phoebe bournei plantations

Fertilizer input is one of the effective forest management practices, which improves soil nutrients and microbial community compositions and promotes forest productivity. However, few studies have explored the response of rhizosphere soil microbial communities to various fertilization regimes across seasonal dynamics. Here, we collected the rhizosphere soil samples from Phoebe bournei plantations to investigate the response of community assemblages and microbial interactions of the soil microbiome to the short-term application of four typical fertilizer practices (including chemical fertilizer (CF), organic fertilizer (OF), compound microbial fertilizer (CMF), and no fertilizer control (CK)). The amendments of organic fertilizer and compound microbial fertilizer altered the composition of rhizosphere soil bacterial and fungal communities, respectively. The fertilization regime significantly affected bacterial diversity rather than fungal diversity, and rhizosphere fungi responded more sensitively than bacteria to season. Fertilization-induced fungal networks were more complex than bacterial networks. Stochastic processes governed both rhizosphere soil bacterial and fungal communities, and drift and dispersal limitation dominated soil fungal and bacterial communities, respectively. Collectively, these findings demonstrate contrasting responses to community assemblages and interactions of rhizosphere bacteria and fungi to fertilizer practices. The application of organic fertilization strengthens microbial interactions and changes the succession of key taxa in the rhizosphere habitat. KEY POINTS: • Fertilization altered the key taxa and microbial interaction • Organic fertilizer facilitated the turnover of rhizosphere microbial communities • Stochasticity governed soil fungal and bacterial community assembly.

Prairie restoration promotes the abundance and diversity of mutualistic arbuscular mycorrhizal fungi

Predicting how biological communities assemble in restored ecosystems can assist in conservation efforts, but most research has focused on plants, with relatively little attention paid to soil microbial organisms that plants interact with. Arbuscular mycorrhizal (AM) fungi are an ecologically significant functional group of soil microbes that form mutualistic symbioses with plants and could therefore respond positively to plant community restoration. To evaluate the effects of plant community restoration on AM fungi, we compared AM fungal abundance, species richness, and community composition of five annually cultivated, conventionally managed agricultural fields with paired adjacent retired agricultural fields that had undergone prairie restoration 5-9 years prior to sampling. We hypothesized that restoration stimulates AM fungal abundance and species richness, particularly for disturbance-sensitive taxa, and that gains of new taxa would not displace AM fungal species present prior to restoration due to legacy effects. AM fungal abundance was quantified by measuring soil spore density and root colonization. AM fungal species richness and community composition were determined in soils and plant roots using DNA high-throughput sequencing. Soil spore density was 2.3 times higher in restored prairies compared to agricultural fields, but AM fungal root colonization did not differ between land use types. AM fungal species richness was 2.7 and 1.4 times higher in restored prairies versus agricultural fields for soil and roots, respectively. The abundance of Glomeraceae, a disturbance-tolerant family, decreased by 25% from agricultural to restored prairie soils but did not differ in plant roots. The abundance of Claroideoglomeraceae and Diversisporaceae, both disturbance-sensitive families, was 4.6 and 3.2 times higher in restored prairie versus agricultural soils, respectively. Species turnover was higher than expected relative to a null model, indicating that AM fungal species were gained by replacement. Our findings demonstrate that restoration can promote a relatively rapid increase in the abundance and diversity of soil microbial communities that had been degraded by decades of intensive land use, and community compositional change can be predicted by the disturbance tolerance of soil microbial taxonomic and functional groups.

Genomic fingerprints of the world's soil ecosystems

Despite the explosion of soil metagenomic data, we lack a synthesized understanding of patterns in the distribution and functions of soil microorganisms. These patterns are critical to predictions of soil microbiome responses to climate change and resulting feedbacks that regulate greenhouse gas release from soils. To address this gap, we assay 1,512 manually curated soil metagenomes using complementary annotation databases, read-based taxonomy, and machine learning to extract multidimensional genomic fingerprints of global soil microbiomes. Our objective is to uncover novel biogeographical patterns of soil microbiomes across environmental factors and ecological biomes with high molecular resolution. We reveal shifts in the potential for (i) microbial nutrient acquisition across pH gradients; (ii) stress-, transport-, and redox-based processes across changes in soil bulk density; and (iii) greenhouse gas emissions across biomes. We also use an unsupervised approach to reveal a collection of soils with distinct genomic signatures, characterized by coordinated changes in soil organic carbon, nitrogen, and cation exchange capacity and in bulk density and clay content that may ultimately reflect soil environments with high microbial activity. Genomic fingerprints for these soils highlight the importance of resource scavenging, plant-microbe interactions, fungi, and heterotrophic metabolisms. Across all analyses, we observed phylogenetic coherence in soil microbiomes-more closely related microorganisms tended to move congruently in response to soil factors. Collectively, the genomic fingerprints uncovered here present a basis for global patterns in the microbial mechanisms underlying soil biogeochemistry and help beget tractable microbial reaction networks for incorporation into process-based models of soil carbon and nutrient cycling.IMPORTANCEWe address a critical gap in our understanding of soil microorganisms and their functions, which have a profound impact on our environment. We analyzed 1,512 global soils with advanced analytics to create detailed genetic profiles (fingerprints) of soil microbiomes. Our work reveals novel patterns in how microorganisms are distributed across different soil environments. For instance, we discovered shifts in microbial potential to acquire nutrients in relation to soil acidity, as well as changes in stress responses and potential greenhouse gas emissions linked to soil structure. We also identified soils with putative high activity that had unique genomic characteristics surrounding resource acquisition, plant-microbe interactions, and fungal activity. Finally, we observed that closely related microorganisms tend to respond in similar ways to changes in their surroundings. Our work is a significant step toward comprehending the intricate world of soil microorganisms and its role in the global climate.

Soil bacterial community diversity and life strategy during slope restoration on an uninhabited island: changes under the aggregate spray-seeding technique

AIMS

We investigated the effects of the aggregate spray-seeding (ASS) technique on soil bacterial community diversity, life strategies, and seasonal change.

METHODS AND RESULTS

Soil from six plots with original vegetation (CK, n = 6) was compared to soil from 15 plots with spray-seeding restoration (SR, n = 15) using environmental DNA sequencing. The bacterial Shannon and Chao1 indices of SR soils were significantly greater (P < 0.05) than those of CK soils. The Chao1 index for the SR soil bacterial community was significantly greater in summer (P < 0.05) than in winter. The ratio of the relative abundance of bacterial K-strategists to r-strategists (K/r) and the DNA guanine-cytosine (GC) content in the SR soil were significantly lower (P < 0.05) than those in the CK soil. Principal coordinate analysis revealed significant differences between the SR and CK bacterial communities. The GC content was positively correlated with the K/r ratio. Soil conductivity was negatively associated with the K/r ratio and GC content, indicating that ionic nutrients were closely related to bacterial life strategies.

CONCLUSIONS

The ASS technique improved soil bacterial diversity, altered community composition, and favored bacterial r-strategists.

Interruption after Short-Term Nitrogen Additions Improves Ecological Stability of Larix olgensis Forest Soil by Affecting Bacterial Communities

Atmospheric nitrogen deposition can alter soil microbial communities and further impact the structure and function of forest ecosystems. However, most studies are focused on positive or negative effects after nitrogen addition, and few studies pay attention to its interruption. In order to investigate whether interruption after different levels of short-term N additions still benefit soil health, we conducted a 2-year interruption after a 4-year short-term nitrogen addition (10 and 20 kg N·hm-2·yr-1) experiment; then, we compared soil microbial diversity and structure and analyzed soil physicochemical properties and their correlations before and after the interruption in Larix olgensis forest soil in northeast China. The results showed that soil ecological stabilization of Larix olgensis forest further improved after the interruption compared to pre-interruption. The TN, C:P, N:P, and C:N:P ratios increased significantly regardless of the previous nitrogen addition concentration, and soil nutrient cycling was further promoted. The relative abundance of the original beneficial microbial taxa Gemmatimonas, Sphingomonas, and Pseudolabrys increased; new beneficial bacteria Ellin6067, Massilia, Solirubrobacter, and Bradyrhizobium appeared, and the species of beneficial soil microorganisms were further improved. The results of this study elucidated the dynamics of the bacterial community before and after the interruption of short-term nitrogen addition and could provide data support and a reference basis for forest ecosystem restoration strategies and management under the background of global nitrogen deposition.

Keystone taxa enhance the stability of soil bacterial communities and multifunctionality under steelworks disturbance

Continuous discharge of wastewater, emissions, and solid wastes from steelworks poses environmental risks to ecosystems. However, the role of keystone taxa in maintaining multifunctional stability during environmental disturbances remains poorly understood. To address this, we investigated the community diversity, assembly mechanisms, and soil multifunctionality of soils collected from within the steelworks (I), within 2.5 km radius from the steelworks (E), and from an undisturbed area (CK) in Jiangsu Province, China, via 16 S rRNA sequencing. Significant differences were found in the Chao1 and the richness indexes of the total taxa (p < 0.05), while the diversity of keystone taxa was not significant at each site (p > 0.05). The deterministic processes for total taxa were 42.9%, 61.9% and 47.7% in CK, E, and I, respectively. Steelworks stress increased the deterministicity of keystone taxa from 52.3% in CK to 61.9% in E and I soils. The average multifunctionality indices were 0.518, 0.506 and 0.513 for CK, E and I, respectively. Although the soil multifunctionality was positive correlated with α diversity of both the total and keystone taxa, the average degree of keystone taxa in functional network increased significantly (79.96 and 65.58, respectively), while the average degree of total taxa decreased (44.59 and 51.25, respectively) in the E and I. This suggests keystone taxa contribute to promoting the stability of ecosystems. With increasing disturbance, keystone taxa shift their function from basic metabolism (ribosome biogenesis) to detoxification (xenobiotics biodegradation, metabolism, and benzoate degradation). Here we show that keystone taxa are the most important factor in maintaining stable microbial communities and functions, providing new insights for mitigating pollution stress and soil health protection.

Kalidium cuspidatum colonization changes the structure and function of salt crust microbial communities

The changes of soil moisture, salinity, and nutrients by halophyte colonization in high-salinity environment profoundly affect the assembly and structure of microbial communities. However, salt marshes in arid region have received little attention. This study was conducted in Lianhuachi Lake, a typical inland salt marsh wetland in China, to determine the physicochemical characteristics of salt crusts in [Kalidium cuspidatum (Ung.-Sternb.) Grub.] colonization areas and bulk soil, respectively, and to analyze the microbial community structure of salt crusts by high-throughput sequencing. Kalidium cuspidatum colonization significantly decreased total salinity, soil water content, and water-soluble ions of salt crusts and increased total carbon, total nitrogen, and total phosphorus content. At the same time, changes in physicochemical properties caused by Kalidium cuspidatum colonization affect the ecological processes of bacterial, fungal, and archaeal community assemblies in salt crusts. In addition, cross-kingdom network analysis showed that Kalidium cuspidatum colonization increased the complexity and stability of microbial networks in salt crust soils. Functional projections further showed that bacterial diversity had a potential driving effect on the nitrogen cycle function of salt crust. Our study further demonstrated the different ecological strategies of microorganisms for halophyte colonization in extreme environments and contributed to the understanding of restoration and management of salt marsh wetlands in arid region.

Mercapto-based palygorskite modified soil micro-biology and reduced the uptake of heavy metals by Salvia miltiorrhiza in cadmium and lead co-contaminated soil

Salvia miltiorrhiza is an important traditional Chinese medicinal and edible plant that can easily accumulate excessive cadmium (Cd) and lead (Pb) from contaminated soils. The soil contaminated with heavy metals severely threatened the quality of S. miltiorrhiza products. In this study, we investigated the effects of mercapto-based palygorskite (MPAL), a new passivation amendment, on restraining the uptake of Cd and Pb by S. miltiorrhiza, and the impact on soil micro-ecology. Results showed that the application of MPAL prominently enhanced the biomass and antioxidant enzyme activities of S. miltiorrhiza. With the treatment of 4% MPAL, the Cd and Pb contents in the roots were significantly decreased by 81.42% and 69.09%, respectively. The active ingredients of S. miltiorrhiza, including Danshensu, Cryptotanshinone, Tanshinone I and Tanshinone II were remarkedly increased by 1899.46%, 5838.64%, 54.23% and 200.78%, respectively. In addition, MPAL decreased the bio-availability of Cd and Pb by speciation transformation, which simultaneously boosted the activities of cellulase and sucrase. The application of MPAL also improved the bacterial community composition. These findings revealed that the application of MPAL regulated the soil micro-ecology, positively modified the growth and obstructed the Cd and Pb accumulation in S. miltiorrhiza.

Enzymatic fermentation of rapeseed cake significantly improved the soil environment of tea rhizosphere

BACKGROUND

Rapeseed cake is an important agricultural waste. After enzymatic fermentation, rapeseed cake not only has specific microbial diversity but also contains a lot of fatty acids, organic acids, amino acids and their derivatives, which has potential value as a high-quality organic fertilizer. However, the effects of fermented rapeseed cake on tea rhizosphere microorganisms and soil metabolites have not been reported. In this study, we aimed to elucidate the effect of enzymatic rapeseed cake fertilizer on the soil of tea tree, and to reveal the correlation between rhizosphere soil microorganisms and nutrients/metabolites.

RESULTS

The results showed that: (1) The application of enzymatic rapeseed cake increased the contents of soil organic matter (OM), total nitrogen (TN), total phosphorus (TP), available nitrogen (AN), and available phosphorus (AP); increased the activities of soil urease (S-UE), soil catalase (S-CAT), soil acid phosphatase (S-ACP) and soil sucrase (S-SC); (2) The application of enzymatic rapeseed cake increased the relative abundance of beneficial rhizosphere microorganisms such as Chaetomium, Inocybe, Pseudoxanthomonas, Pseudomonas, Sphingomonas, and Stenotrophomonas; (3) The application of enzymatic rapeseed cake increased the contents of sugar, organic acid, and fatty acid in soil, and the key metabolic pathways were concentrated in sugar and fatty acid metabolisms; (4) The application of enzymatic rapeseed cake promoted the metabolism of sugar, organic acid, and fatty acid in soil by key rhizosphere microorganisms; enzymes and microorganisms jointly regulated the metabolic pathways of sugar and fatty acids in soil.

CONCLUSIONS

Enzymatic rapeseed cake fertilizer improved the nutrient status and microbial structure of tea rhizosphere soil, which was beneficial for enhancing soil productivity in tea plantations. These findings provide new insights into the use of enzymatic rapeseed cake as an efficient organic fertilizer and expand its potential for application in tea plantations.

Seasonal variation in soil algal community structure in different forest plantations in subtropic China

Algae exert great impact on soil formation and biogeochemical cycling. However, there is no full understanding of the response of soil algal community structure to the seasonal fluctuations in temperature and moisture and changes of soil physicochemical properties across different forests. Here, based on 23S rRNA gene sequencing, we analyzed soil algal community structure in four different forest plantations in two seasons and examined soil physiochemical properties. The results showed the significantly seasonal variation in soil algal community structure, with the higher overall diversity in summer than in winter. In addition, there existed significant correlations between soil algae (species composition, relative abundance, diversity index) and physicochemical properties (pH, total phosphorus, organic matter and nitrate nitrogen), suggesting that edaphic characteristics are also largely responsible for the variation in soil algal community. Nevertheless, the seasonal variation in algal community structure was greater than the variation across different forest plantations. This suggest temperature and moisture are more important than soil physicochemical properties in determining soil algal community structure. The findings of the present study enhance our understanding of the algal communities in forest ecosystems and are of great significance for the management and protection of algal ecosystem.