Increased Plant Biomass Research Articles

Precipitation events and long-term nitrogen addition synergistically stimulate heterotrophic respiration in a semi-arid meadow steppe

Variation in precipitation event size and nitrogen deposition are important global change factors, which have the potential to affect soil respiration and its components, especially in water- and nitrogen-limited semi-arid ecosystems. However, interactive effects of precipitation events and nitrogen input on soil respiration and its components remain largely unknown. We conducted a mesocosm simulation experiment to examine responses of soil respiration and its components, heterotrophic respiration and autotrophic respiration, to changes in precipitation event size (0, 5, 10, 20, and 50 mm; July 2020) and long-term nitrogen addition (0 and 10 g m−2 yr−1; since 2011). The precipitation events triggered the pulsing release of soil respiration and its components, but heterotrophic respiration and autotrophic respiration had different response thresholds, response times, and flux magnitude. The precipitation events significantly stimulated the cumulative soil respiration and its components, among which the cumulative soil respiration and heterotrophic respiration increased quadratically, and the cumulative autotrophic respiration increased linearly, with the increase in precipitation event size. The nitrogen addition suppressed the rates of soil respiration and heterotrophic respiration before the precipitation events but improved the net increment of cumulative soil respiration and heterotrophic respiration after the precipitation events. The precipitation events and long-term nitrogen addition synergistically stimulated the cumulative soil respiration and heterotrophic respiration but had no synergistic effect on the cumulative autotrophic respiration. Precipitation events and nitrogen addition increased soil moisture and dissolved inorganic nitrogen, enhancing microbial biomass and activity, which in turn drove cumulative soil respiration and heterotrophic respiration, and by increasing plant biomass, promoted cumulative autotrophic respiration. Overall, our results highlight the importance of the interactive effects of precipitation events and long-term nitrogen addition on soil respiration and heterotrophic respiration, suggesting that such interactions should be considered to accurately assess and predict carbon budget in future global change scenarios.

Arbuscular mycorrhizal fungi enhance drought resistance and alter microbial communities in maize rhizosphere soil

Although the benefits of inoculation with arbuscular mycorrhizal fungi (AMF) for mitigating drought stress and enhancing plant growth of host are well‐studied, our understanding of their interactions with soil attributes and rhizosphere microbial communities remains limited. In the present study, we conducted a pot experiment to explore how AMF affects maize growth, antioxidant activity, soil properties, and the rhizosphere microbial communities under drought stress. The results showed that AMF inoculation during drought stress resulted in improved maize seedling growth, significantly increasing plant biomass (42.7%), chlorophyll content (13.4%), and antioxidant capacity. It also enhanced soil nutrient availability and microbial biomass. We observed significant shifts in the structure and composition of the rhizosphere microbial community with AMF inoculation under drought conditions when compared to those under well-watered conditions. Significantly, bacterial diversity and composition showed greater sensitivity to drought stress than fungal communities. This was attributed to plants preferentially reducing the supply of carbon sources to bacterial rather than to fungal communities under drought conditions. AMF inoculation also enhanced the complexity (e.g., degree) and stability of the rhizosphere microbial ecological network, suggesting closer ecological interactions within the soil microbial community. Furthermore, bacterial diversity and richness played a more important role in soil function than those of fungal communities under drought stress, particularly with AMF inoculation. Overall, our findings suggest that AMF inoculation alters soil microbial diversity and interactions, highlighting their key roles in enhancing plant stress tolerance and mitigating the negative effects of drought on agricultural ecosystems.

Long-term nitrogen application decreased mineral-associated organic carbon while increasing particulate organic carbon in purple soil in southwest China

In recent years, anthropogenic activities have increased nitrogen (N) input into terrestrial ecosystems, profoundly impacting soil organic carbon (SOC) sequestration. However, the potential mechanisms through which N affects mineral-associated organic carbon (MAOC) and particulate organic carbon (POC) remain unclear. To address this gap, we conducted a 12-year field trial applying continuous N application (0, 90, 180, 270, and 360 kg N·ha−1) in a maize agro-ecosystem. We assessed plant biomass (yield, straw, and root biomass), microbial properties (enzyme activity, biomass, and diversity), soil chemistry (pH, N availability, and base ions), mineralogy (oxides and silicates), and SOC fractions to elucidate the primary control mechanisms influencing MAOC and POC. Our findings showed that N application increased SOC and POC by 6.56%–10.4% and 43.1%–54.0%, respectively, but decreased MAOC by 7.31%–17.1%. And N application increased plant biomass, but decreased soil pH (pH from 6.7 to 5.6), base ion concentrations (K⁺, Na⁺, Ca2⁺, Mg2⁺), amorphous oxides, and illite content. Partial least squares path model (PLS-PM) and correlation analyses indicated that N application enhances root biomass while increasing microbial decomposition, and ultimately their combined effect increased POC. The decline in MAOC is primarily attributed to soil acidification decreasing the C input from microbial residues, altering mineral composition and diminishing the minerals' capacity to protect SOC. Thus, our study demonstrates that N addition predominantly increases POC through enhanced root biomass, while reducing MAOC by decreasing microbial biomass and weakening mineral protection. These insights provide a deeper understanding of the mechanisms governing SOC fraction dynamics in answer to N inputs in agroecosystems.

Sulfur redirects carbon metabolism to optimize nitrogen utilization and promote andrographolide biosynthesis in Andrographis paniculata seedlings

Sulfur (S) is an important mineral nutrient element that improves plant growth and secondary metabolism. S affects the biosynthesis of andrographolide in medicinal plant Androgaphis paniculata by regulating nitrogen (N) metabolism. However, its specific role in N utilization and the connection with andrographolide biosynthesis have not yet been thoroughly understood. Here, a soilless cultivation experiment with low S (LS, 0.1 mM) and high S (HS, 2.4 mM) was conducted to investigate how S influences carbon (C) metabolism and N utilization to promote andographolide biosynthesis in Andrographis paniculata. The results showed that HS significantly increased plant biomass and N use efficiency (NUE), accompanying with remarkable enhanced andrographolide content. HS promoted the expression of photosynthetic genes, and redirected C metabolism towards to sugars accumulation by enhancing the activities of NAD-dependent glutamate dehydrogenase (NAD-GDH), malic enzyme (ME) and phosphoenolpyruvate carboxykinase (PEPCK) (P < 0.05). On the other hand, HS reduced N and S assimilation, and stimulated a greater N allocation in photosynthesis. Accordingly, NUE was increased and andrographolided biosynthesis could profit from the shift of C resource reallocation. Additionally, the significantly increased activities of ME, glucose 6-phosphate dehydrogenase (G6PDH) and isocitrate dehydrogenase (ICDH) provided reductants for secondary metabolism. HS also considerably upregulated the expression of genes in andrographolide biosynthetic pathway, including ApDXS, ApDXR, ApHDS and ApHDR in the MEP pathway, and ApGGPS. Transcription factors in the families of MYB, WRKY, ERF and bHLH, and plant hormones ABA and JA were in response to HS. Our results revealed that S synergistically promotes NUE and andrographolide biosynthesis via remodeling of C metabolism in A. paniculata.

Endophytic Colonization of Beauveria bassiana Enhances Drought Stress Tolerance in Tomato via "Water Spender" Pathway.

Drought stress is one of the most important climate-related factors affecting crop production. Tomatoes (Solanum lycopersicum L.) are economically important crops which are highly sensitive to drought. The entomopathogenic fungus Beauveria bassiana, a widely used biological insecticide, can form symbiotic relationships with plants via endophytic colonization, increasing plant biomass and the ability to resist biotic stress. Under simulated drought stress conditions, the biomass of tomato seedlings such as plant height, root length, stem diameter, fresh weight, and relative water content, as well as the density and size of stomata in tomato leaves were significantly increased after B. bassiana colonization via root irrigation (p < 0.05). Meanwhile, the physicochemical properties associated with drought resistance such as peroxidase activity and proline content increased significantly (p < 0.05), while malondialdehyde reduced significantly (p < 0.05), and the expression levels of key genes related to stomatal development and drought tolerance pathways increased significantly (p < 0.05). These results indicate that the colonization of B. bassiana enhances the water absorption capacity of tomato seedlings and the rate of transpiration significantly and increases drought tolerance in tomato via the "water spender" pathway, which provides a new strategy for improving crop resistance to drought stress.

Reseeding increased plant biomass production and soil fertility, but not plant species diversity in degraded grasslands in China

Reseeding is a primary measure to restore degraded grasslands. Numerous studies have conducted experiments to investigate how the properties of grassland ecosystems respond to reseeding in China. However, there is a lack of summary of the results of these studies. Here, we conducted a hierarchical random-effects meta-analysis on the effects of reseeding on plant, soil, and microbial properties. We collected 19 variables, including plant biomass, species diversity and richness, soil organic carbon content, soil total and available nutrients, soil water content, soil microbial biomass and diversity, and enzyme activity, from a dataset of 1363 paired observations (degraded vs. reseeded) from 75 publications. The results showed that reseeding increased aboveground and belowground plant biomass by 70.2% and 68.0% on average, respectively. Reseeding increased soil organic carbon, phosphorus, and potassium contents, but did not affect soil nitrogen levels. Reseeding increased soil microbial nitrogen under conditions of tillage and fertilization. Reseeding age was found to have a positive correlation with species richness, while planting type, fertilization, and tillage did not have a significant impact on the species richness and diversity. Under the treatments of fertilization, non-tillage, and mix-planting, the response ratio of aboveground biomass to reseeding was positively correlated with the response ratio of species diversity to reseeding. Our results concluded that current reseeding practices can significantly improve plant biomass production and soil fertility but have minor effects on plant species diversity. These findings indicate that the preservation of biodiversity should receive greater attention from both researchers and practitioners in grassland remediation in China.

Synergistic effects of AMF and PGPR on improving saline-alkaline tolerance of Leymus chinensis by strengthening the link between rhizosphere metabolites and microbiomes

Arbuscular mycorrhizal fungi (AMF) and plant growth-promoting rhizobacteria (PGPR) can synergistically enhance their promotional effects on plants. The positive effects are closely related to their modulation on rhizosphere microbiomes. Leymus chinensis is widely used in restoration of saline-alkaline grasslands. However, the information is unavailable on mechanisms of inoculating AMF and PGPR in enhancing saline-alkaline tolerance of L. chinensis. We conducted a pot experiment to examine effects of separate and combined inoculation of AMF and PGPR, with a focus on the pathways of AMF and PGPR effects by regulating complex interactions in plant rhizosphere. The combined inoculation significantly increased plant biomass (by 40.18–193.18 %) and Na+ accumulation, and decreased soil EC and pH to a greater extent than the separate inoculation did, and it was also superior in terms of multiple nutrient accumulation, root ion homeostasis ratios and soil enzyme activities. The combined inoculation significantly enriched beneficial bacterial and symbiotic mycorrhizal taxa, and increased complexity and stability of rhizosphere microbiome. Coexistence of AMF and PGPR activated beneficial secondary metabolic pathways and higher expression of beneficial metabolites, which regulates plant growth and stress response. The inoculation of AMF and PGPR synergically promoted interactions among keystone microbial species from different cluster modules and rhizosphere soil metabolites, and strengthened the roles of core microorganisms and core metabolites, and their interrelations and their relations with host plant. These results implies that the synergistic positive effects of AMF and PGPR on saline-alkaline tolerance of L. chinensis is realized by strengthening the links between rhizosphere metabolites and microbiomes.

Regulatory mechanism of bamboo biochar dosage on cadmium accumulation in Salix psammophila: insights from rhizosphere microbial communities, assembly processes, and interactions

Soil amendments play a pivotal role in regulating rhizosphere microbial communities, which is essential for maintaining robust plant growth under adverse environmental conditions. However, the microbial mechanisms that underlie the impact of biochar on phytoremediation performance remain incompletely understood in the context of different application rates. Here, we compared the phytoremediation performance, rhizosphere microbial community characteristics, and microbial interactions in Salix psammophila across different biochar application rates (1%, 3%, 5%, and 7%) in Cd-contaminated soil. Applying 5% biochar increased plant biomass by 10.02%, root activity by 183.82%, and Cd accumulation by 13.65%. Lower biochar rates (1% and 3%) decreased Cd accumulation in plants by 21.89% and 42.05%, respectively, compared to the control. Rhizosphere soil properties and Cd content, except for nitrogen, showed a gradient change with increasing biochar application rates. This was accompanied by an elevation in the Chao1 index for the bacterial community, although the fungal community remained unaffected in terms of diversity and structure. Null-model analyses indicated that fungal community assembly was mainly driven by ecological drift, explaining its unresponsiveness to biochar application. Applying 1% biochar enhanced microbial network stability while reducing bacterial network complexity. Conversely, 3% biochar application resulted in the lowest microbial network stability. Biochar application, except 3%, reduced the proportion of bacteria-fungi associations, suggesting increased independence between two microbial kingdoms. Random forest and piecewise structural equation models revealed that phytoremediation performance is influenced by microbial network stability, complexity, and bacteria-fungi associations. Fungal complexity and stability, along with bacterial stability, were identified as key predictors of phytoremediation performance. Our findings reveal potential mechanisms by which biochar influences phytoremediation through altering microbial interactions. For long-term microbial stability and cost-effectiveness, a 1% biochar application is recommended for phytoremediation. Conversely, for rapid Cd accumulation in plants, a 5% biochar application is optimal.Graphical

Microbial Inoculants Modify the Functions of Resident Soil Microbes to Expedite the Field Restoration of the Abandoned Mine

ABSTRACTGlobal‐scale mining activities have had significant deleterious impacts on local ecosystems and the overall environment, which will necessitate robust restoration efforts. A practical approach includes combining microbial inoculants with the technology of external soil spray seeding. This approach holds the potential for sustainable abandoned mine site restoration by enhancing plant growth through the modulation of soil nutrients and microbial communities. Nonetheless, the detailed effects of microbial inoculants on specific aspects of soil microbial community functions and their complex interactions with plant growth remain underexplored, particularly in the context of restoration efforts. To bridge this gap, we performed a four‐year field study at an abandoned carbonate mine location, using metagenomic sequencing to evaluate the influence of microbial inoculants on soil microbial functionality. Our research revealed that introducing microbial inoculants greatly enhanced essential soil parameters and notably increased plant biomass. Additionally, these inoculants altered the functional gene makeup of the microbial community, significantly boosting the relative abundance of processes such as nitrogen fixation, nitrification, denitrification, assimilatory nitrate reduction (ANRA), dissimilatory nitrate reduction (DNRA), and organic phosphorus mineralization. Conversely, there was a decrease in the relative abundance of carbon degradation, phosphorus regulation, and transport processes. We observed strong correlations between the abundance of nitrogen and phosphorus cycles and plant biomass. Crucially, microbial inoculants affect plant biomass by initially altering soil properties and subsequently coordinating nitrogen and phosphorus cycles. These findings provide valuable insights into the role of microbial inoculants in mine site restoration and offer a theoretical foundation for their broader practical application.

Enhancing phytoremediation of bauxite mine subsoil by Jatropha curcas L. using sewage sludge and poultry sludge

Phytoremediation is a sustainable technology for cleaning up heavy metal contamination at mining sites. However, degraded soils at these sites create a harsh environment for plants to survive and properly yield biomass. In this study, sewage sludge and poultry sludge were applied as soil amendments in bauxite mine subsoil to determine their impact on the growth and heavy metal uptake of Jatropha curcas L. Both sewage sludge and poultry sludge were applied at 25% and 50%. J. curcas was grown in the amended soils for 120 days under greenhouse conditions. Changes in soil physico-chemical properties, plant growth and heavy metal uptake of J. curcas were determined after that. An increase in EC, CEC, total C, total N, total available P and total extractable K was detected in the amended soils. These improvements enhanced the growth of J. curcas, particularly in the development of above-ground plant biomass. Increased plant biomass subsequently led to higher bioaccumulation and translocation efficiency of Al, Fe, Pb and Zn. As a result, higher heavy metal removal of up to 98.03% was detected in the amended treatments. The findings indicated that the application of sewage sludge and poultry sludge improves soil conditions for plant development.

PagNAC2a promotes phloem fiber development by regulating PagATL2 in poplar

Phloem fiber is a key component of phloem tissue and is involved in supporting its structural integrity. NAC domain transcription factors are master switches that regulate secondary cell wall (SCW) biosynthesis in xylem fibers, but the mechanism by which NACs regulate phloem fiber development remains unexplored. Here, a NAC2-like gene in poplar, PagNAC2a, was shown to be involved in phloem fiber differentiation. qRT-PCR and GUS staining revealed that PagNAC2a was specifically expressed in the phloem zone of poplar stems. The overexpression of PagNAC2a in poplar increased plant biomass by increasing plant height, stem diameter, and leaf area. Stem anatomy analysis revealed that overexpression of PagNAC2a resulted in enhanced phloem fiber differentiation and cell wall deposition. In addition, PagNAC2a directly upregulated the expression of PagATL2, a gene involved in phloem development, as revealed by yeast one hybrid (Y1H) and electrophoretic mobility shift assay (EMSA) assays. Overall, we proposed that the PagNAC2a was a positive regulator of phloem fiber development in poplar, and these results provided insights into the molecular mechanisms involved in the differentiation of phloem fibers.

The effects of roots and earthworms on aggregate size distribution and their associated carbon under contrasting soil types and soil moisture conditions

Soil’s potential as a carbon sink is uncertain due to biotic and abiotic interactions. Soil aggregates are important carriers of organic carbon (OC), and clarifying the response of aggregates and their associated OC to plant roots and earthworms can better understand the carbon cycle in terrestrial ecosystems. Herein, we determined the regulatory role of plant roots (Lolium perenne) and earthworms (Metaphire tschiliensis) in isolation and in combination on aggregate size distribution and their associated OC and readily oxidizable OC (ROOC) under contrasting soil types (Phaeozems and Anthrosols) and soil moisture conditions (constant wetting, CW; wetting–drying cycle repeated four times, 4WD) by a laboratory microcosm experiment. Results showed that earthworm presence significantly increased plant biomass by 30 % and 221 % in Phaeozems and Anthrosols, respectively (p < 0.05). For Phaeozems, plant alone (P) and plant and earthworm in combination (PE) had lower proportion of large aggregate (5–8 and 2–5 mm) than bare soil (CK) under 4WD condition (p < 0.05). For Anthrosols, the PE treatment decreased the proportion of 5–8 and 2–5 mm aggregate by 45 % and 25 %, respectively, under CW condition, and decreased the proportion of 5–8 mm aggregate by 37 % under 4WD condition (p < 0.05). Moreover, the proportion of 5–8 and 2–5 mm aggregate in P treatment was lower under CW condition (6.92 % and 22.13 %) but was higher under 4WD condition (11.49 % and 32.55 %) than those in CK (14.69 % and 29.91 %; 8.85 % and 20.56 %) (p < 0.05). Our results further indicated that the PE treatment had relatively higher OC and ROOC contents, especially for small aggregates in Anthrosols. The study indicates that plant roots and earthworms significantly influence aggregate turnover and the carbon cycle, with soil type and moisture playing a crucial role.

Plant community responses to the individual and interactive effects of warming and herbivory across multiple years.

Anthropogenic climate warming affects plant communities by changing community structure and function. Studies on climate warming have primarily focused on individual effects of warming, but the interactive effects of warming with biotic factors could be at least as important in community responses to climate change. In addition, climate change experiments spanning multiple years are necessary to capture interannual variability and detect the influence of these effects within ecological communities. Our study explores the individual and interactive effects of warming and insect herbivory on plant traits and community responses within a 7-year warming and herbivory manipulation experiment in two early successional plant communities in Michigan, USA. We find stronger support for the individual effects of both warming and herbivory on multiple plant morphological and phenological traits; only the timing of plant green-up and seed set demonstrated an interactive effect between warming and herbivory. With herbivory, warming advanced green-up, but with reduced herbivory, there was no significant effect of warming. In contrast, warming increased plant biomass, but the effect of warming on biomass did not depend upon the level of insect herbivores. We found that these treatments had stronger effects in some years than others, highlighting the need for multiyear experiments. This study demonstrates that warming and herbivory can have strong direct effects on plant communities, but that their interactive effects are limited in these early successional systems. Because the strength and direction of these effects can vary by ecological context, it is still advisable to include levels of biotic interactions, multiple traits and years, and community type when studying climate change effects on plants and their communities.

Synergistic effects of boron and cadmium on the metal enrichment and cell wall immobilization capacity of Cosmosbipinnatus

Cadmium (Cd), as a heavy metal pollutant, can seriously affect plant growth and development. Boron (B), as an indispensable nutrient element, plays an important role in plant growth and cell wall (CW) synthesis. However, the physiological effects of B and Cd on plant growth and the mechanism of Cd chelation by the CW remain unclear. Here, we investigate the effect of exogenous B on Cd accumulation in CW components of Cosmos bipinnatus roots and its mechanism of Cd mitigation. Under B deficiency and single Cd (30 μM) treatments, the growth of C. bipinnatus was significantly inhibited, but the addition of exogenous B significantly increased plant biomass, which increased the Cd content in the underground parts of C. bipinnatus by 20.18% and reduced the Cd translocation factor by 22.22%. Meanwhile, application of exogenous B affected the subcellular Cd content across various Cd forms and alleviated Cd-induced oxidative stress in C. bipinnatus. Additionally, exogenous B and Cd and their mixtures affected the functional groups of the root CW, the proportion of polysaccharide components, the Cd content of polysaccharides, and the polysaccharide uronic acid content of C. bipinnatus. However, B application increased 3-deoxy-oct-2-ulosonic acid content, pectin esterase activity, low esterified pectin content, and its Cd content by 149.52%, 55.69%, 206.38%, and 150.02%, respectively, compared to Cd treatment alone. Thus, our study showed that B mitigates the toxicity of Cd to plants, revealing the effect of B on the physiological aspects of Cd tolerance in plants.

Rehabilitation of a degraded acid Mediterranean soil after 11 years of by‐product calcium amendments and pasture improvement

AbstractThe clearing of natural vegetation and tillage for agricultural purposes makes acid soils highly vulnerable to degradation, resulting in significant losses of soil fertility and crop productivity. This work focused on nature‐based agricultural solutions to rehabilitate degraded acid soils in low‐resource systems. We studied after 6 and 11 years how the introduction of a legume‐rich pasture replacing a natural pasture or a tilled forage crop, with and without Ca‐amendment, contributed to recover the soil health, the fertility and the productivity of degraded Ultisols in Western Spain. Industrial by‐products, mainly sugar foam, were used as Ca‐amendment to promote circular economy. The Ca‐amendment factor influenced soil chemistry to 30 cm depth, while the type of soil use affected soil organic matter (SOM) to 15 cm; and both factors had positive effects on biomass productivity. Except for pH and Ca, no interaction between factors was found. Ca‐amendment increased nutrient availability and soil pH, and Al ion precipitated at 0–15 cm depth. As a result, biomass production increased by 35% relative to no Ca‐amendment. Forage cop produced 66% more biomass than pastures, but this increase did not translate into an increase in SOM. In fact, the legume‐rich pasture was the best option to recover soil organic C and N levels, earlier and deeper. Over the 11 years, the use of pastures and Ca‐amendment enhanced biomass production stability. Relative to natural, the improved pasture did not increase plant biomass but provided higher biomass stability and quality in terms of legume abundance, which was promoted when sugar foam was applied. Pastures also favoured key biological variable as earthworm's population, increasing it by four times with respect to forage crops. Compared to the non‐amended and unfertilized natural pasture out of the experiment, the use of improved pasture, followed by natural pasture, combined with sugar foam and fertilization enhanced soil health, soil fertility and biomass production stability. Thus, this solution has proven effective for restoring degraded acid soils, promoting diversity and mitigating climate change, while offering a more economically beneficial alternative.

Plant community‐specific greening patterns predict population size increases in a temperate herbivore

Climate change‐driven impacts on vegetation productivity have been shown to drive mammalian herbivore population dynamics in Arctic and alpine environments. However, there is less evidence for temperate systems. To address this, we examined the contribution of increasing plant biomass in different vegetation communities (measured by NDVI, normalised difference vegetation index) and winter weather on the observed long‐term upward trend in the population of the Soay sheep of Hirta, St Kilda, UK. We found that biomass had increased in all vegetation communities present and increased the fastest in vegetation types preferred by the sheep. Specifically, those communities with high specific leaf area and Ellenberg's N, low leaf dry matter content. Peak summer NDVI and either winter average wind speed or winter North Atlantic Oscillation data added to the variance explained by a simple density dependence model of yearly sheep population growth rates. The highest explanatory power was found for preferred vegetation types including maritime cliff communities dominated by Plantago species, but also for both inaccessible (Rumex acetosa‐dominated) or unpreferred (Eriophorum vaginatum‐ or Sphagnum‐dominated) communities where seasonal variation more closely reflects productivity due to minimal grazing. Although the climate is getting windier and wetter, it is also getting warmer allowing increased plant productivity and this appears to be behind the long‐term increases in the Soay sheep population. Our study indicates that analysing key vegetation communities may reveal these links better than using landscape‐level averages, and that oceanic‐temperate systems may show similar climate‐driven herbivore population trends to those reported in Arctic and alpine systems.

Effect of copper on nitrogen uptake, transportation, assimilation processes, and related gene expression in Chinese cabbage [Brassica campestris L. ssp. Chinensis (L.)] under various nitrate-to-ammonium ratios.

Improving vegetable yield and optimizing its quality through nutrient management have long been central to plant nutrition and horticultural science. Copper (Cu) is recognized as an essential trace element that promotes plant growth and development. However, the mechanisms by which Cu influences nitrogen (N) metabolism remain largely unknown, with limited studies exploring the interaction between Cu and varying nitrate-to-ammonium (nitrate/ammonium) ratios. In this study, Chinese cabbage was exposed to two Cu concentrations (0 and 0.02 mg L-1) in combination with three nitrate/ammonium ratios (10/90, 50/50, and 90/10) under hydroponic conditions. The results showed that Cu application increased plant biomass, nitrate reductase (NR) and glutamine synthetase (GS) enzyme activities, the expression of NR (NIA) and GS2 (Gln2) genes, and N content in both shoots and roots. Additionally, Cu treatment decreased nitrate and free amino acid contents, as well as the expression of nitrate transporters NRT1.1 and NRT2.1 in roots while increasing these four parameters in shoots. Additionally, these effects were significantly modulated by the nitrate/ammonium ratios. In conclusion, Cu may facilitate nitrate transportation, enhance nitrate reduction, promote ammonium assimilation, and influence the transformation of organic N compounds, highlighting its potential role in improving N metabolism in Chinese cabbage.

Insights into the interactions of plant-associated bacteria and their role in the transfer of antibiotic resistance genes from soil to plant

This study discussed the role of plant-associated microbiome in regulating ARG transfer in soil-plant systems. Results showed that target ARGs in plants were mainly derived from rhizosphere soil. Cooperative interactions among bacteria in rhizosphere soil, plant-roots, plant-shoots, and soil-roots-shoots systems occurred during ARG transfer. The number of modules and keystone taxa identified as positively correlated with ARG transfer in rhizosphere soil, roots, and shoots was 3 and 49, 3 and 41, 2 and 5, respectively. Among these modules, module 3 in roots was significantly positively correlated with module 3 in rhizosphere soils and module 2 in shoots, indicating that module 3 in roots played central hub roles in ARG transfer from rhizosphere soil to roost and shoots. This may be because module 3 in roots increased cell motility and xenobiotics biodegradation and metabolism. These keystone taxa mainly belonged to Proteobacteria that can carry ARGs to transfer in soil-plant systems, especially Clostridium-sensu_stricito and Pseudomonas in rhizosphere soil carried ARGs into the shoot. Additionally, they promoted ARG transfer by increasing plant biomass, net photosynthetic rate and water use efficiency. The findings helped reveal the mechanism of plant-associated bacterial interactions and provided understanding for potential risks of ARG transfer from soil to plants.

Response Surface Methodology for Optimizing Water and Fertilizer Requirements for Maize (Zea mays L.) Growth in Sandy Soil

AbstractTo foster sustainable agricultural practices, the utilization of irrigation, fertilizers, and recycled soil enhancements is essential, particularly in regions with limited resources. This investigation sought to ascertain the optimal water and fertilizer prerequisites for the cultivation of maize by employing Response Surface Methodology (RSM) in arenosol enriched with spent mushroom substrate (SMS) in a controlled pot experiment. The experimental treatments were determined using the Central Composite Design based on varying levels of irrigation (50%, 75%, and 100% of soil field capacity), nitrogen (0, 1, and 2 g pot−1), and SMS (0, 5, and 10%, v/v). The investigation's findings demonstrated that augmented irrigation and nitrogen fertilization positively influenced all agronomic traits, as well as nitrogen concentrations in the roots, shoots, and soil. SMS increased shoot fresh weight, shoot dry weight, leaf area per plant, and dissolved and total soil organic carbon. The optimal levels of irrigation, nitrogen fertilizer, and SMS to improve agronomic attributes were determined to be 81.43–97.80%, 1.38–1.69 g pot−1, and 5.77–8.48%, respectively. The optimal amounts for NPK retention in soil and plant uptake were 69.50–98.00%, 1.20–1.98 g pot−1, and 4.72–9.74%, respectively. The study concluded that irrigation and nitrogen levels had a greater impact on optimizing maize growth response than SMS. However, SMS was found to be more effective in increasing plant biomass due to its enhancement of both dissolved and total soil organic carbon. Furthermore, the interaction of irrigation and mineral nitrogen with SMS improved soil nutrient retention, plant uptake, and plant biomass productivity.

A strategy for the addition of plant biomass to constructed wetlands to increase nitrogen removal in treating sewage: A full-scale experiment

Plant biomass has been widely used as an exogenous carbon source for constructed wetlands to increase nitrogen removal efficiency, but a convenient and efficient addition strategy is lacking. In this study, a new strategy was developed and tested in full-scale horizontal subsurface flow constructed wetlands, i.e., designing a decomposition zone in front of the constructed wetland, adding plant biomass directly to the decomposition zone, and re-adding the refractory parts to the decomposition zone after removal from the decomposition zone and treatment with alkaline leachate. Adding straw significantly increased the average total nitrogen removal efficiency from 36.0% to 44.9% without a significant increase in the chemical oxygen demand concentration. The refractory straw significantly increased the total nitrogen removal efficiency after it was removed, treated with alkaline leachate, and re-added to the system. Every 1 g of raw straw or refractory straw removed 0.088 g or 0.038 g of nitrate, respectively. The relative abundances of Bacillacea, Gemmatimonadaceae, Blastocatellaceae, and Caldilineaceae, which are associated with denitrification, increased after straw addition. The relative abundances of the functional groups of the bacterial community associated with organic matter degradation increased with straw addition, and the functional groups of the bacterial communities associated with nitrogen cycling were positively correlated with the nitrogen concentration. The strategy developed in this study is convenient and efficient for increasing the nitrogen removal efficiency by increasing plant biomass and can be applied in several scenarios.