Crown development and architecture of Fraxinus pennsylvanica var. subintegerrima (Vahl) Fern. at different stages of growth and under different environmental conditions

Abstract

The objectives of the thesis were to examine spatial (crown location) differences and temporal (aging) differences on various aspects of F. pennsylvanica crown architecture characteristics. The major characteristics examined were the number of shoot units per shoot, shoot-unit length and the fate of buds. The other objective was to examine how shoot development and architecture are affected by the light environment when the whole tree is shaded. To examine the spatiotemporal change in architecture, trees of approximately 8, 10, 20, 50, and 60-years-old were selected at the Agriculture and Agri-Food Centre in Morden, Manitoba and measurements in each of 3 crown locations were made. To examine the relationship between light and shoot architecture, 2-years-old seedlings were transplanted and subsequently covered with shade cloth of varying shade intensities (60, 80, 92, and 96%) and a control grown in the open at the University of Manitoba. Architectural measurements along with environmental variables (soil moisture content, air temperature, relative humidity and the red to far-red light ratio) were made in each treatment. (Abstract shortened by UMI.)