Changes in satellite‐derived vegetation growth trend in temperate and boreal Eurasia from 1982 to 2006

Abstract

Monitoring changes in vegetation growth has been the subject of considerable research during the past several decades, because of the important role of vegetation in regulating the terrestrial carbon cycle and the climate system. In this study, we combined datasets of satellite-derived Normalized Difference Vegetation Index (NDVI) and climatic factors to analyze spatio-temporal patterns of changes in vegetation growth and their linkage with changes in temperature and precipitation in temperate and boreal regions of Eurasia (423.51N) from 1982 to 2006. At the continental scale, although a statistically significant positive trend of average growing season NDVI is observed (0.5 Â 10 À3 year À1 , P 5 0.03) during the entire study period, there are two distinct periods with opposite trends in growing season NDVI. Growing season NDVI has first significantly increased from 1982 to 1997 (1.8 Â 10 À3 year À1 , Po0.001), and then decreased from 1997 to 2006 (À1.3 Â 10 À3 year À1 , P 5 0.055). This reversal in the growing season NDVI trends over Eurasia are largely contributed by spring and summer NDVI changes. Both spring and summer NDVI significantly increased from 1982 to 1997 (2.1 Â 10 À3 year À1 , P 5 0.01; 1.6 Â 10 À3 year À1 Po0.001, respectively), but then decreased from 1997 to 2006, particularly summer NDVI which may be related to the remarkable decrease in summer precipitation (À2.7 mm yr À1 , P 5 0.009). Further spatial analyses supports the idea that the vegetation greening trend in spring and summer that occurred during the earlier study period 1982-1997 was either stalled or reversed during the following study period 1997-2006. But the turning point of vegetation NDVI is found to vary across different regions.

Temperature and Snow-Mediated Moisture Controls of Summer Photosynthetic Activity in Northern Terrestrial Ecosystems between 1982 and 2011

“…Most of the Eurasian boreal forests and Arctic regions have greened, whereas in North America only the Arctic region underlain by continuous permafrost north of the treeline has greened and most of the boreal forests have undergone browning trends. Although these contrasting continental and biome trends have been documented in earlier analyses of the GIMMS NDVI record [9,[15][16][17]19,22], our empirical results highlight the significant role of factors other than temperature and moisture on these vegetation patterns. A similar regional heterogeneity in the drivers of the greening trends in northern ecosystems has been found in attribution studies based on ecosystem models [85].…”

“…The analysis of the global satellite record of Normalized Difference Vegetation Index (NDVI) imagery since 1981 (e.g., [14]) has shown that increases in vegetation photosynthetic activity have been stronger in Eurasia than in North America and more sustained in the colder tundra biome than over the boreal forests [15][16][17][18][19]. The most recent studies have found that after the initial increasing trend in NDVI (i.e., greening) observed in the first decade of the record [5,20], longer and hotter growing seasons appear to have resulted in reductions of summer NDVI (i.e., browning) in the drier and more continental regions of the boreal forest since the 1990s [15][16][17]21].…”

“…The most recent studies have found that after the initial increasing trend in NDVI (i.e., greening) observed in the first decade of the record [5,20], longer and hotter growing seasons appear to have resulted in reductions of summer NDVI (i.e., browning) in the drier and more continental regions of the boreal forest since the 1990s [15][16][17]21]. The most extensive vegetation browning has occurred in the North American boreal forests in Canada and Alaska [22].…”

Modelling Tundra Vegetation Response to Recent Arctic Warming

“…This period is the same as that covered by recent studies documenting productivity and biomass changes in Arctic environments as derived from satellite measurements, for example, Bhatt et al (2010), Beck andGoetz (2011), Goetz et al (2011) and Piao et al (2011). It also encompasses the 1990-2006 period studied by McGuire et al (2012) for the purposes of constraining a carbon balance for the Arctic.…”

The Greenness of Major Shrublands in China Increased from 2001 to 2013

“…The monthly EVI, temperature, and precipitation maps were spatially averaged over the six shrubland types and then averaged seasonally and growing seasonally to obtain the times series of the EVI and the climate variables. Our study focused on the growing season (from April to October), which can be divided into three seasons: spring (April and May), summer (June, July and August) and fall (September and October) [50,52]. To explore the effects of winter climate change on the starting days of the growing season, we defined winter as November of the prior year to March of the following year [53].…”