From seeds to saplings

Details

Full Title
FS 3.141: From seeds to saplings. Challenges and innovations in regenerating mountain forests
Scheduled
Talks:
2025-09-15, 16:00 - 17:30 (LT), MCI – Aula 302
Convener
Georg Gratzer
Co-Conveners
Andreas Rigling,
Assigned to Synthesis Workshop
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Thematic Focus
ES-Forests
Keywords
Mountain forests, tree regeneration ecology, tree seed production, climate-smart assisted migration, mountain forest dynamics

Description

As climate change progresses, not only will temperatures continue to rise, but amount and distribution of precipitation and intensity and frequency of disturbances will also change. Droughts will increase globally, and reduced snow cover in temperate and boreal climates will lead to additional dry spells. Abiotic disturbances create additional needs for forest regeneration, alter biophysical conditions and habitat quality for wild ungulates. In addition, tree seed production patterns are changing and germination capacity of tree seeds is decreasing. This calls for an increased focus on tree seed production, assisted migration with climate-smart species and innovative methods for the regeneration of mountain forests. In semi-arid mountain and Mediterranean regions, natural processes such as nurse-shrub regeneration are becoming increasingly important. Furthermore, the question on which tree species will be able to increase the resilience of mountain forests in a drier future is increasingly pressing. Research on processes and patterns of tree seed production and establishment of tree regeneration are often conducted separately, which may limit the understanding of emergent properties of tree population dynamics. This focus session will therefore link tree seed production and availability with climate-smart assisted migration and innovative tree regeneration methods. It will provide a forum to present advances in regeneration ecology embedded in an understanding of forest dynamics in mountain forests. Emerging research needs will be identified and challenges for securing future mountain forests will be discussed.

Registered Abstracts

ID: 3.9215

Introducing system mapping methods and analytics to overcome seed shortages in mountain forests during the climate crisis: The case of the Austrian Tree Seed System

Martina Perzl

Spittler, Nathalie; Pesendorfer, Mario; Haider, Jamila; Gratzer, Georg

Abstract/Description

The urgent need for forest restoration and tree regeneration in disturbed forests, along with the climate-driven decline in the quantity and quality of tree seeds, has resulted in a critical shortage of seeds, putting unprecedented pressure on tree seed production worldwide. To address these challenges, we recommend examining coupled and co-evolved social-ecological tree seed and seedling systems from multi-actors’ perspectives. The application of systems analysis to study tree seed and seedling systems has primarily focused on Asian, African, and Latin American countries, with less emphasis on the European context. Therefore, our research focused on the Austrian case of tree seed and seedling systems, encompassing seed sources such as seed tree stands and tree seed plantations, where declining germination percentages and crop failures have been observed in recent years. Using two system mapping methods and analytical approaches—a participatory causal loop diagram mapping workshop and a qualitative relational network analysis—our results highlight the importance of defining system elements, their co-evolved relationships and dynamics, identifying systemic challenges, and, most importantly, interventions for sustainable development. We discuss specific challenges for seed production in and for mountain areas. Furthermore, the findings contribute to (1) a more holistic framing of problems for multiple actors (both scientific and non-scientific) and (2) amplifying voices of system actors that are often marginalized or hidden within implicit or tacit knowledge. These insights illuminate the need for and applicability of policies and promote networking and knowledge exchange among the involved system actors to foster sustainable systems’ development.

ID: 3.10779

Strategies for post disturbance forest regeneration in mixed species mountain forests

Klaus Katzensteiner

Gadermaier, Josef; Leyerer, Lisa; Proell, Gisela; Simon, Alois

Abstract/Description

Protection forests in the European Alps are frequently overaged and lack sufficient advanced regeneration. Accelerating disturbance regimes, particularly on steep, sun-exposed slopes with shallow soils, cause challenging conditions for the restoration of forest functions. In the present study we analyse the performance of artificially regenerated trees at four disturbed sites in the mixed spruce-beech-fir vegetation belt of the Northern Calcareous Alps over 14 years. We established the experiment with pioneering and late successional species. We excluded the effect of ungulate herbivory via fencing. Overall, soil and microsite conditions as well as competition/facilitation by grass, shrubs and herbs explain only a minor proportion of the variance of survival time (r²=0.03 to 0,17; Picea abies < Fagus sylvatica < Abies alba <Larix decidua < Pinus sylvestris < Sorbus aucuparia < S. aria < Alnus incana < Acer pseudoplatanus). Biotic and abiotic factors caused severe mortality already in the first year after planting. Delayed planting at a site already covered by ground vegetation leads to overall higher survival compared to immediate planting after disturbance. There is a species-specific substrate effect on survival and growth. After 14 years, average height of the surviving trees is lowest on dolomite (1.1 m) and does not differ significantly between sites on limestone (2.6 to 3.0 m). Larix is partly outgrowing the resources – a prolonged drought period in 2018 caused desiccation of several well growing trees. On the other end Abies alba grows slow. Foliar analyses show severe deficiencies of phosphorus at all sites and of potassium, sulfur, manganese and partly nitrogen at Tyrolian sites with a history of intensive forest grazing. The results confirm the complex interaction of biotic and site factors for the performance of regeneration and the limited possibilities of post disturbance establishment of Fagus in drought prone mixed mountain forests. Natural regeneration of Acer, Popolus, Salix, Sorbus, Ulmus, Fraxinus etc. additionally contribute to canopy cover and species diversity, demonstrating the importance of pioneer species in post-disturbance forest regeneration. This work was co-funded by the European Union (INTERREG Bavaria-Austria Projects SicAlp (J00183), StratAlp (J00316) and WINALP 21 (BA0100020).

ID: 3.11219

Fertilization modified hydraulics and growth of seedlings of three European tree species under drought

Feng Feng

Losso, Adriano; Beikircher, Barbara; Ganthaler, Andrea; Tyree, Melvin; Mayr, Stefan

Abstract/Description

Fertilization is a common practice in forestry nurseries to promote seedling growth and enhance future survival in the field, particularly as climate change-induced droughts increasingly threaten forest ecosystems. However, the interplay between nutrient availability and drought stress on hydraulics and growth of young trees is not well understood. We investigated the combined effects of fertilization and drought on seedlings of three European tree species (Pinus sylvestris, Fagus sylvatica, and Quercus robur) focusing on hydraulic traits, gas exchange, and growth. Our findings revealed that fertilized seedlings exhibited reduced water transport capacity (specific stem conductivity, root conductance), lower stomatal conductance and net photosynthesis, and stunted growth, especially under severe drought, with species-specific variation. Stem embolism resistance and leaf drought tolerance remained unchanged. However, in fertilized P. sylvestris and F. sylvatica, low root biomass combined with reduced water transport capacity is likely to have impaired survival under severe drought, leading to 30–40% mortality. In contrast, fertilized Q. robur demonstrated higher drought resilience and no mortality, possibly due to greater water-use efficiency. These results highlight species-specific risks associated with fertilization under drought, posing potential threats to F. sylvatica and P. sylvestris, while potentially benefiting Q. robur. Our study highlights the importance of tailored fertilization strategies for sustainable forest management in the face of climate change.

ID: 3.11883

Seed(ing the) data of tomorrow – but how? A closer look at seed monitoring methods

Iris Oberklammer

Pesendorfer, Mario; Gratzer, Georg

Abstract/Description

The intermittent availability of certain tree seeds has preoccupied people for thousands of years, yet we lack a comprehensive overview of available seed monitoring methods. Currently, these methods are scattered in the literature, making it a challenge to get an overview of their advantages and shortcomings, as each method has different characteristics that need to be considered before setting up long-term monitoring.
The interest in seed monitoring is currently reinforced by policy, tree species shift, increasing awareness of the links between seed production and public health, and the demand for seed and recruitment data needed to model the impact of the climate crisis on forest dynamics.
Our aim here is to inform people potentially interested in seed monitoring about different options and their specific applicability in mountain forests. We present a variety of commonly used seed monitoring methods, as well as some niche and possible future ones, and discuss their characteristics with a focus on mountain areas. Understanding different monitoring methods is fundamental for asking the right question (if you have data) and for choosing the right method to answer a specific question (if you do not yet have data). For closing the loop, we offer inspiration for moving beyond seed monitoring to full life cycle monitoring and discuss ways to link seed data to other long-term ecological data.