Influence of light availability on growth, leaf morphology and plant architecture of beech (Fagus sylvatica L.), maple (Acer pseudoplatanus L.) and ash (Fraxinus excelsior L.) saplings

Abstract

In a field study, we measured saplings of beech, ash and maple growing in a fairly even-aged mixed-species thicket established by natural regeneration beneath a patchy shelterwood canopy with 3-60% of above canopy radiation reaching the saplings. Under low light conditions, maple and ash showed a slight lead in recent annual length increment compared with beech. With increasing light, ash and maple constantly gained superiority in length increment, whereas beech approached an asymptotic value above 35% light. A suite of architectural and leaf morphological attributes indicated a more pronounced ability of beech to adapt to shade than ash and maple. Beech displayed its leaves along the entire tree height (with a concentration in the middle crown), yielding a higher live crown ratio than ash and maple. It allocated biomass preferentially to radial growth which resulted in low height to diameter ratios, and expressed marked plagiotropic growth in shade indicating a horizontal light-foraging strategy. In addition, beech exhibited the highest specific leaf area, a greater total leaf area per unit tree height, a slightly greater leaf area index, and a greater plasticity to light in total leaf area. Ash and maple presented a ''gap species'' growth strategy, characterized by a marked and constant response in growth rates to increasing light and an inability to strongly reduce their growth rates in deep shade. In shade, they showed some plasticity in displaying most of their leaf area at the top of the crown to minimize self-shading and to enhance light interception. Through this, particularly, maple developed an ''umbrella'' like crown. These species-specific responses may be used for controlling the development of mixed-species regeneration in shelterwood systems. Keywords Shade tolerance Á Juvenile growth Á Mixed species broad leaf stand Á Tree architecture Á Leaf morphology Á Light availability Communicated by R. Matyssek.

Effects of root trenching of overstorey Norway spruce (Picea abies) on growth and biomass of underplanted beech (Fagus sylvatica) and Douglas fir (Pseudotsuga menziesii) saplings

“…Under limiting light conditions, diameter increment of Douglas fir saplings in our study responded to trenching not as responsive as length increment. This agrees with a frequently observed characteristic of many less shade-tolerant species tending to invest preferentially into height growth rather than into lateral growth and by this increasing the chance to reach the forest canopy more quickly (Chen 1997;Chen and Klinka 1998;Petritan et al 2009). …”

“…Of the environmental factors governing the growth conditions in the understorey, light is considered the most important factor (Kimmins 1997) and therefore has been widely investigated (inter alia Röhrig 1967;Kobe et al 1995;Kunstler et al 2005;Stancioiu and O'Hara 2006;Petritan et al 2007Petritan et al , 2009). On the other hand, the influence of overstorey root competition on growth of underplanted seedlings remains poorly investigated and understood (Coomes and Grubb 2000), although some studies found a strong below-ground competition between overstorey and understorey vegetation for water and nutrients (Christy 1986;McCune 1986;Riegel et al 1992;Walters and Reich 1997;Wagner 1999;Lindth et al 2003;Machado et al 2003).…”

Growth and morphology of three forest understorey species (Calluna vulgaris, Molinia caerulea and Pteridium aquilinum) according to light availability

“…This effect is not illustrated in the literature for herbaceous or shrubby species, but it can be placed in parallel with results observed on tree response to light availability. Numerous studies have shown that the stem height / diameter ratio of trees decreases with light availability, suggesting that shade affects stem diameter growth more negatively than it does height growth (Petritan et al, 2009). For shadeintolerant species, a height increment can even occur in response to shade, in a "shade-avoidance reaction", corresponding to a height increment added to potentially seek more light (Dehlin et al, 2004).…”

Biomass allocation in natural regeneration of Fagus sylvatica and Picea abies trees in Italian Alps

“…Leaf area also infl uences the amount of diffuse light, which is a good predictor of plant growth (Jarčuška, 2011). Light availability can explain growth; shade-tolerant species can survive long periods in deep shade by greatly reducing their growth in height (Petriţan et al, 2008). Growth responses in individual plants are diffi cult to predict because the factors involved are numerous.…”

“…In particular, light plays an outstanding role in forests, at least on mesic sites in temperate regions, and it can easily be manipulated by silvicultural treatments (Petriţan et al, 2008).…”