Germination requirements of the subordinate fen meadow species Valeriana dioica L

Abstract

Plant species of the intermediate life strategy type are characteristic for species-rich grasslands, which are sensitive to changes in the level of disturbance. Germination and early establishment of seedlings is expected to be the most crucial stage, limiting the successful colonization of appropriate sites. Valeriana dioica is a typical plant of calcareous fens, which are dependent on regular suppression of strong competitors by means of moderate land use. It is endangered in many parts of Central Europe, including Lower Austria. We studied the effects of light, temperature and pre-treatment (cold stratification) on the germination success of V. dioica seeds and the role of litter produced by different competitors on the early establishment of seedlings. We tested seeds from five populations differing in the level of competition for light and considered also the morphological variability of propagules and maternal plants. We found that V. dioica is able to germinate without light. It showed high germination percentages both under high summer temperatures independent of cold stratification and at low temperatures, but only after the stratification. Litter produced by dicotyledonous forbs was less hampering for the seedlings than that of small sedges or grasses. Valeriana dioica possesses a broad regeneration niche and is able to use gaps for germination and establishment both in spring and in summer. It reproduces successfully in herb-dominated fen meadow vegetation but disappears from reed communities. This study demonstrates the significant plasticity of the regeneration niche for a species with an intermediate life strategy and also stresses the importance of gaps for its reproduction.