https://dx.doi.org/10.1007/s11104-015-2623-1">
 

Abstract

Background and Aims

The importance of the uptake of nitrogen in organic form by plants and mycorrhizal fungi has been demonstrated in various ecosystems including temperate forests. However, in previous experiments, isotopically labeled amino acids were often added to soils in concentrations that may be higher than those normally available to roots and mycorrhizal hyphae in situ, and these high concentrations could contribute to exaggerated uptake.

Methods

We used an experimental approach in which we added 13C-labeled and 15N-labeled whole cells to root-ingrowth cores, allowing proteolytic enzymes to release labeled organic nitrogen at a natural rate, as roots and their associated mycorrhizal fungi grew into the cores. We employed this method in four forest types representing a gradient of soil pH, nitrogen mineralization rate, and mycorrhizal type.

Results

Intact uptake of organic nitrogen was detected in mycorrhizal roots, and accounted for at least of 1-14% of labeled nitrogen uptake. Forest types did not differ significantly in the importance of organic uptake.

Conclusions

The estimates of organic N uptake here using 13C-labeled and 15N-labeled whole cells are less than those reported in other temperate forest studies using isotopically labelled amino acids, and likely represent a minimum estimate of organic N-use. The two approaches each have different assumptions, and when used in tandem should complement one another and provide upper and lower bounds of organic N use by plants.

Department

Earth Systems Research Center

Publication Date

12-2015

Journal Title

Plant and Soil

Publisher

Springer

Digital Object Identifier (DOI)

https://dx.doi.org/10.1007/s11104-015-2623-1

Document Type

Article

Comments

This is an Accepted Manuscript. The final publication is available at Springer via https://dx.doi.org/10.1007/s11104-015-2623-1

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