Reduced global plant respiration due to the acclimation of leaf dark respiration coupled with photosynthesis

Leaf dark respiration (R-d) acclimates to environmental changes. However, the magnitude, controls and time scales of acclimation remain unclear and are inconsistently treated in ecosystem models.We hypothesized that R-d and Rubisco carboxylation capacity (V-cmax) at 25 degrees C (R-d,R-25, V-cmax,V-25) are coordinated so that R-d,R-25 variations support V-cmax,V-25 at a level allowing full light use, with V-cmax,V-25 reflecting daytime conditions (for photosynthesis), and R-d,R-25/V-cmax,V-25 reflecting night-time conditions (for starch degradation and sucrose export). We tested this hypothesis temporally using a 5-yr warming experiment, and spatially using an extensive field-measurement data set. We compared the results to three published alternatives: R-d,R-25 declines linearly with daily average prior temperature; R-d at average prior night temperatures tends towards a constant value; and R-d,R-25/V-cmax,V-25 is constant.Our hypothesis accounted for more variation in observed R-d,R-25 over time (R-2 = 0.74) and space (R-2 = 0.68) than the alternatives. Night-time temperature dominated the seasonal time-course of R-d, with an apparent response time scale of c. 2 wk. V-cmax dominated the spatial patterns.Our acclimation hypothesis results in a smaller increase in global R-d in response to rising CO2 and warming than is projected by the two of three alternative hypotheses, and by current models.