The Adaptability to Light Intensity of Seedlings of Quercus Petraea (Matt.) Liebl.

In a classic study Watt (1919) discussed many of the factors limiting the natural regeneration of oaks in Britain. His conclusions relating to biotic and edaphic factors are, however, likely to be primarily of local interest and his investigations of factors such as light intensity were more superficial. Jones (1959) in a summary of existing knowledge emphasized the lack of critical information about the effects of factors such as soil structure, nutrient status and water content, and light intensity on seedling and tree growth. To the west of Sheffield on the Derbyshire gritstone there are many small fragments of relict sessile oakwoods of the types described by Moss (1913) and Tansley (1939). In many of these woods growth and regeneration are very poor. As part of an investigation into factors which might be causing the poor regeneration, seedling response to light intensity was investigated experimentally. The experiments may be conveniently divided into three sections: (1) Experiments in which seedlings were grown outside with different degrees of shading and assessments were made of their gross morphological and physiological responses. (2) Laboratory experiments with sunand shade-grown plants, to help in the physiological interpretation of the growth experiments. (3) Field experiments to estimate the relative importance of light as an ecological factor for the survival and growth of seedlings in the field. The experiments were carried out at the research garden of the Sheffield University Department of Botany, at the Institute of Physiological Botany and the Department of Genetics, Uppsala, and at an enclosure at Padley wood, near Sheffield (described by Pigott 1956), respectively.