As Arctic soils warm, thawed permafrost releases nitrogen (N) that could stimulate plant productivity and thus offset soil carbon losses from tundra ecosystems. Although mycorrhizal fungi could facilitate plant access to permafrost‐derived N, their exploration capacity beyond host plant root systems into deep, cold active layer soils adjacent to the permafrost table is unknown. We characterized root‐associated fungi (RAF) that colonized ericoid (ERM) and ectomycorrhizal (ECM) shrub roots and occurred below the maximum rooting depth in permafrost thaw‐front soil in tussock and shrub tundra communities. We explored the relationships between root and thaw front fungal composition and plant uptake of a15N tracer applied at the permafrost boundary. We show that ERM and ECM shrubs associate with RAF at the thaw front providing evidence for potential mycelial connectivity between roots and the permafrost boundary. Among shrubs and tundra communities, RAF connectivity to the thaw boundary was ubiquitous. The occurrence of particular RAF in both roots and thaw front soil was positively correlated with15N recovered in shrub biomass Taxon‐specific RAF associations could be a mechanism for the vertical redistribution of deep, permafrost‐derived nutrients, which may alleviate N limitation and stimulate productivity in warming tundra.
- Award ID(s):
- 1936752
- NSF-PAR ID:
- 10252154
- Date Published:
- Journal Name:
- Frontiers in Plant Science
- Volume:
- 11
- ISSN:
- 1664-462X
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Abstract Rapid Arctic climate change is leading to woody plant‐dominated ecosystems with potential consequences for caribou foraging and nutritional ecology. While warming has been clearly linked to shrub expansion, the influence of higher temperatures on variables linked to the leaf‐level quality of caribou forage is equivocal. Moreover, warming results in a complex set of ecosystem changes that operate on different timescales such as not only rapidly accelerating phenology, but also slowly increasing thaw depth and plant access to soil resources. Here, we compare changes in leaf nitrogen (N) concentration, digestibility, and protein‐precipitating capacity (PPC) in short‐term (i.e., <1–2 summers) and long‐term (approximately 25 years) experimental warming plots with ambient temperature plots for three species commonly included in caribou summer diets:
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- Root-associated fungi (RAF) and root traits regulate plant acquisition of nitrogen (N), which is limiting to growth in Arctic ecosystems. With anthropogenic warming, a new N source from thawing permafrost has the potential to change vegetation composition and increase productivity, influencing climate feedbacks. Yet, the impact of warming on tundra plant root traits, RAF, and access to permafrost N is uncertain. - We investigated the relationships between RAF, species-specific root traits, and uptake of N from the permafrost boundary by tundra plants experimentally warmed for nearly three decades at Toolik Lake, Alaska. - Warming increased acquisitive root traits of nonmycorrhizal and mycorrhizal plants. RAF community composition of ericoid (ERM) but not ectomycorrhizal (ECM) shrubs was impacted by warming and correlated with root traits. RAF taxa in the dark septate endophyte, ERM, and ECM guilds strongly correlated with permafrost N uptake for ECM and ERM shrubs. Overall, a greater proportion of variation in permafrost N uptake was related to root traits than RAF. - Our findings suggest that warming Arctic ecosystems will result in interactions between roots, RAF, and newly thawed permafrost that may strongly impact feedbacks to the climate system through mechanisms of carbon and N cycling.more » « less
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.3389/fpls.2020.588098
