Vegetation classifications for random points in the Agashashok River watershed in 1952, 1979 and 2015
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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NSF Arctic Data Center
2020
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ftdatacite:10.18739/a27d2q78x 2023-05-15T14:50:07+02:00 Vegetation classifications for random points in the Agashashok River watershed in 1952, 1979 and 2015 Sullivan, Patrick Dial, Roman Terskaia, Anna 2020 text/xml https://dx.doi.org/10.18739/a27d2q78x https://arcticdata.io/catalog/view/doi:10.18739/A27D2Q78X en eng NSF Arctic Data Center treeline shrub encroachment climate warming Picea glauca Arctic Salix Alnus dataset Dataset 2020 ftdatacite https://doi.org/10.18739/a27d2q78x 2021-11-05T12:55:41Z 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 meters (m), corresponding with a June-August mean air temperature >11° Celsius (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. Dataset Arctic Climate change Tundra Alaska DataCite Metadata Store (German National Library of Science and Technology) Arctic |
institution |
Open Polar |
collection |
DataCite Metadata Store (German National Library of Science and Technology) |
op_collection_id |
ftdatacite |
language |
English |
topic |
treeline shrub encroachment climate warming Picea glauca Arctic Salix Alnus |
spellingShingle |
treeline shrub encroachment climate warming Picea glauca Arctic Salix Alnus Sullivan, Patrick Dial, Roman Terskaia, Anna Vegetation classifications for random points in the Agashashok River watershed in 1952, 1979 and 2015 |
topic_facet |
treeline shrub encroachment climate warming Picea glauca Arctic Salix Alnus |
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 meters (m), corresponding with a June-August mean air temperature >11° Celsius (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 |
Dataset |
author |
Sullivan, Patrick Dial, Roman Terskaia, Anna |
author_facet |
Sullivan, Patrick Dial, Roman Terskaia, Anna |
author_sort |
Sullivan, Patrick |
title |
Vegetation classifications for random points in the Agashashok River watershed in 1952, 1979 and 2015 |
title_short |
Vegetation classifications for random points in the Agashashok River watershed in 1952, 1979 and 2015 |
title_full |
Vegetation classifications for random points in the Agashashok River watershed in 1952, 1979 and 2015 |
title_fullStr |
Vegetation classifications for random points in the Agashashok River watershed in 1952, 1979 and 2015 |
title_full_unstemmed |
Vegetation classifications for random points in the Agashashok River watershed in 1952, 1979 and 2015 |
title_sort |
vegetation classifications for random points in the agashashok river watershed in 1952, 1979 and 2015 |
publisher |
NSF Arctic Data Center |
publishDate |
2020 |
url |
https://dx.doi.org/10.18739/a27d2q78x https://arcticdata.io/catalog/view/doi:10.18739/A27D2Q78X |
geographic |
Arctic |
geographic_facet |
Arctic |
genre |
Arctic Climate change Tundra Alaska |
genre_facet |
Arctic Climate change Tundra Alaska |
op_doi |
https://doi.org/10.18739/a27d2q78x |
_version_ |
1766321182542397440 |