• The impact of shade on photosynthetic characteristics in Fagus sylvatica and Quercus robur seedlings

      Sevillano, Ignacio; Short, Ian; O'Reilly, Conor (Teagasc, 10/03/2014)
    • Morphological and physiological responses of Fagus sylvatica and Quercus robur seedlings to light availability

      Sevillano, Ignacio; COFORD; Teagasc Walsh Fellowship Programme (2016-06)
      The need to develop forest management systems other than clearfelling has resulted in a requirement for improved understanding of the potential of continuous cover forestry (CCF). One suggested method for the conversion of forest stands into CCF systems and for bringing under-performing forests into productivity is thinning in conjunction with underplanting. This study was an attempt to provide information on species suitability for underplanting of two important trees in European forestry: pedunculate oak (Quercus robur L.) and European beech (Fagus sylvatica L.). To determine the morphological, physiological and growth responses of these two species to different light conditions, beech and oak seedlings previously grown at full light for two years were covered by shading nets that provide different shade levels (62%, 51% or 28% of full light) or continued to be exposed to full light. The different shade levels were intended to mimic a range of underplanted conditions and the process of acclimation to shade was studied to provide information on the ecology and adaptation of underplanted seedlings. In addition to the controlled-shade experiment another study to determine the physiological responses of beech natural regeneration to shade was conducted under natural light conditions (from open gaps to closed canopy). Both oak and beech displayed similar acclimation in response to shade for most of the traits investigated. At the plant level, seedling acclimation to shade included higher biomass allocation to above than below-ground parts and greater energy investment on height than diameter growth. At the leaf level, seedlings grown under shade reduced their leaf thickness and photosynthetic rates per unit area and increased their specific leaf area. This increase in specific leaf area seems to be one mechanism that allows seedlings to perform well under shade conditions. Another acclimation to low light conditions was to increase the efficiency of the photosystem II under shade. Photosynthetic rates were higher and leaves were retained for longer in seedlings grown at full light than under shade. Hence, this probably led to a greater growth in the full light than under shade. Despite this greater growth at full light, the results of this study suggest that beech and oak seedlings would be able to acclimate and perform well if underplanted below overstories that reduce the available light to as low as 28% of full light without having any significant adverse effect on the quality of the final crop.
    • Physiological Responses of Fagus sylvatica and Quercus robur Seedlings to Light Intensity

      Sevillano, Ignacio; Short, Ian; O'Reilly, Conor; Grant, Olga M.; COFORD (FESPB/EPSO, 22/06/2014)
      Broadleaf planting has become increasingly important in Ireland over the recent years and light is recognised as one of the main environmental factors affecting stand development, but to date there has been little research on broadleaf responses to light intensity, particularly in Ireland. Continuous cover forestry (CCF) is increasing as an alternative to clear-cutting and uses the control of light to produce plantation benefits. The physiological responses of beech (Fagus sylvatica) and oak (Quercus robur) seedlings to four different shade environments (100%, 62%, 51% and 28% of incident photosynthetically active radiation, PAR) were studied in a shadehouse experiment during the summer of 2013. Light-response curves (only measured in the extreme treatments) differed between beech seedlings of the Control treatment (PAR=100%) and those of the heavy shade treatment (PAR=28%) when PAR > 100 μmol m-2 s-1, while there was little difference for oak between both treatments. Light-response curves generally showed maximum photosynthetic rates (Amax) at 1500 μmol m-2 s-1 in both treatments, and this PAR value was used while measuring stomatal conductance (gs) and water use efficiency (WUE). Significantly higher values of Amax and gs were found in oak than in beech in the 62%, 51% and 28% treatments. There were no significant differences between oak and beech for Amax and gs in the Control treatment or for WUE in the four treatments.