Nutrient addition increases grassland resistance during dry and wet climate extremes despite functional diversity loss

Abstract

SummaryEutrophication impacts plant diversity such as species richness, functional trait diversity and composition of grassland communities globally, but whether and how these changes affect the functional stability of grasslands under increasing climate extremes is unknown.We quantify the direct and diversity-mediated effects of nutrient addition on functional stability as measured by resistance during and resilience after dry and wet growing seasons, and temporal invariability of community productivity across 19 grasslands spanning four continents.We found that nutrient addition increased resistance during dry and wet growing seasons, although the increased resistance during wet growing seasons was partly offset by the indirect negative effects of nutrient addition promoting fast-growing communities and reducing ‘slow-fast’ functional diversity. Nutrient addition had, however, weak net effects on resilience and invariability.Thus, eutrophication strongly impacts plant diversity, but diversity-mediated indirect effects may be weaker on stability.