CREAF/Unitat d'Ecologia, Department Biologia Animal, Biologia Vegetal i Ecologia, Universitat Autònoma de Barcelona, Bellaterra, Barcelona, Spain.
Plant Biol (Stuttg). 2012 May;14(3):458-66. doi: 10.1111/j.1438-8677.2011.00523.x. Epub 2011 Dec 2.
Extreme climate events, such as severe drought episodes, may induce changes in vegetation if they induce species-specific adult mortality and changes in the seedling recruitment pattern. In 2005 a severe drought occurred in Doñana National Park (south Spain) causing extensive shrubland mortality. Over the following years we monitored the soil seed bank and seedling emergence via a gradient of canopy dieback induced by the drought episode. The canopy dieback corresponded to an increase in emergence of seedlings of woody species in 2007, probably because of the reduced competition induced by canopy loss. The soil seed bank of woody species sampled in 2008 was less abundant on plots with a higher proportion of dead vegetation, probably because of depletion of the seed bank as a result of the increased germination in the previous year and also as a result of a reduction in seed supply in these sites. Accordingly, in 2009 we detected reduced emergence of woody species on plots that had suffered the greatest shrub mortality. We failed to find any significant changes in patterns of the soil seed bank and seedling emergence of short-lived herbaceous species, indicating greater resilience in these types of species. This study highlights the resilience of Mediterranean shrublands to climate fluctuations at one extreme of the variability characteristic of these ecosystems. An increase in the frequency of severe drought episodes - increasingly probable under the new climate conditions - does have the potential, however, to induce changes in vegetation, especially in woody communities that need more time to replenish their seed banks.
极端气候事件，如严重的干旱期，如果导致特定物种的成年个体死亡和幼苗补充模式的变化，可能会对植被产生影响。2005 年，多尼亚纳国家公园（西班牙南部）发生了严重的干旱，导致大面积灌木死亡。在接下来的几年里，我们通过监测由干旱事件引起的树冠凋萎梯度，来监测土壤种子库和幼苗萌发。树冠凋萎与 2007 年木本物种幼苗萌发的增加相对应，这可能是由于树冠损失导致的竞争减少所致。2008 年在具有更高死亡植被比例的样地中，采样的木本物种的土壤种子库较少，这可能是由于前一年种子库因过度萌发而枯竭，以及这些地点的种子供应减少所致。因此，2009 年我们在遭受最大灌木死亡率的样地上发现木本物种的萌发减少。我们没有发现短命草本物种的土壤种子库和幼苗萌发模式有任何显著变化，这表明这些物种具有更强的恢复力。这项研究强调了地中海灌木林对这些生态系统特征变异性极端之一的气候波动的恢复力。然而，严重干旱事件的频率增加（在新的气候条件下越来越有可能）确实有可能导致植被发生变化，特别是在需要更多时间来补充种子库的木本社区。
