Greening Hiatus in Eurasian Boreal Forests Since 1997 Caused by a Wetting and Cooling Summer Climate. Issue 9 (31st August 2020)

• Record Type: Journal Article
• Authors: Gao, Xueyuan; Liang, Shunlin; Sauer, Jeffery
• Is Part Of: Journal of geophysical research. Volume 125:Issue 9(2020)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2020-08-31
• Subjects: Eurasian boreal forest -- greening -- vegetation productivity -- climate change -- growing season -- remote sensing; Geobiology -- Periodicals; Biogeochemistry -- Periodicals; Biotic communities -- Periodicals; Geophysics -- Periodicals; 577.14
• DOI: 10.1029/2020JG005662
• Languages: English
• ISSNs: 2169-8953

Abstract

Abstract: The Eurasian boreal forest ecosystem is a strong sink in the global carbon cycle. Satellite observations show significant change in the ecosystem in recent decades, specifically an increase in vegetation productivity since 1982 and a hiatus after 1997. Previous studies attributed this enhanced vegetation growth (also known as greening) to air temperature increases and a longer growing season, and the recent greening hiatus as a result of a warmer and drier climate. However, using satellite data, we found observational evidence that increases in summer peak growth dominated the overall greening trend and that a wetting and cooling climate during the peak growing season was the primary cause of the hiatus. Plain Language Summary: Increases in vegetation growth or productivity is referred to as "greening." Scientists have found that the vegetation growth or productivity in Eurasian boreal forests increased from 1982. However, in 1997 that greening stagnated. Previous studies suggested that increases in air temperature prolonged the growing season, which may have been the driving force of the greening. Additionally, previous studies pointed to enhanced drought stress by warmer and drier summers as the reason for the greening hiatus. However, in revisiting this hypothesis we found evidence of an alternative explanation. First, we found that increases in summer peak growth, rather than a longer growing season, dominated the overall greening trends. Second, we found that wetting and cooling summer climates instigated the hiatus. Our findings suggest a more complex mechanism behind the shift in climate and vegetation growth in Eurasian boreal forests around 1997. This mechanism deserves further study. Key Points: Eurasian boreal forests experienced a greening trend from 1982 before stagnating in 1997 Increases in summer peak growth, rather than prolongation of the growing season, dominated greening trends in earlier decades A wetter and cooler, rather than a warmer and drier summer climate, was the primary cause of the recent greening hiatus