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Abstract:
Plant photosynthesis and respiration are the largest carbon fluxes between the terrestrial biosphere and the atmosphere1,
and their parameterizations represent large sources
of uncertainty in projections of land carbon uptake in Earth
system models2,3 (ESMs). The incorporation of temperature
acclimation of photosynthesis and foliar respiration, commonly
observed processes, into ESMs has been proposed as a
way to reduce this uncertainty2. Here we show that, across
15 flux tower sites spanning multiple biomes at various
locations worldwide (10 S–67 N), acclimation parameterizations4,5
improve a model’s ability to reproduce observed
net ecosystem exchange of CO2. This improvement is most
notable in tropical biomes, where photosynthetic acclimation
increased model performance by 36%. The consequences of
acclimation for simulated terrestrial carbon uptake depend
on the process, region and time period evaluated. Globally,
including acclimation has a net eect of increasing carbon
assimilation and storage, an eect that diminishes with time,
but persists well into the future. Our results suggest that land
models omitting foliar temperature acclimation are likely to
overestimate the temperature sensitivity of terrestrial carbon
exchange, thus biasing projections of future carbon storage
and estimates of policy indicators such as the transient climate response to cumulative carbon emissions.
