Dataset Information

Coupled molecular and isotopic evidence for denitrifier controls over terrestrial nitrogen availability.

ABSTRACT: Denitrification removes ecologically available nitrogen (N) from the biosphere and influences both the pace and magnitude of global climate change. Disagreements exist over the degree to which this microbial process influences N-availability patterns across Earth's ecosystems. We combine natural stable isotope methods with qPCR to investigate how denitrifier gene abundance is related to variations in nitrate (NO₃^-) pool sizes across diverse terrestrial biomes and conditions. We analyze NO₃^- isotope composition (¹⁵N/¹⁴N, ¹⁸O/¹⁶O) and denitrifier gene nirS in 52 soil samples from different California ecosystems, spanning desert, chaparral, oak-woodland/savanna and forest. ?¹⁵N-NO₃^- correlates positively with ?¹⁸O-NO₃^- (P?0.03) and nirS abundance (P=0.00002) across sites, revealing the widespread importance of isotopic discrimination by soil denitrifiers. Furthermore, NO₃^- concentrations correlate negatively to nirS (P=0.002) and ?¹⁵N-NO₃^- (P=0.003) across sites. We also observe these spatial relationships in short-term (7-day), in situ soil-incubation experiments; NO₃^--depletion strongly corresponds with increased nirS, nirS/16 rRNA, and enrichment of heavy NO₃^- isotopes over time. Overall, these findings suggest that microbial denitrification can consume plant-available NO₃^- to low levels at multiple time scales, contributing to N-limitation patterns across sites, particularly in moist, carbon-rich soils. Furthermore, our study provides a new approach for understanding the relationships between microbial gene abundance and terrestrial ecosystem functioning.

SUBMITTER: Lennon EF

PROVIDER: S-EPMC5322299 | biostudies-literature | 2017 Mar

REPOSITORIES: biostudies-literature

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Coupled molecular and isotopic evidence for denitrifier controls over terrestrial nitrogen availability.

Lennon Erin F E EF Houlton Benjamin Z BZ

The ISME journal 20161209 3

Denitrification removes ecologically available nitrogen (N) from the biosphere and influences both the pace and magnitude of global climate change. Disagreements exist over the degree to which this microbial process influences N-availability patterns across Earth's ecosystems. We combine natural stable isotope methods with qPCR to investigate how denitrifier gene abundance is related to variations in nitrate (NO<sub>3</sub><sup>-</sup>) pool sizes across diverse terrestrial biomes and conditions ...[more]

PMID: 27935591

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Project description:Grasslands are subject to considerable alteration due to human activities globally, including widespread changes in populations and composition of large mammalian herbivores and elevated supply of nutrients. Grassland soils remain important reservoirs of carbon (C) and nitrogen (N). Herbivores may affect both C and N pools and these changes likely interact with increases in soil nutrient availability. Given the scale of grassland soil fluxes, such changes can have striking consequences for atmospheric C concentrations and the climate. Here, we use the Nutrient Network experiment to examine the responses of soil C and N pools to mammalian herbivore exclusion across 22 grasslands, under ambient and elevated nutrient availabilities (fertilized with NPK + micronutrients). We show that the impact of herbivore exclusion on soil C and N pools depends on fertilization. Under ambient nutrient conditions, we observed no effect of herbivore exclusion, but under elevated nutrient supply, pools are smaller upon herbivore exclusion. The highest mean soil C and N pools were found in grazed and fertilized plots. The decrease in soil C and N upon herbivore exclusion in combination with fertilization correlated with a decrease in aboveground plant biomass and microbial activity, indicating a reduced storage of organic matter and microbial residues as soil C and N. The response of soil C and N pools to herbivore exclusion was contingent on temperature - herbivores likely cause losses of C and N in colder sites and increases in warmer sites. Additionally, grasslands that contain mammalian herbivores have the potential to sequester more N under increased temperature variability and nutrient enrichment than ungrazed grasslands. Our study highlights the importance of conserving mammalian herbivore populations in grasslands worldwide. We need to incorporate local-scale herbivory, and its interaction with nutrient enrichment and climate, within global-scale models to better predict land-atmosphere interactions under future climate change.

Dataset Information

Coupled molecular and isotopic evidence for denitrifier controls over terrestrial nitrogen availability.

Publications

Coupled molecular and isotopic evidence for denitrifier controls over terrestrial nitrogen availability.

Similar Datasets

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