Drought intensity and duration interact to magnify losses in primary productivity

Terrestrial ecosystem productivity losses are expected to magnify over
time with increased drought duration, a likely future scenario. Yet, some
ecosystems appear resistant to progressive losses in productivity with
multi-year drought. We quantified the combined effects of drought duration
and severity on aboveground productivity in 74 grasslands and shrublands.
Productivity declined 29% when drought severity was within the range of
historic variability, with little evidence for progressive loss over time.
Resistance was lost when drought severity was extreme (≤ 1-in-100-year
likelihood). When extreme drought occurred over consecutive years,
productivity losses increased 3-fold. Our results portend a shift in
ecosystem behavior under future drought scenarios – from maintenance of
reduced functioning over time to progressive and profound loss of
functioning as drought duration and severity increase.