Fragility of the Plant Cover in the Arctic )

Abstract

During their evolutionary history, plants have adopted different survival strategies with a view to securing the maintenance of their functional structure under the prevailing conditions. Depending on the strategy chosen, plants therefore react differently to outside impacts, man-induced included. This is illustrated by the behaviour of four plant life formes, dwarfbushes, grasses, cushion plants and lichens, each representing a particular survival strategy, during the short arctic summer. The question of the fragility of the arctic plant cover is discussed on the basis of the results obtained. It is concluded that it varies substantially from place to place with the type of vegetation involved, the time horizons considered and the nature of the impact, grazing or other. Lack of sufficient insight into the basic mechanisms which determines how plants behave when exposed to stress, makes it difficult to realize long term managements schemes. Experiments were carried out in Greenland at three sites, one inland, with continental climate, two on the coast. They included growth analyses, CO 2 -measurements and determination of nitro-genase activity, emphasis being put on CO 2 -exchange which can readly be correlated with the rapidly fluctuating photon flux densities and air temperatures, characteristic of the climate of the region. Man‘s growing impact on the biosphere has created a need for better management of its living resources. Management, however, implies capability of prediction, which again presupposes knowledge about the basic mechanisms which determine how ecosystems react when exposed to extraneous influences. Only little is known about these mechanisms, in particular in the arctic regions. In the present text, data are given which illustrate the situation in Greenland where multiuse management of the plant cover is recommended. Emphasis is put on the description of the behaviour of four life or growth forms, dwarfbushes, grasses, cushion plants and lichens which each represent a particular survival strategy, during the short arctic summer. The problem of the fragility of the plant cover is considered in various time and space perspectives.