Are regional precipitation-productivity relationships robust to decadal-scale dry period?

Precipitation (PPT) is the primary climatic determinant of plant growth and aboveground net primary productivity (ANPP) for many of the world's major terrestrial ecosystems. Thus, relationships between PPT and productivity can provide insight into how changes in climate may alter ecosystem functions globally. Spatial PPT-ANPP relationships for grasslands are found remarkably similar around the world, but whether and how they change during periods of extended climatic anomalies remain unknown. Here, we quantified how regional-scale PPT-ANPP relationships vary between an extended wet and a dry period by taking advantage of a 35-year record of PPT and NDVI (as a surrogate for ANPP) at 1700 sites in the temperate grasslands of northern China. We found a sharp decrease in the strength of the spatial PPT-ANPP relationship during an 11-year period of below average PPT. We attributed the collapse of this relationship to asynchrony in the responses of different grassland types to this decadal period of increased aridity. Our results challenge the robustness of regional PPT-productivity if aridity in grasslands is increased globally by climate change.