Plant and Soil最新文献

Background and aims

In the wheat–maize cropping system, the return of substantial maize straw to the field can hinder winter wheat germination and growth. This study aims to clarify the mechanisms that accelerate maize straw decomposition, thereby mitigating these effects.

Methods

This study evaluated three tillage methods: zero tillage, chisel tillage, and plow tillage, and three nitrogen fertilization rates (180, 240, and 300 kg·N ha⁻¹). It examined the relationships between straw decomposition rates and factors such as straw chemical composition, soil properties, enzyme activities, and microbial community.

Results

In this study, chisel tillage and 240 kg·N ha⁻¹ significantly improved soil properties and biological activity and promoted straw decomposition. The combination of chisel tillage and 240 kg N ha⁻¹ resulted in the highest rate of straw degradation of 52%. Chisel tillage significantly reduced easily degradable functional groups (methoxyl C and carbonyl C) and enhanced the activities of β-glucosidase, N-acetyl glucosaminidase, peroxidase, and polyphenol oxidase, as well as fungal diversity (P < 0.05). Nitrogen fertilization further increased enzyme activity and the fungal Shannon index (P < 0.05). Proteobacteria and Ascomycota were dominant phyla during the decomposition process, with microbial dominant order shifts linked to decomposition stages, straw chemical structure, and soil conditions. Proteobacteria contributed primarily to hydrolase activity, while Mortierellomycota were closely related to oxidative enzymes.

Conclusions

The finding reveals the principal drivers of maize straw decomposition and provide guidance for optimizing nitrogen fertilization strategies in conservation tillage systems to accelerate straw breakdown.

Background and scope

Mangroves distributed in intertidal zones along tropical and subtropical coastlines play key roles in nutrient cycling, energy transfer, and maintenance of ecosystem balance. The maintenance of mangroves’ high productivity and ecosystem functionality in nutrient-limited environmental conditions is very important. This paper comprehensively elucidates how mangroves sustain ecological balance and survive in nutrient-limited coastal environments.

Methods and results

The foliar nitrogen and phosphorus (N-P) concentrations and N:P ratios in different mangrove plant species and regions of the world are summarized, and results show that 73.7% and 16.4% of mangrove plants are N- and P-deficient, respectively. A comprehensive overview on the strategies employed by mangrove plants to conserve N-P in both above- and below-ground components is discussed. These strategies include N-P resorption efficiency, in short NRE and PRE, respectively, N-P use efficiency, litter quality, soil microbial activity, and N-P turnover rate. All these strategies are influenced by N-P content and their interactions, as well as secondary metabolites such as total phenolics and tannins in leaf and litter. Published data reveal mangrove leaves have higher NRE (56.2%) than PRE (48.8%), and NRE positively relates to PRE. Nutrient uptake by mangrove plants and N-P availability under different conditions, particularly global warming, rising sea levels and elevated atmospheric carbon dioxide (CO₂) situations, are discussed. A framework for gaining in-depth and targeted understanding of the trade-offs associated with N-P in mangrove ecosystems is proposed.

Conclusion

This comprehensive overview, based on the published results on N and P conservation and their trade-off in mangrove plants, provides useful information on ecological services and functioning of mangrove wetlands.

Graphical abstract

Background and aims

Neighbouring plants compete for resources in intensive cropping systems when the plant density is high. Most studies on plant density have focused on yield responses, whereas only few studies have paid attention to belowground root-soil-interactions. Knowledge about belowground responses to different plant densities under nitrogen (N) or phosphorus (P) limitation remains scant.

Methods

Two pot experiments were conducted in a glasshouse using a calcareous soil (pH 8.4). Five treatments were applied with different amounts of N or P and planted with different plant densities. Shoot and root biomass, and root morphological traits including total root length and proportions of root length in different diameter classes were examined in both the N and P experiment. Root physiological traits including rhizosheath pH, phosphatase activity and carboxylate concentration were measured in the P experiment.

Results

Plant biomass, P content and total root length increased with increasing plant density in the P experiment, while plant biomass, N content and total root length decreased with increasing plant density in the N experiment. Maize with high plant density released carboxylates and phosphatases under P deficiency.

Conclusion

Growing in calcareous soil, maize showed a competition effect at increasing plant density under N limitation, but an intraspecific facilitation effect at increasing plant density under P limitation. This study shows that maize (Zea mays L. cv. ZD958) released carboxylates and phosphatases in response to high soil pH under P-limiting conditions. The findings of this work are important towards the sustainability of intensive cropping systems.

Aims

Nitrogen (N) and phosphorus (P) deposition, along with climate warming, are key environmental factors driving soil organic carbon (SOC) dynamics in forests. The study aimed to explore the impact of N and P enrichment on soil respiration (SR) and its temperature sensitivity (Q₁₀) under short-term warming, and to reveal the underlying microbial mechanisms.

Methods

We collected soil samples from subtropical forests with 7 years of N and P additions, and conducted an incubation experiment at 15 °C, 25 °C, and 35 °C. SR and its Q₁₀, microbial carbon use efficiency (CUE), the Q₁₀ of soil extracellular enzyme activities (EEAs) and extracellular enzyme stoichiometry (EES) were evaluated.

Results

N and P additions reduced the Q₁₀ of SR within the temperature interval of 15–25 °C (moderate environment, MoE), indicating that increased nutrient availability weakens the positive feedback of SOC decomposition to warming in the MoE. The Q₁₀ of SR in the MoE was positively correlated with the Q₁₀ of β-D-cellobiohydrolase, but not with the CUE or Q₁₀ of EES, indicating that the reaction of SOC decomposition to warming depends on changes in C cycle-related enzymes rather than microbial resource availability. N addition reduced SR at 25 °C and 35 °C, and the vector length and angle of EEAs were closely related to SR, suggesting that SR depends on microbial nutrient limitation.

Conclusion

Our study highlights the importance of the Q₁₀ of soil enzymes in predicting SOC dynamics under short-term warming. Nutrient enrichment will promote SOC sequestration under climate warming in moderate environments.

Aims

Understanding the long-term effects of elevated atmospheric CO₂ (eCO₂) and warming on soil organic carbon (SOC), along with the microbial mechanisms involved, is important for predicting SOC stability in the context of future climate change.

Methods

Open-top chambers were used to simulate an increase in the atmospheric CO₂ concentration to 700 ppm (eCO₂) and an air temperature of 2 °C above the ambient temperature (warming) in a six-year experiment to examine the effects of eCO₂ and warming on the SOC fractions and bacterial community diversity. Maize plants were grown in four major farming soils, namely, Phaeozem, Kastanozem, Fluvisol and Acrisol.

Results

Six years of eCO₂ did not increase the SOC concentration in any soil but altered the distribution of the SOC fractions. In comparison, eCO₂ and warming decreased fine particulate organic C (fPOC) but increased the mineral-associated organic C (MOC) concentrations in Phaeozem and Kastanozem. In comparison, eCO₂ and warming significantly decreased the MOC in Fluvisol and tended to increase it in Acrisol. For Phaeozem, Kastanozem and Acrisol, fPOC was negatively correlated with MOC (p < 0.05). Warming altered the bacterial community composition in Kastanozem, Acrisol and Fluvisol. The increased abundance of Aquicella in Fluvisol under eCO₂ and warming was associated with accelerated MOC decomposition.

Conclusions

Long-term eCO₂ and warming might not alter the SOC stock but affect the bacterial community, accelerating C turnover among different SOC pools. The decrease in the MOC fraction of Fluvisol raises concerns about the SOC sustainability of this soil under climate change.

Background & aims

Tea tree (Melaleuca alternifolia) is an economically important crop with a narrow natural distribution in eastern Australia. Coastal and upland tea tree ecotypes have been identified based on unique shoot and root traits, but their mycorrhizal associations remain unknown. Dual mycorrhization—the ability of plants to associate with both arbuscular mycorrhizal (AM) and ectomycorrhizal (ECM) fungi—is particularly common among Australian Myrtaceae, including Melaleuca species, but has not yet been investigated in tea tree.

Methods

We investigated the mycorrhizal associations of tea tree in three coastal and two upland populations using ITS2 metabarcoding and root anatomical observations.

Results

Our results revealed that tea tree is a dual mycorrhizal plant, showing variability in root symbioses among ecotypes. ECM percentage root colonisation was significantly lower in the coastal tea tree ecotype compared to the upland ecotype, despite the coastal ecotype exhibiting significantly higher levels of ECM fungal richness. In contrast, the richness of the AM order Glomerales was significantly higher in the coastal tea tree ecotype than in the upland ecotype, yet comparable levels of AM root colonisation were observed between these two ecotypes. Mycorrhizal fungal community composition also differed significantly between coastal and upland ecotypes.

Conclusions

Our study provides evidence that tea tree is a dual mycorrhizal species that can host AM and ECM fungi simultaneously within individual plants. Our findings suggest that coastal and upland tea tree ecotypes vary in their associations with mycorrhizal fungi across native habitats, which differ in climate, soil characteristics, and vegetation structure.

Background and aims

Soil amendments with rock dust have been proposed for restoring regeneration on ultra-acidified forest soils. Rock dust is a poorly defined amendment, and its mode of action remains unclear. This study was set up to identify rock dust properties that predict plant responses in the field.

Methods

A field experiment with sycamore maple (Acer pseudoplatanus L.) saplings in two sites in the Campine region (NL) was constructed, both at a clearcut (soil pH = 3.5) and under the canopy of Pinus sylvestris L. (pH = 3.1). Treatments included six rock dusts and four reference treatments (TSP, dolomite, KCl, their combination). Rock dusts were amended in the planting pit and broadcast after being characterised for chemical composition and tested for dissolution in accelerated laboratory tests. Sapling growth was monitored for 40 months.

Results

Tree growth was affected by the site and rock dust type. The highest tree volume increases relative to the unamended control were with phonolite that increased volume by a factor 2 (clearcut) and by a factor 8 (under-canopy). On the clearcut, these increases were larger than the reference conventional dolomite and fertilisation treatments. Here, growth was only explained by rock dust’s water retention, which was superior for a zeolite-containing rock dust. Under-canopy, both growth and foliar nutrition were best related to liming and nutrient release by rock dust inferred from an 8-week laboratory-based soil + rock dust suspension test.

Conclusion

Rock dusts are effective to regenerate acid forest soils and laboratory tests of accelerated weathering can inform their potential.

Background and aims

Nickel (Ni) hyperaccumulator Odontarrhena chalcidica can absorb high levels of zinc (Zn) in its roots but fails to hyperaccumulate Zn in its shoots. The reasons behind the absence of this Zn hyperaccumulation trait in O. chalcidica, in contrast to known Zn hyperaccumulators, remain elusive. Nicotianamine (NA) is an organic ligand which can increase the mobility of metals in vivo by forming stable metals-NA complex. Thus, this study evaluated the influence of NA on root-shoot transport of Zn in O. chalcidica by comparison with the Zn hyperaccumulator Noccaea caerulescens.

Methods

Both species were cultivated under + Ni and + Zn treatments in hydroponic solutions. NA concentrations, the expression levels of NA synthesis related genes and Zn distribution in subcellular fractions of roots were evaluated. Additionally, the effect of exogenous NA supply on Zn transport was explored.

Results

NA concentrations in the roots of O. chalcidica declined from 2.30 to 0.600 mg kg⁻¹ under Zn exposure, whereas that of N. caerulescens significantly increased by 40.5% (to 3.09 mg kg⁻¹). Zn treatment suppressed the expression of OcNAS3 and OcSAMS2, which involved in NA biosynthesis, by 97.0% and 89.7%, respectively. Nevertheless, pretreatment with NA enhance soluble Zn fraction in roots, and increased root-shoot transport of Zn in O. chalcidica, raising the shoot-to-root Zn concentration ratio from 0.548 to 0.919.

Conclusions

The inhibition of NA synthesis by Zn is an important reason for the impaired root-shoot transfer for Zn in O. chalcidica. And NA plays a key role on the Zn mobility within plants.

Background and aims

The ability of plant microbial symbionts to enhance hosts´ fitness depends on the abiotic and biotic context, including the presence of co-existing symbionts. We studied how the presence of arbuscular mycorrhizal fungi (AMF) affects the performance of a host grass associated or not with fungal asexual endophytes, growing either alone or in interaction with a legume hosting nitrogen-fixing bacteria. We hypothesized that the presence of legume-rhizobia symbiosis enables endophytes and AMF to promote host grass growth and nutrition, as well as host and symbionts fitness through nitrogen acquisition-mediated effects even when their primary benefits (herbivore protection and phosphorous provision) are not required.

Methods

In pots with sterile, nitrogen-limited soil either inoculated or not with AMF, we grew Lolium multiflorum grass plants associated or not with a vertically-transmitted endophyte (Epichloë occultans), either in monocultures or in mixtures with rhizobia-inoculated Trifolium repens.

Results

In monocultures, grass C, N and P acquisition were reduced by AMF. Conversely, in mixtures with legumes, AMF increased grass growth, soil N uptake, and transfer of biologically fixed N from the legume to the grass. Endophyte and AMF both decreased grass fitness, but endophyte presence increased AMF spore density.

Conclusions

AMF can increase nitrogen transfer and increase grass growth, a benefit that relies on the presence of rhizobia-associated neighboring legumes. Notably, the fitness of plants and symbionts does not always align with the benefits provided to each other. The success of each host or symbiont may depend on their ability to capitalize on the benefits.

Background and Aims

Soil microorganisms are crucial contributors to the regulation of diverse ecosystem functions in natural ecosystems. However, the influence of land use types on the relationships between soil microbial diversity and soil multifunctionality (SMF) has been scarcely evaluated at a landscape level.

Methods

A high-resolution field survey was undertaken with 228 sites (2 × 2 km² grid each) to investigate the influence of four land uses on the relationship between soil microbial diversity (bacteria, fungi and protists) and SMF in Pinggu District, China.

Results

Soil microbial diversity index and multifunctionality were the highest in orchards and natural forests compared to plantations and cropland. Also, while soil microbial diversity index and SMF were positively correlated across all land uses and in natural forests. However, this relationship was decoupled within cropland, orchards and plantations. Increases in module richness within ecological networks were also important predictors of SMF, especially in cropland and orchards.

Conclusion

This study provides new insights on the impacts of land use types in changing the fundamental relationship between soil microbial diversity and function.