Plant and Soil最新文献

Background and aims

Seasonal precipitation regimes can affect soil nitrogen (N) transformation rates, yet the underlying driving factors remain poorly studied.

Methods

To address this knowledge gap, we conducted a precipitation manipulation experiment in a subtropical forest in China from 2020 to 2022. We utilized the in situ resin-core method to assess soil physicochemical properties, microbial biomass, net nitrification rate (N_nit) and net N mineralization rate (N_min) under three treatments: control (CK), decreased precipitation by 50% during the dry season with extremely increased precipitation (≥ 50 mm) during the wet season (IE) and decreased precipitation by 50% during the dry season with proportionally increased precipitation (≤ 20 mm) during the wet season (IP).

Results

IE and IP significantly decreased N_nit (57.9% and 72.5%, respectively) and N_min (82.5% and 89.6%, respectively) during the dry season. However, the results were reversed during the wet season (increased by 64.3% and 79.5% and by 64.2% and 81.1%, respectively), and the effects of IP were significantly stronger than those of IE. Structural equation modeling indicated that seasonal precipitation regimes significantly affected N_nit and N_min by changing soil water content, NH₄⁺-N, microbial biomass N and soil C:N ratio. Moreover, N_nit and N_min were mainly influenced by soil physicochemical properties during the dry season, whereas microbial biomass played a more important role during the wet season.

Conclusions

Seasonal precipitation regimes can significantly affect N_nit and N_min in forest ecosystems, with the magnitude of these effects varying depending on the specific form of the seasonal precipitation regime. 

Background and aims

The effects of elevated tropospheric ozone (O₃) concentrations on terrestrial ecosystems have been extensively researched by numerous O₃ fumigation experiments and syntheses. While the detrimental impacts of O₃ stress on aboveground plant physiological traits are well-documented, there remains a gap in our understanding of how elevated O₃ influences soil microbes and plant–microbe interactions.

Methods

Here, we synthesized data from 71 O₃ fumigation experiments conducted globally to evaluate the effects of elevated O₃ on soil microbial characteristics, including biomass, community composition, and extracellular enzyme activities (EEAs).

Results

Elevated O₃ led to an average reduction of 14.2% in microbial biomass carbon (MBC). It was largely attributable to decreased plant carbon input, as the effect size of MBC was closely correlated with declines in both aboveground and root biomass. Fungal communities appeared more vulnerable to O₃ stress than bacterial communities, as evidenced by a 10.7% decrease in fungal phospholipid fatty acids (PLFAs), while total and bacterial PLFAs were only marginally affected. Furthermore, the negative impacts on microbes intensified with increasing O₃ concentrations but tended to diminish over time. In addition, elevated O₃ significantly reduced hydrolytic EEAs, which target simple compounds, by 12.9%, while increasing oxidative EEAs, which degrade recalcitrant compounds, by 12.0%. It suggests that O₃ stress would affect the decomposition of soil organic matter by shifting EEAs.

Conclusion

Elevated O₃ impairs soil microbial growth and changes microbial C utilization strategies, which could profoundly impact C cycling in terrestrial ecosystems.

Background and aims

Hyperspectral imaging is becoming a key, high-throughput technique in plant research. However, its application to roots has not yet received sufficient attention. The aims of this study are to identify spectral features that distinguish fine roots from soil, non-woody roots of different species, and dead from living roots, and to identify appropriate analytical techniques.

Methods

Roots of Alopecurus pratensis (meadow foxtail) and Urtica dioica (nettle) and the rhizosphere were imaged in rhizoboxes in the wavelength range 400–1700 nm, covering both visible near- (VISNIR) and shortwave infrared (SWIR) regions. Principal Component Analysis, K-means clustering, and Generalised Linear Model, Partial Least Squares Discriminant Analysis, and Distributed Random Forest models were used to classify groups. Wavebands critical for classification were identified.

Results

Our results demonstrate the intricate nature of spectra clustering, highlighting the challenges in the VISNIR range and the promise of SWIR data for enhanced separability. While species differentiation is challenging, the determination of the living conditions of the roots is possible within the SWIR range. The analysis reveals the significance of specific spectral regions, notably those associated with water content and senescence, in distinguishing between living and dead roots. Water content regions (mainly 1245 nm and 1450 nm) were most important in discriminating between roots and soil.

Conclusions

This study highlights the potential of spectral analysis, particularly in the SWIR region, for distinguishing roots by species and vitality. Further efforts are needed to develop robust methods for mixed data sets containing roots of different species and degrees of vitality.

Graphical abstract

Aims

The objective of this study was to evaluate the effect of different mixed grass-legume pastures compared to single grass cultivation as the second crop of an integrated crop livestock system (ICLS) in Brazilian Cerrado on (i) soil organic carbon and nitrogen pools, (ii) microbial biomass, enzyme and microbial activity of the soil, (iii) soil health, and (iv) soybean grain yield in succession.

Methods

In this experiment, the soybean was cultivated in the summer season, with the subsequent treatments with two grasses (Urochloa ruziziensis or Urochloa brizantha), single or intercropped with Cowpea (Vigna unguiculata) or Pigeon pea (Cajanus cajan), and soil collections were carried out 2 years after the implementation of the experiment, which was in 2015.

Results

Regardless of the grass species, Cowpea intercropping yielded 28% more soybeans than single-cropped grasses. The intercropping effects on soybean yield were directly related to improvements in soil biological and biochemical properties since there was a higher microbial biomass and activity, and enzymatic activity in the soil. In addition to the higher basal respiration and metabolic quotient (qCO₂), the lower microbial quotient (qMIC) indicates a microbial stress condition in grass monoculture compared to mixed grass-legume pastures.

Conclusions

The mixed grass-legume pastures are effective strategies to increase C and N stocks in different soil pools under integrated crop-livestock systems, reflecting increases in soybean grain yield. Grass-legume intercropping in the pasture phase of ICLS is an additional tool to maximize soil health improvements and soybean yields in the short term.

Graphical abstract

Background and aims

A nano-silica/polymer composite (NSPC) was developed as an environmentally friendly agent and applied as a sustainable sand-fixing material. This study aimed to investigate the effects of the NSPC curing agent on enhancing the growth of plants in sandy soil and the role of silicon (Si) in plant metabolism.

Methods

Four different grasses (Poa pratensis, Festuca arundinacea, F. rubra and Lolium perenne) were grown in a monoculture pot experiment in a controlled growth chamber at 3 °C with a 12 h photoperiod. After the addition of NSPC to sandy soil, grass seeds were allowed to grow for 60 days. The changes in the total chlorophyll (Chl a + b) and carotenoid (Car) contents and the amount of Si, defined as the total silica, in grasses at different growth stages were determined. Seedling growth was measured manually by using measuring tape or handheld instruments such as Vernier callipers. The uptake and translocation of silica nanoparticles in the grass plants were investigated by transmission electron microscopy.

Results

The results revealed that, compared with the control, NSPC treatment positively affected the seedling growth and Chl and Car contents of the grass. Furthermore, NSPC significantly promoted photosynthesis and increased the Si content of grass in sandy soil by facilitating the uptake of silica nanoparticles into cells.

Conclusion

NSPC application to sandy soil improved the morphophysiological and biochemical responses of grass plants, leading to improved grass yield potential. This effect was attributed to the increased photosynthetic efficiency mediated by the cellular uptake of silica nanoparticles.

Graphical Abstract

Background and aims

Soil organic carbon (SOC) content is regulated by the combined effects of multifactorial drivers. However, the interactions between SOC and these drivers, as well as the potential networks linking them, have rarely been quantitatively assessed.

Methods

Based on a large-scale soil survey from 260 sites across the Mongolian Plateau, we examined the direct and indirect effects of climatic, edaphic, ecological, and mineral factors (a total of 11 variables) on SOC, and assessed the sensitivity of SOC and reactive minerals (amorphous, free forms of Fe/Al-(hydr) oxides) to the aridity index (AI) through meta-analysis (n = 2405).

Results

The mineral-associated organic carbon (MAOC) increased linearly with SOC accumulation across the Mongolian Plateau. Boosted regression trees (BRT) analysis indicated that the mineral factor exhibited the greatest impact on SOC, accounting for 35.4% of the variance, followed by soil properties (23.6%), ecological (22.8%), and climatic factor (18.2%). Path analysis and variance partitioning analysis (VPA) revealed the distinguishing role of reactive minerals in SOC retention and the smaller direct effect of climate compared to its indirect effects.

Conclusion

SOC and reactive minerals exhibited a positive responded to AI on a global scale, with a higher sensitivity to AI in arid regions. On the Mongolian Plateau, AI promoted substantial accumulation of metal-bound organic carbon (OC) and enhanced metal–organic associations. These findings revealed the complex interactions between climate, soil, mineral, and ecological factors in regulating SOC and highlighted the critical role of reactive minerals in SOC preservation in arid regions.

Graphical Abstract

Background and aims

The Allchar site in North Macedonia has a unique geology exceptionally enriched in arsenic and thallium, making the local soils extremely toxic to plant life. Surprisingly, the mineralized soils at Allchar host a diverse flora, with unknown metal(loid) accumulation potential for most of these plant species. The main aim of this study was to determine the elemental profiles ('elementomes') of plant species growing naturally in the Allchar area and to assess their elemental accumulation in relationship to concentrations in the soil in which the plants grow.

Methods

Samples of in total 23 plant species (with at least 4 replicates per species) and their associated rhizospheric soils were collected in the field at the Allchar site in North Macedonia and analysed with monochromatic X-ray fluorescence analysis for total and DTPA-extractable metal and metalloid concentrations.

Results

High foliar concentrations of thallium were found in some plant species, being the most extreme in Silene latifolia, at 79,200 µg g⁻¹ thallium, whilst arsenic concentrations are generally low in most of the plant species analysed. Thallium hyperaccumulation (> 100 µg g⁻¹) was found in the families Violaceae, Lamiaceae and Caryophyllaceae. Particularly high foliar thallium concentrations were found in Viola arsenica and V. tricolor subsp. macedonica, reaching up to 31,600 and 11,700 μg g⁻¹ thallium, respectively. The elemental concentrations in soil and plant samples reflect that of the local mineralogy of the three different areas investigated at the Allchar site, with the highest mean values for thallium and arsenic in the Crven Dol area, and 249 and 3970 μg g⁻¹, respectively, in the plants that were analysed.

Conclusion

The present study led to the discovery of several new thallium hyperaccumulating plant species, such as Clinopodium alpinum, Anthyllis vulneraria and Linum hirsutum, whereas the thallium concentrations found in Silene latifolia are the highest thus far recorded in nature highlighting the potential of this species for thallium phytomining applications.

Background and aims

Trace metal (TM) contamination has been and still is a major environmental threat as pollutants are frequently released to the environment through various channels. High biomass plants used for energy production can be a good option for decontamination or stabilization of soils. In the present study we have tested Szarvasi-1 energy grass (Elymus elongatus subsp. ponticus cv. Szarvasi-1) under single or combined treatment with three TMs (Cu, Cd, and Pb) in three concentrations aiming to reveal bioaccumulation and ionomic characteristics.

Methods

The plants were grown in soil spiked with Cd, Cu and Pb in single or combined treatments. Physiological and elemental data were collected, and the changes were evaluated using several multivariate analyses.

Results

Germination, growth, chlorophyll (Chl) content and photochemical reflectance index (PRI) declined in the Pb < Cu ~ Cd order whereas the relative water content and malondialdehyde (MDA) content of the shoots were stable across the treatments. In the combined treatments the growth variables, Chl and PRI declined rapidly and MDA increased showing the exhaustion of detoxification capacity of the plant. The accumulation of TMs (bioconcentration factor) decreased in the following order Cd > Cu > Pb in both single and combined treatments but in the latter the accumulation pattern slightly changed in favour of Pb. The nutrient and trace elements showed a characteristic change in their pattern in the shoots.

Conclusions

Our study points to the limitations of the application of grasses such as Szarvasi-1 energy grass in phytoremediation projects conducted on soils with multiple metal contamination.

Background and aims

Litter decomposition shapes nutrients dynamics and ecosystem functioning. Effects of component leaf litter abundance and species richness in a mixture on its own decomposition remain unclear.

Methods

Using leaf litter of 1 to 5 coexisting species, we manipulated the proportions of mixed litters (resulting in 106 different mixtures), and monitored the biomass decomposition of individual species component in mixtures over a year. For each species, we separately recognized two gradients: focal species abundance (i.e., leaf litter abundance) and species richness (i.e., the number of other plant species surrounding the focal species in mixtures) in mixtures. We then simultaneously considered both effects of litter abundance and richness on litter mass loss at species level.

Results

Species abundance could increase its own litter decomposition (i.e., abundance effects) at least for Thermopsis lanceolata and Anemone rivularis, and species richness promoted litter decomposition of the reference species (i.e., richness effects) for each species. High quality of leaf litter (low cellulose:nitrogen, etc.) at species level promoted abundance effects, while low quality (high hemicellulose:phosphorus, etc.) enhanced richness effects.

Conclusion

There were positive effects of component litter abundance and species richness in the mixture on its own decomposition, and the effects of both depended on its own initial litter quality. These results set a new path to improving our understanding of litter decomposition in natural ecosystems. This study suggests that in the future, theoretical models and experimental studies of litter decomposition need to consider the influence of abundance of litter components in the mixture.

Background and aim

Soil health is vital for the sustainability of ecosystem services such as food and fiber production, nutrient cycling and water supply. Soil health can be assessed through a combination of physical, biological and chemical metrics. There is emerging evidence that reactive silica is a strong factor controlling soil functions.

Scope

We explain how reactive silica, specifically dissolved silicic acid and amorphous silica, can be used as a new metric for assessing soil health, complementing traditional metrics or even substituting for them.

Conclusion

The pivotal role of reactive silica for soil health is particularly important under stress conditions that are typically associated with drought and soil degradation. The status of reactive silica indicates soil degradation earlier than the currently used metrics, because reactive silica depletion is followed by soil degradation. We recommend suitable methods and benchmarks for assessing reactive silica. Furthermore, we suggest further research to improve our understanding of the importance of reactive silica for soil health. We call upon the soil research community to include reactive silica as a metric for soil health assessment.