Conservation of forest genetic resources with seed practicum: Podcast 11
Eleventh episode: Seed and Forest Reproductive Material Data for Selected Tree Species
Voice: Camilla Stefanelli
Written by: OpenAI. (2024). ChatGPT 4 (9. August). https://chat.openai.com/
Preparation of requirements for ChatGPT 4 by: Boris Rantaša and Hojka Kraigher
Preparation of drafts: Hojka Kraigher
Postproduction: Camilla Stefanelli, Hojka Kraigher, Donatella Paffetti, Patrizia Rossi, Cristina Vettori
Introduction
Welcome to the eleventh episode of our podcast series, where we delve into the intricacies of forest management and conservation. Today, we will focus on forest reproductive material (FRM) data for several important European tree species: European Beech (Fagus sylvatica L.), Pedunculate Oak (Quercus robur L.), Sessile Oak (Quercus petraea Liebl.), European Ash (Fraxinus excelsior L.), Norway Maple (Acer platanoides L.), Sycamore (Acer pseudoplatanus L.), Black Alder (Alnus glutinosa (L.) Gaertn.), and Wild Cherry (Prunus avium L.). Understanding the reproductive biology, seed handling, and storage techniques for these species is essential for ensuring the successful regeneration and long-term sustainability of our forests.
European Beech (Fagus sylvatica L.)
Beech is a cornerstone species in many European forests, valued for its high-quality timber and ecological importance. The reproductive cycle of Beech is characterised by infrequent but prolific seed production events known as mast years, which typically occur every 5 to 10 years.
Flowering and Seed Production
Beech trees begin to flower between the ages of 40 and 60. The flowering occurs in early spring, with both male and female flowers present on the same tree. These flowers are wind-pollinated, and successful pollination leads to the production of seeds, commonly referred to as beech nuts or acorns. Mast years, which are characterised by abundant seed production, are crucial opportunities for seed collection.
Harvesting and Processing of Beech Acorns
The collection of beech acorns usually takes place in autumn, after they have fallen naturally to the forest floor. Once harvested, the acorns are cleaned to remove debris and non-viable seeds, which is typically done through a flotation method—viable seeds sink while non-viable seeds float. After cleaning, the seeds are dried to a specific moisture content to prepare them for storage or immediate sowing.
Storage of Acorns, Dormancy Breaking, and Germination
Beech seeds exhibit dormancy, which must be broken before germination can occur. The acorns are stored in cool, moist conditions, such as in sand or peat, to maintain their viability. Cold stratification, which involves exposing the seeds to low temperatures for an extended period, is often used to break dormancy. After stratification, the seeds are ready for sowing, where they can germinate and grow into seedlings.
Pedunculate Oak (Quercus robur L.) and Sessile Oak (Quercus petraea Liebl.)
Oaks are iconic species in European forests, known for their durability and long lifespan. Both Pedunculate Oak and Sessile Oak are vital for timber production and biodiversity.
Flowering and Seed Production
Oaks generally begin to flower at around 40 years of age. The flowering period occurs in late spring, with separate male and female flowers on the same tree. Like Beech, Oaks are also mast-seeding species, with substantial seed production every 5 to 8 years. The seeds, known as acorns, are crucial for natural regeneration and reforestation projects.
Harvesting and Processing of Acorns
Acorn harvesting occurs in autumn, following their natural drop. Acorns are typically collected from the ground or by shaking the trees. Post-harvest, acorns are cleaned and sorted to remove any damaged or non-viable seeds, ensuring only the healthiest acorns are stored or planted. To prevent development of black rot and mumification (Ciboria batschiana (Zopf) Buchwald) they are often submitted to thermotherapy (at around 41-48oC for 5 hours).
Storage, Dormancy Breaking, and Germination
Acorns require careful storage in cool, moist conditions to retain viability. Unlike some other species, acorns do not require extensive dormancy-breaking treatments but must be kept just around freezing to prevent premature germination. Once conditions are suitable, acorns are sown directly in well-drained soil to encourage germination.
European Ash (Fraxinus excelsior L.)
European Ash is widely distributed across Europe and is valued for its strong, flexible wood. However, it faces significant challenges due to ash dieback, a disease that threatens its populations.
Flowering and Seed Production
European Ash begins flowering at around 30 years of age, with flowers appearing in early spring before the leaves. The species is dioecious, meaning individual trees may produce only male or only female flowers, though some trees are hermaphroditic. Seed production can vary greatly from year to year, with some years yielding a significant number of seeds.
Harvesting and Processing of Ash Seeds
Ash seeds, known as samaras, are harvested in late autumn when they turn brown. The seeds are typically collected directly from the trees or from the ground after they have fallen. After harvesting, the seeds are cleaned and dried, ready for storage or immediate planting. In order to prevent dormancy development, they can also be collected ‘green’ at the end of August and sown immediately after collection.
Storage and Germination
Ash seeds have double dormancy and generally require cold stratification to break it. After hot and cold stratification, seeds are sown in spring, where they germinate and grow into seedlings. Careful management of these seeds is essential to ensure the survival of this species, particularly in areas affected by ash dieback.
Norway Maple (Acer platanoides L.)
Norway Maple is a common species in European forests, valued for its ornamental beauty and adaptability to a wide range of soil types.
Flowering and Seed Production
Norway Maple begins to flower between 20 and 30 years of age, with flowering occurring in early spring, often before the leaves emerge. The seeds, known as samaras, are produced in pairs and are dispersed by the wind.
Harvesting, Processing, and Storage
Samaras are harvested in late summer or early autumn. After collection, the seeds are separated from the wings, cleaned, and dried. Norway Maple seeds typically require cold stratification to break dormancy before they are sown.
Sycamore (Acer pseudoplatanus L.)
Sycamore is a versatile, fast-growing tree species, widely used in reforestation and landscaping due to its hardiness and ability to thrive in a variety of conditions.
Flowering and Seed Production
Sycamore typically flowers in late spring. It produces large quantities of winged seeds, also known as samaras, which are easily dispersed by the wind.
Harvesting, Processing, and Storage
Sycamore seeds are collected in autumn, cleaned, and dried. Similar to Norway Maple, Sycamore seeds often require cold stratification to break dormancy before they can be successfully sown.
Black Alder (Alnus glutinosa (L.) Gaertn.)
Black Alder is a water-loving species that plays a crucial role in stabilising soil in riparian zones, making it an important species for ecological restoration projects.
Flowering and Seed Production
Black Alder flowers early in the spring, producing both male and female catkins on the same tree. The small seeds are housed in woody cones that mature in autumn.
Harvesting, Processing, and Storage
The cones are collected in late autumn, and the seeds are extracted, cleaned, and stored. Cold stratification may be required to break dormancy, depending on the specific storage conditions and timing of sowing.
Wild Cherry (Prunus avium L.)
Wild Cherry is prized not only for its high-quality timber but also for its ecological benefits, providing food for wildlife and supporting biodiversity.
Flowering and Seed Production
Wild Cherry typically flowers in early spring. It produces small, fleshy fruits that contain seeds, which are dispersed by animals.
Harvesting, Processing, and Storage
The seeds are extracted from the fruits in late summer, cleaned, and stratified before storage. Warm and cold stratification is necessary to break dormancy and ensure successful germination when the seeds are sown.
Conclusion
In conclusion, understanding the specific requirements for seed collection, processing, storage, and germination for these selected tree species is crucial for effective forest management and conservation. By leveraging this knowledge, forestry professionals can enhance the success of reforestation efforts, support the genetic diversity of our forests, and contribute to their long-term resilience. As environmental conditions continue to change, the careful management of these vital resources becomes even more essential.
Thank you for joining us in this eleventh episode. We hope you’ve gained valuable insights into the complexities of managing seed and forest reproductive material data for these important tree species. In our next twelfth episode, we will explore the FRM data for selected key coniferous tree species commonly found in European forests and essential for timber production, biodiversity, and the overall health of forest ecosystems. Stay tuned!