N Fixation in Insects: Its Potential Contribution to N Cycling in Ecosystems and Insect Biomass

2015 ◽  
pp. 1143-1152 ◽  
Author(s):  
Domancar orona Tamayo ◽  
Martin Heil
Keyword(s):  
N Cycling ◽  
N Fixation ◽  
Potential Contribution ◽  
Insect Biomass

scholarly journals The soil N cycle: new insights and key challenges

SOIL ◽  
2015 ◽  
Vol 1 (1) ◽  
pp. 235-256 ◽  
Author(s):  
J. W. van Groenigen ◽  
D. Huygens ◽  
P. Boeckx ◽  
Th. W. Kuyper ◽  
I. M. Lubbers ◽  
...  
Keyword(s):  
N Cycling ◽  
Greenhouse Gas Mitigation ◽  
Future Research ◽  
N Fixation ◽  
Gaseous Emissions ◽  
Soil N ◽  
Personal View ◽  
Total N ◽  
N Cycle ◽  
Soil N Cycle

Abstract. The study of soil N cycling processes has been, is, and will be at the centre of attention in soil science research. The importance of N as a nutrient for all biota; the ever-increasing rates of its anthropogenic input in terrestrial (agro)ecosystems; its resultant losses to the environment; and the complexity of the biological, physical, and chemical factors that regulate N cycling processes all contribute to the necessity of further understanding, measuring, and altering the soil N cycle. Here, we review important insights with respect to the soil N cycle that have been made over the last decade, and present a personal view on the key challenges of future research. We identify three key challenges with respect to basic N cycling processes producing gaseous emissions: 1. quantifying the importance of nitrifier denitrification and its main controlling factors; 2. characterizing the greenhouse gas mitigation potential and microbiological basis for N2O consumption; 3. characterizing hotspots and hot moments of denitrification Furthermore, we identified a key challenge with respect to modelling: 1. disentangling gross N transformation rates using advanced 15N / 18O tracing models Finally, we propose four key challenges related to how ecological interactions control N cycling processes: 1. linking functional diversity of soil fauna to N cycling processes beyond mineralization; 2. determining the functional relationship between root traits and soil N cycling; 3. characterizing the control that different types of mycorrhizal symbioses exert on N cycling; 4. quantifying the contribution of non-symbiotic pathways to total N fixation fluxes in natural systems We postulate that addressing these challenges will constitute a comprehensive research agenda with respect to the N cycle for the next decade. Such an agenda would help us to meet future challenges on food and energy security, biodiversity conservation, water and air quality, and climate stability.

Effects of balsam poplar (Populus balsamifera) tannins and low molecular weight phenolics on microbial activity in taiga floodplain soil: implications for changes in N cycling during succession

1996 ◽  
Vol 74 (1) ◽  
pp. 84-90 ◽  
Author(s):  
Joshua P. Schimel ◽  
Keith Van Cleve ◽  
Rex G. Cates ◽  
Thomas P. Clausen ◽  
Paul B. Reichardt
Keyword(s):  
Molecular Weight ◽  
Secondary Compounds ◽  
N Cycling ◽  
Low Molecular Weight ◽  
N Fixation ◽  
N Availability ◽  
Populus Balsamifera ◽  
Floodplain Soil ◽  
Balsam Poplar ◽  
River Floodplains

The transition from alder (Alnus tenuifolia) to balsam poplar (Populus balsamifera) is a critical turning point in primary succession on river floodplains in interior Alaska. Associated with the change in plant species are large changes in N cycling. N-fixation and nitrification decrease and the system becomes N-limited, with NH4+ dominating the inorganic N pool. Balsam poplar leaves contain large quantities of tannins and low molecular weight phenolic compounds. We evaluated the effect of these compounds on microbial respiration and N cycling in laboratory assays on soils from an alder-dominated site. Plant compounds were purified and applied to silica gel as an inert carrier. Both tannins and phenolics caused net N-immobilization over a 30-day assay. However, tannins inhibited respiration while phenolics stimulated it. There were no specific effects on nitrification. Thus, tannins acted as a general microbial inhibitor, while phenolics acted as a growth substrate. By inhibiting mineralization while stimulating immobilization, poplar secondary compounds may reduce soil N-availability during the transition betwen alder and poplar stages in succession. Keywords: respiration, mineralization, tannins, secondary chemicals, succession, plant–microbe interactions.

scholarly journals The soil N cycle: new insights and key challenges

2014 ◽  
Vol 1 (1) ◽  
pp. 623-676 ◽  
Author(s):  
J. W. van Groenigen ◽  
D. Huygens ◽  
P. Boeckx ◽  
T. W. Kuyper ◽  
I. M. Lubbers ◽  
...  
Keyword(s):  
Root Traits ◽  
Science Research ◽  
N Cycling ◽  
Greenhouse Gas Mitigation ◽  
Future Research ◽  
N Fixation ◽  
Soil N ◽  
Personal View ◽  
N Cycle ◽  
Soil N Cycle

Abstract. The study of soil N cycling processes has been, is, and will be at the center of attention in soil science research. The importance of N as a nutrient for all biota; the ever increasing rates of its anthropogenic input in terrestrial (agro)ecosystems; its resultant losses to the environment; and the complexity of the biological, physical, and chemical factors that regulate N cycling processes all contribute to the necessity of further understanding, measurement and mitigation of the soil N cycle. Here, we review important insights with respect to the soil N cycle that have been made over the last decade, and present a personal view on the key challenges for future research (Fig. 1). We identified four key questions with respect to N cycling processes: 1. How large is the contribution of non-symbiotic N fixation in natural systems? 2. How important is nitrifier denitrification and what are its main controlling factors? 3. What is the greenhouse gas mitigation potential and microbiological basis for N2O consumption? 4. How can we characterize hot-spots and hot-moments of denitrification? Furthermore, we propose three questions about proximal controls on N cycling processes: 1. How does functional diversity of soil fauna affect N cycling beyond mineralization? 2. What is the functional relationship between root traits and soil N cycling? 3. To what extent do different types of mycorrhizal symbioses (differentially) affect N cycling? Finally, we identified a key challenge with respect to modelling: 1. How can advanced 15N/18O tracing models help us to better disentangle gross N transformation rates? We postulate that addressing these questions would constitute a comprehensive research agenda with respect to the N cycle for the next decade. Such an agenda would help us to meet future challenges on food and energy security, biodiversity conservation and climate stability.

scholarly journals Different Effects of Soil Fertilization on Bacterial Community Composition in the Penicillium canescens Hyphosphere and in Bulk Soil

2020 ◽  
Vol 86 (10) ◽  
Author(s):  
Yuan Zhang ◽  
Xiuli Hao ◽  
Adriana M. Garcia-Lemos ◽  
Inês Nunes ◽  
Mette H. Nicolaisen ◽  
...  
Keyword(s):  
Bacterial Communities ◽  
N Cycling ◽  
N Fixation ◽  
Organic P ◽  
Penicillium Canescens ◽  
Soil Fertilization ◽  
Content Type ◽  
N Nutrition ◽  
Soil Communities

ABSTRACT This study investigated the effects of long-term soil fertilization on the composition and potential for phosphorus (P) and nitrogen (N) cycling of bacterial communities associated with hyphae of the P-solubilizing fungus Penicillium canescens. Using a baiting approach, hyphosphere bacterial communities were recovered from three soils that had received long-term amendment in the field with mineral or mineral plus organic fertilizers. P. canescens hyphae recruited bacterial communities with a decreased diversity and an increased abundance of Proteobacteria relative to what was observed in soil communities. As core bacterial taxa, Delftia and Pseudomonas spp. were present in all hyphosphere samples irrespective of soil fertilization. However, the type of fertilization showed significant impacts on the diversity, composition, and distinctive taxa/operational taxonomic units (OTUs) of hyphosphere communities. The soil factors P (Olsen method), exchangeable Mg, exchangeable K, and pH were important for shaping soil and hyphosphere bacterial community compositions. An increased relative abundance of organic P metabolism genes was found in hyphosphere communities from soil that had not received P fertilizers, which could indicate P limitation near the fungal hyphae. Additionally, P. canescens hyphae recruited bacterial communities with a higher abundance of N fixation genes than found in soil communities, which might imply a role of hyphosphere communities for fungal N nutrition. Furthermore, the relative abundances of denitrification genes were greater in several hyphosphere communities, indicating an at least partly anoxic microenvironment with a high carbon-to-N ratio around the hyphae. In conclusion, soil fertilization legacy shapes P. canescens hyphosphere microbiomes and their functional potential related to P and N cycling. IMPORTANCE P-solubilizing Penicillium strains are introduced as biofertilizers to agricultural soils to improve plant P nutrition. Currently, little is known about the ecology of these biofertilizers, including their interactions with other soil microorganisms. This study shows that communities dominated by Betaproteobacteria and Gammaproteobacteria colonize P. canescens hyphae in soil and that the compositions of these communities depend on the soil conditions. The potential of these communities for N and organic P cycling is generally higher than that of soil communities. The high potential for organic P metabolism might complement the ability of the fungus to solubilize inorganic P, and it points to the hyphosphere as a hot spot for P metabolism. Furthermore, the high potential for N fixation could indicate that P. canescens recruits bacteria that are able to improve its N nutrition. Hence, this community study identifies functional groups relevant for the future optimization of next-generation biofertilizer consortia for applications in soil.

scholarly journals Upper Midwest lakes are supersaturated with N2

2020 ◽  
Vol 117 (29) ◽  
pp. 17063-17067 ◽  
Author(s):  
Brianna M. Loeks-Johnson ◽  
James B. Cotner
Keyword(s):  
Trophic Status ◽  
N Cycling ◽  
N Fixation ◽  
Upper Midwest ◽  
Gaseous Nitrogen ◽  
Inorganic N ◽  
N Limitation ◽  
Large Size ◽  
Traditional Paradigm ◽  
Biological Nitrogen

Little is known about the exchange of gaseous nitrogen (N2) with the atmosphere in freshwater systems. Although the exchange of N2, driven by excess or deficiencies relative to saturation values, has little relevance to the atmospheric N2pool due to its large size, it does play an important role in freshwater and marine nitrogen (N) cycling. N-fixation converts N2to ammonia, which can be used by microbes and phytoplankton, while denitrification/anammox effectively removes it by converting oxidized, inorganic N to N2. We examined N2saturation to infer net biological nitrogen processes in 34 lakes across 5° latitude varying in trophic status, mixing regime, and bathymetry. Here, we report that nearly all lakes examined in the upper Midwest (USA) were supersaturated with N2(>85% of samples,n= 248), suggesting lakes are continuously releasing nitrogen to the atmosphere. The traditional paradigm is that freshwaters compensate for N-limitation through N-fixation, but these results indicate that lakes were constantly losing N to the atmosphere via denitrification and/or anammox, suggesting that terrestrial N inputs are needed to balance the internal N cycle.

Nitrogen cycling in silvopastoral systems in the Pacific Northwest: A review

2000 ◽  
Vol 80 (1) ◽  
pp. 21-28 ◽  
Author(s):  
D. J. Thompson ◽  
R. F. Newman ◽  
G. Hope ◽  
K. Broersma ◽  
D. A. Quinton
Keyword(s):  
British Columbia ◽  
Lodgepole Pine ◽  
Cattle Grazing ◽  
N Cycling ◽  
Native Vegetation ◽  
N Fixation ◽  
Forage Production ◽  
N Losses ◽  
Understorey Vegetation

Clearcuts in interior British Columbia are often aerially seeded with domestic forages such as orchardgrass and alsike clover to prevent erosion and help control understorey vegetation during establishment of lodgepole pine plantations. These seeded clearcuts provide valuable mid-summer range for cattle and with careful management there is little damage to planted trees. There is growing concern about N losses due to clearcutting and site preparation and what effect these might have on long-term forest productivity. The literature indicates that without cattle or forage seeding natural N inputs from the atmosphere and N fixation are barely sufficient to provide adequate nutrition for a lodgepole pine stand. This literature review addresses what effect introducing domestic forages and cattle grazing can have on N cycling on clearcuts. Forage seeding alone may reduce N losses due to runoff and leaching and legumes can fix atmospheric N, but grazing by cattle can counteract some of these benefits. Estimates of N losses due to cattle grazing were calculated using summary data from a long-term grazing trial conducted in interior British Columbia where experimental pastures were either aerially seeded with clover-orchardgrass mixtures or left unseeded. Using forage yields, cattle gains, and a number of assumptions, N losses due to cattle grazing on the seeded pastures were calculated as 2.4 kg N ha−1 yr−1 compared with 0.8 kg N ha−1 yr−1 on native vegetation. Losses were from N in new cattle tissue and N volatilized from urine as ammonia. Increased losses due to grazing seeded forages were short-lived as the forage production of seeded pastures was equal to that of native vegetation by the seventh year. During this period, the losses due to grazing seeded forages may be balanced by increased capture of labile N by the forages. Key words: N cycling, seeded clearcuts, cattle grazing

scholarly journals Nitrogen Dynamics in an Established Alfalfa Field under Low Biochar Application Rates

Soil Systems ◽  
2019 ◽  
Vol 3 (4) ◽  
pp. 77 ◽  
Author(s):  
Katherine S. Rocci ◽  
Steven J. Fonte ◽  
Joseph C. von Fischer ◽  
M. Francesca Cotrufo
Keyword(s):  
Crop Production ◽  
Temporal Dynamics ◽  
N Uptake ◽  
N Cycling ◽  
Growth Stages ◽  
N Fixation ◽  
N Availability ◽  
Soil N ◽  
Application Rates ◽  
Alfalfa Field

Sustainable nitrogen (N) management in agroecosystems is crucial for supporting crop production and reducing deleterious N losses. Biochar application with N-fixing legumes offers promise for increasing soil N retention and input. Strategic, low application rates (112 kg ha−1) of pine and coconut feedstock biochars were tested in an established alfalfa (Medicago sativa) field. Soil inorganic N and plant growth, N concentrations, and δ15N were monitored over a growing season to follow mineral N availability, and plant N uptake and sourcing. Microbial and gene abundance and enzyme activity were measured to assess the potential for N cycling processes to occur. Biochar application had minimal effects on measured parameters. However, significant temporal dynamics in N cycling and correlations between alfalfa δ15N and soil N availability indicate differing plant N sourcing over time. Our findings indicate that low application rates of biochar in established alfalfa fields do not significantly affect N cycling, and that managing alfalfa to maximize N fixation, for example by intercropping, may be a better solution to increase N stocks and retention in this system. To determine when biochar can be beneficial for alfalfa N cycling, we need additional research to assess various economically-feasible biochar application rates at different alfalfa growth stages.

The potential contribution of psychology to nuclear war issues.

1988 ◽  
Vol 43 (4) ◽  
pp. 318-321 ◽  
Author(s):  
Michael D. Intriligator ◽  
Dagobert L. Brito
Keyword(s):  
Potential Contribution ◽  
Nuclear War

Optical imaging probes and their potential contribution to radiotracer development

2016 ◽  
Vol 55 (02) ◽  
pp. 51-62 ◽  
Author(s):  
S. Hermann ◽  
M. Schäfers ◽  
C. Höltke ◽  
A. Faust
Keyword(s):  
Optical Imaging ◽  
Fluorescent Dyes ◽  
Great Influence ◽  
Potential Contribution ◽  
Preclinical Evaluation ◽  
Guided Surgery ◽  
Fluorescence Guided Surgery ◽  
Imaging Probes ◽  
Unspecific Binding

SummaryOptical imaging has long been considered a method for histological or microscopic investigations. Over the last 15 years, however, this method was applied for preclinical molecular imaging and, just recently, was also able to show its principal potential for clinical applications (e.g. fluorescence-guided surgery). Reviewing the development and preclinical evaluation of new fluorescent dyes and target-specific dye conjugates, these often show characteristic patterns of their routes of excretion and biodistribution, which could also be interesting for the development and optimization of radiopharmaceuticals. Especially ionic charges show a great influence on biodistribution and netcharge and charge-distribution on a conjugate often determines unspecific binding or background signals in liver, kidney or intestine, and other organs.Learning from fluorescent probe behaviour in vivo and translating this knowledge to radio-pharmaceuticals might be useful to further optimize emerging and existing radiopharmaceuticals with respect to their biodistribution and thereby availability for binding to their targets.

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