Demographic and growth dynamics jointly shape grassland productivity under extreme drought

Using two independent 4-year drought experiments with a 66% reduction in growing season precipitation in a semi-arid grassland, we found that reductions in plant density and individual size jointly contributed to drought-induced declines in aboveground net primary productivity (ANPP), and that their relative importance depends on drought duration, intensity, and plant functional group.

For graminoids, ANPP decline was primarily driven by reduced individual size, whereas for forbs it was driven by reduced plant density. There was a trade-off between the contributions of plant density and individual size to productivity, which was mediated by leaf functional traits, including leaf carbon content and leaf nitrogen. Our findings highlight the role of the trade-off between demographic and growth-related processes in regulating productivity under climate change.