scholarly journals 15N Natural Abundance of Soil Microbial Biomass in Alpine and Tundra Ecosystems

2021 ◽  
Vol 54 (6) ◽  
pp. 907-917
Author(s):  
M. I. Makarov ◽  
M. S. Kadulin ◽  
T. I. Malysheva
Keyword(s):  
Microbial Biomass ◽  
Isotopic Composition ◽  
Nitrogen Availability ◽  
Soil Microbial Biomass ◽  
Nitrogen Use ◽  
Soil Microbial ◽  
Use Efficiency ◽  
N Enrichment ◽  
Tundra Ecosystems ◽  
Extractable Nitrogen

Abstract Isotopic composition of nitrogen in soil microbial biomass (δ15Nmicr) is connected with the transformation of nitrogen compounds and with the balance of carbon and nitrogen availability for microorganisms. We have studied the dependence of δ15Nmicr on nitrogen isotopic composition in the substrate (δ15N of total and extractable nitrogen), as well as the dependence of δ15Nmicr and 15N-enrichment of microbial biomass (Δ15Nmicr = δ15Nmicr – δ15Nsubstr) on nitrogen availability parameters (the C/N ratio in soil, the N-mineralization activity, the content of extractable nitrogen, and the nitrogen use efficiency) in soils of four alpine ecosystems in the North Caucasus and four tundra ecosystems in the Khibiny Mountains. It has been shown that δ15Nmiсr varies from –0.2 to +8.4‰ and may be characterized by both 15N-enrichment and depletion (negative Δ15Nmiсr values) relative to the total and extractable soil nitrogen. As a rule, Δ15Nmicr is 1.5–3.1‰ relative to 15Ntotal and 0.6–4.8‰ relative to 15Nextr. However, under the most N-deficiency conditions in soils of mountain tundra lichen and shrub heaths, Nmicr does not accumulate an increased amount of 15N. We have not revealed a close correlation of δ15Nmicr and Δ15Nmicr with the C/N ratio. The accumulation of 15N in microbial biomass is much stronger related to N-mineralization (positively) and the nitrogen use efficiency (negatively). This testifies to the important role of microbial nitrogen dissimilation in controlling the isotopic composition of soil microbial biomass nitrogen.

scholarly journals Influence of legumes on N cycling in a heathland in northwest Spain

Web Ecology ◽  
2007 ◽  
Vol 7 (1) ◽  
pp. 87-93 ◽  
Author(s):  
A. Rodríguez ◽  
J. Durán ◽  
A. Gallardo
Keyword(s):  
Microbial Biomass ◽  
Nitrogen Availability ◽  
Soil Microbial Biomass ◽  
N Uptake ◽  
Microbial Biomass N ◽  
Natural Ecosystems ◽  
Mixed Stands ◽  
Soil Microbial ◽  
Soil Microbial Biomass N ◽  
Biomass N

Abstract. Nitrogen availability frequently limits plant growth in natural ecosystems. N-fixers should have a substantial competitive advantage in N-limited systems, and as a byproduct of their activity they should increase the quantity and availability of N in the system as a whole. However, this effect has rarely been quantified in natural ecosystems. Heathlands in northwest Spain are frequently occupied by legume scrubs. We tested whether the presence of these legumes affected the N cycle in these communities. Specifically, we addressed the following questions: is nitrogen availability higher beneath legume canopies than beneath non-legume canopies? Is soil microbial biomass acting as a sink of extra N mineralized beneath legume canopies? Does the presence of legume scrubs change the soil pools of labile N and P? Is N plant uptake different under N-fixer scrubs than under non-N-fixer scrubs? To answer these questions, we sampled soil beneath the canopy of randomly selected individuals of Erica umbellata, Ulex gallii, and Genista tridentata twice during the growing season. Soil samples were analyzed for organic matter, NH4-N, NO3-N, DON, PO4-P, N mineralization and nitrification rates, and soil microbial biomass-N. In addition, we estimated N uptake by plants and the N concentration in green tissue to compare internal N cycles between legume and non-legume scrubs. Nitrification rates, DON (dissolved organic nitrogen), soil NO3 concentration, and N uptake were significantly higher beneath legume canopies. However, soil microbial biomass-N and extractable-P were significantly lower under legumes. Our results showed that the presence of legume scrubs modify the size of N pools and the dominant form of available N for plants, increasing spatial heterogeneity in mixed stands.

scholarly journals ¿La incorporación de residuos de diferentes especies de Lupinus, como abono verde, afecta la actividad microbiana del suelo?

2020 ◽  
Vol 38 (1) ◽  
pp. 45
Author(s):  
Isidro Zapata Hernández ◽  
Juan Francisco Zamora Natera ◽  
Ma Nieves Trujillo Tapia ◽  
Eustacio Ramirez Fuentes
Keyword(s):  
Microbial Biomass ◽  
Green Manure ◽  
Nitrogen Availability ◽  
Soil Microbial Biomass ◽  
Basal Respiration ◽  
Nitrifying Bacteria ◽  
Co2 Production ◽  
Aerobic Incubation ◽  
Soil Microbial ◽  
C And N

In the state of Jalisco, corn and tequila agave are the most important agricultural crops. The soils to cultivate these species are characterized by low content of organic matter and nitrogen. The amendments applied to the soil provide an important source of energy and nutrients for microorganisms; promotes the diversity of nitrogen-f ixing bacteria and nitrifying bacteria, which increases nitrogen availability in the soil. The aim of this study was to evaluate the use of two species of wild legumes: Lupinus exaltatus and Lupinus rotundiflorus as green manure (AV), and its effect on soil microbial biomass. An aerobic incubation experiment (14 days) was carried out on soil samples with green manure and without green manure (control). Under laboratory conditions, the microbial activity of soil was monitored through the response in basal respiration and the concentration of C and N in the microbial biomass. The CO2 production and C and N content in the microbial biomass showed significant differences (P < 0.05) due to the effect of green manure. The residues of Lupinus are considered better quality than the residues of Zea mays due to its nitrogen content and low C: N ratio. The response of microorganisms presented a positive primer effect with the input of AV. Therefore, we conclude that the input of L. exaltatus and L. rotundiflorus as a green manure to the soil increases the biological activity of the soil and promotes the enrichment of C and N of the microbial biomass.

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