Changes in Plant Ecophysiology Across a Central European Hedgerow Ecotone

Abstract

In past decades, ecological research often concentrated on processes and patterns of homogenous ecological systems. This research produced important estimates of primary production, standing crop, nutrient cycling (e.g., Larcher 1980, Lange et al. 1983), vegetation processes (e.g., Harper 1977, Grime 1979), and classifications of vegetational composition (e.g., Braun-Blanquet 1964, Ellenberg 1978, Walter and Breckle 1986). Transition zones between relatively homogenous systems have often been neglected due to the perception that their importance is minimal because of the small ecosystem area they represent (Weinstein, Chapter 19, this volume). The unique characteristcs of boundary areas, however, have long been recognized by some ecologists (see van der Maarel 1976, di Castri et al. 1988). Clements (1905) introduced the term ecotone, referring to the tension supposedly manifested to underly these zones. For example, plants growing in such zones often show specific stress symptoms or adaptations (e.g., Tranquillini 1979; Küppers 1987; Slatyer and Noble, Chapter 17, this volume). Because of their transitional characteristics, some ecotones may be sensitive to external disturbances (Hansen et al. 1988). Therefore, at a time when global atmospheric changes are the focus of increasing attention (Schneider 1987), the lack of systematic information on ecotones becomes evident.