Satellite-Based Evidence for Shrub and Graminoid Tundra Expansion in Northern Quebec from 1986-2010
Global vegetation models predict rapid poleward migration of tundra and boreal forest vegetation in response to climate warming. Local plot and air-photo studies have documented recent changes in high-latitude vegetation composition and structure, consistent with warming trends. To bridge these two...
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ftnasantrs:oai:casi.ntrs.nasa.gov:20120010311 2023-05-15T18:39:57+02:00 Satellite-Based Evidence for Shrub and Graminoid Tundra Expansion in Northern Quebec from 1986-2010 Wang, D. Masek, J. G. Nagol, J. Ropars, P. Boudreau, S. Sexton, J. O. Morton, D. C. McManus, K. M. Unclassified, Unlimited, Publicly available [2012] application/pdf http://hdl.handle.net/2060/20120010311 unknown Document ID: 20120010311 http://hdl.handle.net/2060/20120010311 Copyright, Distribution as joint owner in the copyright CASI Earth Resources and Remote Sensing GSFC.JA.00241.2012 GSFC.JA.6432.2012 2012 ftnasantrs 2019-07-21T06:21:15Z Global vegetation models predict rapid poleward migration of tundra and boreal forest vegetation in response to climate warming. Local plot and air-photo studies have documented recent changes in high-latitude vegetation composition and structure, consistent with warming trends. To bridge these two scales of inference, we analyzed a 24-year (1986-2010) Landsat time series in a latitudinal transect across the boreal forest-tundra biome boundary in northern Quebec province, Canada. This region has experienced rapid warming during both winter and summer months during the last forty years. Using a per-pixel (30 m) trend analysis, 30% of the observable (cloud-free) land area experienced a significant (p < 0.05) positive trend in the Normalized Difference Vegetation Index (NDVI). However, greening trends were not evenly split among cover types. Low shrub and graminoid tundra contributed preferentially to the greening trend, while forested areas were less likely to show significant trends in NDVI. These trends reflect increasing leaf area, rather than an increase in growing season length, because Landsat data were restricted to peak-summer conditions. The average NDVI trend (0.007/yr) corresponds to a leaf-area index (LAI) increase of ~0.6 based on the regional relationship between LAI and NDVI from the Moderate Resolution Spectroradiometer (MODIS). Across the entire transect, the area-averaged LAI increase was ~0.2 during 1986-2010. A higher area-averaged LAI change (~0.3) within the shrub-tundra portion of the transect represents a 20-60% relative increase in LAI during the last two decades. Our Landsat-based analysis subdivides the overall high-latitude greening trend into changes in peak-summer greenness by cover type. Different responses within and among shrub, graminoid, and tree-dominated cover types in this study indicate important fine-scale heterogeneity in vegetation growth. Although our findings are consistent with community shifts in low-biomass vegetation types over multi-decadal time scales, the response in tundra and forest ecosystems to recent warming was not uniform. Other/Unknown Material Tundra NASA Technical Reports Server (NTRS) Canada |
institution |
Open Polar |
collection |
NASA Technical Reports Server (NTRS) |
op_collection_id |
ftnasantrs |
language |
unknown |
topic |
Earth Resources and Remote Sensing |
spellingShingle |
Earth Resources and Remote Sensing Wang, D. Masek, J. G. Nagol, J. Ropars, P. Boudreau, S. Sexton, J. O. Morton, D. C. McManus, K. M. Satellite-Based Evidence for Shrub and Graminoid Tundra Expansion in Northern Quebec from 1986-2010 |
topic_facet |
Earth Resources and Remote Sensing |
description |
Global vegetation models predict rapid poleward migration of tundra and boreal forest vegetation in response to climate warming. Local plot and air-photo studies have documented recent changes in high-latitude vegetation composition and structure, consistent with warming trends. To bridge these two scales of inference, we analyzed a 24-year (1986-2010) Landsat time series in a latitudinal transect across the boreal forest-tundra biome boundary in northern Quebec province, Canada. This region has experienced rapid warming during both winter and summer months during the last forty years. Using a per-pixel (30 m) trend analysis, 30% of the observable (cloud-free) land area experienced a significant (p < 0.05) positive trend in the Normalized Difference Vegetation Index (NDVI). However, greening trends were not evenly split among cover types. Low shrub and graminoid tundra contributed preferentially to the greening trend, while forested areas were less likely to show significant trends in NDVI. These trends reflect increasing leaf area, rather than an increase in growing season length, because Landsat data were restricted to peak-summer conditions. The average NDVI trend (0.007/yr) corresponds to a leaf-area index (LAI) increase of ~0.6 based on the regional relationship between LAI and NDVI from the Moderate Resolution Spectroradiometer (MODIS). Across the entire transect, the area-averaged LAI increase was ~0.2 during 1986-2010. A higher area-averaged LAI change (~0.3) within the shrub-tundra portion of the transect represents a 20-60% relative increase in LAI during the last two decades. Our Landsat-based analysis subdivides the overall high-latitude greening trend into changes in peak-summer greenness by cover type. Different responses within and among shrub, graminoid, and tree-dominated cover types in this study indicate important fine-scale heterogeneity in vegetation growth. Although our findings are consistent with community shifts in low-biomass vegetation types over multi-decadal time scales, the response in tundra and forest ecosystems to recent warming was not uniform. |
format |
Other/Unknown Material |
author |
Wang, D. Masek, J. G. Nagol, J. Ropars, P. Boudreau, S. Sexton, J. O. Morton, D. C. McManus, K. M. |
author_facet |
Wang, D. Masek, J. G. Nagol, J. Ropars, P. Boudreau, S. Sexton, J. O. Morton, D. C. McManus, K. M. |
author_sort |
Wang, D. |
title |
Satellite-Based Evidence for Shrub and Graminoid Tundra Expansion in Northern Quebec from 1986-2010 |
title_short |
Satellite-Based Evidence for Shrub and Graminoid Tundra Expansion in Northern Quebec from 1986-2010 |
title_full |
Satellite-Based Evidence for Shrub and Graminoid Tundra Expansion in Northern Quebec from 1986-2010 |
title_fullStr |
Satellite-Based Evidence for Shrub and Graminoid Tundra Expansion in Northern Quebec from 1986-2010 |
title_full_unstemmed |
Satellite-Based Evidence for Shrub and Graminoid Tundra Expansion in Northern Quebec from 1986-2010 |
title_sort |
satellite-based evidence for shrub and graminoid tundra expansion in northern quebec from 1986-2010 |
publishDate |
2012 |
url |
http://hdl.handle.net/2060/20120010311 |
op_coverage |
Unclassified, Unlimited, Publicly available |
geographic |
Canada |
geographic_facet |
Canada |
genre |
Tundra |
genre_facet |
Tundra |
op_source |
CASI |
op_relation |
Document ID: 20120010311 http://hdl.handle.net/2060/20120010311 |
op_rights |
Copyright, Distribution as joint owner in the copyright |
_version_ |
1766228995211264000 |