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.   Amplified
drought conditions reduced seedling emergence and increased seedling
mortality for both Silene species but these negative effects were
dependent on soil disturbance conditions. Emergence of S. italica
decreased only in undisturbed plots (-7%) whereas emergence of S. nutans
decreased only in disturbed plots (-10%) under amplified drought
conditions. The seedling mortality rate of S. italica was 51% higher under
amplified drought conditions in undisturbed plots while that of S. nutans
was 38% higher in disturbed plots.   Aridification due to lower
precipitation in the Mediterranean region will negatively impact the
seedling recruitment of these two Silene species. Climate change
effects on early vital rates may likely have major negative impacts on the
overall population dynamic.