Timing of extreme drought modifies reproductive output in semi-natural grassland

摘要: Questions Do extreme dry spells in late summer or spring affect abundance and species composition of the reproductive shoots seed rain next annual crop? Are drought effects on related to rooting depths species? Location Species-rich semi-natural grassland at Negrentino, Switzerland. Methods In plots under automated rain-out shelters, rainwater was added simulate normal conditions compare them with two experimentally effected long spells, (2004) following (2005). For 28 plots, numbers per were counted 1-m2 areas estimated using nine sticky traps 102 cm2 after spells. Results The similar length their probability recurrence. They independently reduced subsequent output community, while seasonal timing modified its composition. Compared spring, soil moisture more number species. The negative decreased species’ depth. shallow-rooted graminoids showed a consistent susceptibility drought, legumes other forbs varied responses both droughts. Spring strongly density (–53%) richness (–43%) community rain, had only marginally significant impact (–44%). Reductions shoot vs distinguished impacts respect timing. Conclusion The essentially different seasons suggests that frequent could contribute local plant diversity loss by aggravating deficiency species-rich grassland.