Seedling bank dynamics in managed holm oak (Quercus ilex) forests

Abstract

-The present study reports spatiotemporal variations in seedling bank dynamics during a 5-year period in thinned and unthinned holm oak (Quercus ilex) plots in the Montseny Massif (NE Spain). Large spatial and temporal variations in seedling density have been found in the three plots studied, while the spatial pattern has shown low temporal fluctuations. However, differences in recruitment and survival among thinned and unthinned plots were small, but both variables had large between-year variability. The monitoring of seedling growth over time demonstrated that holm oak seedlings hardly grew in height after five years. According to these results, holm oak seedlings persisted through time in the understory and remained suppressed while in the shade, but did not show any release after thinning. Thus, the seedling bank only represents a reserve of small individuals that do not have any evident role in holm oak forest dynamics under the present disturbance/management regime. holm oak / seedling / recruitment / growth / survival Résumé -Dynamique du banc de plantules dans des taillis coupés et non coupés de chêne vert (Quercus ilex). Cette étude analyse les variations spatiales et temporelles de la dynamique du banc de plantules de chêne vert (Quercus ilex) pendant cinq ans, dans des taillis coupés et non coupés dans le massif du Montseny (NE Espagne). Nous avons trouvé de grandes variations spatiales et temporelles de la densité de plantules dans les trois taillis étudiés. Cependant, les différences de recrutement et survivance des plantules entre les trois taillis sont minimes, mais les deux variables ont montré une grande différence interannuelle. L'échantillonnage de la croissance des plantules au fur et à mesure a montré qu'elles ne poussent pas après cinq ans. En accord avec ces résultats, les plantules de chêne vert survivent sans être altérées pendant des années dans le sous-bois, mais elles ne présentent aucune libération après la coupe. Pour cette raison, le banc de plantules de chêne vert peut être consideré comme une réserve de petits individus qui n'a aucun rôle évident dans la dynamique des chênaies sous le régime actuel de perturbation/gestion de ces forêts. chêne vert / plantule / recrutement / croissance / survivance Ann. For. Sci. 58 (2001) [843][844][845][846][847][848][849][850][851][852] 843

Diversity of woody plant seedling banks under closed canopy in fragmented coppice forests

“…Despite the observations made on seedling distribution patterns according to distance from the forest edge and conspecific adult presence, the spatio-temporal variability of seedling patterns prevents us from making definite predictions about the future of these seedlings (Houle, 1994). Substantial seedling establishment does not ensure the subsequent renewal of the species (Gracia et al, 2001) since sapling survival may be particularly dependent on an opening of the canopy for some species such as oak (Espelta et al, 1995). A long-term study of regeneration in these forests should provide some interesting supplementary information about the spatio-temporal dynamics of this seedling bank (Frey et al, 2007).…”

“…These processes have received less attention than events after logging disturbances, despite their possible influence on the future adult tree community (Hodgson and Grime, 1990). Few studies, however, have considered the seedling bank and its determinants in coppice forests, a forest management system frequently found in Europe (Gracia et al, 2001;Le Duc and Havill, 1998).…”

Analysis of the seed regeneration process in a

“…Si nota anche una spiccata variabilità nel tempo per cui zone ricche di semenzali nel 1980 ne presentavano pochissimi nel 1998 e viceversa. Una spiccata variabilità nella distribuzione di semenzali è stata rilevata anche da Gracia et al (2001) in un ceduo di leccio del nord-est della Spagna.…”

“…E' stato inoltre rilevato (Gracia et al 2001) che le operazioni di utilizzazione ed esbosco possono provocare danni alle piantine, ed in particolare l'accumulo di ramaglia sul terreno può provocare la morte dei semenzali. Nel nostro caso quest'ultima eventualità deve essere esclusa, dal momento che la ramaglia è stata asportata, e questo può anche spiegare le differenze rilevate con altri lavori citati in questo lavoro, in cui la diminuzione del numero di semenzali è più forte fin dai primi anni.…”

“…In realtà alcuni studi condotti in campo negli ultimi decenni sia in Italia (La Marca et al 1996a, La Marca et al 1996b, Giovannini et al 1992) che all'estero (Matsuda 1985, Ducrey 1988, Montgolfier 1988, Espelta et al 1995, Turchin 1993, Gracia et al 2001 hanno evidenziato come il processo di rinnovazione da seme nei cedui sia tutt'altro che scontato, e che già la prima fase di passaggio dallo stato di semenzale a quello di sapling (piante con diametro basale di almeno 1 cm e con diametro a petto d'uomo DBH ≤ 3 cm, così come definite da Swiecki et al 1997), sia un evento estremamente raro.…”