Abstract
Plants in terrestrial systems obtain nitrogen primarily by root uptake from soil, yet current models of ecosystem nitrogen cycling assume little interaction of plant roots with the soil microbial community. The objective of this study was to determine how soil microorganisms in biological soil crusts interact with herbaceous plants for nitrogen in a pyrogenic ecosystem in Florida (USA), using a combination of natural abundance and tracer isotope methods. I demonstrate that plant nitrogen is strongly affected by interactions with mycorrhizal fungi and biological soil crusts. Measurements of nitrogenase activity indicated a high capacity of crusts to fix nitrogen that dramatically decreased after disturbance. Natural abundance of δ15N differed between arbuscular mycorrhizal and nonmycorrhizal herbs. When a small amount of enriched nitrogen was used as a tracer, crusts initially captured a greater amount of the 15N that was added compared to plants, with some turnover of nitrogen from the crusts to plants observed after 15 days. Observations in this study indicate that crusts have more than one function in nitrogen dynamics: cyanobacteria in crusts fix nitrogen, crusts retain nitrogen in the system that would otherwise be lost to leaching, and though some of this nitrogen is available to plants, they also face competition from heterotrophic bacteria in crusts. Corresponding Editor: P. M. Groffman.
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Claims 9
Claim · model-written summary
Plant nitrogen was strongly affected by interactions with mycorrhizal fungi and soil crusts.
- Taxon
- plante0
- Interactor
- mycorrhizal fungie0symbiont
- Second interactor
- biological soil crustse0other
- Outcome
- plant nitrogene0
Not reportedDirection
Verbatim
e0“plant nitrogen is strongly affected by interactions with mycorrhizal fungi and biological soil crusts”
Claim · model-written summary
Disturbance dramatically reduced nitrogen fixation capacity of biological soil crusts.
Not reportedTaxonComparator
Verbatim
e0“Measurements of nitrogenase activity indicated a high capacity of crusts to fix nitrogen that dramatically decreased after disturbance”
Claim · model-written summary
Natural δ15N abundance differed between arbuscular mycorrhizal and nonmycorrhizal herbs.
Verbatim
e0“Natural abundance of δ15N differed between arbuscular mycorrhizal and nonmycorrhizal herbs”
Claim · model-written summary
Crusts initially captured more added 15N than plants.
Not reportedTaxon
Verbatim
e0“crusts initially captured a greater amount of the 15N that was added compared to plants”
Claim · model-written summary
Some nitrogen transferred from crusts to plants after 15 days.
- Taxon
- plantsViridiplantaee0
- Interactor
- crustse0other
- Outcome
- turnover of nitrogen from the crusts to plantse0
- Qualifier
- after 15 dayse0
Verbatim
e0“some turnover of nitrogen from the crusts to plants observed after 15 days”
Claim · model-written summary
Cyanobacteria in crusts fix nitrogen.
- Taxon
- cyanobacteriaCyanobacteriotae0
- Outcome
- fix nitrogene0
Verbatim
e0“cyanobacteria in crusts fix nitrogen”
Claim · model-written summary
Crusts retain nitrogen that would otherwise leach from the system.
Not reportedTaxon
Verbatim
e0“crusts retain nitrogen in the system that would otherwise be lost to leaching”
Claim · model-written summary
Some crust nitrogen is available to plants.
- Taxon
- plantsViridiplantaee0
- Outcome
- nitrogen is available to plantse0
Verbatim
e0“some of this nitrogen is available to plants”
Claim · model-written summary
Plants face nitrogen competition from heterotrophic bacteria in crusts.
Not reportedDirection
Verbatim
e0“they also face competition from heterotrophic bacteria in crusts”