Plant and Soil最新文献

Background

The significant variability in agricultural ecosystems leads to considerable differences in soil microbial community responses to nitrogen, attributed to the diverse combinations of agronomic practices, such as planting patterns and fertilization strategies.

Results

There is no doubt that reducing nitrogen fertilizer inputs is a crucial step in minimizing greenhouse gas emissions; however, determining the optimal nitrogen fertilizer inputs for different ecosystems, while maintaining crop yields, remains a significant challenge. The observed differences in microbial community responses to nitrogen appear to provide targeted insights in this regard. We systematically review and discuss the variances in soil microbial responses to nitrogen across different agricultural systems, aiming to assist researchers and farm managers in providing focused references for scaling up agricultural systems.

Conclusion

From a practical standpoint, targeted support for nitrogen management in various agricultural ecosystems is essential to reduce nitrogen waste, maintain soil health, and curb global warming trends. These factors are closely linked to crop types, management practices, and the local environmental conditions of the agricultural systems. Furthermore, the rational utilization of M genes to assist in regulating the assembly of soil nitrogen, cycling-related microbial communities may serve as an effective approach to achieving precision agriculture and promoting ecosystem sustainability.

Background and aims

Greenspace soils are a critical component of urban ecosystems, playing an essential role in delivering ecosystem services. Soil organic carbon (SOC) in these areas show considerable variability and uncertainty due to urbanization. However, it remains poorly understood how urbanization intensity and vegetation type affect greenspace SOC concentration.

Methods

This study examines how urbanization intensity (low, medium and high) and vegetation type (trees, shrubs and grasses) influence SOC concentration in urban parks in Hangzhou city, China. Urbanization intensity is measured by population, economy and urban built-up area. In addition, the response of particulate organic carbon (POC) and mineral-associated organic carbon (MAOC) in greenspace soil to urbanization intensity was also assessed in the study to further understand the stability of SOC in urban parks.

Results

Total SOC and its fractions (POC and MAOC) increased significantly in urban parks with the increase of urbanization intensity. Despite this increase, SOC did not reach saturation levels, even under high urbanization intensity. Urbanization affected SOC concentration indirectly by modifying soil total nitrogen (+ 17.1%), total phosphorus (+ 7.1%), microbial biomass carbon (+ 10.9%), microbial biomass nitrogen (+ 0.7%), clay and fine silt contents (+ 1.9%), calcium ion (+ 1.1%), and P-acquiring enzyme activity (+ 1.0%). Among SOC fractions, MAOC, rather than POC, was the dominant form along the suburb-urban gradient, with the greater increase in MAOC driving the increase in overall SOC concentration. No significant difference in total SOC was found among vegetation types, but SOC accumulation in grasses was more responsive to urbanization than in trees and shrubs.

Conclusions

Intensified urbanization leads to higher SOC concentration, particularly MAOC. These findings are crucial for quantifying the impact of urbanization on SOC in urban parks and achieving better carbon management.

Background and aim

Realizing that in vitro cultivation of plant microbiota is crucial to access core resources of the microbial members of the holobiont; culturing strategies are currently advanced based on plant-based culture media. Followed was the introduction of “in situ similis” cultivation strategy depending on the use of plant intact organs, e.g. leaves/ roots that finger print plant nutritional composition and expose compartment-affiliated microbiota.

Methods

Here, we advance a practical strategy to in vitro cultivation of tomato microbiota, making use of veggie-discs of homologous tomato and heterologous vegetables (potato and taro), as well as plant broth-based culture medium. Colony forming units (CFUs) are well-developed on water agar plates with veggie-discs as such or immersed with over-lay agar technique and/or membrane filters. The culturable bacteria community (CFUs) was analyzed by DGGE, and representative pure isolates were subjected to morpho-physiological studies and 16S rRNA gene sequencing.

Results

Veggie-discs acted as compatible natural/nutritional mat developing copious/fully-grown CFUs of bacteria, including actinomycetes, and fungi. The strategy uncovered the highly divergent composition of tomato culturable community, being extended to representatives of Actinomycetota, Bacillota, Bacteroidota and Pseudomonadota. Genuinely, the strategy expanded the diversity of tomato microbiota: brought into cultivation additional 18 genera not previously reported; novel cultivation of unique isolates that showed higher similarity to previously-uncultured clones representing Pseudomonadaceae, Oxalobacteraceae and Sphingomonadaceae.

Conclusion

The presented veggie-discs cultivation offers additional tools to in vitro render the hidden compartment-affiliated microbiota (bacteria/actinomycetes/fungi) accessible for future application of synthetic community approach (SynCom) and microbiota-target interventions, towards improved vegetables nutrition, health and quality, especially under soilless cultivation.

Graphical abstract

The graphical abstract that illustrates the idea of in situ-similis cultivation, where tomato microbiota are transferred to friendly and compatible veggie-discs compared to exotic and incompatible chemically-synthetic culture media.

Aims

The aim of this study was to investigate the effects of varying nitrogen (N) and carbon (C) levels on soil phosphorus (P) compositions, abiotic factors (pH and moisture content), and biotic factors (dehydrogenase (DHA) and phosphatases).

Methods

A field experiment was conducted at the Inner Mongolia prairie, where different levels of N (0, 25, 50, 100, 200 kg N ha⁻¹ yr⁻¹) and C (0, 250, 500 kg C ha⁻¹ yr⁻¹) were applied to study their effects on soil P transformations.

Results

High N levels significantly decreased soil pH, concentrations of diesters, activities of DHA and acid phosphomonoesterase (AcP), phosphodiesterase, and inorganic pyrophosphatase (IPP); whereas, increased concentrations of phosphonate, polyphosphate, and myo-IHP; which could potentially affect nutrient availability, microbial processes and soil fertility. Additionally, C supplementation significantly increased concentrations of diesters and myo-IHP, and activities of DHA and IPP, suggesting C supplementation may improve P stability in contexts of excessive natural and anthropogenic N enrichment. SEM revealed two discrepant nutrition-driven modes in P transformation: i) the N-driven mode, where N addition directly affected phosphonate concentrations and indirectly affected P transformation through both abiotic (pH and moisture content) and biotic (AcP and IPP) factors; ii) the C-driven mode, where C addition directly affected concentrations of monoesters and indirectly affected pyrophosphate concentrations through a biotic (IPP) factor.

Conclusion

Our findings reveal how biotic and abiotic factors regulate P transformation through C management under N enrichment, enhancing our understanding of environmental influences on P cycling via phosphatase and benefiting sustainable grassland practices.

Background

Soil macro- and mesofauna play a critical role in regulating (mixed-)litter decomposition. In shrub-encroached temperate graminoid wetlands, shrub and graminoid litters, with contrasting chemical quality, often interact to affect decomposition. However, little is known about how fauna contribute to decomposition and mixing effects in situ.

Methods

We collected litters of two graminoid species (Deyeuxia angustifolia and Carex schmidtii) and two shrubs (Betula fruticosa and Salix floderusii) in a shrub-encroached wetland. By a one-year field microcosm experiment involving 8 mm- and 0.5 mm-mesh sizes to control soil fauna sizes in B. fruticosa and S. floderusii islands, we measured litter mass loss of graminoid species, shrubs, and their mixtures.

Results

In both islands, the 8-mm treatment increased mass loss by 11.4% ~ 35.9% relative to the 0.5-mm, irrespective of monospecific and mixed-species litter. For mixed-species litter, positive non-additive effects on mass loss were common, especially in the 8-mm treatment (in three of four mixtures in the S. floderusii island, and in all mixtures in the B. fruticose island). Specifically, graminoid litters generally had greater mass loss in the shrub-graminoid mixtures than that decomposing alone, with a higher incidence in the 8-mm treatment. For the mixtures, the mesh size explained most variation (26.9%, followed by species composition and litter chemical dissimilarity) in mass loss.

Conclusions

This study provides field evidences for the critical role of macro- and mesofauna in regulating litter decomposition in freshwater wetlands. Following shrub encroachment, the fauna contributes greatly to positive mixing effects on decomposition of shrub-graminoid litter assemblages.

Background and Aims

The growing rates of production of edible insects is leading to an increase in the availability of insect frass, comprising mostly the solid excretions of larvae and undigested substrate. Insect frass is considered a novel organic fertilizer, rich in nutrients and believed to further boost plant growth through its high content of substances like chitin. This study investigated the fertiliser potential of black soldier fly larvae (BSFL) frass, its ecotoxicity, and its interactions with arbuscular mycorrhizal fungi (AMF).

Methods

Two commercial BSFL frass products were analysed for plant nutrient concentration and effects on seed germination under laboratory conditions. In a greenhouse bioassay, using only one of the products, its impact on tomato biomass production and AMF colonisation was evaluated.

Results

Chemical analysis of the frass products revealed more macro-nutrients than typically found in composts with between 1.3% to 1.6% total phosphorus and 3.6% and 3.9% total nitrogen (N). 98% of the mineral N was in the form of ammonium. Total carbon was between 44 and 45% for both products. Micronutrient concentrations varied between the products, with iron reaching up to 1236 mg kg⁻¹ or zinc up to 206 mg kg⁻¹. Variability was also observed in seed germination inhibition, with one product demonstrating stronger inhibitory effects than the other. The greenhouse bioassay revealed issues around ammonia toxicity at higher application rates of 150 to 250 kg N ha⁻¹ and an almost complete inhibition of arbuscular mycorrhizal root colonization between 100 and 250 kg N ha⁻¹. Biomass production increased rapidly with higher frass application rates and plateaued between 150 and 250 kg N ha⁻¹.

Conclusion

Insect frass shows significant potential as a nutrient-rich organic fertiliser, with some imbalances that, if improved, could further strengthen its efficiency as a fertiliser.

Background and aim

Soil organic carbon (SOC) is crucial for soil fertility and combating climate change, which may be regulated by aboveground litter input. However, how SOC accumulation responds to litter manipulation remains unclear.

Methods

In this study, we conducted a 7-year litter manipulation experiment, including litter addition, litter removal, and control treatments. We used an elemental analyzer, along with measurements of bulk density, to estimate SOC stock, the wet-sieving method to analyze soil aggregate distribution, amino sugar content to calculate microbial necromass carbon (C) in aggregates, and a Fourier transform midinfrared spectrometer (FIRT) to determine the SOC chemical functional groups along a 60 cm profile in a Chinese fir (Cunninghamia lanceolata) plantation.

Results

We found that litter addition significantly increased SOC stock by 44.59% in the 0–10 cm layer, while litter removal had no effect on SOC stock. Litter addition increased the proportion of macroaggregates (> 2 mm) and the geometric mean diameter (GMD). Moreover, litter addition increased the bacterial necromass C in macroaggregates, which was positively correlated with SOC. SOC stock in topsoil was explained by GMD and fractal dimension, which might increase the protection for bacterial necromass C. However, litter addition decreased the chemical stability of SOC.

Conclusion

Long-term C input increased topsoil SOC accumulation by strengthening the physical protection of aggregates rather than by the chemical protection of SOC functional groups in this Chinese fir plantation, particularly through the accumulation of bacterial necromass C in macroaggregates.

Background and aims

Conservation agriculture (CA) has gained traction as a climate-smart management strategy to enhance food security and maintain soil quality. However, nearly all investigations are based on controlled experimental studies with few long-term on-farm trials. The objective of the study was to assess the effect of CA on maize yield and soil fertility at smallholder farms in Zambia (2016–2021).

Methods

About 100 on-farm trials were established. CA plots with maize (Zea mays L.) in annual rotation with soybean were compared pairwise with conventional plots, with maize monocropping, which were managed in accordance with local practices. Maize grain yield and soil pH, organic carbon, phosphorus and nitrogen were investigated.

Results

Maize grain yield was significantly higher in CA (+ 24% to + 39%) compared to conventional management, due to early sowing and more effective use of precipitation. However, after 5 years, there was no significant difference in soil fertility between CA and conventional agriculture.

Conclusion

CA provides a viable option for climate change adaptation due to increased yields and drought resilience. The higher yield under CA provides an opportunity to enhance food security. However, our results do not support that CA enhances soil organic carbon, available phosphorus and nitrogen after 5 years of maize-soybean rotation.

Aims

Biogenic volatile organic compound (BVOC) emissions from leaf litter play an important role in forest carbon (C) cycles. This study investigated the combined effects of nitrogen (N) addition and leaf litter species on BVOC emissions and the relative contribution of C emissions in the form of BVOCs to CO₂ emissions.

Methods

An incubation experiment was conducted using two levels of N addition and two leaf litter species (Schima superba and Cunninghamia lanceolata). We measured BVOC and CO₂ emissions and litter chemical properties during litter decomposition.

Results

Total BVOC-C emitted from two leaf litter species accounted for 0.19%–0.47% of CO₂-C emissions. N addition decreased the total BVOC emissions, but increased CO₂ emissions from the decomposition of both litter species. N addition increased total N and soluble sugar contents of leaf litter but reduced the starch content and C/N ratio. Following N addition, the fluxes of most BVOC types were positively correlated with starch and nonstructural carbohydrate contents of S. superba leaf litter and with the C/N ratio of C. lanceolata leaf litter. In addition, the total BVOC and CO₂ emissions from S. superba leaf litter were higher than those from C. lanceolata. Corresponding, S. superba leaf litter had higher N and soluble sugar contents but lower C/N ratio and starch content than C. lanceolata leaf litter.

Conclusion

N addition inhibited BVOC emissions and promoted CO₂ emissions during leaf litter decomposition. Leaf litter with a high labile substrate content is likely to release more BVOCs during the early-stage of litter decomposition.

Aims

Soil microorganisms play a pivotal role in forest ecosystems geochemical cycle, yet their responses to variations in aboveground and belowground carbon inputs remain insufficiently understood. Variations in plant-derived carbon inputs are expected to influence microbial community structures. This study aims to investigate how changes in these carbon inputs affect the composition and diversity of soil microbial communities across different forest ecosystems in the subtropics forest.

Methods

Natural forest and plantation of Castanopsis carlesii in the subtropics were selected, with three 20 m × 20 m plots established in each forest. Six treatments were applied in a randomized complete block design, with aboveground litter excluded using nylon nets and root exclusion achieved by trenching. Soil microbial community structure under each treatment was analyzed using high-throughput amplicon sequencing.

Results

Litter and root treatments significantly altered microbial community composition and diversity. Bacterial communities, dominated by Acidobacteria, Proteobacteria, and Actinobacteria, showed no significant structural changes in response to treatments but were influenced by forest type. In contrast, fungal communities, dominated by Basidiomycota and Ascomycota, exhibited reduced diversity under root exclusion and litter treatments in natural forests. Soil properties such as moisture, temperature, DOC, and DON were key drivers of microbial community structure and diversity.

Conclusion

These results underscore the role of ecological niche differences between forest forests and alterations in soil chemical properties induced by litter and root inputs in shaping soil microbial communities. These findings offer insights into the mechanisms governing nutrient cycling and soil carbon dynamics in subtropical forest ecosystems.