Effects of canopy opening on height and diameter growth in naturally regenerated beech seedlings

Abstract

-In order to analyze the growth dynamics of beech seedlings growing under contrasting canopy conditions, a beech stand in which two types of canopy opening (canopy release or gap creation) had been applied in 1995 was selected. Three and four years after the canopy had been opened, 113 naturally regenerated seedlings were sampled in gaps or under the canopy. The effects of canopy opening and seedling age on annual height and diameter growth were analyzed using mixed models. Under closed canopy, average annual seedling height and diameter increments were 1.2 cm and 0.18 mm, respectively. Diameter growth increased in the first year after the canopy had been opened, and exhibited considerable inter-annual variation related to climatic conditions. Conversely, height growth did not increase immediately after canopy opening, but increased regularly in the following years. Four years after the gap had been created, annual seedling height and diameter growth were 9.5 cm and 0.49 mm respectively in the gaps, and 3.8 cm and 0.21 mm respectively under released canopy. Age did not affect the dynamics of seedling growth.gap / shade tolerance / natural regeneration / Fagus sylvatica L. / mixed model Résumé -Effets de l'ouverture du couvert sur la croissance en hauteur et en diamètre de semis naturels de hêtre. La dynamique de croissance de jeunes semis de hêtre poussant dans les conditions de couvert contrastées a été étudiée dans un peuplement à base de hêtre dans lequel deux types d'ouverture du peuplement ont été réalisés. En 1995, un simple relevé de couvert a été effectué dans l'ensemble du peuplement et des trouées ont été ouvertes dans certaines parties. En 1998 et 1999, 113 semis naturels de hêtre ont été récoltés sous couvert ou dans les trouées. Les effets combinés de l'ouverture du couvert et de l'âge des semis sur la croissance en hauteur et en diamètre des semis ont été analysés à l'aide de modèles linéaires mixtes. Les semis sous couvert présentaient un accroissement annuel en hauteur de 1,2 cm et un accroissement annuel en diamètre de 0,18 mm. La croissance en diamètre a augmenté dès la premère année après l'ouverture du couvert et a ensuite montré de fortes variations inter-annuelles liées à des variatons climatiques. En revanche, l'augmentation de la croissance en hauteur à la suite de l'ouverture du peuplement n'a pas été immédiate, et a continué de manière progressive dans les quatre années suivantes. Quatre ans après l'ouverture du peuplement, les accroissements annuels en hauteur en en diamètre étaient de 9,5 cm and 0,49 mm respectivement pour les semis dans les trouées et de 3,8 cm and 0,21 mm respectivement pour les semis sous relevé de couvert. La croissance des semis n'est pas apparue liée à l'âge. trouée / tolérance à l'ombrage / régénération naturelle / Fagus sylvatica L. / modèle mixte

Plasticity in growth, biomass allocation and root morphology in beech seedlings as induced by irradiance and herbaceous competition

“…Marked differences in the biomass of Fagus seedlings were found two years after plantation, our data being within the range reported in the literature at similar age [6,11,43,49]. This confirms current indications that although Fagus tolerates shade and appreciates shelterwood, it responds favourably to canopy opening with enhanced growth [8,11].…”

“…This confirms current indications that although Fagus tolerates shade and appreciates shelterwood, it responds favourably to canopy opening with enhanced growth [8,11]. Seedlings in full light in the weeded meadow had a three-fold higher biomass than those planted in shade under dense Pinus stands.…”

“…Morphological responses of aerial parts to competition from overstory and understory vegetation have been widely investigated for most temperate tree species. Converging evidence from the literature indicates that the shoots of Fagus seedlings display a large morphological and physiological acclimation capacity to light regime at crown-level [33,39], branch-level [11,26] as well as at leaf-level [5,32,37,39]. In particular, shading is expected to result in leaves with larger specific leaf area (SLA) [42].…”

Competition for water between beech seedlings and surrounding vegetation in different light and vegetation composition conditions

“…The ecological requirements for beech establishment and development in forest stands have been studied in different site conditions [9,20,28,29]. A light value of about 40% of incident radiation at ground level has generally been reported as optimal for beech seedling growth [23].…”

Effects of traditional coppice practices and microsite conditions on tree health in a European beech forest at its southernmost range

“…Extensive coppicing in the analyzed plots A, C and D increased environmental stress. Coppicing amplified the ecological effects of forest fragmentation and canopy gap formation, affecting growth patterns, regeneration processes, and sunlight effects ( Topoliantz & Ponge 2000, Collet et al 2001, Caquet et al 2009, Robson et al 2009). …”