Plant and Soil最新文献

Background and aims

Increased soil salinization is the major cause of soil degradation. With the increase in soil salinization, accompanied by nutrient deficiency, the mechanisms of improving nutrient uptake and utilization by rhizosphere microorganisms under saline-alkaline conditions are largely unknown.

Methods

The growth parameters and accumulation of nutrients by broomcorn millet (Panicum miliaceum L.) were assessed under saline-alkaline conditions. Furthermore, the soil physicochemical properties and the types of rhizosphere microorganisms were determined.

Results

Broomcorn millet adapted to high saline-alkaline conditions by reducing its height and leaf area and increasing its root-shoot ratio. Salinity is an important factor that regulates the composition of the microbial community. Under high salinity (HS) treatment, the rhizosphere reshaped the microbial communities by recruiting specific beneficial microbes, namely Nocardioides, Saccharimonadal, and Nitriliruptoraceae bacteria that promote soil nutrient cycling and Operculomyces, Alternaria and Cryptococcus fungi that are involved in the decomposition of organic matter and the absorption of nutrients. In addition, the microbial community is influenced by the rhizosphere compartment, and more unique fungal operational taxonomic units (OTUs) are recruited in the high salinity rhizosphere (HS_R) compared to the high salinity non-rhizosphere (HS_NR). The changes in the microbial communities may promote the cycling of soil nitrogen (N) and phosphorus (P) in high salinity soil and ultimately promote the accumulation of P in all the organs and improve the N use efficiency of the plants.

Conclusion

The findings of this study reveal the mechanism of the adaptation of broomcorn millet to different levels of salinity stress and provide insights into microbial and fertilizer management in saline-alkali land.

Background and aims

Understanding soil nematode responses is crucial for assessing and predicting the effects of afforestation on soil food webs. While we possess good knowledge of the nematode taxonomic indicators (e.g., abundance and richness), the response of nematode trait distribution (e.g., body size) to afforestation, offering insights into community assembly, remains poorly understood.

Methods

We investigated the influence of afforestation (19-, 11- and 3-year-old forests and unplanted meadows) on soil nematode structure and trait distribution in a subalpine ecosystem.

Results

Taxonomically, afforestation did not enhance nematode community performance, e.g., nematode abundance in 11- and 3-year-old forests was lower than in unplanted meadows. However, afforestation significantly impacted distributions of body size. In 11- and 19-year-old forests, nematodes tended to be large-bodied, with body sizes more evenly distributed and less skewed, suggesting niche differentiation. However, in 3-year-old forests and unplanted meadows, nematodes were highly concentrated around smaller sizes, with only a few large-bodied individuals, indicating environmental filtering. According to redundancy analysis, we found that small-bodied nematodes in 3-year-old forests and unplanted meadows related to poor soil fertility with high carbon: nitrogen ratio, while large-bodied nematodes in 11- and 19-year-old forests were associated with fertile soils, as indicated by high nitrate and available phosphorus.

Conclusion

Our study reveals assembly rules for soil nematodes: afforestation leads to the replacement of smaller nematodes in meadows with larger ones in older forests, mainly due to increased niche differentiation. This research highlights the importance of trait distribution in understanding afforestation’s ecological impacts on soil food webs.

Background and aims

The increasing occurrence of extreme drought events under climate change alters the composition and functioning of plant communities worldwide. Drought-induced changes in plant-soil feedback (PSF), reciprocal effects on fitness between plants and their associated soil microbial communities, are one mechanism through which these changes in vegetation occur, but they remain difficult to predict. Because of their direct link to rhizosphere microbial communities, we expect root traits to predict drought-induced PSF shifts.

Methods

In the conditioning phase of a greenhouse experiment, we subjected 12 common grassland species to drought. In the feedback phase, all species were grown under ambient conditions with their own microbial inoculum. Their growth was compared to growth in sterile soil to assess total PSF or soil inoculated with microbes from three other species to assess specific PSF. We used root traits to predict PSF under drought and ambient conditions.

Results

Drought altered the magnitude and direction of PSF in a quarter of the species, which was consistent between total and specific PSF. Total PSF was best predicted by the first axis of the root trait space (high specific root length to high root diameter and root nitrogen content) and was not responsive to drought. Specific PSF was weakly predicted by root traits and changed in response to drought.

Conclusion

Our results show that drought can modify the feedbacks between plants and their microbial communities with implications for vegetation dynamics. Root traits have limited capacity to predict these shifts, but can predict PSF of the total microbial community independent of drought.

Background and aims

To provide insight into the patterns of soil organic matter decomposition, changes in the quantity of biopolymers and the correlation between them were followed using 2D correlation spectroscopy (2DCOS) FTIR.

Methods

Soil organic matter fractions with different vegetation/land use (grass, spruce, oak and arable) were examined in a 1-year laboratory incubation. The non-protected organic matter fraction was calculated in terms of particulate organic matter (POM), the carbon stabilized in aggregates as S + A (sand + aggregates), and the mineral-associated organic matter (MAOM) as the s + c (silt and clay) fraction.

Results

Forest soils (spruce, oak) exhibited high C and N accumulation in the POM fraction (48, 43% and 29, 22% for spruce and oak, respectively) due to the limited decomposition, caused by low pH and high soil C/N ratio. The 2DCOS analysis revealed that carbohydrate-protein and carbohydrate-lignin correlations could be observed most frequently during incubation. The carbohydrate-protein correlation was negative in all cases, for all fractions and for all vegetation types, which suggests biogeochemical linkage between these biopolymers. The temporal order of the spectral changes was widely varied for the vegetation types and especially for the SOM fractions. Lipid/Lignin → Carbohydrate or Lipid → Lignin/Carboxyl/Protein sequences were found for the protected carbon pools (S + A and s + c), possibly because of the readily available abundant N compounds present in MAOM.

Conclusion

Although lipids and lignin are considered as chemically stable materials that commonly remain constant during decomposition, these compounds were found to be very susceptible in all the fractions.

Background and aims

Campo rupestre is an ecosystem in the Espinhaço Mountain Range with high species richness and endemism. The tolerance of Vellozia epidendroides, predominant in this ecosystem, to dehydration seems to facilitate the survival of other plant species. Hence, the importance of V. epidendroides in ecological restoration projects is high. The objective of this study was to evaluate the survival and ecophysiological vegetative performance of V. epidendroides associated with other native species - Apochloa molinioides (Poaceae), Cipocereus minensis (Cactaceae), and Vellozia resinosa (Velloziaceae) - in a project to rescue and reintroduce plants in an area of campo rupestre.

Methods

Vellozia epidendroides was reintroduced isolated or as the main plant in seven combinations of intercrops with the three other species (seven treatments), randomized in three blocks. V. epidendroides (T1), V. epidendroides + V. resinosa (T2), V. epidendroides + C. minensis + A. molinioides (T3), V. epidendroides + C. minensis (T4), V. epidendroides + V. resinosa + C. minensis (T5), V. epidendroides + V. resinosa + A. molinioides (T6), V. epidendroides + V. resinosa + C. minensis + A. molinioides (T7).

Results

Overall (all treatments), the survival of V. epidendroides and V. resinosa was 100% and that of C. minensis was 58.3%. The survival of V. epidendroides + C. minensis + A. molinioides, together, was the lowest (66.67%), with all plants of C. minensis dying after 365 days of planting. Shoot emergence was the only ecophysiological performance parameter that varied among treatments, with the highest value for V. epidendroides in T7 when associated with the other three species; V. resinosa associated to V. epidendroides, and C. minensis in the treatment with all four species.

Conclusion

The reintroduction of species is feasible with V. epidendroides as a companion plant in the reintroduction with the other species, A. molinioides, C. minensis, and V. resinosa, in quartzite areas of campo rupestre.

Graphical abstract

Background and aim

Global nitrogen (N) deposition has been proposed to enhance phosphorus (P) limitation in various terrestrial ecosystems. The impact of N addition on soil P transformation, considering both microbial and abiotic properties, is not well understood.

Methods

In this study, the experiment with three levels of N addition (0 (N0, no fertilizer), 25 (N25) and 50 kg N ha⁻¹ yr⁻¹ (N50)) was implemented in a temperate broad-leaved forest to assess the long-term (12 years) effects of N addition on soil P fractions associated with soil properties, iron, aluminum, calcium, phospholipid fatty acids (PLFAs), and enzyme activities.

Results

The results indicated a significant decrease in labile P, despite of a significant increase of approximately 54.0% in available P under N addition (N50). In contrast, the moderately labile P significantly increased under N addition treatment because of the increase in organic P in less labile fractions. The redundancy analysis and mantel-test found soil pH and MBP contributed to the variation of soil P fractions. The results of structural equation model confirmed that the microbial biomass P play a key role in the transformation of soil available P into moderately and occluded P fractions.

Conclusion

These results suggested that the long-term addition of N decreased soil labile P and increased moderate and occluded P fractions through increasing microbial P use efficiency with increased MBP, leading to the enhancement of soil P limitation in the broad-leaved temperate forest.

Background and aims

Soil acidification can negatively affect agricultural production by reducing uptake of essential nutrients and increasing aluminium toxicity in crops. This study investigated whether hyperspectral imaging could accurately measure wheat response to soil acidification and subsequent remediation via liming.

Methods

A high-throughput, automated greenhouse and hyperspectral imaging facility was used to evaluate differences between hyperspectral data of wheat plants in either acidic soil or soil that had been limed. Using RGB imaging and growth rate prediction, plant growth was measured to assess if it increased with lime application. The study also used partial least squares regression analysis (PLSR) to assess whether hyperspectral imaging could predict plant tissue nutrient concentration and indicate nutrient deficiencies and toxicities associated with soil acidity.

Results

Spectral differences were observed between plants in acidic and non-acidic soil around the end of tillering and beginning of stem elongation. The red edge spectral region contributed significantly to this difference and, when used in vegetation indices, confirmed increases in plant growth following lime application, observed via high throughput phenotypic analysis. PLSR analysis was ineffective in predicting nutrient concentration of plant tissue in this context, likely due to low concentrations of nutrients associated with acidification, limited sample size, and small variation in nutrient concentrations.

Conclusions

Findings suggest that hyperspectral imaging could prove useful in the detection of soil acidification effects on wheat crops under contained controlled environmental conditions, and may, with further in-field testing, enable improved spatial mapping of paddocks to help remediate this significant agricultural issue.

Aims

Forest gaps disturb soil available nutrients and microbial biomass unparallelly along precipitation gradients, leading to stoichiometric mismatches that limit the growth of microbial communities. However, adaptions of microbial physiological and metabolic processes to the stoichiometric limitations and the resulting effects on soil carbon (C) dynamics are still poorly understood. The main aims here were to understand how microbial metabolic limitation is affected by interactions of forest gaps and mean annual precipitation in relation to plant and soil physiochemical properties, and how the metabolisms impact rates of key soil processes such as soil microbial respiration.

Methods

We compared microbial physiological adaptive traits (metabolic limitation, C use efficiency (CUE) and extracellular enzyme activities) and respiration rate between harvested gaps and unharvested stands within Robinia pseudoacacia plantations along the mean annual precipitation gradient in northern Shaanxi, China.

Results

Forest gaps strengthened metabolic limitation for soil microbes, as well as their dependence on mean annual precipitation. Plant biomass (58.9%) predominantly accounted for variations in microbial relative C limitation, while soil water content (29.1%), dissolved nutrient availability and stoichiometry (52.0%) were primary predictors for microbial P limitation. In this context, soil microbial communities adapted by altering their ecoenzymatic production, CUE, and biomass composition simultaneously. The PiecewiseSEM analysis revealed that the elevated microbial respiration after forest gap formation was directly associated with a reduction in microbial biomass and indirectly related to lower microbial CUE and higher enzymatic activity. These findings indicate that the synchronized regulation of lower CUE and higher enzymatic production results in a greater expenditure of energy on the maintenance of microorganisms than on the formation of cells.

Conclusion

This study presents novel insights into microbial-driven C dynamics response to interactive effects of forest gaps and precipitation variabilities, having implications for evaluating sustainability of forest management strategies in the anticipated climate-change scenario.

Background

Precipitation regimes in arid and semi-arid regions are exhibiting a trend of increase in rainfall intensity but reduction in frequency, affecting soil communities and ecosystem functions. Soil nematodes are essential components of soil communities, partaking in multiple energy channels and underpinning various crucial ecosystem functions. Understanding the impact of precipitation regime changes on energy fluxes within soil nematode food webs has a decisive impact on ecosystem function under global climate change.

Methods

This study conducted a long-term field experiment established in 2012 to simulate precipitation regime changes (the total precipitation added was 80 mm unchanged, but the size and frequency of applied precipitation events were varied) in a semi-arid grassland of Inner Mongolia. We quantified the metabolism and energetic structure of soil nematodes. We further investigated the responses of metabolic rate of trophic groups and energy fluxes within soil nematode to changes in precipitation regime, and how such changes in nematode energy dynamics affect ecosystem multifunctionality (EMF).

Results

We found that heavy precipitation intensity increased the metabolic rates and energy fluxes of all trophic groups, and the EMF index was maximized. The EMF values were positively correlated with the metabolic rates and energy fluxes of bacterivores and omnivores/predators.

Conclusions

These results suggest that a shift toward higher-intensity and lower-frequency precipitation events could lead to an increase in energy fluxes within soil nematode food webs, thereby enhancing their contributions to EMF. These findings provide insights into the role of energy dynamics in affecting EMF under various scenarios of precipitation pattern changes.

Aims

This study aims to investigate the impact of exopolysaccharides (EPS) from Rhizobium tropici on the growth of wheat (Triticum aestivum) seedlings under varying aluminum (Al) concentrations. We explored EPS mitigation of Al toxicity, a major growth-limiting factor in global acidic soils.

Methods

The effects of EPS on wheat were assessed by measuring shoot and root growth, photosynthesis, and lipid peroxidation under different Al concentrations. The study also examined Al uptake and transport within the plant as affected by EPS.

Results

Al exposure was found to substantially decrease shoot and root growth, impede photosynthesis, and cause intense lipid peroxidation in wheat. Application of EPS notably enhanced wheat growth, increasing shoot and root lengths by 86% and 244%, respectively, and dry biomasses of both shoots and roots by 100% and 104%, respectively, compared to the non-EPS treated group. EPS also limited Al absorption and transport in wheat, bolstering antioxidant defense against the oxidative stress. Subcellular analysis revealed that EPS promoted Al accumulation in cell walls and cytosol compartmentalization. Additionally, EPS appeared to regulate phosphorus (P) distribution within subcellular components, mitigating membrane lipid peroxidation and thereby enhancing plant’s Al resistance.

Conclusions

EPS effectively mitigates Al toxicity in wheat seedlings, suggesting its potential application for alleviating Al stress in plants. The study offers new perspectives for potential using EPS in agricultural practices, particularly in acidic soils. Future research should focus on field trials to validate these findings.