Plant–soil interactions in a deglaciated landscape: Root exudation reflects environmental severity.

Abstract

The growth of shrubs in the Arctic is a key factor affecting environmental and vegetation changes framed by the currently accelerated dynamics of global warming. One of the phenomena involved in the shrubification of the Arctic is root exudation, which plays a part in nutrient acquisition by plants and thus the growth of both individual plants and whole communities. It is not known, however, to what extent root exudation differs across different environments in the Arctic tundra, how importantits role is in covering the nutrient demands of plants and what significance this might have for soil properties and vegetation succession. To shed light on the topic, we studied the content of biogenic elements in soils of different maturity following deglaciation, the age structure of the climax species Salix polaris, exudation by its roots,and the concentrations of different nutrients in its roots and leaves in the forefield of the Nordenskiöld glacier in the Svalbard archipelago. Our results reveal that polar willow shrubs have a greater relative propensity towards exudation, and thus larger potential for investing into growth, under more severe environmental conditions, which may be attributable to the stage of their root system development or the level of competition they face. This finding should be taken into consideration when interpreting current vegetation development and plant succession in the Arctic. Nevertheless, to what extent this relationship stays stable in the context of ongoing climate change remains a question to be explored.