Seed dormancy and consequences for direct tree seeding
Résumé
Direct tree seeding was used in the past in afforestation and has nowadays a renewed interest due to its potential low cost, better tree seedling establishment and easiness to use in comparison with tree plantation. However many problems must still be solved before its full development. Seeds of forest trees are frequently dormant when harvested or after a period of storage and their germination needs the release of dormancy, either by exposition to natural climate, or by artificial means when known. Tree dormancy feature was studied in a controlled experiment in nursery in Nancy for 20 different common species in East of France, corresponding to 3 successional stages after field abandonment: thorny shrubs, pioneer fruit trees and forest trees. No prepared seeds were sown either in spring or in autumn, buried or not into the soil and watered or not, each modality being replicated 4 times. Tree emergence and growth were regularly recorded during 3 years. For most species best emergence rates were recorded one or two years after a sowing in spring, meaning that they need several months of exposure to natural conditions to release from dormancy. Results are discussed relative to the technique of direct tree seeding.
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