Shrub and Tree Expansion in Siberian Low Arctic Ecotones Since the 1960s
Patterns of tree and tall shrub occurrence form conspicuous and dynamic ecological boundaries at the interface of the Arctic tundra and boreal forest biomes. Reports from the North American and European Arctic indicate that climatic warming over the last century is promoting circumpolar tree and tal...
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ftdatacite:10.18130/v3c225 2023-05-15T14:49:54+02:00 Shrub and Tree Expansion in Siberian Low Arctic Ecotones Since the 1960s Frost, Gerald 2013 https://dx.doi.org/10.18130/v3c225 https://libraetd.lib.virginia.edu/public_view/sf268539b unknown University of Virginia All rights reserved (no additional license for public reuse) forest-tundra Arctic tundra shrub expansion treeline alder larch permafrost patterned-ground Landsat Siberia global change vegetation dynamics Thesis Text Dissertation thesis 2013 ftdatacite https://doi.org/10.18130/v3c225 2021-11-05T12:55:41Z Patterns of tree and tall shrub occurrence form conspicuous and dynamic ecological boundaries at the interface of the Arctic tundra and boreal forest biomes. Reports from the North American and European Arctic indicate that climatic warming over the last century is promoting circumpolar tree and tall shrub increase in tundra ecotones, but little evidence exists for northern Siberia, despite its immense geographic extent. Here I address this knowledge gap, by examining recent changes in ecotonal landscapes spanning the Siberian Low Arctic utilizing three approaches: (1) spatially-explicit comparisons of high-resolution satellite imagery from the mid-1960s, and recent years for eleven Siberian tundra ecotones; (2) field studies of landscape-scale mechanisms that facilitate shrub proliferation in permafrost patterned-ground ecosystems; and (3) spatio-temporal analyses of Landsat-observed trends in tundra vegetation productivity and shrub-driven land-cover change in northwest Siberia since 1984. Tree and tall shrub abundance increased in nine of eleven Siberian ecotones since the 1960s; however, most land-cover changes were driven by the proliferation of tall shrubs, particularly alder (Alnus), rather than trees. Alder increase was greatest in the northwest Siberian region, and was largely linked to permafrost disturbance processes that facilitate shrub recruitment within widespread mosaics of small, disturbed microsites in patterned-ground landscapes. Landsat time-series of the normalized difference vegetation index (NDVI), a spectral metric of vegetation biomass, indicate increasing tundra productivity in most of northwest Siberia since 1984, but there was high regional variability linked to differences in landscape physiography, soil properties, and permafrost geomorphology. Increases in shrubland productivity were ubiquitous, however, indicating that shrubland expansion is occurring throughout the region. The primary conclusions I reached are that (1) recent tree and shrub expansion is virtually ubiquitous in Siberian ecotones, with rapid changes evident in moister, shrub-dominated regions; (2) disturbed landforms in general, and patterned-ground landscapes in particular, are highly susceptible to shrub expansion; and (3) at least in the near-term, increasing shrub abundance within the present-day tundra biome is likely to be a dominant form of high-latitude environmental change, rather than shifts in the spatial extent of the Arctic tundra and boreal forest biomes per se. Thesis Arctic permafrost Tundra Siberia 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 |
unknown |
topic |
forest-tundra Arctic tundra shrub expansion treeline alder larch permafrost patterned-ground Landsat Siberia global change vegetation dynamics |
spellingShingle |
forest-tundra Arctic tundra shrub expansion treeline alder larch permafrost patterned-ground Landsat Siberia global change vegetation dynamics Frost, Gerald Shrub and Tree Expansion in Siberian Low Arctic Ecotones Since the 1960s |
topic_facet |
forest-tundra Arctic tundra shrub expansion treeline alder larch permafrost patterned-ground Landsat Siberia global change vegetation dynamics |
description |
Patterns of tree and tall shrub occurrence form conspicuous and dynamic ecological boundaries at the interface of the Arctic tundra and boreal forest biomes. Reports from the North American and European Arctic indicate that climatic warming over the last century is promoting circumpolar tree and tall shrub increase in tundra ecotones, but little evidence exists for northern Siberia, despite its immense geographic extent. Here I address this knowledge gap, by examining recent changes in ecotonal landscapes spanning the Siberian Low Arctic utilizing three approaches: (1) spatially-explicit comparisons of high-resolution satellite imagery from the mid-1960s, and recent years for eleven Siberian tundra ecotones; (2) field studies of landscape-scale mechanisms that facilitate shrub proliferation in permafrost patterned-ground ecosystems; and (3) spatio-temporal analyses of Landsat-observed trends in tundra vegetation productivity and shrub-driven land-cover change in northwest Siberia since 1984. Tree and tall shrub abundance increased in nine of eleven Siberian ecotones since the 1960s; however, most land-cover changes were driven by the proliferation of tall shrubs, particularly alder (Alnus), rather than trees. Alder increase was greatest in the northwest Siberian region, and was largely linked to permafrost disturbance processes that facilitate shrub recruitment within widespread mosaics of small, disturbed microsites in patterned-ground landscapes. Landsat time-series of the normalized difference vegetation index (NDVI), a spectral metric of vegetation biomass, indicate increasing tundra productivity in most of northwest Siberia since 1984, but there was high regional variability linked to differences in landscape physiography, soil properties, and permafrost geomorphology. Increases in shrubland productivity were ubiquitous, however, indicating that shrubland expansion is occurring throughout the region. The primary conclusions I reached are that (1) recent tree and shrub expansion is virtually ubiquitous in Siberian ecotones, with rapid changes evident in moister, shrub-dominated regions; (2) disturbed landforms in general, and patterned-ground landscapes in particular, are highly susceptible to shrub expansion; and (3) at least in the near-term, increasing shrub abundance within the present-day tundra biome is likely to be a dominant form of high-latitude environmental change, rather than shifts in the spatial extent of the Arctic tundra and boreal forest biomes per se. |
format |
Thesis |
author |
Frost, Gerald |
author_facet |
Frost, Gerald |
author_sort |
Frost, Gerald |
title |
Shrub and Tree Expansion in Siberian Low Arctic Ecotones Since the 1960s |
title_short |
Shrub and Tree Expansion in Siberian Low Arctic Ecotones Since the 1960s |
title_full |
Shrub and Tree Expansion in Siberian Low Arctic Ecotones Since the 1960s |
title_fullStr |
Shrub and Tree Expansion in Siberian Low Arctic Ecotones Since the 1960s |
title_full_unstemmed |
Shrub and Tree Expansion in Siberian Low Arctic Ecotones Since the 1960s |
title_sort |
shrub and tree expansion in siberian low arctic ecotones since the 1960s |
publisher |
University of Virginia |
publishDate |
2013 |
url |
https://dx.doi.org/10.18130/v3c225 https://libraetd.lib.virginia.edu/public_view/sf268539b |
geographic |
Arctic |
geographic_facet |
Arctic |
genre |
Arctic permafrost Tundra Siberia |
genre_facet |
Arctic permafrost Tundra Siberia |
op_rights |
All rights reserved (no additional license for public reuse) |
op_doi |
https://doi.org/10.18130/v3c225 |
_version_ |
1766320979381846016 |