Effects of Sheep Grazing on Availability and Leaching of Soil Nitrogen in Low-Alpine Grasslands
Alpine ecosystems are generally nitrogen (N) limited with low rates of N mineralization. Herbivory may affect N cycling and N losses and thus long-term productivity of ecosystems. Using a controlled grazing experiment in a low-alpine region at Hol, southern Norway, with three density levels of sheep...
Published in: | Arctic, Antarctic, and Alpine Research |
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University of Colorado at Boulder, Institute of Arctic and Alpine Research
2012
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Online Access: | http://hdl.handle.net/11250/2467498 https://doi.org/10.1657/1938-4246-44.1.67 |
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ftntnutrondheimi:oai:ntnuopen.ntnu.no:11250/2467498 2023-05-15T14:14:02+02:00 Effects of Sheep Grazing on Availability and Leaching of Soil Nitrogen in Low-Alpine Grasslands Martinsen, Vegard Mulder, Jan Austrheim, Gunnar Hessen, Dag Olav Mysterud, Atle 2012 http://hdl.handle.net/11250/2467498 https://doi.org/10.1657/1938-4246-44.1.67 eng eng University of Colorado at Boulder, Institute of Arctic and Alpine Research Norges forskningsråd: 179569 Arctic, Antarctic and Alpine research. 2012, 44 (1), 67-82. urn:issn:1523-0430 http://hdl.handle.net/11250/2467498 https://doi.org/10.1657/1938-4246-44.1.67 cristin:927602 67-82 44 Arctic, Antarctic and Alpine research 1 Journal article Peer reviewed 2012 ftntnutrondheimi https://doi.org/10.1657/1938-4246-44.1.67 2019-09-17T06:52:34Z Alpine ecosystems are generally nitrogen (N) limited with low rates of N mineralization. Herbivory may affect N cycling and N losses and thus long-term productivity of ecosystems. Using a controlled grazing experiment in a low-alpine region at Hol, southern Norway, with three density levels of sheep, we determined effects of grazing on in situ availability of inorganic N, potential N mineralization, and mobility of dissolved inorganic N (DIN) and dissolved organic N (DON) in soil water of O-horizons in grazing-preferred grassland habitats. In addition, we studied the within-season and spatial variation of these processes. The low alpine grasslands at Hol were characterized by small rates of N mineralization and relatively large plant demands for N. Significantly greater rates of potential N mineralization were found at sites with high sheep density compared to those with low density or no grazing. Effects of grazing on bioavailable N (as determined by buried PRS™ exchange resins) were greater at low as compared to high altitudes. At low altitudes, low sheep density reduced amounts of bioavailable N. Nitrogen concentration of plants as a proxy of N availability in soils revealed, however, no significant effects of grazing. There was a strong seasonal effect on inorganic N and DIN∶DON ratios of the soil water, with decreasing values in the course of the growing season, probably due to increasing nutrient demand of plants and/or microbes. We conclude that grazing may significantly stimulate N-cycling, but not sufficiently to release the system from its strong N deficiency, as we found no evidence for short-term increased risk in N loss via soil water due to herbivore activity. Nitrogen removal through grazing is small compared to the total soil N pool and at high sheep density is about half of the N deposition. This suggests that grazing in grassland habitats in this low alpine ecosystem is sustainable from a nutrient point of view. publishedVersion © 2012 University of Colorado at Boulder, Institute of Arctic and Alpine Research Article in Journal/Newspaper Antarctic and Alpine Research Arctic Arctic Institute of Arctic and Alpine Research NTNU Open Archive (Norwegian University of Science and Technology) Arctic Norway Arctic, Antarctic, and Alpine Research 44 1 67 82 |
institution |
Open Polar |
collection |
NTNU Open Archive (Norwegian University of Science and Technology) |
op_collection_id |
ftntnutrondheimi |
language |
English |
description |
Alpine ecosystems are generally nitrogen (N) limited with low rates of N mineralization. Herbivory may affect N cycling and N losses and thus long-term productivity of ecosystems. Using a controlled grazing experiment in a low-alpine region at Hol, southern Norway, with three density levels of sheep, we determined effects of grazing on in situ availability of inorganic N, potential N mineralization, and mobility of dissolved inorganic N (DIN) and dissolved organic N (DON) in soil water of O-horizons in grazing-preferred grassland habitats. In addition, we studied the within-season and spatial variation of these processes. The low alpine grasslands at Hol were characterized by small rates of N mineralization and relatively large plant demands for N. Significantly greater rates of potential N mineralization were found at sites with high sheep density compared to those with low density or no grazing. Effects of grazing on bioavailable N (as determined by buried PRS™ exchange resins) were greater at low as compared to high altitudes. At low altitudes, low sheep density reduced amounts of bioavailable N. Nitrogen concentration of plants as a proxy of N availability in soils revealed, however, no significant effects of grazing. There was a strong seasonal effect on inorganic N and DIN∶DON ratios of the soil water, with decreasing values in the course of the growing season, probably due to increasing nutrient demand of plants and/or microbes. We conclude that grazing may significantly stimulate N-cycling, but not sufficiently to release the system from its strong N deficiency, as we found no evidence for short-term increased risk in N loss via soil water due to herbivore activity. Nitrogen removal through grazing is small compared to the total soil N pool and at high sheep density is about half of the N deposition. This suggests that grazing in grassland habitats in this low alpine ecosystem is sustainable from a nutrient point of view. publishedVersion © 2012 University of Colorado at Boulder, Institute of Arctic and Alpine Research |
format |
Article in Journal/Newspaper |
author |
Martinsen, Vegard Mulder, Jan Austrheim, Gunnar Hessen, Dag Olav Mysterud, Atle |
spellingShingle |
Martinsen, Vegard Mulder, Jan Austrheim, Gunnar Hessen, Dag Olav Mysterud, Atle Effects of Sheep Grazing on Availability and Leaching of Soil Nitrogen in Low-Alpine Grasslands |
author_facet |
Martinsen, Vegard Mulder, Jan Austrheim, Gunnar Hessen, Dag Olav Mysterud, Atle |
author_sort |
Martinsen, Vegard |
title |
Effects of Sheep Grazing on Availability and Leaching of Soil Nitrogen in Low-Alpine Grasslands |
title_short |
Effects of Sheep Grazing on Availability and Leaching of Soil Nitrogen in Low-Alpine Grasslands |
title_full |
Effects of Sheep Grazing on Availability and Leaching of Soil Nitrogen in Low-Alpine Grasslands |
title_fullStr |
Effects of Sheep Grazing on Availability and Leaching of Soil Nitrogen in Low-Alpine Grasslands |
title_full_unstemmed |
Effects of Sheep Grazing on Availability and Leaching of Soil Nitrogen in Low-Alpine Grasslands |
title_sort |
effects of sheep grazing on availability and leaching of soil nitrogen in low-alpine grasslands |
publisher |
University of Colorado at Boulder, Institute of Arctic and Alpine Research |
publishDate |
2012 |
url |
http://hdl.handle.net/11250/2467498 https://doi.org/10.1657/1938-4246-44.1.67 |
geographic |
Arctic Norway |
geographic_facet |
Arctic Norway |
genre |
Antarctic and Alpine Research Arctic Arctic Institute of Arctic and Alpine Research |
genre_facet |
Antarctic and Alpine Research Arctic Arctic Institute of Arctic and Alpine Research |
op_source |
67-82 44 Arctic, Antarctic and Alpine research 1 |
op_relation |
Norges forskningsråd: 179569 Arctic, Antarctic and Alpine research. 2012, 44 (1), 67-82. urn:issn:1523-0430 http://hdl.handle.net/11250/2467498 https://doi.org/10.1657/1938-4246-44.1.67 cristin:927602 |
op_doi |
https://doi.org/10.1657/1938-4246-44.1.67 |
container_title |
Arctic, Antarctic, and Alpine Research |
container_volume |
44 |
container_issue |
1 |
container_start_page |
67 |
op_container_end_page |
82 |
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1766286539730452480 |