Details

Autor(en) / Beteiligte

• Moyes, Andrew B
• Kueppers, Lara M
• Pett‐Ridge, Jennifer
• Carper, Dana L
• Vandehey, Nick
• O'Neil, James
• Frank, A. Carolin

Titel

Evidence for foliar endophytic nitrogen fixation in a widely distributed subalpine conifer

Ist Teil von

• The New phytologist, 2016-04, Vol.210 (2), p.657-668

Ort / Verlag

England: Academic Press

Erscheinungsjahr

2016

Quelle

Access via Wiley Online Library

Beschreibungen/Notizen

• Coniferous forest nitrogen (N) budgets indicate unknown sources of N. A consistent association between limber pine (Pinus flexilis) and potential N₂‐fixing acetic acid bacteria (AAB) indicates that native foliar endophytes may supply subalpine forests with N. To assess whether the P. flexilis–AAB association is consistent across years, we re‐sampled P. flexilis twigs at Niwot Ridge, CO and characterized needle endophyte communities via 16S rRNA Illumina sequencing. To investigate whether endophytes have access to foliar N₂, we incubated twigs with ¹³N₂‐enriched air and imaged radioisotope distribution in needles, the first experiment of its kind using ¹³N. We used the acetylene reduction assay to test for nitrogenase activity within P. flexilis twigs four times from June to September. We found evidence for N₂ fixation in P. flexilis foliage. N₂ diffused readily into needles and nitrogenase activity was positive across sampling dates. We estimate that this association could provide 6.8–13.6 μg N m⁻² d⁻¹ to P. flexilis stands. AAB dominated the P. flexilis needle endophyte community. We propose that foliar endophytes represent a low‐cost, evolutionarily stable N₂‐fixing strategy for long‐lived conifers. This novel source of biological N₂ fixation has fundamental implications for understanding forest N budgets.