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Abstract:
Global environmental change is rapidly altering the dynamics of terrestrial vegetation, with consequences for the functioning
of the Earth system and provision of ecosystem services1,2.
Yet how global vegetation is responding to the changing
environment is not well established. Here we use three
long-term satellite leaf area index (LAI) records and ten global
ecosystem models to investigate four key drivers of LAI trends
during 1982–2009. We show a persistent and widespread
increase of growing season integrated LAI (greening) over
25% to 50% of the global vegetated area, whereas less
than 4% of the globe shows decreasing LAI (browning).
Factorial simulations with multiple global ecosystem models
suggest that CO2 fertilization eects explain 70% of the
observed greening trend, followed by nitrogen deposition
(9%), climate change (8%) and land cover change (LCC) (4%).
CO2 fertilization eects explain most of the greening trends
in the tropics, whereas climate change resulted in greening of
the high latitudes and the Tibetan Plateau. LCC contributed
most to the regional greening observed in southeast China and
the eastern United States. The regional eects of unexplained
factors suggest that the next generation of ecosystem models
will need to explore the impacts of forest demography,
dierences in regional management intensities for cropland
andpastures,andother emerging productivity constraints such as phosphorus availability.
