Establishment of the invasive perennial herb Bunias orientalis L.:: An experimental approach

A 2-year field experiment was performed to assess regeneration, establishment and growth of the invasive polycarpic perennial Brassicaceae Bunias orientalis L. from transplanted juveniles and propagules (seeds, fruits and root fragments). Further treatments were: different planting depths of the propagules, different root fragment sizes and a varied competition intensity by the matrix vegetation. In contrast to a high number of individuals established from planted juveniles (ca. 90 %), only relatively few propagules gave rise to seedlings or regenerating plants (0-16 %). However, upon emergence, all plants showed low mortality. Although the number of regenerated or recruited plants was affected by all treatments, only one treatment level (the use of very small root fragments of 1 cm length) completely failed in establishing plants. Plants experiencing low competition intensity attained high aboveground performance and reproductive output as well as reproductive success within two growth periods. Under high competition intensity recruitment, regeneration and growth were strongly negatively affected. The high morphological plasticity of rosette growth of B. orientalis seems to be advantageous for persistence in such situations. The results show that young B. orientalis plants are robust and can efficiently sequester and translate elevated resources into rapid growth and early reproductive output although the species is a rather long-lived iteroparous perennial. In addition, population foundation or regeneration can be based on both seeds and root fragments, even when buried under a thick soil layer. This seems to be a very efficient adaption to habitats which are subject to anthropogenic soil perturbations. (C) 1999 Editions scientifiques et medicales Elsevier SAS.