Summary
The quantum yield (α) of photosynthesis represents the maximum efficiency of light use as indicated by the initial slope of photosynthetic light response curves. Understanding α is crucial for accurate modeling of photosynthesis and terrestrial carbon cycle. Despite its importance, the spatial and temporal variations in α at large scales remain largely elusive.
We leveraged long-term eddy-covariance observations from 90 sites globally and examined the spatiotemporal variations in α due to climatic drivers, using statistical and machine learning approaches.
We found significant spatial variability in α across and within biomes, primarily driven by atmospheric vapor pressure deficit and soil moisture variations. Meanwhile, the temporal changes in α are mainly driven by the negative effect of vapor pressure deficit, which weakens the positive effects of elevated CO2 and leaf area index.
Our results highlight the dominant role of vapor pressure deficit in controlling the spatiotemporal variations of α as well as the unneglectable impacts of soil water content, CO2, and leaf area on α. Those new results provide insights for improving the representation of α in ecosystem photosynthesis models.
Competing Interest Statement
The authors have declared no competing interest.