Insights into post-fire establishment of three Alpine conifer species after an experimental fire in Tyrol, Austria

TL;DR

This study examines how three Alpine conifer species establish seedlings after a controlled fire in Tyrol, Austria, showing that timing and species traits affect post-fire regeneration.

Contribution

The study provides the first insights into post-fire seedling establishment of Alpine conifers and highlights the role of sowing timing and species traits.

Findings

Fire-exposed seeds of Pinus cembra had significantly reduced germination and establishment in the field.

Pinus cembra established best when sown immediately after the fire, while Picea abies and Larix decidua required improved soil conditions.

Small-seeded species showed limited establishment after the fire, emphasizing the importance of seed size and reserves.

Abstract

Successful post-fire seedling establishment is critical for restoring the protective function of mountain forests, determining long-term forest regeneration dynamics. However, seedling establishment is a vulnerable phase, and little is known about post-fire dynamics and survival performance of Alpine species. In June 2024, an experimental fire was conducted to assess how fire exposure of seeds and the time of sowing under post-fire conditions influence seedling establishment of three conifer species in Tyrol, Austria. Before the fire, seeds of Pinus cembra, Picea abies, and Larix decidua were sown to assess germination and establishment following fire exposure. After the fire, new seeds of the same species were sown at 10-day intervals over six weeks in the burned and control plots. Next, seedling establishment was monitored, and seedling biomass was determined at the end of September. Air and soil temperatures, as well as edaphic factors, were also monitored during the fire and until the end of September. Under controlled laboratory conditions, fire exposure reduced germination of P. cembra by 35.5%, whereas P. abies and L. decidua were only slightly negatively affected (< 20% reduction). In the burned field, however, only 15.3% of fire-exposed P. cembra seeds established seedlings, while no seedlings of L. decidua or P. abies emerged. P. cembra seeds sown immediately after the fire established up to 29.3% (control: 52.0%), whilst P. abies and L. decidua established only when sown one month after the fire, when soil conditions had improved. P. abies reached a maximum establishment of 14.0% and L. decidua of 4.7% (control: 23.3 and 7.3%, respectively). After the experimental fire, establishment of the small-seeded species was limited. P. cembra, which forms large seeds with ample reserves, established the best from seeds sown directly after the fire. This study provides the first insight into seedling establishment of Alpine conifers and highlights the importance of species selection and sowing timing for post-fire regeneration in mountain forests.

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