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Abstract

The terrestrial carbon cycle is not well quantified1. Biomass turnover time is a crucial parameter in the global carbon
cycle2–4, and contributes to the feedback between the terrestrial
carbon cycle and climate2–7. Biomass turnover time
varies substantially in time and space, but its determinants
are not well known8,9, making predictions of future global
carbon cycle dynamics uncertain5,10–13. Land use—the sum
of activities that aim at enhancing terrestrial ecosystem
services14—alters plant growth15 and reduces biomass stocks16,
and is hence expected to aect biomass turnover. Here we
explore land-use-induced alterations of biomass turnover at
the global scale by comparing the biomass turnover of the
actual vegetation with that of a hypothetical vegetation state
with no land use under current climate conditions. We find
that, in the global average, biomass turnover is 1.9 times faster
with land use. This acceleration aects all biomes roughly
equally, but with large dierences between land-use types.
Land conversion, for example fromforests to agricultural fields,
is responsible for59%of the acceleration; the use of forestsand
natural grazing land accounts for 26% and 15% respectively.
Reductions in biomass stocks are partly compensated by
reductions in net primary productivity. We conclude that land
use significantly and systematically aects the fundamental
trade-off between carbon turnover and carbon stocks.