Debating the greening vs. browning of the North American boreal forest: differences between satellite datasets

A number of remote sensing studies have evaluated the temporal trends of the normalized difference vegetation index (NDVI or vegetation greenness) in the North American boreal forest during the last two decades, often getting quite different results. To examine the effect that the use of different d...

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Vydáno v:	Global change biology Ročník 16; číslo 2; s. 760 - 770
Hlavní autoři:	ALCARAZ-SEGURA, DOMINGO, CHUVIECO, EMILIO, EPSTEIN, HOWARD E, KASISCHKE, ERIC S, TRISHCHENKO, ALEXANDER
Médium:	Journal Article
Jazyk:	angličtina
Vydáno:	Oxford, UK Oxford, UK : Blackwell Publishing Ltd 01.02.2010 Blackwell Publishing Ltd Wiley-Blackwell
Témata:	AVHRR Biological and medical sciences boreal forest Boreal forests burned areas Canada Carbon Carbon sequestration data collection fire severity Forest and land fires forest fires Forestry Forests Fundamental and applied biological sciences. Psychology General forest ecology Generalities. Production, biomass. Quality of wood and forest products. General forest ecology GIMMS heteroskedasticity inventories monitoring NDVI trends net ecosystem exchange normalized difference vegetation index Phytopathology. Animal pests. Plant and forest protection Remote sensing satellites seasonal Mann-Kendall trend test Seasonal variations variance Vegetation Weather damages. Fires Canada North America America Burned ground Boreal forest Vegetation index burned areas seasonal Mann-Kendall trend test Satellite observation Satellite AVHRR Canada forest fires Seasonal variation Vegetation fire Forest fire GIMMS NDVI trends
ISSN:	1354-1013, 1365-2486
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Shrnutí:	A number of remote sensing studies have evaluated the temporal trends of the normalized difference vegetation index (NDVI or vegetation greenness) in the North American boreal forest during the last two decades, often getting quite different results. To examine the effect that the use of different datasets might be having on the estimated trends, we compared the temporal trends of recently burned and unburned sites of boreal forest in central Canada calculated from two datasets: the Global Inventory, Monitoring, and Modeling Studies (GIMMS), which is the most commonly used 8 km dataset, and a new 1 km dataset developed by the Canadian Centre for Remote Sensing (CCRS). We compared the NDVI trends of both datasets along a fire severity gradient in order to evaluate the variance in regeneration rates. Temporal trends were calculated using the seasonal Mann-Kendall trend test, a rank-based, nonparametric test, which is robust against seasonality, nonnormality, heteroscedasticity, missing values, and serial dependence. The results showed contrasting NDVI trends between the CCRS and the GIMMS datasets. The CCRS dataset showed NDVI increases in all recently burned sites and in 50% of the unburned sites. Surprisingly, the GIMMS dataset did not capture the NDVI recovery in most burned sites and even showed NDVI declines in some burned sites one decade after fire. Between 50% and 75% of GIMMS pixels showed NDVI decreases in the unburned forest compared with <1% of CCRS pixels. Being the most broadly used dataset for monitoring ecosystem and carbon balance changes, the bias towards negative trends in the GIMMS dataset in the North American boreal forest has broad implications for the evaluation of vegetation and carbon dynamics in this region and globally.
Bibliografie:	http://dx.doi.org/10.1111/j.1365-2486.2009.01956.x istex:10C0C2A2FE9F6B15B49F11A35AE5E8D5428E8055 ArticleID:GCB1956 ark:/67375/WNG-QCLKGK63-S SourceType-Scholarly Journals-1 ObjectType-Feature-1 content type line 14 ObjectType-Article-1 ObjectType-Feature-2 content type line 23 ObjectType-Article-2
ISSN:	1354-1013 1365-2486
DOI:	10.1111/j.1365-2486.2009.01956.x