© 2004 by Institute of Chartered Foresters
| ||||||||||||||||||||||||||||||||||||||||||||||||||||
Spatial aspects of the influence of silver birch (Betula pendula L.) on growth and quality of young oaks (Quercus spp.) in central Germany
A1 Potsdam Institute for Climate Impact Research, Telegrafenberg A 51, D-14473 Potsdam, Germany A2 Department of Forest Science, Oregon State University, 321 Richardson Hall, Corvallis, OR 97331-5752, USA A3 Staatliches Forstamt Bad Driburg, Stiftstr. 15, D-33014 Bad Driburg, Germany A4 Institute of Landscape Ecology, Westfälische Wilhelms-Universität Münster, Robert-Koch-Strasse 26, D-48149 Münster, Germany
This study was carried out to examine the influence of interference by silver birch (Betula pendula L.) on oaks (Quercus spp.) planted in clusters. On two sites in the north-eastern Hessian Mountains, Germany, transects starting with a birch were laid through oak clusters. Height, diameter at breast height (d.b.h.) and crown radii of the birch and the nearest three oaks on the transect were taken. The stem form and crown type of the oaks were noted and distances between birch and oaks were measured. Oaks on transects with birch interference were compared with oaks from birch-free transects. Results showed that, on the site where oaks were smaller, the birch did not consistently influence oak growth. On the other hand, the larger oaks on the second site were negatively influenced by the competing birch. Other measures than height or d.b.h. growth may be a more sensitive indicator of competition as all oaks shifted their crown centre away from the birch. Also, the proportion of trees with good stem form increased with the distance from the birch and the ratio of trees with bent stems decreased. Crown type was not affected by interference. To generalize, foresters should pay attention to the spatial aspects of birch, i.e. its location with reference to neighbouring oaks, and they may be able to use crown shift as an indicator of when to remove overtopping birch competitors before they influence growth of oak.