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Dryad

Data from: Increasing temperature threatens post-fire auto-successional dynamics of a Mediterranean obligate seeder

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Oct 03, 2024 version files 8.29 MB

Abstract

Reproductive traits influence plant auto-successional dynamics in post-fire regeneration. Obligate seeding species rely on their seedbank and on climatic conditions following the fire to ensure a successful recovery, defining the window of opportunity for seedling emergence. In the Mediterranean basin, emergence opportunities generally begin with autumnal rains. However, climate-change induced increases in temperature and drought could jeopardise the regeneration ability of seeding species by causing temporal shifts in emergence opportunities or by modifying wildfire seasonality. 
This study aims to explore the impact of experimentally induced climate-change on post-fire regeneration dynamics of Aleppo pine (Pinus halepensis), a serotinous Mediterranean obligate seeder. 
In March 2021, we set up an 18-month climate-change simulation experiment with 15 Open Top Chambers (OTC), each paired with a control subplot (CON) on top of Aleppo pines naturally regenerating after a stand-replacing wildfire in SW Catalonia (June 2019). We tagged 178 young Aleppo pine recruits in OTC and CON subplots (98 and 81 respectively), classified according to their initial size, to periodically measure height growth and survival throughout the experiment duration. Furthermore, Aleppo pine seeds were seasonally sown (7900 total seeds) in 10 subplot pairs between May 2021 and April 2022, to monthly monitor temporal patterns of seedling emergence and survival. 
We found that OTCs reduced overall emerging rates and caused the loss of the autumnal window of opportunity for emergence of Aleppo pine seedlings. Furthermore, seedlings emerged inside OTCs faced higher mortality rates in all seasons, with just 1% of surviving seedlings against the 21.1% of CON seedlings. OTC-induced conditions were detrimental also for the survival of recruited seedling, especially for those with smaller initial size, although no significant effects of temperature increase were found on growth. 
Synthesis: Climate change is likely to interfere with post-fire regeneration dynamics of obligate seeders by shortening the temporal window of opportunities for emergence and by enhancing the bottleneck effects throughout the recruitment process in the early phases of pine demographic recovery. Altogether, it could threaten post-fire regeneration by increasing the hazard of a demographic collapse of Aleppo pine.