Applied Soil Ecology最新文献

Soil pollution by organic contaminants like phthalates (PAEs) significantly impacts root-associated microbial community and soil health. However, the rhizosphere effects of different vegetable cultivars on root-associated bacterial communities and their effects on PAE degradation in rhizosphere are not well uncovered. Here, two cultivars (i.e., Huaguan and Lvbao) of vegetable Brassica parachinensis significantly enhanced the dissipation of di-(2-ethylhexyl) phthalate (DEHP) in rhizosphere (higher by 23.9 % - 86.8 % compared with bulk soil). PERMANOVA tests demonstrated that the bacterial community structure was significantly impacted by niche variation and DEHP pollution, but not by vegetable genotypes, with significant gradient divergences along bulk soil to (far-) rhizosphere to rhizoplane. Niche variation and DEHP pollution also remarkably influenced the ecological networks of bacterial communities in soil-root continuum with high proportions of positive microbial interaction. Furthermore, rhizosphere and DEHP pollution significantly enriched PAE-degrading functions and bacteria (e.g., Aeromicrobium and TM7a, as keystone taxa), which is beneficial for enhancing DEHP degradation. Meanwhile, metagenomic binning identified various bacterial families such as Chitinophagaceae and Nocardioidaceae capable of degrading PAEs in rhizosphere, which may play important roles in PAE biodegradation through cooperation and co-metabolism. This study advances our understandings on the promotion of vegetables for PAE removal in rhizosphere and its related mechanisms.

Globally, increased atmospheric nitrogen (N) deposition has comprehensively altered phosphorus (P) biogeochemical cycling in terrestrial ecosystems. Phosphorus is the second most common nutrient limiting for ecosystem productivity. Even though, ultimately under enhanced atmospheric N deposition it is likely to be the primary one. However, the response of soil P leaching to the elevated atmospheric N deposition in subalpine forests are still elusive. Here, we examined the effects of >7-year N additions on soil P leaching in a subalpine forest of eastern Tibetan Plateau. We found that independent of soil horizon (organic versus mineral horizons) and N addition rate (control 0, low 8 and high 40 kg N/ha yr⁻¹), dissolved inorganic P (DIP), rather than dissolved organic P (DOP), dominated soil P leaching. The N addition treatments reduced the leaching of total P and DIP throughout the soil profile by 13 % and 14 %, respectively. The enhanced biological immobilization and P adsorption capacity (increased by 15–33 % in organic horizon and 9–35 % in mineral horizon) under the N addition contributed to the decrease in soil P leaching. We conclude that the reduction in soil P leaching under the elevated atmospheric N deposition should boost the enhanced N driven forest productivity and ecosystem carbon sequestration in the subalpine forests.

Shrub encroachment became widespread in grass-dominated ecosystem regions. However, there is still limited attention on the changes in plant-soil system C:N:P stoichiometry and soil microbial metabolic limitation status caused by anthropogenic encroachment of shrubs in the desert grassland of northwest China, as well as their driving mechanisms. In this study, we quantified the C:N:P stoichiometry of plant-litter-soil, soil physicochemical properties, microbial biomass, extracellular enzyme activities, and microbial metabolic limitation status during the anthropogenic transition from grassland to shrubland. Here, our results showed that anthropogenic shrub encroachment reduced plant C, soil water, and soil nutrient contents while increasing N and P contents in both plants and litter. The correlation also suggested that litter nutrient content relied on plant nutrients, while plants depleted soil nutrients. Secondly, with the gradient of shrub encroachment, the stoichiometry (except for soil C:N ratio) of plant-litter-soil showed a decreasing trend and a positive correlation. Furthermore, our study indicated that shrub encroachment reduced soil microbial biomass and extracellular enzyme activities, altering microbial stoichiometry and patterns of enzyme allocation. Redundancy analysis revealed that microbial biomass, extracellular enzyme activities, and stoichiometry were mainly driven by soil water content, nutrient content, and nutrient stoichiometry. The vector-threshold element ratio model revealed that along the transition from desert grassland to shrubland, soil microbial nutrient limitation shifted from P to N, while energy (C) limitation intensified. The soil microbial metabolic limitation was driven jointly by plants and litter through modifications of soil properties and microbial biomass. Additionally, soil properties played a crucial role among these factors. In summary, over the past 40 years, shrub anthropogenic encroachment has formed a desert grassland-shrub mosaic landscape, depleted soil water and nutrient contents, and altered ecological stoichiometry and microbial metabolic limitation patterns in northwest China. This study provides new insights into the C, N, and P cycling in plant-soil systems following shrub encroachment caused by global climate change and anthropogenic disturbances.

The present work aimed to investigate and quantify the diversity of arbuscular mycorrhizal fungi (AMF) found in the soil adjacent to the roots of Vellozia ramosissima and Eremanthus incanus in two ferruginous campo rupestre environments (FCR) and two quartzitic campo rupestre environments (QCR) of Serra do Espinhaço, Brazil. Spore density of AMF in the soil, quantity of glomalin-related soil protein (GRSP), and degree of root colonization by AMF were analyzed. Eremanthus incanus exhibited 24 species of arbuscular mycorrhizal fungi (AMF) in its rhizosphere, with four being exclusive to quartzitic rupestrian fields (QCR) and six to ferruginous rupestrian fields (FCR). Vellozia ramosissima had 20 AMF, with five exclusive to QCR and one to FCR. The high richness of AMF associated with the rhizosphere of the two studied species may be the determining factor for the successful establishment of these plants in environments under adverse edaphoclimatic conditions and low productivity. The genera Acaulospora, Glomus, and Scutellospora were distributed among all the studied areas and had the greatest species richness. Species richness of AMF tended to be higher in environments with higher floristic richness, although these areas had lower spore density. There was a greater quantity of GRSP in the ferruginous environments while root colonization by AMF was higher for E. incanus than V. ramosissima. Principal component analysis of chemical attributes of the soil revealed two groups influenced by lithology (ferruginous vs. quartzitic). Indicator species analysis revealed the prevalence of five indicator species in the studied environments; two of the species were specific to QCR1, one to FCR1, and two to FCR2. Contrary to expectations, sites with lower species richness of AMF had higher values for the Shannon diversity index (H′), because the sampled spores in these environments were distributed more uniformly among the registered AMF species.

We investigated the outcome of the interaction between the arbuscular mycorrhizal fungus (AMF) Rhizophagus (R) irregularis DAOM 197198 and the Plant-Growth-Promoting Rhizobacteria (PGPR) (mix of Bacillus megaterium, Burkholdria cedrus and Streptomyces beta-vulgaris) by conducting an olive field experiment. Our data provide evidence that the co-inoculation of R. irregularis and PGPR has important effects on the rhizosphere microbial community. The largest proportional increase was found for the PLFA biomarkers indicative of Gram-negative bacteria (16:1ω9, 18:1ω7 and 18:1ω9), fungi (18:2ω6) and actinobacteria (10Me16:0 and 10Me18:0). Microbial inoculants application of all tested treatments caused a significant decrease in the level of trehalose in the olive rhizosphere. The most pronounced decrease was observed in the plant inoculated with R. intraradices only, suggesting that the presence of AMF may have relaxed the bacterial stress. Co-inoculation of PGPR and AMF significantly improved the nutritional status of olive roots. Specifically, the interaction of PGPR and R. intraradices led to an increase in N (26 %), P (60 %), Fe (25 %), Mn (18 %), Zn (26 %), B (22 %) and Cu (14 %) compared with the control. We also found that the co-inoculation of AMF with PGPR causes a shift in the accumulation of secondary metabolites in olive roots. In particular, the most important effect induced by AMF was an improvement of oleuropein concentration, while co-inoculation of R. irregularis and PGPR positively modulated verbascoside concentration. The novelty of the present work lies in the use of microbial inoculants in the field of olive trees. This approach provided direct information regarding the advantages of using AMF and PGPR inoculants, allowing the reduction of chemical inputs and positively influencing the olive tree performance.

The impact of nitrogen (N) deposition on soil microbial community structure and function has been a focal point of research; however, the influence of forest age and N form on the microbial response to N deposition has yet not to be fully understood. To address this gap, metagenomic sequencing was utilized to explore the responses of soil microbial community structure and functional genes to five years of N addition in middle-aged and mature coniferous forests in southwest China. Adopting a randomized block design, the experiment included two N forms ((NH₄)₂SO₄ and KNO₃) across four levels of addition (0, 10, 20 and 40 kg N ha⁻¹ yr⁻¹). Our findings reveal that the composition of the microbial community structure and functional genes involved in the carbon (C), N, phosphorus (P), and sulphur (S) cycling varied significantly between middle-aged and mature forest (P < 0.001). At the phylum level, the soil microbial community in the mature forest were dominated by Proteobacteria (30.4–38.8 %), Acidobacteriota (8.5–24.1 %), and Chloroflexota (8.1–21.5 %), and the soil microbial community in the middle-aged forest showed a greater presence of Acidobacteriota (28.9–34.0 %) and Actinobacteriota (13.3–19.2 %) with a lower proportion of Chloroflexota (0.4–1.2 %). In both middle-aged and mature forests, functional gene abundance, and the composition of microbial community and functional genes were unaffected by N addition rate (P = 0.793) and N form (P = 0.725). The taxonomic composition of soil microbial community in the mature forest showed a significant positive correlation with soil pH, soil organic carbon (SOC) and total nitrogen (TN) (P < 0.01), while the microbial community composition in the middle-aged forests was not significant correlated with soil pH, SOC and TN (P > 0.05). These findings underscore that N addition in the middle-aged and mature coniferous forest does not significantly impact the soil microbial community structure and function across different N forms and N addition rate, suggesting that soil microorganisms of the forest ecosystem exhibit strong resilience to increased N supply.

Parasitic plants can mediate soil conditioning by invasive and native host plant species, but how this may affect the competitive ability of these plants when they later grow in the conditioned soil has never been tested. This study tested whether soil conditioned by three invasive and three native plant species, either parasitized by a holoparasitic plant Cuscuta gronovii or non-parasitized, would differentially affect the competitive ability of those species. In the first phase, field soil was conditioned using individuals of the six host plant species, either parasitized or non-parasitized. The second phase tested the competitive ability of individuals of those invasive and native plants by growing them alone or in competition with Trifolium repens in either live or sterilized conditioned soil. In the soil conditioning phase, parasitism significantly increased soil NH₄⁺-N concentration by 17 %, decreased soil organic carbon by 18 %, and marginally decreased microbial biomass carbon concentration by 21 %. In the soil feedback phase, native plant species generally had higher competitive ability in soil that was conditioned by parasitized plants than in soil that was conditioned by non-parasitized plants. In contrast, soil conditioned by parasitized plants had only a marginal effect on the competitve ability of invasive plants, compared to growth in soil conditioned by non-parasitized plants. Native plants had greater competitive ability in soil with lower soil organic carbon, while invasive plants had greater competitive ability in soil with higher microbial biomass carbon and lower NH₄⁺-N. These findings demonstrate that parasitism by C. gronovii mediated different soil legacy effects of invasive and native plant species through changes in soil organic carbon, soil NH₄⁺-N, and microbial biomass carbon levels. Broadly, these results suggest that parasitic plants may limit invasions by alien plant species and promote the co-existence of the invaders with native plant species through soil-mediated legacy effects.

Sustainable manure management is crucial for minimising environmental impacts as the livestock industry expands to meet the increasing demand for protein. Black soldier fly (Hermetia illucens L.) larvae (BSFL) farming is an emerging waste management method that efficiently processes large volumes of organic waste, including manure, to produce valuable protein, oil and chitin products. Frass, a nutrient-rich by-product of black soldier fly farming, has potential as an organic fertiliser. However, research has primarily focused on frass derived from food waste, with little exploration of manure-derived BSFL frass. This study aimed to determine whether frass derived from manure could enhance the growth of chilli (Capsicum annuum L.) over 14 weeks under controlled glasshouse conditions. The impacts of manure-derived BSFL frass on soil properties and soil bacterial communities were characterised. The results indicated that a 0.6 % w/w application rate yielded the highest chilli plant biomass, with reduced growth observed at higher rates. The enhanced growth at optimal manure-derived BSFL frass application rates was due to increased nitrogen content, whereas reduced growth at higher rates was likely caused by phytotoxicity from not completely decomposed frass. Soil microbial biomass carbon and nitrogen also increased with manure-derived BSFL frass, implying microbial carbon and nitrogen immobilisation. Additionally, the changes in pH and nutrients due to manure-derived BSFL frass caused shifts in the bacterial community in the chilli plant rhizosphere, enriching the relative abundance of bacteria with potential growth-promoting properties. This study highlights the potential of integrating manure into black soldier fly waste management processes, demonstrating that manure-derived BSFL frass can be used as an organic fertiliser with circular economy benefits.

The mutualistic association between mycorrhizal fungi and plants is well known to improve plant drought resistance. However, the influence of external inoculants on the interactions between soil microbial communities and plant functional traits and how these interactions improve plant drought tolerance under drought stress remain unclear. We conducted a pot inoculation experiment to assess the effect of two inoculated fungal strains (Clitopolius hobsonii NL-19 and C. sp. HSL-YX-7-A) on morphological traits and rhizosphere fungal communities of eight Quercus species seedlings. Plant and soil fungal traits were measured 2 months after inoculation and then underwent a short-term (33 days) drought rewetting treatment. The biomass of all tree species reduced significantly under drought stress followed by rewetting (drought treatment) compared with that in the control treatment (well-watered); however, inoculated mycorrhizal fungi (drought + mycorrhizal inoculation treatment) increased the biomass of five Quercus species (growth-promoting species (GPS) exhibiting a significant increase in biomass under mycorrhizal inoculation treatment than under the uninoculated treatment during drought stress, characterized by a resource-use acquisitive strategy) and had no effect on the other three Quercus species (non-growth-promoting species (NGPS) exhibiting no significant difference in biomass between mycorrhizal inoculation and uninoculated treatments during drought stress, characterized by a resource-use conservative strategy). The leaf traits of the two species groups (GPS and NGPS) varied little among the three treatments. The values of most root traits (e.g., specific root length and root length) of GPS increased significantly under drought and drought + mycorrhizal inoculation treatments compared with those in the control, whereas relatively minor variations were observed in NGPS among the three treatments. The fungal community composition and functional groups (primary trophic modes) in the drought treatment were altered for NGPS but not for GPS; additionally, they changed in the drought + mycorrhizal inoculation treatment for GPS but not for NGPS when compared with those in the drought treatment. Furthermore, the drought tolerance of GPS was improved directly by fungal functional groups (i.e., Pathotroph-Saprotroph- Symbiotrophs proliferation) and indirectly by root traits (e.g., increased specific root length), whereas NGPS may adapt to drought stress through other pathways (e.g., physiological and biochemical regulation). Overall, drought and mycorrhizal inoculation affected the root traits and fungal community structure of Quercus seedlings, which rely on plant resource-use strategies. Our results provide new insights into the relationship between plant resource-use strategies and soil microbes for improving plant performance under drought stress.