Amplified drought induced by climate change reduces seedling emergence and increases seedling mortality for two Mediterranean perennial herbs

Seedling recruitment is a bottleneck for population dynamics and range shift. The vital rates linked to recruitment by seed are impacted by amplified drought induced by climate change. In the Mediterranean region, autumn and winter seedling emergence and mortality may have strong impact on the overall seedling recruitment. However, studies focussing on the temporal dynamic of recruitment during these seasons are rare.
 
This study was performed in a deciduous Mediterranean oak forest located in southern France and quantifies the impact of amplified drought conditions on autumn and winter seedling emergence and seedling mortality rates of two herbaceous plant species with meso-Mediterranean and supra-Mediterranean distribution (respectively, Silene italica and S. nutans). Seedlings were followed from October 2019 to May 2020 in both undisturbed and disturbed plots where the litter and the aboveground biomass has been removed to create open microsites.
 
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幼苗更新（seedling recruitment）是种群动态（population dynamics）与物种分布范围转移（range shift）的关键瓶颈。气候变化加剧引发的极端干旱（amplified drought），会对与种子更新相关的关键生活史速率（vital rates）产生影响。在地中海区域（Mediterranean region），秋、冬两季的幼苗出土（seedling emergence）与幼苗死亡率（seedling mortality），可能对整体幼苗更新量产生显著调控作用。然而，针对该时段幼苗更新的时间动态开展的研究仍较为匮乏。

本研究以法国南部的地中海落叶栎林（deciduous Mediterranean oak forest）为研究样地，量化了极端干旱胁迫对两种分别具有中地中海型、超地中海型分布格局的草本植物——意大利蝇子草（Silene italica）与垂花蝇子草（S. nutans）——秋、冬两季幼苗出土率与幼苗死亡率的影响。研究于2019年10月至2020年5月期间，对两类样地中的幼苗进行了连续监测：一类为未受干扰的对照样地，另一类为通过移除枯落物与地上生物量（aboveground biomass）以构建开放微生境（microsites）的处理样地。

极端干旱胁迫会降低……