Plant and Soil最新文献

Background and aims

‘Earth-air’ refers to air in the vadose zone (VZ). Barometric pumping results in the rising and falling of earth-air in the VZ. Earth-air vertical movement (EVM) has an important effect on water transport in the VZ. However, phreatic water is an important source of water in the Loess Plateau, the effect of earth-air on water content is unclear.

Methods

This paper aims to reveal the effect of earth-air on the water content in the VZ of loessal soil by calculating the amount of earth-air and measuring volumetric water content (VWC), temperature, and relative humidity (RH).

Results

Our results showed that the variation of the VWC in the Loess Plateau is directly proportional to the amount of EVM. It is the sum of water vapor gains and losses from earth-air. Also, the amount of water in the earth-air is positively correlated with the frequency of the fluctuations in the atmospheric pressure (AP), thickness of the loess layer, aerated porosity, and gradient of the soil water vapor concentration. The correlation of recorded every 10 min for 3 years between the calculated VWC of the soil and the monitored values is 0.76.

Conclusion

This study reveals a new way in which soil water migrates in the Loess Plateau and furthers our understanding of the spatiotemporal distribution mechanism. It also provides a scientific basis for the utilization of scarce water resources in semi-arid areas such as the Loess Plateau region.

Background and aims

Functional traits are fundamental for understanding and predicting crop responses to abiotic stress and yield improvement. Root functional traits are key determinants of carbon allocation and water transport efficiency. However, there are few studies integrating the effects of physiological and anatomical phenotypes in roots on yield.

Methods

We performed a global scale data analysis to quantify the ecological effects of root functional traits on yield under abiotic stress. A field study was also conducted to test the relationships between yield and root anatomical traits such as cortex area and xylem area in two semi-arid regions in China.

Key results

The search of literature on the relationships between yield and root phenotypes was fairly consistent with the results in the field. Meta-analysis showed specific root respiration was negatively related to yield under stress. Critical thresholds of whole root respiration (RR = 0.823) and xylem area (RR = 0.912) were observed for better yield under stress. Hydraulic conductance was positively correlated with xylem area, stele diameter and vessel number under stress. In the field study, there were inverse relationships between yield and cortex area and xylem area was positively related to wheat yield at both sites.

Conclusions

Our study suggests that there are inverse relationships between yield and cortex area and respiration. Increased yield was associated with decreased whole root respiration with potentially smaller cortical tissue when whole respiration under stress was reduced by less than 17.7% compared with the control. However, increased xylem area contributed to high yields at both sites under rain-fed conditions.

Highlights

1. 1.

   Specific root respiration was negatively related to yield under stress.

2. 2.

   Whole root respiration was negatively related to yield under stress beyond an optimal value (RR = 0.823).

3. 3.

   There were inverse relationships between yield and root cortical area in two regions.

4. 4.

   A critical threshold of xylem area was observed for yield under stress (RR = 0.912).

Background and aim

Consortia-based inoculants, such as the microbiome method, are advocated over individual biocontrol agents (BCAs), owing to partner reinforcement and rapid rhizospheric establishment. Herein, we screened the sole and dual suppressive effects of selected desert spurge (Euphorbia antiquorum) derived Bacillus spp. vis-à-vis Ralstonia solanacearum.

Methods

The conventional agar diffusion method was used to examine the BCAs' capacity to release antibiotics. Thereafter, the compatibility, the ability to form biofilm and the phytotoxicity of the BCAs towards tobacco leaves were screened. The Box-PCR fingerprinting technique was adopted to ascertain the endophytism of the BCAs, and the wilt suppression test followed by the specific activity of defence-related enzymes was performed.

Results

R. solanacearum was completely inhibited by the extracts from Bacillus velezensis CBv_BE1, Bacillus amyloliquefaciens CBa_BFL2, and Bacillus amyloliquefaciens CBa_RA37 at 0.625 mg/mL. The outstanding candidates could form biofilm and colonize into tomato seedlings, with a plateau at log10 CFU = 4.29/g fresh weight. The consortium from CBa_BFL2 and CBa_RA37 (CBa_BFL2/CBa_RA37) yielded vigorous plants (up to a 319% increase in biomass). Likewise, a 90% and 89% reduction in wilt incidence and severity was recorded by the CBa_BFL2-CBa_RA37 combination. The Guaiacol peroxidases (GPX), phenylalanine ammonia lyase (PAL), and superoxide dismutase (SOD) specific activity were significantly and inversely correlated with wilt severity via Pearson's test. This alludes to a greater innate defence system in tomatoes in response to bacterization.

Conclusions

Our data suggest that tomato priming with a consortium of B. amyloliquefaciens CBa_BFL2 and CBa_RA37 resulted in vigorous and healthier tomato seedlings as referred to their sole effects, with altered activities of key plant distressing enzymes. However, further studies are warranted to reveal its full potential as a pioneering alternative to agrochemicals for the control of bacterial wilt.

Graphical Abstract

Background and aims

Peat-accumulating wetlands have undulating surfaces of raised areas (hummocks) and depressions (hollows). Hummock-hollow microtopography in relation to the water table influences the distribution of plant species, root density, and microbial community composition, which could in turn alter carbon (C) and nitrogen (N) cycling within peatlands. We used paired hummock and hollow cores from a boreal, forested peatland to assess how microtopography influences peatland microbial function and, in turn, ecosystem C and N cycling.

Methods

The peat was analyzed for microbial biomass and potential enzyme activity in 10 cm depth increments relative to the water table, resulting in two increments for hollows and three for hummocks, which has a raised increment above the water table.

Results

Across hummocks and hollows, microbial C and N and fungal biomass generally decreased with depth from the peat surface. In contrast, potential enzyme activity often increased with depth, but this varied within enzyme functional groups according to topography, depth, or both. The potential enzyme activity of C-N degrading peptidases, for example, differed across the five topography × depth increments with the lowest rate in the aerated hummocks. Hummocks compose approximately 66% of the land area at our study site and would therefore underestimate C turnover by an average of 25% if solely used to extrapolate patterns across a forested bog.

Conclusion

Our results suggest that asynchrony in C and N cycling across the undulating surface of forested peatlands impacts our ability to accurately predict biogeochemical cycling across this important ecosystem.

Background and aims

Cereal-legume intercropping (IC) is proposed to address the challenges of increasing yields and improving crop nutrient quality, crucial for food security and human health. This study aimed to characterize the impact of pea-wheat IC on grain ionome composition, and asses its potential relation with the abundance of Pseudomonas spp. and Enterobacterales in plant roots.

Methods

In a field experiment, four pea varieties were cultivated in sole- or intercropping with wheat in two different soil types. Grain ionome was analysed by mass spectrometry, while Pseudomonas spp. and Enterobacterales abundances were quantified by qPCR.

Results

Pea grains intercropped with wheat showed increased concentrations of Ca, Mg, and Mo in one soil type, and higher Mn and Ni concentrations and total grain content in another. Wheat grains intercropped with peas, exhibited increased Cu, Fe, Mn, N, S, and Zn concentrations and/or total grain content, only in one soil type. Pseudomonas spp. showed increased abundance in pea root tissues when intercropped with wheat, specifically in one soil type. Pseudomonas spp. appeared to affect K, Fe, and Zn concentrations or total content in pea grains, depending on the cropping system.

Conclusion

These findings suggest that IC can enhance specific element concentrations and/or total grain content in pea and wheat grains, upon soil type. Pseudomonas spp. may facilitate nutrient uptake and translocation to grains. Further research is needed to understand the mechanisms behind element accumulation in IC grains and to explore the potential benefits of IC for plant nutrition and growth.

Aims

Common Juniper (Juniper communis) populations in western Europe are rapidly declining due to a lack of regeneration, which has been linked to nitrogen (N) deposition. However, the mechanisms by which N deposition affects juniper are not clear. Nitrogen deposition can lead to N eutrophication and soil acidification, which cause nutrient leaching and metal mobilisation with potential negative impacts on juniper regeneration. We investigated associations among soil element concentration (soil [E]), needle element concentration (needle [E]) and plant performance in terms of height growth and viable seed production.

Methods

We sampled adult females and juveniles across 6 natural heathland areas in the Netherlands and Belgium, and applied linear mixed models for eleven elements to test associations among plant performance, soil [E], and needle [E].

Results

Soil [E] was reflected in needle [E], which subsequently was associated with juniper growth. However, direct associations between soil [E] and growth were absent. Seed viability was positively associated with soil Mg concentration, marginally with Ca and needle Ca and K concentrations, and negatively with soil NO₃ and needle N, S and Zn concentrations. Generally seed viability, needle Ca and K concentrations were low. Soil Al/P ratio was a better predictor for needle P than soil P concentration indicating that Al inhibits P uptake.

Conclusion

We conclude that 1) N eutrophication reduces seed viability, but increases growth, 2) nutrient leaching reduces nutrient uptake, seed viability and subsequently growth, and 3) Al mobilisation reduces P uptake and indirectly growth. N deposition amplifies these mechanisms and therefore inhibits regeneration and survival of juniper populations in western Europe.

Aims

Greenhouse tomatoes production with high productivity but also with high fertilizer inputs has rapidly developed in the Yangtze River Delta. It is a great significance to explore methods for reducing environmental cost for the sustainable development of facility agriculture in the region.

Methods

Based on farmer survey data grouped according to yield and efficiency, this study analyzed the resource input, environmental cost, and mitigation potential of plastic-greenhouse tomato production and identified reasonable mitigation measures for tomato production in the Yangtze River Delta.

Results

The average loss of reactive nitrogen (Nr) in the farmers’ tomato production systems was 96.7 kg N ha⁻¹; the N footprint was 1.14 kg N t⁻¹; and the Nr emission per unit net profits (Nr_NP) was 7.75 kg N $1000^–1. There was a large difference in the active nitrogen (Nr) loss and greenhouse gas (GHG) emissions for tomato production among farmers. Compared with the high-yield and high-efficiency (HH) group, Nr loss of the low-yield and low-efficiency (LL) and high-yield and low-efficiency (HL) groups were 60.6% and 80.9% higher, and the GHG emissions of the LL and HL groups were 29.2% and 41.6% higher, respectively. Meanwhile, Nr loss and GHG emissions of the low-yield and high-efficiency (LH) group were 17.5% and 13.4% lower than those of the HH group.

Conclusions

Based on these findings, reducing the amount of nitrogen applied, using organic alternative methods, returning straw to the field, and reducing irrigation water are the recommended mitigations to reduce the environmental costs of greenhouse vegetable production.

Background and aims

Priming effect (PE) plays a crucial role in driving soil organic carbon (SOC) decomposition and it is strongly affected by C addition types and nitrogen (N) addition. However, the understanding of the strength and microbial mechanisms of PE in response to specific root exudates (glucose and oxalic acid) and N addition remains inadequate.

Methods

In this study, we carried out a 60-day incubation experiment using simulated root exudates (i.e., glucose and oxalic acid) and inorganic N in coniferous and broad-leaved forest soils to estimate their effects on PE and microbial mechanisms.

Results

Oxalic acid addition resulted in positive PE through “co-metabolism” (i.e., the accelerated microbial decomposition of native SOC), which was supported by an increase in microbial biomass C (MBC), and the activities of enzyme involved in the C and N metabolism in both forest soils. In contrast, N addition significantly lowered positive PE by moderating N mining, as supported by the decreased ratios of fungi: bacteria (F: B), oxidase activities: hydrolase activities (O: H), and C: N enzyme activities, and increased CO₂ derived from root exudate per MBC. These results indicated that stoichiometric decomposition increased with the partial preferential use of the root exudate. The pattern of increased ratios of F: B, O: H, and C: N enzymes with incubation time revealed the dominance of microbial N mining.

Conclusion

Collectively, our results demonstrate that shifts in driving PE from stoichiometric decomposition to microbial N mining over time predominantly depend on N availability, thereby providing insightful evidence for accurately assessing soil C dynamics for future climate change.

Background and aims

Natural forest succession may modify soil nitrogen (N) cycling and N gas emissions. However, little is known about how this ecological succession modulates soil N₂O and N₂ emissions. We focused on three typical succession chronsequences of subtropical forests: the early stage of an Alnus nepalensis forest (~ 60 years), the intermediate stage of a Populus bonatii forest (~ 100 years), and the late stage of an evergreen broad-leaved forest (> 300 years).

Methods

The acetylene inhibition technique and molecular method were used to investigate the changing patterns of soil N₂O and N₂ emissions, as well as the key abiotic and biotic factors that regulate gas emissions.

Results

The highest rates of soil N₂O and N₂ emissions were observed in the early-successional stage, which were 10–21 times and 6–12 times higher than those of the intermediate and late stages, respectively. This stimulation in the early stage was mainly related to the pure stands of N-fixing trees, thus amplifying soil inorganic N pools and providing additional substrates for nitrification- and denitrification- driven N₂O. Although N₂O emissions under denitrifying conditions were 2–131 times higher than those under nitrifying conditions, N₂ was the dominant N gas loss in subtropical forests. Changes in nirK-denitrifier abundance with forest succession were closely related to N₂O emissions.

Conclusion

Our findings suggest that variations in soil active nitrogen pools and nirK abundance associated with subtropical forest succession could reduce N₂O and N₂ emissions, thus resulting in positive feedbacks for climate change mitigation.

Background and aims

Biochar is a carbon source employed to improve soil properties, promoting plant health and nutrition in agroecosystems. Root associated microorganisms such as arbuscular mycorrhizal fungi (AMF) are also used as bioinoculants in combination with biochar to provide eco-friendly alternatives for crop production under unfavorable growth conditions. However, information on the effects of biochar on multitrophic interactions of plants with herbivorous insects is limited. Therefore, the objective of this work was to evaluate the effect of biochar and arbuscular mycorrhizae on plants and herbivorous insects.

Methods

We established a multifactorial experiment with maize plants, AMF (two strains, Rizhophagus irregularis and a native consortium) and the Fall Armyworm Spodoptera frugiperda with and without soil application of biochar. Variables of biomass, plant nutrition, mycorrhizal colonization and performance of herbivorous insects were measured.

Results

We found that biochar reduced insect herbivory and promoted mycorrhizal association in maize. However, plant growth was reduced. Additionally, AMF increased the weight of fall armyworm larvae.

Conclusion

Our results show that biochar influences maize plant development, AMF, and fall armyworm performance, but did not affect interactions between these below- and above ground components.