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Removal of grazers alters the response of tundra soil carbon to warming and enhanced nitrogen availability

Ylänne, Henni LU ; Kaarlejärvi, Elina ; Väisänen, Maria ; Männistö, Minna ; Ahonen, Saija H K ; Olofsson, Johan and Stark, Sari (2020) In Ecological Monographs 90(1).
Abstract
The circumpolar Arctic is currently facing multiple global changes that have the potential to alter the capacity of tundra soils to store carbon. Yet, predicting changes in soil carbon is hindered by the fact that multiple factors simultaneously control processes sustaining carbon storage and we do not understand how they act in concert. Here, we investigated the effects of warmer temperatures, enhanced soil nitrogen availability, and the combination of these on tundra carbon stocks at three different grazing regimes: on areas with over 50-yr history of either light or heavy reindeer grazing and in 5-yr-old exlosures in the heavily grazed area. In line with earlier reports, warming generally decreased soil carbon stocks. However, our... (More)
The circumpolar Arctic is currently facing multiple global changes that have the potential to alter the capacity of tundra soils to store carbon. Yet, predicting changes in soil carbon is hindered by the fact that multiple factors simultaneously control processes sustaining carbon storage and we do not understand how they act in concert. Here, we investigated the effects of warmer temperatures, enhanced soil nitrogen availability, and the combination of these on tundra carbon stocks at three different grazing regimes: on areas with over 50-yr history of either light or heavy reindeer grazing and in 5-yr-old exlosures in the heavily grazed area. In line with earlier reports, warming generally decreased soil carbon stocks. However, our results suggest that the mechanisms by which warming decreases carbon storage depend on grazing intensity: under long-term light grazing soil carbon losses were linked to higher shrub abundance and higher enzymatic activities, whereas under long-term heavy grazing, carbon losses were linked to drier soils and higher enzymatic activities. Importantly, under enhanced soil nitrogen availability, warming did not induce soil carbon losses under either of the long-term grazing regimes, whereas inside exclosures in the heavily grazed area, also the combination of warming and enhanced nutrient availability induced soil carbon loss. Grazing on its own did not influence the soil carbon stocks. These results reveal that accounting for the effect of warming or grazing alone is not sufficient to reliably predict future soil carbon storage in the tundra. Instead, the joint effects of multiple global changes need to be accounted for, with a special focus given to abrupt changes in grazing currently taking place in several parts of the Arctic. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
Fertilization, Soil carbon storage, Land use, Herbivory, Open-top chamber, Rangifer tarandus, Reindeer, SEM-analyses
in
Ecological Monographs
volume
90
issue
1
article number
e01396
publisher
Ecological Society of America
ISSN
0012-9615
DOI
10.1002/ecm.1396
language
English
LU publication?
yes
id
ea027102-96f5-4baf-a2af-d01860564ab7
date added to LUP
2019-12-20 09:40:59
date last changed
2020-02-05 13:35:49
@article{ea027102-96f5-4baf-a2af-d01860564ab7,
  abstract     = {The circumpolar Arctic is currently facing multiple global changes that have the potential to alter the capacity of tundra soils to store carbon. Yet, predicting changes in soil carbon is hindered by the fact that multiple factors simultaneously control processes sustaining carbon storage and we do not understand how they act in concert. Here, we investigated the effects of warmer temperatures, enhanced soil nitrogen availability, and the combination of these on tundra carbon stocks at three different grazing regimes: on areas with over 50-yr history of either light or heavy reindeer grazing and in 5-yr-old exlosures in the heavily grazed area. In line with earlier reports, warming generally decreased soil carbon stocks. However, our results suggest that the mechanisms by which warming decreases carbon storage depend on grazing intensity: under long-term light grazing soil carbon losses were linked to higher shrub abundance and higher enzymatic activities, whereas under long-term heavy grazing, carbon losses were linked to drier soils and higher enzymatic activities. Importantly, under enhanced soil nitrogen availability, warming did not induce soil carbon losses under either of the long-term grazing regimes, whereas inside exclosures in the heavily grazed area, also the combination of warming and enhanced nutrient availability induced soil carbon loss. Grazing on its own did not influence the soil carbon stocks. These results reveal that accounting for the effect of warming or grazing alone is not sufficient to reliably predict future soil carbon storage in the tundra. Instead, the joint effects of multiple global changes need to be accounted for, with a special focus given to abrupt changes in grazing currently taking place in several parts of the Arctic.},
  author       = {Ylänne, Henni and Kaarlejärvi, Elina and Väisänen, Maria and Männistö, Minna and Ahonen, Saija H K and Olofsson, Johan and Stark, Sari},
  issn         = {0012-9615},
  language     = {eng},
  number       = {1},
  publisher    = {Ecological Society of America},
  series       = {Ecological Monographs},
  title        = {Removal of grazers alters the response of tundra soil carbon to warming and enhanced nitrogen availability},
  url          = {http://dx.doi.org/10.1002/ecm.1396},
  doi          = {10.1002/ecm.1396},
  volume       = {90},
  year         = {2020},
}