Increased Plant Biomass Research Articles

Utilization of biochar in rainfed farming systems: A meta-analysis

Biochar application in rainfed farming can increase crop productivity by improving the water retention capacity and nutritional status of rhizosphere. This meta-analysis was carried out to assess the quantitative effects of biochar addition to the soil on the productivity of crops under rainfed conditions. The results indicated that increments in plant biomass and grain yield production of cereal crops in response to biochar application under rainfed conditions were higher than in legume crops. Low-temperature pyrolyzed biochar (≤500 °C) with high carbon (>50 %) and nitrogen (>1 %) contents and pH <8 was more effective in enhancing biomass and grain production, compared to other types of biochar. The ideal biochar application rate to improve biomass and grain yield of plants under rainfed conditions was about 20–40 tons ha−1. In general, biochar can increase plant biomass (by about 13 %) and grain yield (by about 14 %) of crops under rainfed conditions.

Elucidating the phytotoxicity thresholds of various biosynthesized nanoparticles on physical and biochemical attributes of cotton

BackgroundA pot experiment was conducted to evaluate the phytotoxic thresholds of zinc oxide (ZnO NPs), iron oxide (FeO NPs), copper (Cu NPs), and silver nanoparticles (Ag NPs) on cotton. All the nanoparticles were biosynthesized from Conocarpus erectus L. leaf extract. They were characterized by scanning electron microscope (SEM), X-ray diffraction (XRD), and Fourier transmission infrared spectroscopy (FTIR). Five concentrations (0, 25, 50, 75, and 100 ppm) of all the biosynthesized nanoparticles were foliar applied thrice over the duration of cotton growth. Five cotton seeds were sown in 5 kg soil pot and harvested after 6 weeks. SPAD values were evaluated before harvesting while physical growth parameters, physiological parameters biochemical, and oxidative stress parameters were measured after harvesting.ResultsThe value of all parameters, except oxidative stress, increased by 13–47% in response to ZnO NPs application up to 100 ppm. However, phytotoxic threshold of iron oxide nanoparticles (FeO NPs) and copper nanoparticles (Cu NPs) was only 50 ppm as plant growth was increased by 7.9–24.3%. Above 50 ppm plant growth and biomass were decreased by 6.7–16.2%. Silver nanoparticles (Ag NPs) showed maximum growth (3.7 to 9.12% increased) at 25 ppm concentration. At higher concentrations than 25 ppm, the application of Ag NPs decreased the growth due to toxicity. Foliar application of different biosynthesized nanoparticles showed the different range of threshold value for cotton crop. Threshold value of iron oxide and copper nanoparticles for cotton was 50 ppm, whereas, it was 25 ppm for silver nanoparticles. Since the ZnO NPs application continued increasing the growth till its maximum concentration used i.e., 100 ppm, we cannot say that this is its threshold value.ConclusionOn the basis of obtained results, it can be concluded that nanoparticles should be used within threshold to avoid adverse effects on crops. Application of nanoparticles within threshold optimum concentration,increased plant biomass and antioxidant system.Graphical

Development of Zn biofertilizer microbeads encapsulating Enterobacter ludwigii-PS10 mediated alginate, starch, poultry waste and its efficacy in Solanum lycopersicum growth enhancement

In the present farming era, rhizobacteria as beneficial biofertilizers can decrease the negative effects of Zinc (Zn) agrochemicals. However, their commercial viability and utility are constrained by their instability under field conditions. Thus, to enhance their stability, microbial formulations are considered, which will not only offer an appropriate microenvironment, and protection but also ensure a high rate of rhizospheric-colonization. The goal of this study was to create a new formulation for the Zn-solubilizing bacteria E. ludwigii-PS10. The studied formulation was prepared using the extrusion technique, wherein a composite solution containing alginate, starch, zinc oxide, and poultry waste was uniformly mixed with the bacterial strain PS10 to develop low-cost, eco-friendly, and slow-release microbeads. The produced microbead was spherical, and characterized by SEM, FTIR, and XRD. Further, the microbeads were analyzed for their survival stability over 3 months of storage at room temperature and 4 °C. The effect of the microbead on the vegetative growth of tomato plants was investigated. Results showed that 94 % of the encapsulated microbial beads (EMB) matrix was able to encapsulate the bacterial strain PS10. The dried EMB demonstrated a moisture content of 2.87 % and was able to preserve E. ludwigii-PS10 survival at room temperature at the rate of 85.6 %. The application of the microbead to the tomato plants significantly increased plant biomass and Zn content. As a result, our findings support the use of this novel EMB prepared using an alginate/poultry waste/starch mixture to increase bacterial cell viability and plant growth.

Silicon fertilization enhances the resistance of tobacco plants to combined Cd and Pb contamination: Physiological and microbial mechanisms

Remediation of soil contaminated with cadmium (Cd) and lead (Pb) is critical for tobacco production. Silicon (Si) fertilizer can relieve heavy metal stress and promote plant growth, however, it remains unknown whether fertilization with Si can mitigate the effects of Cd and Pb on tobacco growth and alter microbial community composition in polluted soils. Here we assessed the effect of two organic (OSiFA, OSiFB) and one mineral Si fertilizer (MSiF) on Cd and Pb accumulation in tobacco plants, together with responses in plant biomass, physiological parameters and soil bacterial communities in pot experiments. Results showed that Si fertilizer relieved Cd and Pb stress on tobacco, thereby promoting plant growth: Si fertilizer reduced available Cd and Pb in the soil by 37.3 % and 28.6 %, respectively, and decreased Cd and Pb contents in the plant tissue by 42.0–55.5 % and 17.2–25.6 %, resulting in increased plant biomass by 13.0–30.5 %. Fertilization with Si alleviated oxidative damage by decreasing malondialdehyde content and increasing peroxidase and ascorbate peroxidase content. In addition, Si fertilization increased photosynthesis, chlorophyll and carotenoid content. Microbial community structure was also affected by Si fertilization. Proteobacteria and Actinobacteria were the dominant phylum in the Cd and Pb contaminated soils, but Si fertilization reduced the abundance of Actinobacteria. Si fertilization also altered microbial metabolic pathways associated with heavy metal resistance. Together, our results suggest that both organic and mineral Si fertilizers can promote tobacco growth by relieving plant physiological stress and favoring a heavy metal tolerant soil microbial community.

Auditory predator cues decrease herbivore survival and plant damage.

The high fitness cost of predation selects prey capable of detecting risk cues and responding in ways that reduce their vulnerability. While the impacts of auditory predator cues have been extensively researched in vertebrate prey, much less is known about invertebrate species' responses and their potential to affect the wider food web. We exposed larvae of Spodoptera exigua, a slow-moving and vulnerable herbivore hunted by aerial predators, to recordings of wasp buzzing (risk cue), mosquito buzzing (no-risk cue), or a no-sound control in both laboratory and field settings. In the laboratory, wasp buzzing (but not mosquito buzzing) reduced survival relative to the control; there was, however, no effect on time to or weight at pupation in survivors. In the field, wasp buzzing reduced caterpillar herbivory and increased plant biomass relative to the control treatment. In contrast, mosquito buzzing reduced herbivory less than wasp buzzing and had no effect on plant biomass. The fact that wasp cues evoked strong responses in both experiments, while mosquito buzzing generally did not, indicates that caterpillars were responding to predation risk rather than sound per se. Such auditory cues may have an important but largely unappreciated impacts on terrestrial invertebrate herbivores and their host plants.

Comparison of the Rhizobacteria Serratia sp. H6 and Enterobacter sp. L7 on Arabidopsis thaliana Growth Promotion.

The genera Serratia and Enterobacter belong to the Enterobacteriaceae family and several members have been described as plant growth-promoting rhizobacteria (PGPR). However, how these bacteria influence growth and development is unclear. We performed in vitro interaction assays between either Serratia sp. H6 or Enterobacter sp. L7 with Arabidopsis thaliana seedlings to analyze their effects on plant growth. In experiments of co-cultivation distant from the root tip, Enterobacter sp. decreased root length, markedly increased lateral root number, and slightly increased plant biomass by 33%, 230%, and 69%, respectively, and relative to the control. The volatile organic compounds (VOCs) emitted from Serratia sp. H6 but not those from Enterobacter sp. L7 promoted Arabidopsis growth. A blend of volatile compounds from the two bacteria had effects on plant growth that were similar to those observed for volatile compounds from H6 only. At several densities, the direct contact of roots with Serratia sp. H6 had phytostimulant properties but Enterobacter sp. L7 had clear deleterious effects. Together, these results suggest that direct contact and VOCs of Serratia sp. H6 were the main mechanisms to promote plant growth of A. thaliana, while diffusible compounds of Enterobacter sp. L7 were predominant in their PGPR activity.

A gene regulatory network in Arabidopsis roots reveals features and regulators of the plant response to elevated CO2.

The elevation of CO2 in the atmosphere increases plant biomass but decreases their mineral content. The genetic and molecular bases of these effects remain mostly unknown, in particular in the root system, which is responsible for plant nutrient uptake. To gain knowledge about the effect of elevated CO2 on plant growth and physiology, and to identify its regulatory in the roots, we analyzed genome expression in Arabidopsis roots through a combinatorial design with contrasted levels of CO2 , nitrate, and iron. We demonstrated that elevated CO2 has a modest effect on root genome expression under nutrient sufficiency, but bycontrast leads to massive expression changes under nitrate or iron deficiencies. We demonstrated that elevated CO2 negatively targets nitrate and iron starvation modules at the transcriptional level, associated with a reduction in high-affinity nitrate uptake. Finally, we inferred a gene regulatory network governing the root response to elevated CO2 . This network allowed us to identify candidate transcription factors including MYB15, WOX11, and EDF3 which we experimentally validated for their role in the stimulation of growth by elevated CO2 . Our approach identified key features and regulators of the plant response to elevated CO2 , with the objective of developing crops resilient to climate change.

A novel bud mutant of navel orange (Citrus sinensis) shows tolerance to chlorosis in acidic and magnesium-deficient soils

Interveinal chlorosis in old leaves is a common occurrence in citrus orchards in southern China. The present study investigates the ‘Langfeng’ navel orange (LF, Citrus sinensis) grafted onto a Trifoliate orange (TO, Poncirus trifoliata) rootstock, which exhibits healthy green leaves, and the ‘Newhall’ navel orange (NHE, C. sinensis) grafted onto TO, which has typical magnesium (Mg) deficiency-induced chlorosis. Chemical analysis of the rhizosphere soil revealed that the pH values were around 3.92 and that both Mg and calcium (Ca) were significantly deficient in the rhizosphere soil of both grafting combinations (LF/TO and NHE/TO). Furthermore, the chlorotic leaves of NHE/TO had significantly lower levels of Mg, Ca, and phosphorus (P), and the green leaves of NHE/TO had significantly lower levels of Mg and Ca compared to the green leaves of the LF/TO. This suggests that Mg deficiency may be the primary cause of chlorosis in NHE/TO. A greenhouse study using the same graft combinations showed that the LF/TO plants had better growth than the NHE/TO, possibly by promoting Mg uptake and/or improving Mg distribution to leaves, thereby increasing carbon dioxide (CO2) assimilation and photosynthesis, optimizing carbohydrate distribution, and increasing plant biomass. This results in a phenotype that is tolerant to Mg deficiency. In conclusion, these findings suggest that the LF navel orange could be utilized in the development of new citrus varieties with improved Mg-use efficiency.

Composted biosolids amendments for enhanced soil organic carbon and water storage in perennial pastures in Colorado

Land management of grasslands can play a significant role in climate change mitigation by influencing soil carbon (C) storage. Soil amendments, such as adding compost, have been shown to increase soil C storage while simultaneously increasing plant productivity and soil water holding capacity (WHC), factors that provide immediate benefits to ranchers. Research to date has mainly focused on temperate annual grasslands. However, little is known if irrigated perennial pasturelands in cold, arid climates respond similarly. This study’s objective was to determine the immediate effects of a 5 cm depth application of biosolids compost on plant productivity, soil moisture, and soil C storage. Research sites were established at four ranches in Gunnison, CO, a high-elevation, arid region. During the first year, there was a significant increase in total aboveground biomass (AGB) across three of the four sites (F3,32 = 62.3, p < 0.001), resulting in a difference in total AGB of 199.83 g·m−2 (95% CI 133.6 – 266.1 g·m−2) between the control and treatment, an average increase of 109% (SE ± 20%). There was a significant increase in soil moisture in the treatment plots relative to the controls at each site for most of the growing season (July-Oct). On average, soil organic matter (SOM) increased by 32% SE ± 10.5, with two sites demonstrating a significant increase. Soil C stocks increased across sites with biosolids, but this was only significant at one site (F1,32 = 7.05, p = 0.012), the most degraded of all four pasturelands. This study demonstrated that a single application of biosolids compost could elicit a significant increase in soil moisture throughout the growing season and increase plant biomass production. Biosolid applications can also increase SOC. However, this response's magnitude is site-specific and is associated with the degree of soil degradation, which might be related to land management history. Using biosolids compost on pasturelands seems to be a positive strategy to improve soil health and its associated co-benefits. Still, managers should consider the degree of degradation of their land when determining cost benefits.

Negatively charged nano-hydroxyapatite can be used as a phosphorus fertilizer to increase the efficacy of wollastonite for soil cadmium immobilization.

Improper application of phosphorus (P) fertilizer during soil cadmium (Cd) immobilization reduces the efficiency of fertilizer and Cd remediation. In this study, we synthesized three types of nano-hydroxyapatite (NHAP) with different surface charges as slow-release P fertilizers during Cd immobilization. We also evaluated the effects of wollastonite application with or without NHAP addition, in comparison with triple superphosphate (TSP) or bulk hydroxyapatite, on Cd accumulation in Amaranthus tricolor L. The results showed that adding wollastonite significantly reduced P availability (23.5%) in the soil, but it did not inhibit plant P uptake. In wollastonite-amended soil, the application of negatively/positively charged NHAP significantly increased plant biomass by 643-865% and decreased Cd uptake by 74.8-75.1% compared to the unamended soil as well as showed greater efficiency than those with TSP. This was ascribed to the increased soil pH (from 3.94 to 6.52-6.63) and increased abundance of organic acids (including citric acid, malic acid, lactic acid, and acetic acid) secreted by plants. In addition, the P-preferring bacterial class Bacteroidia was specific to soils amended with both wollastonite and NHAP-. These results suggest that NHAP- may be an appropriate P fertilizer for soil Cd immobilization using wollastonite.

Furrows and, to a Lesser Extent, Seed Priming Improve Restoration Success in the Sagebrush Steppe

Seeding of native perennial species commonly fails in the presence of invasive annual weeds. The ability of weeds to deplete soil moisture through early germination and rapid growth gives them a competitive advantage. A possible solution to help native species compete with weeds is to enhance their germination rate and growth. We primed seeds of bluebunch wheatgrass (Pseudoroegneria spicata) and Lewis flax (Linum lewisii) in a matrix of compost, clay, and biostimulants for 4−7 d. We used an extrusion technique to incorporate the seed and priming matrix into pellets for the priming duration that had the quickest germination. We evaluated primed seeds in pellets at two field sites against seeds in pellets that were not primed and seeds left untreated (control). Seed treatments were planted in shallow (1-cm) and deep (15-cm) furrows, in a complete factorial design, with the expectation that the deep furrow treatment would provide an enhanced microsite to improve plant growth. Results indicated that deep furrows were the strongest driver in enhancing seedling establishment, while priming showed a smaller contribution. In the first month after planting, a combination of priming and furrowing increased seedling emergence by 128% and 303%, for bluebunch wheatgrass and Lewis flax, respectively, compared with control seed planted in shallow furrows. The following year, primed bluebunch wheatgrass and Lewis flax seeds in deep furrows increased plant biomass by 158% and 110%, respectively, compared with control seed in shallow furrows. Overall, this study generally indicates that the rapid germination of primed seeds and the use of deep furrows may assist seedlings in establishing, which may allow them to better compete with invasive weeds.

The Important Roles of Ecomychorizae to Increase Growth Rate of Sacha Inchi (Plukenetia volubilis L.) that Potentially as Raw Material of Biofuel

Recently the use of agricultural waste containing cellulose and lignin as an alternative fuel that is environmentally friendly. The study aimed to determine the important roles of eco-enzymes and mycorrhizae due to increasing the growth rate of sacha inchi plants that are tolerant to nutrient-poor soils such as Inceptisol which are classified as sub-optimal lands. Sacha inchi broadleaf plants are classified as having a high lignin content due to their biomass potentially producing alternative fuels that can reduce dependence on the use of fossils, which were decreasing. This research was conducted in West Reuleut Village, Muara Batu District, North Aceh District and the Laboratory of the Faculty of Agriculture, Malikussaleh University. This research was carried out from April to August 2022.The Application of eco-enzymes on Inceptisol soil has increased the absorption of several macronutrients that were impacted by the fresh weight of the root, root dry weight, and root length of sacha inchi. The activities of eco enzyme and mycorrhizae which were giving a positive impact on the vegetative growth rate of Sacha inchi plants. Eco enzymes contain microorganisms that help the process of decomposition, transport of nutrients, and mycorrhizae as biological fertilizers that can provide nutrient uptake for plants. The impact of synergizing both fertilizers together has increased the suitability and productivity of sub-optimal soil that is able to increase growth and yield plant. The increasing productivity of Sacha inchi plants which contain lignin and cellulose also increases plant biomass which has the potential to produce high bioethanol as well.

Effects of Bacterial and Fungal Inocula on Biomass, Ecophysiology, and Uptake of Metals of Alyssoides utriculata (L.) Medik.

The inoculation of plants with plant-growth-promoting microorganisms (PGPM) (i.e., bacterial and fungal strains) is an emerging approach that helps plants cope with abiotic and biotic stresses. However, knowledge regarding their synergic effects on plants growing in metal-rich soils is limited. Consequently, the aim of this study was to investigate the biomass, ecophysiology, and metal accumulation of the facultative Ni-hyperaccumulator Alyssoides utriculata (L.) Medik. inoculated with single or mixed plant-growth-promoting (PGP) bacterial strain Pseudomonas fluorescens Migula 1895 (SERP1) and PGP fungal strain Penicillium ochrochloron Biourge (SERP03 S) on native serpentine soil (n = 20 for each treatment). Photosynthetic efficiency (Fv/Fm) and performance indicators (PI) had the same trends with no significant differences among groups, with Fv/Fms > 1 and PI up to 12. However, the aboveground biomass increased 4-5-fold for single and mixed inoculated plants. The aboveground/belowground dry biomass ratio was higher for plants inoculated with fungi (30), mixed (21), and bacteria (17). The ICP-MS highlighted that single and mixed inocula were able to double the aboveground biomass' P content. Mn metal accumulation significantly increased with both single and mixed PGP inocula, and Zn accumulation increased only with single PGP inocula, whereas Cu accumulation increased twofold only with mixed PGP inocula, but with a low content. Only Ni metal accumulation approached the hyperaccumulation level (Ni > 1000 mg/kg DW) with all treatments. This study demonstrated the ability of selected single and combined PGP strains to significantly increase plant biomass and plant tolerance of metals present in the substrate, resulting in a higher capacity for Ni accumulation in shoots.

Effects of Arbuscular Mycorrhizal Fungi on Alleviating Cadmium Stress in Medicago truncatula Gaertn.

Heavy metal contamination is a global problem for ecosystems and human health. Remediation of contaminated soils has received much attention in the last decade. Aided mitigation of heavy metal phytotoxicity by arbuscular mycorrhizal fungi (AMF) is a cost-effective and environmentally friendly strategy. This study was carried out to investigate the mitigation effect of AMF inoculation on heavy metal toxicity in Medicago truncatula under soil cadmium stress. Therefore, a pot experiment was designed to evaluate the growth, chlorophyll fluorescence, Cd uptake and distribution, malondialdehyde (MDA) content, root soil physicochemical properties, and metabolite profile analysis of M. truncatula with/without AMF inoculation in Cd (20 mg/Kg)-contaminated soil. The results showed that inoculating AMF under Cd stress might enhance photosynthetic efficiency, increase plant biomass, decrease Cd and MDA content, and improve soil physicochemical properties in M. truncatula. Non-targeted metabolite analysis revealed that inoculation with AMF under Cd stress significantly upregulated the production of various amino acids in inter-root metabolism and increase organic acid and phytohormone synthesis. This study provides information on the physiological responses of mycorrhizal plants to heavy metal stress, which could help provide deeper insight into the mechanisms of heavy metal remediation by AMF.

Compost tea and bioslurry as plant biostimulants. Part 2: biofertilizer test in ornamental flowers

The present study tested the effect of aerated (AM), non-aerated (NAM), a 1:1 combination of both compost teas (A-NAM), and bioslurry (B) as bio-fertilizers in two ornamental plants growing in different substrates. The present study aimed to evaluate the products as biostimulants in ornamental plants. Compost teas were brewed from a composted mixture of residues, while bioslurry was prepared, with fresh material and no aeration. Two ornamental plant species were used: Petunia hybrida and Impatiens walleriana. Experimental presented a completely randomized factorial design, with two factors: Biostimulants with 6 levels: AM, NAM, A-NAM, B, F (traditional fertilizer), and H2O (control); and Substrate, with 3 levels: sand, commercial, and compost. Bio-inputs presented variable properties and effects on plant growth, with significant interaction between factors. In sand, no effect of bioproducts on plant biomass, SPAD index and pigments content were observed. In compost, B significantly increased I. walleriana and P. hybrida dry biomass (1.75 ± 0.42 g and 1.54 ± 0.28 g, respect to 1.33 ± 0.18 g for H2O), while in the commercial substrate, only in P. hybrida (1.35 ± 0.44 g, regarding 0.42 ± 0.11 g for H2O). All bio-inputs increased pigments content of both plant species in all substrates. To our knowledge, this is the first record that B was tested, which increased plant biomass at similar values to traditional fertilizer. We demonstrated that the biostimulants brewed from organic residues might present the same performance as commercial fertilizers.

β-diversity in temperate grasslands is driven by stronger environmental filtering of plant species with large genomes.

Elucidating mechanisms underlying community assembly and biodiversity patterns is central to ecology and evolution. Genome size (GS) has long been hypothesized to potentially affect species' capacity to tolerate environmental stress and might therefore help drive community assembly. However, its role in driving β-diversity (i.e., spatial variability in species composition) remains unclear. We measured GS for 161 plant species and community composition across 52 sites spanning a 3200-km transect in the temperate grasslands of China. By correlating the turnover of species composition with environmental dissimilarity, we found that resource filtering (i.e., environmental dissimilarity that includes precipitation, and soil nitrogen and phosphorus concentrations) affected β-diversity patterns of large-GS species more than small-GS species. By contrast, geographical distance explained more variation of β-diversity for small-GS than for large-GS species. In a 10-year experiment manipulating levels of water, nitrogen, and phosphorus, adding resources increased plant biomass in species with large GS, suggesting that large-GS species are more sensitive to the changes in resource availability. These findings highlight the role of GS in driving community assembly and predicting species responses to global change.

Polyamine metabolizing rhizobacteria Pseudomonas sp. GBPI_506 modulates hormone signaling to enhance lateral roots and nicotine biosynthesis in Nicotiana benthamiana

Beneficial rhizobacteria in the soil are important drivers of plant health and growth. In this study, we provide the draft genome of a root colonizing and auxin-producing Pseudomonas sp. strain GBPI_506. The bacterium was investigated for its contribution in the growth of Nicotiana benthamiana (Nb) and biosynthesis of nicotine. The bacterium showed chemotaxis towards root exudates potentially mediated by putrescine, a polyamine compound, to colonize the roots of Nb. Application of the bacterium with the roots of Nb, increased plant biomass and total soluble sugars in the leaves, and promoted lateral root (LR) development as compared to the un-inoculated plants. Confocal analysis using transgenic (DR5:GFP) Arabidopsis showed increased auxin trafficking in the LR of inoculated plants. Upregulation of nicotine biosynthesis genes and genes involved in salicylic acid (SA) and jasmonic acid (JA) signaling in the roots of inoculated plants suggested increased nicotine biosynthesis as a result of bacterial application. An increased JA content in roots and nicotine accumulation in leaves provided evidence on JA-mediated upregulation of nicotine biosynthesis in the bacterized plants. The findings suggested that the bacterial root colonization triggered networking between auxin, SA, and JA to facilitate LR development leading to enhanced plant growth and nicotine biosynthesis in Nb.

Resource-dependent foraging behaviour of grazers enhances effects of nutrient enrichment on algal biomass

Both the quantity and nutritional quality of food resources can strongly influence the foraging movements of herbivores, which in turn determine the strength of top-down control on primary producer biomass. Nutrient enrichment can alter the biomass and nutritional quality of primary producers, but the consequences for the foraging of herbivores and hence for top-down control are still poorly understood. In this study, we combined a two-factorial experiment (two nutrient levels × grazing by the freshwater gastropod Ancylus fluviatilis) with video analyses tracking grazers’ movements to investigate nutrient enrichment effects on spatial ranges of grazing activity and algal biomass removal. Natural stream biofilms were grown in phosphorus-enriched (P+) and phosphorus-poor flumes (P−) for two weeks before A. fluviatilis were added to the flumes and allowed to graze on biofilm for an additional 2 weeks. Total periphyton biomass was enhanced by P+ and reduced by grazer presence. However, the total grazer effect depended on the nutrient level: at the end of the experiment, on average 95% of algal cover were removed by grazing in the P− flumes versus 26% in the P+ flumes. Fast movements of A. fluviatilis were detected significantly more often in the P− treatment, whereas grazers were detected resting more often in the P+ treatment. Our results demonstrate that nutrient enrichment can increase primary producer biomass both directly and indirectly by limiting the foraging ranges of herbivores. The resulting feedback loop between reduced grazing activity and increased plant biomass might in turn exacerbate eutrophication effects on habitat structure.

Methane and Nitrous Oxide Emissions from a Temperate Peatland under Simulated Enhanced Nitrogen Deposition

Nitrogen (N) deposition has increased in recent years and is significantly affected by global change and human activities. Wetlands are atmospheric CH4 and N2O sources and may be affected by changes in N deposition. To reveal the effects of increased N deposition on peatland greenhouse gas exchange, we observed the CH4 and N2O emissions from controlled microcosms collected from a temperate peatland in the Xiaoxing’an mountains, Northeast China. We found that the moss biomass did not change, but the total herb biomass increased by 94% and 181% with 5 and 10-times-higher N deposition, respectively. However, there were no significant changes in CH4 emissions from the microcosms with N addition. The unchanged CH4 emissions were mainly caused by the opposite effect of increased nitrate and ammonium concentrations on soil CH4 production and the increased plant biomass on CH4 emission. We also found that the manipulated microcosms with 5 and 10-times-higher N deposition had 8 and 20-times-higher seasonal average N2O emissions than the control microcosms, respectively. The increased N2O emissions were mainly caused by short-term (≤7 d) pulse emissions after N addition. The pulse N2O emission peaks were up to 1879.7 and 3836.5 μg m−2 h−1 from the microcosms with 5 and 10-times-higher N deposition, respectively. Nitrate and ammonium concentrations increasing in the soil pore water were the reason for the N2O emissions enhanced by N addition. Our results indicate that the increase in N deposition had no effects on the CH4 emissions but increased the N2O emissions of the temperate peatland. Moreover, pulse emissions are very important for evaluating the effect of N addition on N2O emissions.

Alternative Management Strategies and Impact of the Northern Root-Knot Nematode in Daylily Production

Bare-root production of Hemerocallis spp., daylily, is of major economic importance to Michigan's ornamental industry, but production of clean nursery material is challenging due to plant-parasitic nematodes. The northern root-knot nematode, Meloidogyne hapla, is the most important perennial ornamental pathogen in northern North America; it causes over 20% yield loss in Hemerocallis spp. production and reduces marketability and distribution. A field trial was established in 2018 to 2020 at a Michigan commercial nursery to determine effective and long-term management strategies to reduce nematode population levels. Eleven treatments were tested: a control, four bio-nematicides, two nematicides, a nematicide root dip, and three compost blends. Soil samples were taken three times per year, along with annual root samples and plant height measurements. Results indicated that TerraClean 5.0 (hydrogen peroxide) and Majestene 304 ( Chromobacterium subtsugae) nematicides best controlled M. hapla populations by 49 and 37%, respectively, compared with the control, whereas Indemnify (fluopyram) significantly increased plant biomass and yields by 31%. A greenhouse study was conducted to determine the impact of M. hapla on Hemerocallis spp. production by inoculating daylily with varying nematode inoculation densities. Even at low population levels, plant biomass reductions were observed, and M. hapla was readily able to reproduce on Hemerocallis spp. These experiments highlight the importance of managing M. hapla and provide effective, alternative management methods that can reduce the application of fumigants and prevent yield losses to increase profitability for ornamentals.