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Premise: Current knowledge about defense strategies in plants under herbivore pressure is predominantly based on vascular plants. Bryophytes are rarely consumed by herbivores since they have ample secondary metabolites. However, it is unknown whether bryophytes have induced defenses against herbivory and whether there is a trade‐off between growth and defense in bryophytes. Methods: In an experiment with two peatland bryophytes, Sphagnum magellanicum Brid. and S. fuscum (Schimp.) H. Klinggr., two kinds of herbivory, clipping with scissors and grazing by mealworms (Tenebrio molitor L.) were simulated. At the end of the experiment, we measured growth traits, carbon‐based defense compounds (total phenolics and cellulose) and storage compounds (total nonstructural carbohydrates) of these two Sphagnum species. Results: Grazing but not clipping increased total phenolics and C:N ratio and reduced biomass production and height increment. A negative relationship between biomass production and total phenolics was found in S. magellanicum but not in S. fuscum, indicating a growth–defense trade‐off that is species‐specific. Grazing reduced the sugar starch content of S. magellanicum and the sugar of S. fuscum. Either clipping or grazing had no effect on chlorophyll fluorescence (including actual and maximum photochemical efficiency of photosystem II) except that a significant effect of clipping on actual photochemical efficiency in S. fuscum was observed. Conclusions: Our results suggest that Sphagnum can have induced defense against herbivory and that this defense can come at a cost of growth. These findings advance our knowledge about induced defense in bryophytes, the earliest land plants. [ABSTRACT FROM AUTHOR]

Not only nature but human activities also provide ecosystem services alike agriculture and agroforestry which both host a wide range of ecosystem services besides providing food and fiber for humans and animals. The efficiency of ecosystem services of a cultivated land depends on agricultural management choices. Current conventional land management approaches, that are generally unsustainable by causing various environmental problems such as pollution, loss of biodiversity and organic carbon, need to be well-defined for designing land use for agricultural production. This manuscript focuses on tillage and crop-pattern effect on soil organic carbon, which is a vital component not only for enhancing soil quality but for mitigation of climate change and desertification. The monitored plants for 10-year were peach (Prunus persica), apricot (Prunus armeniaca), cherry (Prunus avium L.), quince, pear, plum, grapevine, wheat, barley and pine that are under various land management methods namely tillage, minimum and no-tillage, cover crops, mineral/organic fertilization. The soil organic carbon trends revealed that in the studied semiarid climate zone for rainfed cultivation grapevine, and for irrigated cropping apricot had the highest organic carbon accumulation potential along with optimal C:N ratio. [ABSTRACT FROM AUTHOR]

Decomposition is a key ecosystem function, and the rate of decomposition in forests affects their carbon storage potentials. Processes and factors determining leaf litter decomposition rates in dry‐land and temperate forests are well understood, but these are generally poorly studied in tropical wetland forests, especially freshwater swamp forests (FSF). The home‐field advantage (HFA) hypothesis predicts that soil microbes specialize in decomposing leaf litter produced by the tree species in their immediate vicinity. However, empirical support for the HFA is equivocal, and the HFA has never been tested in the highly heterogeneous and biodiverse ecosystems of tropical FSFs. We collected leaf litter from swamp and non‐swamp tree species in a tropical FSF in Singapore and monitored the decomposition rates of these in swamp and non‐swamp plots for a period of eight months. Leaf litter decomposed 3.7 times more slowly in swamp plots. Leaf litter from swamp tree species were significantly poorer in quality (higher C:N ratio) than those of non‐swamp FSF tree species, but this had only a weak effect on decomposition rates. There was also only weak evidence for the HFA and only in non‐swamp conditions. Our results show that while the leaf litter of tropical FSF swamp and non‐swamp tree species differ significantly in chemical traits, litter decomposition rate is ultimately determined by local abiotic conditions, such as hydrology. Additionally, the high FSF tree diversity may prevent decomposer communities from specializing on any group of leaf litter types and thus limit the extent of HFA observed in such heterogeneous forests. [ABSTRACT FROM AUTHOR]

Nitrogen (N) deposition and grazing (G) are two disturbances of grassland ecosystems and these can greatly affect soil respiration. To date, few studies have investigated this topic in sandy grasslands. Here, we conducted a manipulative experiment in a sandy grassland in Inner Mongolia, China in the year 2013 and 2014, to investigate the effects of N addition and grazing on soil respiration. The results showed that N addition significantly accelerated soil respiration in both 2013 and 2014. The respiration enhancement under N addition varied during the growing season, being larger in early May 2014 (0.40 μmol·m−2·s−1) and early July 2014 (1.29 μmol·m−2·s−1) than in October 2014 (0.03 μmol·m−2·s−1). Grazing plots yielded a lower cumulative soil respiration rate than the control plots (−5,68% in 2013 and −1.07% in 2014), although the difference was not significant. In this study, soil temperature rather than soil moisture was the main factor affecting the temporal variation in soil respiration during the growing season. The inter-plot analysis showed that the soil ammonium nitrogen (NH4+–N) content, C:N ratio, and root biomass were significantly correlated with soil respiration, indicating that soil respiration under N-addition or grazing treatment could be affected by changing soil microhabitat conditions, thus affecting soil respiration. [ABSTRACT FROM AUTHOR]

No-tillage (NT) management is considered a leading approach for sustaining crop production and improving soil and environmental quality. Based on a long-term no-tillage experiment in a rice–oilseed rape cropping system, we examined differences in soil organic matter (SOM), soil microbial carbon (C) and nitrogen (N) content, and methane (CH4) and carbon dioxide (CO2) fluxes between NT and conventional tillage (CT) management. SOM under NT was 21.0 g kg–1, and a significant difference was detected between 2004 and 2016. SOM increased under NT and CT by averages of 0.60 and 0.32 g kg–1 year–1, respectively. Soil microbial C and N content were higher under CT than under NT. However, soil C:N ratios under NT were 17.4 and 9.7% higher than the CT, respectively, whereas soil microbial C:N ratios under NT were on average 9.47 and 9.70% higher. In addition, about 70% of CO2 net uptake and over 99% of net CH4 emissions occurred during the rice season in May–September in the rice–oilseed rape cropping system. Annual cumulative CH4 and daytime net ecosystem CO2 exchange (NEE) under NT was 1813.9 g CO2 equiv. m–2, 10.8% higher than that under CT. Our results suggest that a higher soil microbial C:N ratio and NEE (CH4 and daytime CO2) could contribute to increasing SOM/C in the surface soil under NT management.

Stable‐isotope analysis (SIA) provides a valuable tool to address complex questions pertaining to elasmobranch ecology. Liver, a metabolically active, high turnover tissue (~166 days for 95% turnover), has the potential to reveal novel insights into recent feeding/movement behaviours of this diverse group. To date, limited work has used this tissue, but ecological application of SIA in liver requires consideration of tissue preparation techniques given the potential for high concentrations of urea and lipid that could bias δ13C and δ15N values (i.e., result in artificially lower δ13C and δ15N values). Here we investigated the effectiveness of (a) deionized water washing (WW) for urea removal from liver tissue and (b) chloroform‐methanol for extraction of lipids from this lipid rich tissue. We then (a) established C:N thresholds for deriving ecologically relevant liver isotopic values given complications of removing all lipid and (b) undertook a preliminary comparison of δ13C values between tissue pairs (muscle and liver) to test if observed isotopic differences correlated with known movement behaviour. Tests were conducted on four large shark species: the dusky (DUS, Carcharhinus obscurus), sand tiger (RAG, Carcharias taurus), scalloped hammerhead (SCA, Sphyrna lewini) and white shark (GRE, Carcharodon carcharias). There was no significant difference in δ15N values between lipid‐extracted (LE) liver and lipid‐extracted/water washed (WW) treatments, however, WW resulted in significant increases in %N, δ13C and %C. Following lipid extraction (repeated three times), some samples were still biased by lipids. Our species‐specific "C:N thresholds" provide a method to derive ecologically viable isotope data given the complexities of this lipid rich tissue (C:N thresholds of 4.0, 3.6, 4.7 and 3.9 for DUS, RAG, SCA and GRE liverLEWW tissue, respectively). The preliminary comparison of C:N threshold corrected liver and muscle δ13C values corresponded with movement/habitat behaviours for each shark; minor differences in δ13C values were observed for known regional movements of DUS and RAG (δ13CDiffs = 0.24 ± 0.99‰ and 0.57 ± 0.38‰, respectively), while SCA and GRE showed greater differences (1.24 ± 0.63‰ and 1.08 ± 0.71‰, respectively) correlated to large‐scale movements between temperate/tropical and pelagic/coastal environments. These data provide an approach for the successful application of liver δ13C and δ15N values to examine elasmobranch ecology. [ABSTRACT FROM AUTHOR]

Aims Leaf size and shape as objects of natural selection can play adaptive roles, and can change with the age of leaves. They can differ between sexes in dioecious species, and in most cases, females have larger leaves. Previous studies showed that sexes of Adriana tomentosa differed in their leaf lobing. In this study, we investigated whether there were other differences between sexes in leaf size, shape and ecophysiology, and if those differences were connected with adaptations and reproductive roles in the sexes of A. tomentosa. Methods Physical and chemical features of young and old leaves originating from female and male A. tomentosa plants growing in two disjunct populations in eastern Australia were measured. We determined leaf area, perimeter length, serration, circularity, aspect ratio (AR), roundness and the ecophysiological factors: specific leaf area, dry matter content, leaf moisture, relative water content, δ 13C, δ 15N isotope compositions, carbon and nitrogen contents and C:N ratio. Leaf lobing, the degree of lamina damage and the content of photosynthetic pigments were also determined. Important Findings In both populations studied, the sex of plants significantly influenced almost all parameters connected with leaf morphology such as area, perimeter length, circularity, AR and roundness. Contrary to expectations, males from both populations had a greater leaf area that was independent of leaf age. Male leaves were more lobed with a longer perimeter, but they were less elongated and less serrated. Only small differences between female and male leaves were observed for the ecophysiological factors. The degree of leaf damage differed between sexes but also with population. Differences between sexes in leaf area and shape were not compensated by measured ecophysiological factors. However, leaf area may be compensated by other ecophysiological mechanisms related to leaf morphology, because females had greater leaf serration in comparison to males despite the smaller leaf area. [ABSTRACT FROM AUTHOR]

Agarwood (Aquilaria malaccensis Lam.) is highly valued for its medicinal, incense and perfumery properties. Due to the illegal harvest and trade in its wood, this species is critically endangered in the wild. Managing the agarwood on farmland is believed to enhance the economic security of smallholder farmers while also contributing to the conservation of the species. However, information is scanty on the cultivation of agarwood in smallholder farmlands and the effect of stand density and managements on the associated vegetation and soil properties. Therefore, the objectives of this study were to quantify (i) the diversity, density distributions and importance values, (ii) functional diversity and (iii) soil carbon and nitrogen contents, and C:N stoichiometry under different agarwood management regimes on smallholder farms. A total of 40 farms were selected for this study, and these were categorised into four management regimes based on the proportion of agarwood trees as: pure stand (100 % agarwood trees), dominant (61–99%), moderate (30–60 %) and non-dominant (

Abstract Litter decomposition restores part of the elements absorbed by the plant back into the soil, acting as a regulator of the biogeochemical cycling of nutrients. This study aimed to evaluate the litter quantity and quality of Eucalyptus grandis in Northern Fluminense region, RJ. Three rotational sequences were studied, the first after 8 years (FR8), the second after 1.5 years (SR2), and a 5year old regrowth (R5). Leaf litter was divided into whole leaves (WL), fragmented pieces (FP), twigs/branches (TB), reproductive structures (RS) and bark (B). The total litter in FR8 was 9.56 Mg ha-1, in SR2, 13.85, and in R5, 22.97 Mg ha-1, corresponding to 83, 163 and 75 kg ha-1 of N, respectively. FP represented 38%, 48% and 55% of N, respectively, in SR2, R5 and FR8. The WL and FP fractions have high recycling potential of organic matter and nutrients due to their lower C/N and Lig/N quality index values.

In this study, we have for the first time analyzed diel microzooplankton grazing selectivity on unicellular cyanobacterial diazotroph (i.e., Crocosphaera watsonii WH8501) and non-diazotrophic unicellular microalga (i.e., Chlorella autotrophica). A mixed diet consisting of these two phytoplankton was supplied to four species of protistal grazers during daytime and nighttime, respectively. C. watsonii fixes nitrogen during nighttime and showed a stronger diel pattern of cellular C:N ratio than C. autotrophica. All four grazers ingested more nighttime C. watsonii than daytime C. watsonii, suggesting the diazotroph became more nutritious (inferred by C:N ratio) and thus a preferred prey for grazers when it fixes nitrogen. In particular, Oxyrrhis marina changed from preferring C. autotrophica during daytime to preferring C. watsonii during nighttime. The rest grazers showed species-specific grazing preferences, which could be explained by extracellular polysaccharide production of C. watsonii, feeding mode, cingulum size and cell size of grazers.

The concentration of greenhouse gases (GHGs) in the atmosphere has been increasing since the beginning of the industrial revolution. Nitrous oxide (N2O) is one of the mightiest GHGs, and agriculture is one of the main sources of N2O emissions. In this paper, we reviewed the mechanisms triggering N2O emissions and the role of agricultural practices in their mitigation. The amount of N2O produced from the soil through the combined processes of nitrification and denitrification is profoundly influenced by temperature, moisture, carbon, nitrogen and oxygen contents. These factors can be manipulated to a significant extent through field management practices, influencing N2O emission. The relationships between N2O occurrence and factors regulating it are an important premise for devising mitigation strategies. Here, we evaluated various options in the literature and found that N2O emissions can be effectively reduced by intervening on time and through the method of N supply (30–40%, with peaks up to 80%), tillage and irrigation practices (both in non-univocal way), use of amendments, such as biochar and lime (up to 80%), use of slow-release fertilizers and/or nitrification inhibitors (up to 50%), plant treatment with arbuscular mycorrhizal fungi (up to 75%), appropriate crop rotations and schemes (up to 50%), and integrated nutrient management (in a non-univocal way). In conclusion, acting on N supply (fertilizer type, dose, time, method, etc.) is the most straightforward way to achieve significant N2O reductions without compromising crop yields. However, tuning the rest of crop management (tillage, irrigation, rotation, etc.) to principles of good agricultural practices is also advisable, as it can fetch significant N2O abatement vs. the risk of unexpected rise, which can be incurred by unwary management.

The priming effect is a strong short-term change of organic matter decomposition that can accelerate or slow residue decomposition, and release or immobilize a large amount of carbon (C) and nitrogen (N) in soil. Our goal here was to (i) monitor the influence of residue additions in stocks of C and N in residues and soil (ii) and identify the main routes of C stabilization and the priming effect in soil. An incubation study was run with residue additions of high C:N (brachiaria and sugarcane) and low C:N (soybean) in soil. CO2 emissions, stocks of C (humic substance; labile C and C mic) and N (soil and residues) were monitored for 50 days, and the priming effect and route of C were calculated. Results showed that after incubation the final stocks of humin increased (31%), while there were reductions of humic (54%) and fulvic acids (42%). The stocks of soil total C and N were constant, while the residue C was decreased. The residues with high C:N immobilized N, while there was a decrease of N in residues with low C:N. There was a positive priming effect and a C stabilization route concentrated from C mic to humic substances with the addition of low C:N, while inputs of high C:N diversified the C stabilization routes from C mic or labile C to humic substances. The C routes were intense because the study was run in control conditions with a loam soil and adequate conditions of water, oxygen, and temperature.

Purpose: Role of no-tillage (NT) in soil conservation has been already established but its influence on soil organic carbon (SOC) is still under debate. Materials and methods: Three paired sites, with NT and chisel-plow (CT) fields adjacent to each other were selected for this study. Fields were under the same tillage practices for more than 20 years. Fields were sampled up to 90 cm depth to determine SOC and different C pools based on soil CO2 flux during 86 d of incubation. Results and conclusion: Significant differences in SOC and its pools were limited within the surface 0–15 cm depth only. Profile SOC did not vary between NT and CT. Tillage had a significant influence on soil C pools but the effect was not consistent across sites.

The flower waste generated from different sources is either mixed with municipal solid waste or thrown into the river in India. Flower waste is rich in organic contents and can be converted into nutrient-enriched compost. The aim of the present study was to determine the changes in physico-chemical and biological changes during the composting of flower waste by using rotary drum technique. For composting the flower, waste was mixed with cow dung, sawdust, and wheat bran. Four different trials were performed, in which 0.5 wt% of sawdust and wheat bran was added in each trial. From the series of trials 1–4, the different proportions of flower waste and cow dung were 5:4, 6:3, 7:2 and 8:1, respectively. Finally, the compost produced by all the trials were found to have pH 7.23–7.51, electrical conductivity 5.5–6.12 mS/cm, reduction in the percentage of total organic carbon 22–33%, the percentage increase in total nitrogen 2.17–2.66%, C:N ratio 13–17, sodium 2.14–2.60 g/kg and calcium 13.35–15.58 g/kg. The analytical hierarchy process was used for the ranking of the trials to find the best proportions from the different combinations performed in this study.

This study aimed to recycle sawdust and blood powder using Eisenia foetida earthworm and investigate some biochemical changes of these waste materials during vermicomposting. Blood powder was mixed with sawdust in proportions of 0, 5 and 10% and the mixture was allowed to pass through earthworm guts for four months. At intervals of 1, 2, 3, 4, 6, 8, 12 and 16 weeks, the biological activity (i.e. basal respiration), pH, EC, total organic carbon, total nitrogen and C:N ratio were determined. The results showed that the period of time, the concentration of blood powder and the interaction between these two significantly affected all parameters. As the incubation time increases, the cumulative amount of mineralized carbon, the total nitrogen and EC increase in all vermicompost treatments whereas organic carbon, C:N ratio and pH decreased. Adding blood powder to sawdust bed resulted in an increase in carbon mineralization rate, EC and total nitrogen while pH, organic carbon and C: N ratio decreased. At the end of incubation time, the treatment of sawdust with 10 % blood powder resulted in the highest amount of released CO2 (142.1 µg C g-1), EC (3.7 dS m-1) and total nitrogen (2.24 %) and the lowest amount of pH (6.6), organic carbon (22.5 %) and C: N ratio (12.4). According to the results, the process of vermicomposting can be used as a safe method for the disposal of sawdust and blood powder

Climate change may alter microscale-effective ecosystem properties such as atmospheric water vapour pressure, but consequences for plant growth are insufficiently understood. Within a northwest German heathland an open-top chamber experiment was established to analyse the effects of elevated vapour pressure deficit (eVPD) on growth responses of Calluna vulgaris considering both plant origin (Atlantic (AP), sub-Atlantic (SAP), sub-Continental (SCP)) and life-history stage (1-year vs. 10-year old plants). We hypothesised that the plants' sensitivity to eVPD decreases (i) from AP to SCP and (ii) with progressing life-history stage. Elevated VPD caused a provenance-specific decrease of shoot increment whilst aboveground biomass productivity remained unaffected. AP and SAP responded with increasing belowground biomass δ13C signatures to eVPD, whereas δ13C values decreased for SCP. Moreover, eVPD increased and decreased belowground biomass δ13C signatures of 1- and 10-year old plants, respectively. These responses to eVPD were related to differences in morphological-chemical traits and the plants' trait plasticity in response to eVPD. SCP showed the highest aboveground tissue mass density and significantly increased tissue C:N ratios under eVPD. One-year old plants had a tenfold higher shoot:root ratio than 10-year old plants, making young plants more sensitive to eVPD. Our findings demonstrate that the atmospheric water status affects the morphology and physiology of Calluna independent of the soil water status. The results have implications for the conservation of heathlands under climate change: (i) SCP may constitute an appropriate ecotype for assisted migration-approaches, and (ii) management needs to weigh different options for heathland rejuvenation. [ABSTRACT FROM AUTHOR]

The elemental composition of primary producers represents a potentially important pathway for linking ecosystem scale, climate-driven changes in nutrient supply to ecological processes at the population and community scales. However, such cross-scale linkages may also be dampened by conservation of species-specific differences in tissue stoichiometry. We investigated biogeographic patterns of elemental composition (%N, %C, and C:N ratio) of four ecologically dominant and functionally diverse marine intertidal macrophyte species (the brown algae Fucus distichus and Hedophyllum sessile, the red alga Mazzaella splendens, and the surfgrass Phyllospadix scouleri) along 900 km of coastline of the California Current System over a 10-year period. We used a nested hierarchical design to identify the dominant spatial and temporal scales of elemental composition variability and to test the sensitivity of macrophyte stoichiometry to changing ocean conditions in upwelling, the El Niño-Southern Oscillation (ENSO), the North Pacific Gyre Oscillation (NPGO), and the Pacific Decadal Oscillation (PDO). Elemental composition was highly conserved at the species level but was also sensitive to the environment, displaying marked species-dependent responses to spatial and temporal variation in ocean conditions. Moreover, the effects of local and seasonal processes were strong and with conserved species-specific differences, likely limited coherent cross-species sensitivity to climate variability from ENSO, NPGO and PDO. Unanticipated long-term steady increases in %C and bimodal increases in %N in brown algae and similar decreases in elemental composition of the red alga generated trimodal changes in C:N for these species. These changes may reflect responses of macrophyte communities to continuing changes in carbonate chemistry from ocean acidification. [ABSTRACT FROM AUTHOR]

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Investigating the correlation between biodiversity and ecosystem function in natural environments using carbon-isotope composition (δ13C) allows distinguishing the nutrient cycling pattern and anthropogenic effects incorporation in plants and soil processes. The mechanisms behind the isotopic composition of soil organic matter (SOM) and parent vegetation in relation to the context of site-specificity was approached in this work. Formation of SOM can be affected by the presence of a high concentration of heavy metals in soils. Still, no systematic studies were performed in most of the industrial sites to support this hypothesis. In order to explore this incomplete understood influence, investigation of carbon isotope signatures (δ 13C) variations in soil organic matter were performed in two industrial areas from Romania (Copșa Mică industrial platform and Baia Sprie mining zone). The current study, also, investigated the C:N ratio variation, as well as the influence of N speciation regarding δ 13C values of SOM. The decrease in C:N ratio indicated an increasing effect of the microbial products on SOM matter at increasing depth, for both regions, while an increase of the denitrification processes with depth was found for both areas. For the most appropriate depth (20-40 cm), the soil from Baia Sprie region was more enriched in 13C comparing with the soil from Copsa Mica region, and this higher isotope fractionation of SOM might be due to a higher carbon content, respectively a higher nitrogen content of Baia Sprie soil. It was concluded that the SOM of the surface soil in the two investigated regions has an 13C isotopic composition similar to the plant remains from which it was formed, offering an integrated value of plant material, time and the local origin and providing useful markers of tree isotopic composition. [ABSTRACT FROM AUTHOR]

Remediation of saline-sodic soils used for cattle breeding is particularly challenging due to the limited alternatives. We hypothesize that introducing salt tolerant and productive forage in a lowland halophytic steppe, typical of saline-sodic soils, increases belowground biomass inputs and activity, generating a series of positive effects on soil biological and chemical properties, and aggregate stability – an accepted indicator of soil degradation resistance. Under natural environmental conditions, we found that the introduction of Panicum coloratum (panicum) increased belowground biomass almost three times, the abundance of mites tended to be greater and that of springtails was 9.4 kg−1 contrasting with none found in the halophytic steppe, after 7 years. The concentration of Ca2+ and Mg2+ increased 26% and 54%, respectively, and that of Na+ was reduced 31% compared with the halophytic steppe. Soil pH decrease 5% and electrical conductivity decreased 37% (changing from moderate to very slightly saline) in panicum compared to the halophytic steppe. However, in panicum, mineral-associated organic matter (MAOM) and aggregate stability decreased 22% and 26%, respectively. We concluded that, although biological and chemical properties improved, aggregate stability – an early indicator of soil recovery – decreased, which was likely determined by MAOM reduction in saline-sodic soils. [ABSTRACT FROM AUTHOR]

Gross rates of nitrogen (N) turnover inform about the total N release and consumption. We investigated how plant diversity affects gross N mineralization, microbial ammonium (NH4+) consumption and gross inorganic N immobilization in grasslands via isotopic pool dilution. The field experiment included 74 plots with 1–16 plant species and 1–4 plant functional groups (legumes, grasses, tall herbs, small herbs). We determined soil pH, shoot height, root, shoot and microbial biomass, and C and N concentrations in soil, microbial biomass, roots and shoots. Structural equation modeling (SEM) showed that increasing plant species richness significantly decreased gross N mineralization and microbial NH4+ consumption rates via increased root C:N ratios. Root C:N ratios increased because of the replacement of legumes (low C:N ratios) by small herbs (high C:N ratios) and an increasing shoot height, which was positively related with root C:N ratios, with increasing species richness. However, in our SEM remained an unexplained direct negative path from species richness to both N turnover rates. The presence of legumes increased gross N mineralization, microbial NH4+ consumption and gross inorganic N immobilization rates likely because of improved N supply by N2 fixation. The positive effect of small herbs on microbial NH4+ consumption and gross inorganic N immobilization could be attributed to their increased rhizodeposition, stimulating microbial growth. Our results demonstrate that increasing root C:N ratios with increasing species richness slow down the N cycle but also that there must be additional, still unidentified processes behind the species richness effect potentially including changed microbial community composition. [ABSTRACT FROM AUTHOR]

This study evaluated the mass decomposition and mineralization of nutrients from a green manure composed of mixtures of legume and grass in tropical conditions. The experiment was carried out in a greenhouse, with green manure biomass mulched on top of the soil in pots and covered with a nylon screen. The five treatments comprised different ratios of jack bean (JB) and millet (M) providing the same amount of total N: 100JB, 75JB:25M, 50JB:50M, 25JB:75M and 100M. Samples were collected at 0, 40, 80, 120 and 160 days after mulching. The contents of C, N, P, K, Ca, Mg, S, cellulose, hemicellulose, lignin and the C:N, C:S and lignin:N ratios were determined. The chemical characteristics varied according to the legume and grass mixtures. The 100JB had the highest N content and lowest contents of cellulose, hemicellulose, lignin, C:N and lignin:N. The opposite was found for the 100M. The N mineralization process correlates positively with total N concentration and negatively with lignin content, C:N and lignin:N ratio and, these were the most important factors to predict the N mineralization in mixtures of legume and grass in tropical conditions. [ABSTRACT FROM AUTHOR]

We describe the ontogenetic variation in elemental and stoichiometric composition of two copepod species with very contrasted life history patterns, the calanoid Paracartia grani and the cyclopoid Oithona davisae. The first species is a broadcasting, highly productive copepod, whereas the latter is an egg-carrying copepod, much less productive. We reared cultures of both species under conditions of excess food and analyzed their C, N and P composition, and their molar ratios, along development. Both species differed on their specific P content, whereas the specific C and N content were similar. As expected, the specific P content of P. grani was higher, resulting in lower C:P and N:P ratios. Furthermore, we compared our elemental composition data with previously reported stage-specific (nauplii and adult female) maximum growth rates of these two species. We found that for O. davisae , the ontogenetic variation in specific P content agreed with the reported differences in growth rate along development; however, in the case of P. grani , in which juvenile and adult maximum growth rates are similar, the variations in specific P content along development did not reflect the growth rate pattern. [ABSTRACT FROM AUTHOR]

Decomposition of crop residue releases nutrients and preserves soil organic matter dynamics. The decomposition rates of six crop residues namely, corn (Zea mays), dry bean (Phaseolus vulgaris), soybean (Glycine max), potato (Solanum tuberosum), sugarbeet (Beta vulgaris) and spring wheat (Triticum aestivum), were studied at three field-sites: Casselton, North Dakota, USA, and Ada and Downer of Minnesota, USA. Litterbags were placed on soil surface on 31 October 2016, and subset was retrieved after 6 months (8 April 2017) and finally after a year (30 October 2017). Crop residue type had significant effect on remaining mass%, carbon (C) and nitrogen (N) release, and C:N ratio. After 1 year, remaining mass% followed the sequence of corn (82%) > soybean (74%) > wheat (72%) > dry bean (55%) > potato (40%) > sugarbeet (17%). Among sites, Ada had higher remaining biomass C and N than Downer but similar to Casselton. Sugarbeet and corn had the highest (0.0054 d−1) and the lowest (0.0005 d−1) decomposition rate, respectively. Decomposition rate had a close relationship with initial residue C:N ratio. Conversion to intensive corn–soybean rotation might increase the residue load on the surface and reduce C and N mineralization loss. [ABSTRACT FROM AUTHOR]

The utilization of bioherbicides in place of chemical herbicides has been described as one of the sustainable eco-friendly technologies that can improve agricultural outputs. This work investigated the impact of different carbon and nitrogen sources on the bioherbicidal efficiency of Lasiodiplodia pseudotheobromae (C1136). The preliminary screening of various carbon and nitrogen sources was carried out, out of which sucrose and peptone were selected for further C:N ratio investigations using strain C1136. The fungus produces a different quantity of mycelium biomass and spores in varied ratios of C:N when compared to the basal medium. Also, the effect of C:N ratio was tested by evaluating for leaf necrosis assay, mortality rate and the dry-matter biomass from the aerial parts of Chromolaena odoratum and Echinochloa crus-galli under guided laboratory and screen house conditions. Both the 7.5:1 and 10:1 ratios produced optimal spores count of 6.1 × 107 and 5.9 × 107 CFU/mL, respectively (p = 0.05) when compared to the control containing potatoes dextrose broth without any carbon or nitrogen amendment produced a spores count of 1.1 × 107 CFU/mL. Also, the phytotoxic metabolite amended with C:N of 10:1 showed a strong herbicidal, high mortality and a significant decrease in dry weight on the seedling on the tested weeds. This demonstrated hypothetically the optimization influence of carbon (sucrose)–nitrogen (peptone) manipulations either in variable combination or as single nutrient based on the cultural development of strain C1136. Spores, mycelium biomass and biocontrol efficacy of the fungus all experienced accretion in sucrose and peptone nutrient environment and likewise support their use as an attractive alternative in the optimization of mycoherbicidal assays. [ABSTRACT FROM AUTHOR]

We examined the concentration of nitrogen (N) and δ15N in vegetation and peat in the Mer Bleue bog, Ontario, Canada. Compared with other ecosystems, N concentration in bog plant foliage is low (generally < 1.2%), with more N stored belowground than in foliar tissues. The natural abundance of 15N varies by plant functional type, indicating different strategies for nutrient acquisition. δ15N values of evergreen shrubs and trees are lower (~− 5 to ~− 9‰) than sedges and herbs (~+ 1 to ~− 1‰), likely the result of ericoid mycorrhizal fungi, which retain 15N in fungal biomass, with preferential transfer of 14N to the host plant. Results suggest that N in Sphagnum moss capitula is derived from uptake of N from decomposing peat and litter, with δ15N values of − 8 to − 2‰, rather than from N2 fixation. Soil δ15N varies with depth, related to degree of decomposition and dominant plant species litter. Foliar N plays a critical role in influencing the rate of photosynthesis and CO2 exchange. Despite paucity of available inorganic N in the system, most bog plants (that is, evergreen shrubs) have adapted with conservative growth strategies. Owing to slow decomposition, N is stored in this system tightly bound with organic matter, with C:N ratios in deep peat ranging from 33:1 to 23:1 and small fluxes into, out of and within the system. An increase in N availability, through atmospheric N deposition or water table lowering, could jeopardize the C sink function of bogs by stimulating microbial decomposition of organic matter. In the long term, an increase in N cycling would shift plant community composition from Sphagnum and evergreen dominated to deciduous species, fundamentally altering bog ecosystem function. [ABSTRACT FROM AUTHOR]

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Identification of novel genotypes with enhanced nitrogen use efficiency (NUE) is a key challenge for a sustainable tomato production. In this respect, the performance of a panel of thirty tomato accessions were evaluated under high (HN; 5 mM N) and low (LN; 0.5 mM N) nitrogen irrigation solutions. For each treatment, when 50% of plants reached the first flower bud stage, plant growth and biomass traits, chlorophyll, flavonol and anthocyanin indexes, nitrogen balance index (NBI), C:N ratio in leaves, stems, and roots, and NUE were evaluated. Significant (p < 0.05) effects were observed for accession, N treatment, and their interaction across all the traits. Under LN, plants showed a delayed development (40 days for HN vs. 65 days for LN) and reduced growth and biomass. On average, LN condition led to 41.8% decrease in nitrogen uptake efficiency (NUpE) but also 189.0% increase in NUtE, resulting in 62.2% overall increase in NUE. A broad range of variation among accessions was observed under both HN and LN conditions. Under LN conditions, chlorophyll index and NBI decreased, while flavonol and anthocyanin indexes increased. Leaf C:N ratio was positively correlated with nitrogen utilisation efficiency (NUtE) in both N treatments. Multi-trait analyses identified top-performing accessions under each condition, allowing to identify one accession among top performers under both conditions. Correlation analysis revealed that high root biomass and leaf C:N ratio are useful markers for selecting high NUE accessions. These findings offer valuable insights for improving tomato NUE under varying nitrogen fertilization conditions and for breeding high-NUE cultivars. • N restriction delays growth and development in tomato. • High variation exists among tomato accessions in response to high and low N fertilisation. • Leaf C:N ratio was correlated with NUtE in high and low N treatments. • NUpE decreased under low N conditions, while NUtE and NUE increased. • Top-performing accessions were identified under high and low N conditions. [ABSTRACT FROM AUTHOR]

Straw incorporation has been widely recommended as an effective management practice to increase soil nitrogen stocks in agroecosystems worldwide. However, the overall trend and magnitude of changes in various soil organic nitrogen fractions in response to crop residue return and their contribution to soil nitrogen sequestration remain uncertain. Here, we show through a long-term experiment (12 years) that straw return increased soil total nitrogen and soil nitrogen sequestration rate by 20.01% and 120.95%, respectively. Ammonia nitrogen, amino acid nitrogen, and amino sugar nitrogen were affected by straw and its interaction with year, and increased by 43.08%, 27.70%, and 46.56%, respectively, with the highest growth rate in amino acid nitrogen (10.51 mg kg−1 yr−1). Furthermore, redundancy analyses showed that soil total organic carbon and C:N ratio were the major factors explaining the variations in soil organic nitrogen fractions, which increased by 46.22% and 21.75%, respectively. The structural equation model further revealed that amino acid nitrogen was a pivotal driver of soil nitrogen sequestration, because the soil C:N ratio indirectly influenced soil nitrogen sequestration via affecting the accumulation of amino acid nitrogen. Our results suggest that long-term straw return can improve nitrogen sequestration by accelerating the accumulation of amino acid nitrogen and that soil nitrogen storage and supply capacity may be improved by adopting straw incorporation and other appropriate management practices to regulate soil stoichiometry. • Straw return promoted soil nitrogen sequestration. • Straw return increased soil organic nitrogen fractions. • Straw return increased the soil TOC and C:N ratio. • TOC and C:N ratio explained the variations of soil organic nitrogen fractions. • Amino acid nitrogen was a pivotal driver of soil nitrogen sequestration. [ABSTRACT FROM AUTHOR]

[Display omitted] • We studied C and N storage in 1992 forest soils across Sweden. • Soil N content was more strongly related to soil texture than soil C content. • C content varied more strongly with pH than N content. • C and N were positively correlated with aluminum, most strongly in sandy soils. • C content was positively correlated with calcium in the organic layer. The aim of this study was to better understand how soil carbon (C) and nitrogen (N) contents and the C:N ratio are related to soil texture, pH, and exchangeable aluminum and calcium in forest soils. For this purpose, we studied 1992 temperate and boreal forest soils located all over Sweden. We measured organic C and N as well exchangeable aluminum, calcium, and pH in the organic layer and three depth increments in the mineral soil (down to 65 cm), and analyzed the relationship between element contents, soil texture, and soil pH as well as their interactions. Soil C concentration and the C:N ratio were negatively related to soil pH. The C concentration was on average 2.6 times higher in very acidic soils (pH ≤ 4.0) than in soils with pH > 5.0, in the uppermost 10 cm of the mineral soil. In contrast, N varied much less with pH, particularly in the organic layer, but was related to soil texture. The N concentration was 2.3 times higher in clayey and fine silty soils than in sandy soils, while the C concentration was only 1.85 times higher in clayey and fine silty soils than in sandy soils (in the uppermost 10 cm). Differences in C and N concentrations between clayey and fine silty soils compared to sandy soils were largest in the class of soils with pH > 5.0 and smallest in the class of soils with pH ≤ 4.0. Furthermore, C and N concentrations were both positively correlated with the concentration of exchangeable aluminum in the mineral soil, and these correlations were stronger in coarse-textured than in fine-textured soils. In addition, the C concentration was positively correlated with the concentration of exchangeable calcium in the organic layer. In conclusion, our results show that C concentration varied much more strongly with pH than N concentration, likely due to effects of pH on microbial respiration. The N concentration was more strongly related to soil texture than the C concentration, which is very likely due to the high charge density of organic N, which gives organic N a high affinity to adsorb to mineral surfaces. Furthermore, exchangeable aluminum seems to play an important role in the sorptive stabilization of organic matter in the mineral soil. [ABSTRACT FROM AUTHOR]

Periodic and repeated water scarcity has become an increasing concern on grasslands, causing not only to a reduction in productivity but also negative alterations in the carbon balance. The objective of this work was to comprehensively investigate some physiological performance traits of forage grasses, their roots morphometric features and distribution of biomass under simulated water deficit applied in different terms over a period of study. Plants were exposed to water shortage for 21 days, and then grown in optimal substrate moisture conditions. The gas exchange parameters and the main traits of root system architecture of three grass forage species and their cultivars were analyzed: Festulolium braunii (Richt.) A. Camus, cvs. Felopa and Sulino, Lolium perenne L., cvs. Bajka and Gagat and Festuca arundinacea Schreb. cvs. Odys and Rahela. Rapid decrease in the values of parameters related to the gas exchange process in grasses in the following days of water shortage was noticed. Water use efficiency (WUE) value was low in drought conditions due to increased transpiration of plants and was associated with a low C:N ratio in shoots. No obvious, positive effect of previously experienced drought stress on survival of tested grass species after another stress was observed. Cutting of plants after drought period most probably underlied the lack of memory and also additional factor weakened plant regrowth. When the drought was applied for the second time in spring during intensive plant growth, higher biomass allocation to the roots was observed. It was associated with the reduction of plant dry biomass, a decrease of carbon accumulation and the C:N ratio in the shoots. Due to the drought applied for the second time in summer, some biometric features of the roots were strongly and positively correlated with WUE, which is an important feature from the point of view of yield optimization and moisture use by plants.

A long-term study on the effect of nitrogen (N) fertilization on soil carbon dioxide (CO2) fluxes in tropical peatland was conducted to (1) quantify the annual CO2 emissions from an oil palm plantation under different N application rates and (2) evaluate the temporal effects of groundwater level (GWL) and water-filled pore space (WFPS) on soil organic carbon (SOC) and CO2 fluxes. Monthly measurement of soil CO2 fluxes using a closed chamber method was carried out from January 2010 until December 2013 and from January 2016 to December 2017 in an oil palm plantation on tropical peat in Sarawak, Malaysia. Besides the control (T1, without N fertilization), there were three N treatments: low N (T2, 31.1 kg N ha−1 year−1), moderate N (T3, 62.2 kg N ha−1 year−1), and high N (T4, 124.3 kg N ha−1 year−1). The annual CO2 emissions ranged from 7.7 ± 1.2 (mean ± SE) to 16.6 ± 1.0 t C ha−1 year−1, 9.8 ± 0.5 to 14.8 ± 1.4 t C ha−1 year−1, 10.5 ± 1.8 to 16.8 ± 0.6 t C ha−1 year−1, and 10.4 ± 1.8 to 17.1 ± 3.9 t C ha−1 year−1 for T1, T2, T3, and T4, respectively. Application of N fertilizer had no significant effect on annual cumulative CO2 emissions in each year (p = 0.448), which was probably due to the formation of large quantities of inorganic N when GWL was temporarily lowered from January 2010 to June 2010 (−80.9 to −103.4 cm below the peat surface), and partly due to low soil organic matter (SOM) quality. A negative relationship between GWL and CO2 fluxes (p < 0.05) and a positive relationship between GWL and WFPS (p < 0.001) were found only when the oil palm was young (2010 and 2011) (p < 0.05), indicating that lowering of GWL increased CO2 fluxes and decreased WFPS when the oil palm was young. This was possibly due to the fact that parameters such as root activity might be more predominant than GWL in governing soil respiration in older oil palm plantations when GWL was maintained near or within the rooting zone (0–50 cm). This study highlights the importance of roots and WFPS over GWL in governing soil respiration in older oil palm plantations. A proper understanding of the interaction between the direct or indirect effect of root activity on CO2 fluxes and balancing its roles in nutrient and water management strategies is critical for sustainable use of tropical peatland.

Soil properties and the ability to sustain agricultural production are seriously impaired by salinity. The cultivation of halophytes is seen as a solution to cope with the problem. In this framework, a greenhouse pot experiment was set up to assess salinity response in the perennial C4 species Atriplex halimus, and in the following three cultivars of the annual C3 Atriplex hortensis: green, red, and scarlet. The four genotypes were grown for 35 days with water salinity (WS) ranging from 0 to 360 mM NaCl. Plant height and fresh weight (FW) increased at 360 vs. 0 WS. The stomatal conductance (GS) and transpiration rate (E) were more severely affected by salinity in the C4 A. halimus than in the C3 species A. hortensis. This was reflected in a lower leaf water potential indicating stronger osmotic adjustment, and a higher relative water content associated with more turgid leaves, in A. halimus than A. hortensis. In a PCA including all the studied traits, the GS and E negatively correlated to the FW, which, in turn, positively correlated with Na concentration and intrinsic water use efficiency (iWUE), indicating that reduced gas exchange associated with Na accumulation contributed to sustain iWUE under salinity. Finally, FTIR spectroscopy showed a reduced amount of pectin, lignin, and cellulose under salinity, indicating a weakened cell wall structure. Overall, both species were remarkably adapted to salinity: From an agronomic perspective, the opposite strategies of longer vs. faster soil coverage, involved by the perennial A. halimus vs. the annual A. hortensis cv. scarlet, are viable natural remedies for revegetating marginal saline soils and increasing soil organic carbon.

In Saudi Arabia, more than 335,000 tons of cow manure is produced every year from dairy farming. However, the produced cow manure is usually added to the agricultural soils as raw or composted manure; significant nitrogen losses occur during the storage, handling, and application of the raw manure. The recovery of ammonia from cow manure through thermochemical treatments is a promising technique to obtain concentrated nitrogen fertilizer and reducing nitrogen losses from raw manure. However, the byproduct effluents from the recovery process are characterized by different chemical properties from the original raw manure; thus, its impact as soil amendments on the soil carbon and nitrogen dynamics is unknown. Therefore, a 90-day incubation experiment was conducted to study the impact of these effluents on CO2 efflux, organic C, microbial biomass C, available NH4+, and NO3− when added to agricultural soil. In addition to the two types of effluents (produced at pH 9 and pH 12), raw cow manure (CM), composted cow manure (CMC), cow manure biochar (CMB), and control were used for comparison. The application of CM resulted in a considerable increase in soil available nitrogen and CO2 efflux, compared to other treatments. Cow manure biochar showed the lowest CO2 efflux. Cumulative CO2 effluxes of cow manure effluents were lower than CM; this is possibly due to the relatively high C:N ratio of manure effluent. The content of P, Fe, Cu, Zn, and Mn decreased as incubation time increased. Soil microbial biomass C for soil treated with cow manure effluents (pH 12 and 7) was significantly higher than the rest of the soil amendments and control.

The spent mushroom substrate (SMS) is a byproduct of cultivation of oyster mushroom (Pleurotus spp.) and represents the composted substrate that remains after completion the harvested crop. This study mentioned the role of some effective date palm wastes in improving spent mushroom substrate properties which containing fibers of date palm Phoenix dactylifera L. (Fibrillum), mixed with white sawdust and wheat straw in three formulas. These mixtures of SMS namely, SMS1 (wheat straw), SMS2 (wheat straw 70%, sawdust 20% and date palm fiber 10%) and SMS3 (wheat straw 50%, sawdust 30% and date palm fiber 20%) were obtained from locally mushroom farm in western Iraq and sent to determine some properties such as moisture content, dry matter, EC, pH, ash, carbon, nitrogen, protein contents and C:N ratio. Generally, determinations of Hydrogen ion concentration (pH) for SMS extracts had acidic value at average 5.06. The higher EC was 3.30 ms/cm for SMS1-P. ostreatus (white), while the lower value reached to 1.13 ms/cm for SMS3 of same species. The higher nitrogen content was 9.98 g/kg for SMS3-P. ostreatus (white), SMS1 of Pleurotus salmoneostramineus and SMS2-P. ostreatus (white), while, SMS3-P. salmoneostramineus had lower nitrogen content (6.65 g/kg). The higher C:N ratio was reported with SMS3 of P. salmoneostramineus at value 35.36, while SMS2-P. ostreatus (grey) had ratio 22.03, significantly (p

ABSTRACT Through field and laboratory experiments we investigated the effects of leaf traits of two tree species and microbial conditioning on the abundance, biomass, and feeding preference of a typical macroinvertebrate shredder. In the field, we compared the association of Phylloicus (Calamoceratidae, Trichoptera) with two tree species commonly found in riparian zones, which are representative of high and low nutritional quality, respectively: Nectandra megapotamica and Chusquea tenella. In the laboratory, we investigated the feeding preference of Phylloicus using unconditioned leaves and leaves conditioned by aquatic fungi. The same tree species used in the field experiment were used in the laboratory. Initially, C. tenella leaves were proved to be more nutritious and softer, while N. megapotamica leaves were harder and more lignified. The shredders preferred conditioned leaf detritus of reduced toughness (field: C. tenella; laboratory: N. megapotamica, both conditioned for 14 days). These leaf traits seem to be crucial for the choice process of Phylloicus. After 14 days, N. megapotamica leaves showed a decreased toughness associated with the microbial conditioning, which explained its consumption rate by Phylloicus. In both field and laboratory experiments, we found evidence that Phylloicus is a selective feeding shredder, and that the leaf traits, especially leaf structure (e.g., leaf toughness and lignin content), determine its association and preferences.

Purpose: Nitrogen loss as ammonia (NH3) in a waste cocoa pod co-composting process was determined following the addition of three potential chemical amendments that could lower NH3 loss. Further, amended compost products were assessed for quality and possible phytotoxicity in a pot experiment. Methods: Pod borer damaged cocoa pods were co-composted in lab-scale vessels under ambient conditions with double superphosphate, phosphoric acid, and gypsum at 2%, 5% and 1% of fresh weight, respectively. NH3 emitted during composting was trapped in standard H2SO4 and determined titrimetrically. Composting mixtures were sampled on days 0, 7, 56 and 90 to monitor pH, total C, total N, and C:N ratio. Mature co-composts were incorporated to the soil at 20 t ha−1 and growth response of Chinese cabbage plants (Brassica rapa chinensis) assessed for the phytotoxicity. Results: The chemical amendments were ineffective (p > 0.05) in preventing loss of NH3 but the quality of composting mixtures were significantly (p < 0.0001) improved. The manure compost generated had acceptable parameters (C, 31.2–31.9% and C:N ratio, 9–10:1) and were free from phytotoxicity for soil application as revealed by the response of Chinese cabbage crop. Conclusions: Chemical amendments used in the co-composting process mainly modulated pH without any detrimental effects on quality. The results also demonstrated that the NH3 loss is insignificant from the cocoa waste-composting process. Further studies are required with increased rates of acidifying amendments like phosphoric acid to further augment the quality of cocoa pod composts. [ABSTRACT FROM AUTHOR]

Aims: Root distributions determine crop nutrient access and soil carbon input patterns. To date, root distribution data are rare but needed to improve knowledge and prediction of cropping system sustainability. In this study, we sought to (i) quantify variation in maize (Zea mays) and soybean (Glycine max) roots by depth and environment across Iowa, USA and (ii) identify environmental factors explaining the most variation. Methodology: Over three years we collected soil cores from 0 to 210 cm in 16 maize and 12 soybean field experiments at grain filling. Root mass, length, carbon (C) and nitrogen (N) were determined at 30 cm increments, coupled with crop, soil, management, and weather-related measurements. Results: Percentage of root mass located in the top 30 cm varied from 52 to 94% in maize and 54–84% in soybean. Variation in maize root distributions was strongly associated with depth to water tables, variation in soybean with soil physical attributes. Root C:N ratios were highly variable with no depth-pattern, averaging 20 and 30 for soybean and maize, respectively. In both crops, specific root lengths increased with depth to 60 cm, and thereafter remained constant. Conclusions: Field studies of roots should consider depth to water tables and soil moisture measurements, as they influence vertical root distributions. [ABSTRACT FROM AUTHOR]

Coccolithophores are cosmopolitan, major calcifying protists that have significant roles in marine carbon cycling. Although the influence of temperature and irradiance fluctuation on coccolithophore physiology have been extensively studied, little is known about these effects on coastal coccolithophore species, including their cell morphology, coccolith formation, life cycle, and photoacclimation. We carried out indoor experiments to investigate the photo-physiological response of Chrysotila dentata at two temperatures (13 °C and 25 °C) and varied light irradiance. Using a geometric model, coccolith volume and mass of C. dentata were estimated. At low temperature (13 °C) and low irradiance (100 μmol photons m−2 s−1) cell size and coccolith calcite mass increased, which was further verified using a geometric model. The ratio of calcification to total carbon fixation rate and certain pigments (chlorophyll a, fucoxanthin and β-carotene concentrations) increased at high temperature (25 °C). Cells had variable C and N quotas (apparent diel cycling of C:N ratio) when cells were forming new coccoliths. Our findings help to better understand environmental controls on coccolith carbonate production and interaction with organic carbon production in C. dentata. [ABSTRACT FROM AUTHOR]

Aim: Leaf litter decomposition in freshwater ecosystems is a vital process linking ecosystem nutrient cycling, energy transfer and trophic interactions. In comparison to terrestrial ecosystems, in which researchers find that litter traits predominantly regulate litter decomposition worldwide, the dominant factors controlling its decomposition in aquatic ecosystems are still debated, with global patterns not well documented. Here, we aimed to explore general patterns and key drivers (e.g., litter traits, climate and water characteristics) of leaf litter decomposition in streams worldwide. Location: Global. Time period: 1977–2018. Major taxa studied: Leaf litter. Methods: We synthesized 1,707 records of litter decomposition in streams from 275 studies. We explored variations in decomposition rates among climate zones and tree functional types and between mesh size groups. Regressions were performed to identify the factors that played dominant roles in litter decomposition globally. Results: Litter decomposition rates did not differ among tropical, temperate and cold climate zones. Decomposition rates of litter from evergreen conifer trees were much lower than those of deciduous and evergreen broadleaf trees, attributed to the low quality of litter from evergreen conifers. No significant differences were found between decomposition rates of litter from deciduous and evergreen broadleaf trees. Additionally, litter decomposition rates were much higher in coarse‐ than in fine‐mesh bags, which controled the entrance of decomposers of different body sizes. Multiple regressions showed that litter traits (including lignin, C:N ratio) and elevation were the most important factors in regulating leaf litter decomposition. Main conclusions: Litter traits predominantly control leaf litter decomposition in streams worldwide. Although further analyses are necessary to explore whether commonalities of the predominant role of litter traits in decomposition exist in both aquatic and terrestrial ecosystems, our findings could contribute to the use of trait‐based approaches in modelling the decomposition of litter in streams globally and exploring mechanisms of land–water–atmosphere carbon fluxes. [ABSTRACT FROM AUTHOR]

The Mexican INIFAP-Hir-2 Hirsutella citriformis strain was cultured in six liquid media at different C:N ratios. Glucose and hydrolysed amino acids were used as C and N sources, respectively. During fermentation, low-cost nitrogen sources were used to obtain an improved biomass production, and these cultures were then air-dried, vacuum packed, and evaluated for germination. Cultures containing mycelia were inoculated on different clays to observe spore formation. The highest biomass yield (19.47 g/L) was obtained from the medium supplemented with 36 g/L glucose and hydrolysed casamino acids added at a C:N ratio of 10:1. Furthermore, upon the use of low-cost nitrogen source, the highest dry biomass weights were obtained when cottonseed flour (51.30 g/L) and soybean meal (48.40 g/L) were used. This showed a significant difference with respect to the media supplemented with casamino acids, yeast extract or corn steep powder. Synnemata production on clays was observed only for those cultures grown on soybean meal. Germination and conidia production were evaluated on 8 different clays and diatomaceous earth (Hyflo®). Here, hydrous aluminosilicate (HAS) and montmorillonite (MONT) clay showed a higher percentage of germination, whereas Attapulgite (GA) granulometry −325 y Verge montmorillonite S-140 showed lower germination percentages. Twelve days post inoculation of liquid cultures on various clays, Attapulgite 16/30, HAS 24/48 and Hyflo® showed a higher production of conidia where values reached more than 1 × 107 conidia/g. [ABSTRACT FROM AUTHOR]