Private, Barbara Beikircher

FS 26.103

Mountain forest regeneration

Session status: Accepted

Content last updated: 2026-04-16 00:06:27

Online available since: 2025-12-16 10:33:17

Details

Full Title
From seeds to sustainable forests - The importance of high-quality seed and plant material for the regeneration of Alpine forests
Scheduled
TBA
TBA
Chair
Gratzer, Georg
Co-chair(s)
Beikircher, Barbara
Thematic Focus
Ecosystems
Keywords
Seeds, Seedlings, Drought, acclimation, afforestation

Abstract/Description

Alpine forests fulfil many important ecological functions. They store carbon and water, provide renewable resources and recreational areas, and are biodiversity hotspots. They also play a vital role in protecting many Alpine regions from natural hazards such as landslides, rockfalls, avalanches and floods. However, Alpine forests are also heavily impacted by climate change. Forest disturbances are becoming both more frequent and intense, and as a result, the areas of forest that need to be regenerated are increasing. Reforestation of these areas will therefore be one of the central challenges for Central European forestry in the coming decades. The mortality rate of young trees is already high, particularly in drier areas, and is expected to rise significantly in future due to reduced soil moisture from snow and an increase in dry periods.

The increasing demand for forest regeneration actions is coinciding with a decline in the quality of seeds and afforestation plant material for important tree species. This poses significant challenges for forest owners, foresters, and other relevant decision-makers. To maintain Alpine forests and their services and functions also in future climates, we must better understand disturbances and following forest regeneration, including the factors impacting temporal variation in tree seed production and seed quality, seed predation and seedling establishment. The potential for acclimatising of seedlings and juvenile plants to changing conditions must be characterised and growing conditions that increase afforestation success must be identified.

This focus session aims to bring together experts in mountain forest ecology, tree seed and plant production, tree ecophysiology and forest regeneration, whereby basic and applied science aspects are equally welcome.

Registered Abstracts

ID: 3.52

Tree seedling recruitment in a 10-year experiment across the alpine treeline ecotone

Melissa Dawes
Risle-Jung, Miriam; Rixen, Christian; Brown, Carissa; Mamet, Steven; Trant, Andrew; Bebi, Peter

Abstract/Description

A better understanding of what conditions promote tree seedling recruitment in the alpine treeline ecotone is essential for predictions about where and how quickly the treeline will advance and which tree species will become dominant. Here, we conducted a multifactorial seed addition and seedbed disturbance (scarification) experiment at the current treeline and in the alpine zone in the Swiss Alps. We quantified the emergence, survival and height growth of seedlings of two high-elevation conifers, Larix decidua and Picea abies, over a 10-year period. Only two seedlings emerged naturally in non-seeded plots during the entire study (both Larix at treeline), pointing to strong recruitment constraints on the series of processes necessary for emergence. In seeded plots, initial emergence was greater at the alpine site (8.0% of viable seeds sown) than at treeline (5.8%), whereas the survival rate of emerged seedlings in subsequent years was higher at treeline (4.1% vs 0.6%). Winter was a survival bottleneck at the treeline and especially the alpine site, with 54% and 94%, respectively, of the initially emerged seedlings dying during the first winter after sowing and 76% of all subsequent mortality occurring outside the growing season. Survival rates were higher and seedlings were taller for Larix than for Picea and no Picea seedlings remained alive beyond 4 years at the alpine site, reflecting the higher distribution limit of Larix in the region. Seedbed scarification led to higher survival rates of both species, suggesting that a single disturbance event can enhance recruitment in this ecotone. Notably, the heights of the few surviving Larix seedlings at the alpine site matched those of the tallest seedlings of this species at the treeline site, highlighting that microsite conditions and ambient temperatures 300+ m above the current treeline support robust growth of this species once it establishes successfully.

ID: 3.109

Growing up in the Mountains: More than a decade of survival and growth monitoring of natural forest regeneration.

Alois Simon
Bischofer, Lisa; Gratzer, Georg; Katzensteiner, Klaus

Abstract/Description

Mixed-species regeneration in mountain forest ecosystems results from the availability of seeds, ecological (micro-) site conditions, the interaction of species traits, and environmental variability over extended time periods. Using long-term monitoring data from a mountain forest in the Northern Calcareous Alps, we analysed survival, recruitment and early growth dynamics of natural regeneration under exclusion of herbivory.

From 2015 to 2025, saplings of Picea abies (n=269), Abies alba (n=406), Fagus sylvatica (n=184) and Pinus sylvestris (n=17) were surveyed annually on two fenced plots, 245 and 233 m² in size. The individual-based assessment allowed for analysis of mortality and interannual growth variability of regeneration up to 14 years old.

Across all species, survival probabilities declined at a remarkably steady rate over time, but clear species- and site-specific differences emerged. With a survival rate of around 80%, Fagus sylvatica consistently showed higher survival rates than coniferous species. By contrast, Picea abies exhibited the strongest decline, with a survival rate of around 60%. Abies alba showed intermediate patterns with a survival rate of around 75% within the first 14 years. Relative growth rates varied substantially between years, indicating a general sensitivity of early growth to environmental variability. While individual drought events, such as the one experienced in 2018, had a notable impact on growth rates, they did not result in a general dieback or substantially increased mortality

The results highlight seedling establishment and sapling mortality as a key process shaping regeneration trajectories in mountain forests. Potential drivers for mortality include density-dependent intraspecific competition, micro-site heterogeneity (forest floor properties, soil moisture, snow cover), episodic events such as late frost or drought, and biotic agents including pathogens. Disentangling the relative importance of and interactions between these drivers requires further long-term monitoring and analyses.

ID: 3.137

The role of disturbance legacies in forest ecosystems restoration

Davide Marangon
Baggio, Tommaso; Meloni, Fabio; Marzano, Raffaella; Lingua, Emanuele

Abstract/Description

Mountain forests are increasingly being affected by stand-replacing disturbances, with several consequences on the provision of fundamental ecosystem services. This can be particularly relevant in complex and densely populated landscapes like those characterizing the Alps. Indeed, when protective forests are involved, forest recovery should be pursued through passive or active restoration strategies, depending on the post-disturbance scenario, but with the aim to maximize the intervention efficacy, to reduce the protection gap and to minimize the costs. To achieve these results, disturbance legacies are precious resources that can foster the recovery process and can thus be exploited to design the most efficient restoration strategy.

Here we describe an innovative approach to estimate the role of disturbance legacies in restoring heavily disturbed forests. We coupled ground-based regeneration data with drone-derived surface roughness as a proxy to assess the disturbance legacies.

Results suggest a positive influence of disturbance legacies on seedling establishment in the short-term, with an increase in regeneration density associated with higher disturbance legacies induced roughness. Model results support the utilization of roughness as a proxy for disturbance legacies after stand replacing disturbance, supporting the high potential of drone derived data at large scale. In addition, distance from living forest edges, post-disturbance treatment and site conditions plays a key role in seedling establishment density in the short-term.

Based on these results, we present some examples of restoration activities currently on-going in the Italian Dolomites where disturbance legacies are being exploited in reforestation projects.

ID: 3.150

Post-fire regeneration in the European Alps: patterns and implications on protective forests

Davide Marangon
Mantero, Giulia; Anselmetto, Nicolò; Berger, Frederic; Kobal, Milan; Krasovskiy, Andrey; Moos, Christine; Mueller, Mortimer; Michaud, Marie-Pierre; Pesenti, Timoté; Teich, Michaela; Vacik, Harald; Garbarino, Matteo; Marzano, Raffella; Lingua, Emanuele

Abstract/Description

Land use and climate change are reshaping natural disturbance regimes globally, with fragile ecosystems, such as the European Alps, being particularly affected. Land abandonment, global warming, and longer dry periods create ideal conditions for larger and more severe wildfires in these areas. These novel disturbance conditions may hinder the protective function of mountain forests for years or decades by removing biomass, changing species composition, and delaying natural regeneration dynamics.

This study investigates ecological drivers and temporal dynamics of post-fire forest regeneration and assesses the potential impact of post-fire recovery dynamics on the protective functions of coniferous and mixed forests across the Alpine region.

We assessed density, species composition, and structure of post-fire forest regeneration, ground cover, and deadwood occurrence across 18 sites across Austria, France, Italy, Slovenia, and Switzerland that had been affected by wildfires up to 25 years prior to the survey. To evaluate key drivers of forest regeneration, we included time since fire (TSF), fire severity, and topo-climatic predictors from global datasets.

Our results confirmed that time since disturbance, topography and climate are the primary factors driving the post-fire regeneration density. After merely 15 years, late seral species started to establish successfully, while early successional species presence began to decline. In addition, seedling density was negatively correlated with distance from forest edge. Overall, our findings suggest that the interplay between species composition, site-specific conditions, and fire severity actually shapes forest regeneration patterns.

As protection forests may experience altered and/or delayed functionality if regeneration fails or shifts toward less resilient compositions, this study offers new insights for land managers and decision makers, emphasizing the importance of targeted restoration planning to sustain protective forest functions in the face of increasing wildfire risks.

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Regional Mountain Conference

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Reg. Mount. Conference

FS 26.103

Mountain forest regeneration

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