| Zdroj: |
Pedersen, E P, Elberling, B & Michelsen, A 2022, ' Upslope release—Downslope receipt? Multi-year plant uptake of permafrost-released nitrogen along an arctic hillslope ', Journal of Ecology, vol. 110, pp. 1896–1912 . https://doi.org/10.1111/1365-2745.13925 |
| Popis: |
As arctic permafrost continues to thaw, previously inaccessible nitrogen (N) becomes available to N-limited arctic plants. Increased N availability could enhance plant growth and thereby potentially offset climate-induced carbon release. Arctic plants can take up newly available permafrost-N locally upon release. However, in a topographically diverse arctic landscape, permafrost-N may be transported along hillslopes, away from the point-of-release. The extent to which topographical N transport can impact arctic vegetation change depends on whether N is retained locally, captured by downslope recipient plant communities, or transported away. We used stable isotope labelling (15N) to simulate upslope release of ammonium (NH4+) and nitrate (NO3−) from thawing permafrost on an arctic hillslope, western Greenland. We tracked the plant species-specific uptake of simulated permafrost-released N from the upslope point-of-release to the bottom of the slope through 4 years. We found that arctic tundra plants successfully acquired locally released permafrost-N, even in sloping terrain, and that N was strongly retained in the plant–soil system through multiple years. At the same time, we also importantly demonstrate that permafrost-N can be transported and taken up by plants up to 30 m downslope from the point-of-release. Especially NO3− was more easily redistributed vertically within the soil column compared to NH4+ and therefore potentially more accessible to plants. Specifically, plant species with fast N uptake capacity and deep-soil foraging strategies may have competitive advantages for capitalising on deep-soil released and topographically transported permafrost-N (here exemplified by Equisetum arvense and Salix glauca). Nevertheless, even mosses gained access to permafrost-N via vertical and lateral redistribution on the slope. Ultimately, the intricate balance between strong local N retention, downslope transport and plant species-specific uptake strategies may contribute to shaping arctic vegetation change. Synthesis. Across spatially complex arctic ecosystems, arctic plants can take up permafrost-released N both at the local point-of-release and at a considerable distance downslope. The potential for arctic plants to take advantage of topographically transported permafrost-N could lead to long-term and landscape-scale changes in species composition, plant productivity, and ultimately carbon and climate feedbacks across the Arctic. |
