Pathways of tundra encroachment by trees and tall shrubs in the western Brooks Range of Alaska
Climate change is expected to increase woody vegetation abundance in the Arctic, yet the magnitude, spatial pattern and pathways of change remain uncertain. We compared historical orthophotos photos (1952 and 1979) with high‐resolution satellite imagery (2015) to examine six decades of change in abu...
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crwiley:10.1111/ecog.05015 2024-09-30T14:30:07+00:00 Pathways of tundra encroachment by trees and tall shrubs in the western Brooks Range of Alaska Terskaia, Anna Dial, Roman J. Sullivan, Patrick F. 2020 http://dx.doi.org/10.1111/ecog.05015 https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1111%2Fecog.05015 https://onlinelibrary.wiley.com/doi/pdf/10.1111/ecog.05015 https://onlinelibrary.wiley.com/doi/full-xml/10.1111/ecog.05015 en eng Wiley http://creativecommons.org/licenses/by/3.0/ Ecography volume 43, issue 5, page 769-778 ISSN 0906-7590 1600-0587 journal-article 2020 crwiley https://doi.org/10.1111/ecog.05015 2024-09-17T04:43:24Z Climate change is expected to increase woody vegetation abundance in the Arctic, yet the magnitude, spatial pattern and pathways of change remain uncertain. We compared historical orthophotos photos (1952 and 1979) with high‐resolution satellite imagery (2015) to examine six decades of change in abundance of white spruce Picea glauca and tall shrubs ( Salix spp., Alnus spp.) near the Agashashok River in northwest Alaska. We established ~3000 random points within our ~5500 ha study area for classification into nine cover types. To examine physiographic controls on tree abundance, we fit multinomial log‐linear models with predictors derived from a digital elevation model and with arctic tundra, alpine tundra and ‘tree’ as levels of a categorical response variable. Between 1952 and 2015, points classified as arctic and alpine tundra decreased by 31% and 15%, respectively. Meanwhile, tall shrubs increased by 86%, trees mixed with tall shrubs increased by 385% and forest increased by 84%. Tundra with tall shrubs rarely transitioned to forest. The best multinomial model explained 71% of variation in cover and included elevation, slope and an interaction between slope and ‘northness’. Treeline was defined as the elevation where the probability of tree presence equaled that of tundra. Mean treeline elevation in 2015 was 202 m, corresponding with a June–August mean air temperature > 11°C, which is > 4°C warmer than the 6–7°C isotherm associated with global treeline elevations. Our results show dramatic increases in the abundance of trees and tall shrubs, question the universality of air temperature as a predictor of treeline elevation and suggest two mutually exclusive pathways of vegetation change, because tundra that gained tall shrubs rarely transitioned to forest. Conversion of tundra to tall shrubs and forest has important and potentially contrasting implications for carbon cycling, surface energy exchange and wildlife habitat in the Arctic. Article in Journal/Newspaper Arctic Brooks Range Climate change Tundra Alaska Wiley Online Library Arctic Ecography 43 5 769 778 |
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Open Polar |
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Wiley Online Library |
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crwiley |
language |
English |
description |
Climate change is expected to increase woody vegetation abundance in the Arctic, yet the magnitude, spatial pattern and pathways of change remain uncertain. We compared historical orthophotos photos (1952 and 1979) with high‐resolution satellite imagery (2015) to examine six decades of change in abundance of white spruce Picea glauca and tall shrubs ( Salix spp., Alnus spp.) near the Agashashok River in northwest Alaska. We established ~3000 random points within our ~5500 ha study area for classification into nine cover types. To examine physiographic controls on tree abundance, we fit multinomial log‐linear models with predictors derived from a digital elevation model and with arctic tundra, alpine tundra and ‘tree’ as levels of a categorical response variable. Between 1952 and 2015, points classified as arctic and alpine tundra decreased by 31% and 15%, respectively. Meanwhile, tall shrubs increased by 86%, trees mixed with tall shrubs increased by 385% and forest increased by 84%. Tundra with tall shrubs rarely transitioned to forest. The best multinomial model explained 71% of variation in cover and included elevation, slope and an interaction between slope and ‘northness’. Treeline was defined as the elevation where the probability of tree presence equaled that of tundra. Mean treeline elevation in 2015 was 202 m, corresponding with a June–August mean air temperature > 11°C, which is > 4°C warmer than the 6–7°C isotherm associated with global treeline elevations. Our results show dramatic increases in the abundance of trees and tall shrubs, question the universality of air temperature as a predictor of treeline elevation and suggest two mutually exclusive pathways of vegetation change, because tundra that gained tall shrubs rarely transitioned to forest. Conversion of tundra to tall shrubs and forest has important and potentially contrasting implications for carbon cycling, surface energy exchange and wildlife habitat in the Arctic. |
format |
Article in Journal/Newspaper |
author |
Terskaia, Anna Dial, Roman J. Sullivan, Patrick F. |
spellingShingle |
Terskaia, Anna Dial, Roman J. Sullivan, Patrick F. Pathways of tundra encroachment by trees and tall shrubs in the western Brooks Range of Alaska |
author_facet |
Terskaia, Anna Dial, Roman J. Sullivan, Patrick F. |
author_sort |
Terskaia, Anna |
title |
Pathways of tundra encroachment by trees and tall shrubs in the western Brooks Range of Alaska |
title_short |
Pathways of tundra encroachment by trees and tall shrubs in the western Brooks Range of Alaska |
title_full |
Pathways of tundra encroachment by trees and tall shrubs in the western Brooks Range of Alaska |
title_fullStr |
Pathways of tundra encroachment by trees and tall shrubs in the western Brooks Range of Alaska |
title_full_unstemmed |
Pathways of tundra encroachment by trees and tall shrubs in the western Brooks Range of Alaska |
title_sort |
pathways of tundra encroachment by trees and tall shrubs in the western brooks range of alaska |
publisher |
Wiley |
publishDate |
2020 |
url |
http://dx.doi.org/10.1111/ecog.05015 https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1111%2Fecog.05015 https://onlinelibrary.wiley.com/doi/pdf/10.1111/ecog.05015 https://onlinelibrary.wiley.com/doi/full-xml/10.1111/ecog.05015 |
geographic |
Arctic |
geographic_facet |
Arctic |
genre |
Arctic Brooks Range Climate change Tundra Alaska |
genre_facet |
Arctic Brooks Range Climate change Tundra Alaska |
op_source |
Ecography volume 43, issue 5, page 769-778 ISSN 0906-7590 1600-0587 |
op_rights |
http://creativecommons.org/licenses/by/3.0/ |
op_doi |
https://doi.org/10.1111/ecog.05015 |
container_title |
Ecography |
container_volume |
43 |
container_issue |
5 |
container_start_page |
769 |
op_container_end_page |
778 |
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1811635183973040128 |