Soil Organic Carbon Shapes AMF Communities in Soils and Roots of Cynodon dactylon under Anti-Seasonal Drying-Wetting Cycles

Strategies for phosphorus management and greenhouse gas reduction via plant harvesting in the water-level fluctuation zone of the Three Gorges Reservoir

The water-level fluctuation zones (WLFZ) in Three Gorges Reservoir encounter several ecological challenges, particularly potential greenhouse gas (GHG) emissions and water eutrophication due to water level variations. Therefore, to address those challenges, our study explores the relationships between soil properties (Phosphorus cycle), plant conditions, microbial community, and GHG emissions. Our findings reveal that aboveground plants are the key link in the WLFZ ecosystem, which has previously been overlooked. Hydrological variations are continuously resetting the soil microbial system, keeping their ecological function in a primary state. Variations in elevation and soil nutrients have a minimal impact on GHG emissions in harvested plant areas. In contrast, in native plant areas, these variations significantly influence both GHG emissions and the phosphorus cycle. A strategic harvesting approach targeting high and low-elevation areas is also proposed, focusing on plants with high phosphorus enrichment coefficients (ECp > 1) to effectively counter eutrophication and GHG emissions. This selective harvesting in specific elevations could reduce CO2, CH4, and N2O emissions by 27378, 21, and 5 tonnes, respectively, and remove over 228934 tonnes of phosphorus. Our study emphasizes the significance of targeted vegetation management in WLFZ, providing a sustainable pathway to counter water eutrophication and achieve carbon neutrality.

Ecology and diversity of arbuscular mycorrhizal fungi (AMF) in rice (Oryza sativa L.) in South India: an ecological analysis of factors influencing AMF in rice fields

AIMS

This study examined the diversity of arbuscular mycorrhizal fungi (AMF), mean spore density (MSD), and root colonization in relation to factors such as agroclimatic zones, rice varieties and soil types in paddy fields of South India. The aim was to understand how these factors influence AMF association in rice, facilitating their effective use as a biological tool in paddy cultivation.

METHODS AND RESULTS

AMF were identified through light microscopy of spores, while MSD and percentage-root-length colonization (PRLC) were measured using standard methods. Correlation and principal component analyses were performed to explore the interrelationships between AMF characteristics and various environmental, soil, and plant variables. Sixteen AMF species were identified across 29 rice varieties from three agroclimatic zones, 6 soil orders, and 18 soil series over 2 seasons. Notably, 70% of chemicalized rice fields lacked AMF spores, and only 50% exhibited root colonization. This study offers new insights into the role of AMF in rice cultivation.

CONCLUSION

The AMF diversity and root colonization in relation to environmental variables underscore their significant impact on AMF in particular crop fields.

Effects of riparian pioneer plants on soil aggregate stability: Roles of root traits and rhizosphere microorganisms

Pioneer plants are vital in stabilizing soil structure while restoring reservoir drawdown areas. However, uncertainties persist regarding the mechanism of pioneer plants to soil stability in these delicate ecosystems. This study aims to unravel the plant-soil feedback mechanisms from the roles of root traits and rhizosphere microorganisms. We conducted a mesocosm experiment focusing on four common pioneer plants from the drawdown area of Three Gorges Reservoir, China. Using the wet sieving methodology, trait-based approach and high-throughput sequencing technology, we explored soil aggregate stability parameters, plant root traits and rhizosphere microbial communities in experimental plant groups. The interacting effect of pioneer plant species richness, root traits, and rhizosphere microbial communities on soil aggregate stability was quantified by statistical and machine-learning models. Our results demonstrate that diverse pioneer plant communities significantly enhance soil aggregate stability. Notably, specific species, such as Cynodon dactylon (L.) Pers. and Xanthium strumarium L., exert a remarkably strong influence on soil stability due to their distinctive root traits. Root length density (RLD) and root specific surface area (RSA) were identified as crucial root traits mediating the impact of plant diversity on soil aggregate stability. Additionally, our study highlights the link between increased rhizosphere fungal richness, accompanied by plant species richness, and enhanced soil aggregate stability, likely attributable to elevated RLD and RSA. These insights deepen our understanding of the role of pioneer vegetation in soil structure and stability, providing valuable implications for ecological restoration and management practices in reservoir drawdown areas.

Effects of arbuscular mycorrhizal fungi on the reduction of arsenic accumulation in plants: a meta-analysis

Arsenic (As) accumulation in plants is a global concern. Although the application of arbuscular mycorrhizal fungi (AMF) has been suggested as a potential solution to decrease As concentration in plants, there is currently a gap in a comprehensive, quantitative assessment of the abiotic and biotic factors influencing As accumulation. A meta-analysis was performed to quantitatively investigate the findings of 76 publications on the impacts of AMF, plant properties, and soil on As accumulation in plants. Results showed a significant dose-dependent As reduction with higher mycorrhizal infection rates, leading to a 19.3% decrease in As concentration. AMF reduced As(V) by 19.4% but increased dimethylarsenic acid (DMA) by 50.8%. AMF significantly decreased grain As concentration by 34.1%. AMF also improved plant P concentration and dry biomass by 33.0% and 62.0%, respectively. The most significant reducing effects of As on AMF properties were seen in single inoculation and experiments with intermediate durations. Additionally, the benefits of AMF were significantly enhanced when soil texture, soil organic carbon (SOC), pH level, Olsen-P, and DTPA-As were sandy soil, 0.8%-1.5%, ≥7.5, ≥9.1 mg/kg, and 30-60 mg/kg, respectively. AMF increased easily extractable glomalin-related soil protein (EE-GRSP) and total glomalin-related soil protein (T-GRSP) by 23.0% and 28.0%, respectively. Overall, the investigated factors had significant implications in developing AMF-based methods for alleviating the negative effects of As stress on plants.

Diversity of Arbuscular Mycorrhizal fungi under different agroforestry practices in the drylands of Southern Ethiopia

The conversion of an agroforestry based agricultural system to a monocropping farming system influences the distribution and composition of arbuscular mycorrhizal fungi (AMF). The aim of this paper was to analyze AMF species diversity, spore density, and root colonization across different agroforestry practices (AFP) in southern Ethiopia. Soil and root samples were collected from homegarden, cropland, woodlot, and trees on soil and water conservation-based AFP. AMF spores were extracted from the soil and species diversity was evaluated using morphological analysis and root colonization from root samples. The AMF spore density, root colonization and composition were significantly different among the AFP (P < 0.05). In this study, 43 AMF morphotypes belonging to eleven genera were found, dominated by Acaulospora (32.56%), followed by Claroideoglomus (18.60%). Home gardens had the highest spore density (7641.5 spore100 g- 1 dry soil) and the lowest was recorded in croplands (683.6 spore100 g- 1 dry soil). Woodlot had the highest root colonization (54.75%), followed by homegarden (48.25%). The highest isolation frequency (63.63%) was recorded for Acaulospora scrobiculata. The distribution of AMF species and diversity were significantly related to soil total nitrogen and organic carbon. The homegarden and woodlot AFP were suitable for soil AMF reserve and conservation.

Response of dominant plant species to periodic flooding in the riparian zone of the Three Gorges Reservoir (TGR), China

Human-induced disturbances such as dam construction and regulation often change the duration and frequency of flooding and thus notably influence plant dominance in riparian zones. Even though numerous studies have indicated that the oxidative stress and antioxidative stress systems are essential for plant defenses against adverse flooding stress, the mechanism of vegetation distribution due to hydrological regimes is still unclear. In the current study, the riparian zone of the Three Gorges Reservoir (TGR), which experiences seasonal and anti-seasonal water-level fluctuations, was used to investigate the dominant species. To our knowledge, this is the first study that links molecular-physiological-morphological mechanisms to explore the development of flooding tolerance of dominant riparian species. Physiological traits (e.g., chlorophyll and protein contents), morphological traits (e.g., leaf length), and molecular traits (e.g., enzymatic antioxidant activity and the malondialdehyde content) were analyzed at different water-level gradient zones of the dominant species to evaluate the influence of flooding. To explore the regulation mechanisms of submergence for the vegetation distribution, correlation analysis, PCA (principal component analysis) and laboratory flooding experiments were conducted. The results showed that Cynodon dactylon, which has a rapid antioxidative system, was the dominant species in the riparian zone of the TGR. The leaf length varied significantly along with water level gradients (p < 0.05) with the minimum values appearing in the lowest part of the riparian zone and the maximum values observed in the highest areas. The chlorophyll and protein contents fluctuated in different water level gradient zones, but significant differences were not observed. Within the antioxidative system, catalase was found to be essential for riparian plants in their response to flooding. The current study could provide insight to explore the specific mechanism of resistance for dominant plants to periodic flooding, and the reason why dominant species can survive adverse stress.