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- Title
Isotopic constraints on plant nitrogen acquisition strategies during ecosystem retrogression.
- Authors
Dynarski, Katherine A.; Houlton, Benjamin Z.
- Abstract
Plant root associations with microbes such as mycorrhizal fungi or N-fixing bacteria enable ecosystems to tap pools of nitrogen (N) that might otherwise be inaccessible, including atmospheric N or N in large soil organic molecules. Such microbially assisted N-foraging strategies may be particularly important in late-successional retrogressive ecosystems where productivity is low and soil nutrients are scarce. Here, we use natural N-stable isotopic composition to constrain pathways of N supplies to different plant functional groups across a well-studied natural soil fertility gradient that includes a highly retrogressive stage. We demonstrate that ectomycorrhizal fungi, ericoid mycorrhizal fungi, and N-fixing bacteria support forest N supplies at all stages of ecosystem succession, from relatively young, N-rich/phosphorus (P)-rich sites, to ancient sites (ca. 500 ky) where both N supplies and P supplies are exceedingly low. Microbially mediated N sources are most important in older ecosystems with very low soil nutrient availability, accounting for 75–96% of foliar N at the oldest, least fertile sites. These isotopically ground findings point to the key role of plant–microbe associations in shaping ecosystem processes and functioning, particularly in retrogressive-phase forest ecosystems.
- Subjects
ATMOSPHERIC nitrogen; NITROGEN in soils; ECTOMYCORRHIZAS; ECTOMYCORRHIZAL fungi; MYCORRHIZAL fungi; ECOSYSTEMS; PLANT communities; SOIL fertility
- Publication
Oecologia, 2020, Vol 192, Issue 3, p603
- ISSN
0029-8549
- Publication type
Article
- DOI
10.1007/s00442-020-04606-y