Risk of short?term biodiversity loss under more persistent precipitation regimes

Recent findings indicate that atmospheric warming increases the persistence of weather patterns in mid-latitudes, resulting sequences longer dry and wet periods compared to historic averages. The alternation progressively extremes could increasingly select for species with a broad environmental tolerance. As consequence, biodiversity may decline. Here we explore relationship between summer precipitation regimes plant diversity by subjecting experimental grassland mesocosms gradient dry–wet frequencies whilst keeping total constant. varied duration consecutive periods, from 1 up 60 days or without precipitation, over 120 days. An spells led severe loss richness (up –75% relative current rainfall pattern W-Europe) functional (enhanced dominance grasses nitrogen (N)-fixers non-N-fixing forbs). Loss N-fixers forbs treatments was linked lower baseline competitive success higher physiological sensitivity changes soil moisture grasses. extent losses also strongly depended on timing periods. Regimes which long droughts (?20 days) coincided above-average temperatures showed significantly more stress period, greater mortality, impoverished communities end season. Across all regimes, longest period below permanent wilting point an accurate predictor mortality across communities, indicating persistent reduce opportunities drought alleviation. We conclude recruitment, precluded this experiment, will likely diminish diversity, at least short term.