The increasing intensity and frequency of droughts predicted for the Mediterranean basin with ongoing climate change will impact plant communities and ecosystem functioning. This study investigated the effect of severe recurrent droughts and the role of the neighbor plant identity on the growth and survival of three abundant and co-existing species of a typical Mediterranean shrubland. Two juvenile plants, either of the same species or in all possible combinations of the two woody species Quercus coccifera and Cistus albidus and the perennial grass species Brachypodium retusum were grown together in rhizotrons under controlled watering regimes for two years. Compared to a treatment with only one drought cycle, three successive droughts reduced the relative growth rates (RGR) of shoots and roots in B. retusum, but not in woody species, and increased the mortality of the woody species, but not that of the grass. The survival of C. albidus and of B. retusum, but not of Q. coccifera, increased when the neighbor individual was a different species than when it was the same species. Our data suggest that both species composition and frequency of drought events will impact the dynamics of plant communities in Mediterranean shrublands under ongoing climate change. The abundance of dehydration sensitive woody species will likely decrease under more frequent drought events at the expense of dehydration-tolerant grass species, resulting in potentially strong changes in the functioning of these ecosystems.

预计随着气候变化的持续不断，地中海盆地干旱的强度和频率将增加，将影响植物群落和生态系统的功能。这项研究调查了严重的反复干旱的影响以及邻近植物身份对典型地中海灌木丛中三种丰富并存物种的生长和存活的作用。两种幼小植物，它们是相同的物种，或者是两种木本物种的球茅栎和长毛水仙的所有可能组合，以及多年生草种短枝曲霉在控制浇水的条件下，在根茎中一起生长了两年。与仅具有一个干旱周期的处理相比，连续三个干旱降低了斑节芽孢杆菌（B. retusum）而不是木本物种的芽和根的相对生长速率（RGR），并且增加了木本物种的死亡率，但没有增加草。C. albidus和B. retusum的生存，但Q. coccifera的生存，当邻居个体是不同物种时比同种物种时增加。我们的数据表明，在持续的气候变化下，物种组成和干旱事件的频率都会影响地中海灌木丛植物群落的动态。在更频繁的干旱事件下，对脱水敏感的木本物种的丰度可能会降低，但会以耐脱水的草木种为代价，从而导致这些生态系统功能的潜在强大变化。