Temperature effects on the global patterns of photosynthetic quantum efficiency

SummaryO_LIHistorically, terrestrial biosphere models (TBMs) have assigned the intrinsic (maximum) quantum yield of photosynthesis ({varphi}0) a constant value for each plant functional type. However, experimental studies have shown that {varphi}0- when measured on light-adapted leaves - depends on temperature. It is unclear whether this dependence is universal or biome-specific; how it is manifested at the ecosystem level; and how it should be represented in TBMs. C_LIO_LIBy fitting empirical light-response curves to a global set of eddy-covariance CO2 flux measurements and correcting for photorespiration, we inferred apparent, ecosystem-level {varphi}0values and their temperature responses across a wide range of environments. C_LIO_LIThe temperature response of apparent ecosystem-level {varphi}0 follows a universal bell-shaped curve. The shape of this curve does not markedly differ among biomes, but the maximum value of {varphi}0 decreases with increasing aridity, its temperature optimum increases with increasing growth temperature, and its sensitivity to temperature increases as growth temperature declines. C_LIO_LIOur model for {varphi}0(T) aligns with recent theory highlighting the role of cytochrome b6f in regulating the light reactions of photosynthesis. If implemented in TBMs, this model should allow better predictions of the responses of terrestrial ecosystem function to a warming climate. C_LI