Autotoxicity as a cause for natural regeneration failure inNyssa yunnanensisand its implications for conservation

Abstract

Autotoxicity is known to regulate density-dependent intraspecific competition in plants, but at the same time due to the effects on regeneration and hence population size, it may have implications for conservation. Nyssa yunnanensis is an endangered plant species with extremely small populations. There are only eight wild individuals left in Yunnan Province, Southwestern China. The mechanism governing the restricted ability for surviving in their natural environment is not known. In order to understand the causes of endangerment and take effective conservation measures, in situ and laboratory experiments were carried out to examine the autotoxicity of N. yunnanensis. In situ field experiments demonstrated that seed germination of N. yunnanensis was significantly inhibited by both litter and seed capsule. Extracts of different organs of N. yunnanensis had significant negative effects on its seed germination, and the inhibition rate of root extracts (80.9%) was significantly higher compared with the leaves and stems. Seedling growth also was suppressed by extracts of different organs, whereas no significant differences were found in the root/shoot ratio. The degree of inhibition of both germination and seedling growth increased with extract concentration. Soil experiments demonstrated also that seed germination and seedling growth were suppressed in soil where N. yunnanensis had previously grown. The results suggest that N. yunnanensis may negatively affect its natural regeneration through autotoxic effects on seed germination and seedling growth. Conservation strategies should be dedicated to ameliorating the autotoxic effects and enhancing natural regeneration. These may include litter clearance, activated carbon addition, and managed relocation.